Colloquiam: Documents published in 2022

Effective range of integrated fluidic actuators in structural elements

Scipedia content — Wed, 06 Jul 2022 17:15:02 +0200

High demand for living and working space as well as the corresponding infrastructure, caused by a growing population and increasing prosperity worldwide, leads to increased consumption of mineral resources. This is accompanied by high usage of grey energy and a high output of greenhouse gas emissions. Adaptive structures represent a promising approach for mass and resource savings. Through the interaction of actuators, sensors and control units, the structure can adapt to the external loads to reduce stresses and deformations. As a result, the building material required can be reduced. For actuators integrated into slabs, new challenges arise due to the multi-axial load transfer. In particular, the aim is to achieve the largest possible effective range of the applied moment to reduce the number of actuators required. One approach is to optimize the geometry of the force-introducing surfaces inside the structural element. This paper presents a study about the correlations of the geometric parameters using numerical simulations. This enables the pre-dimensioning of the actuator and is thus a first step in its design.

Development of two-phase flow simulation using SPH Method

Scipedia content — Wed, 06 Jul 2022 17:14:46 +0200

Gas entrainment is one of the major defects caused in the casting filling process. Since the particle method is a Lagrangian method that does not use a lattice, it can easily analyze large deformations and boundary movements, so it has the potential to be applied to gas defect prediction as a methodology. However, in the two-phase flow simulation including gas entrainment, the analysis fails when the gas / liquid density ratio becomes smaller than about 1/10 in the conventional SPH. Therefore, two dimensional two-phase flow SPH methodology was developed. Then, authors extended the methodology to three dimensions that can be applied to gas entrainent during a die cast filling process.

Development of Mold Filling Process Simulation considering Air Entrainment using SPH Method

Scipedia content — Wed, 06 Jul 2022 17:14:34 +0200

Die-casting is a casting method suitable for mass production because it can accurately form complicated shapes. However, when the mold is filled with the molten metal, casting cavities (gas porosity) are generated due to air entrainment, and the strength of the product varies. In this study, the mold filling process considering air entrainment in the die cast are simulated using the two-phase flow SPH method. And then, the behavior of air entrainment due to the filling of molten metal (Aluminum alloy), especially the efect of injection speeds are investigated. In concluson, it is possible to investigate the air entrainment behavior at the time of filling the molten metal and the flow behavior due to different filling speeds. In addition, to speed up the two-phase flow program by SPH method, a parallel algorithm using OpenMP is implemented.

Development of Low-Cost Solver for Incompressible Viscous Fluid Flow based on the Fundamental and Particular Solutions of Differential Operator

Scipedia content — Wed, 06 Jul 2022 17:14:20 +0200

In industrial numerical simulation of the complex and/or large-scale fluid flow, the computation cost must be reduced. In order to develop numerical low-cost solver for incompressible fluid flow problems based on BEM an effective scheme of DRM is proposed.

Development of Isolated Element Method and Analysis of Upper and Lower bound solutions by a New Mixed-Hybrid Variational principle

Scipedia content — Wed, 06 Jul 2022 17:14:07 +0200

A new discretization analysis method named the isolated element method, that differ from conventional FEM, for solid mechanical problems is proposed. An object to be analyzed is divided into the elements that are separated from each other. A set of displacement functions providing arbitrary number of degrees of freedom is used for each isolated element which expresses the translation and rotation of a rigid body. The extended principle of minimum potential energy is applied to satisfy the continuity of the displacement of isolated elements adjoining to each other. Any node or spring, penalty functions and Lagrange multipliers are not used in this method. The displacement functions of the power series are used to describe the mechanical state of the isolated element and finally, the coefficients of series are determined by a variational principle derived from the extended principle of minimum potential energy. Furthermore, a new mixed and hybrid variational principle which is composed from the potential and the complemental energy functional is proposed. The pair of these energy are constrained by a formula. Using this new principle, in which stress and displacement can be used as independent variables, the stress and displacement are computed at the same time. Besides, upper and lower bounds solutions are analyzed using the new principle and the isolated element method. Some computed examples of the plane stress problems are presented. We show the good convergency of the numerical results, and also present the upper and lower bound results of stress and displacement by the new mixed and hybrid variational principle using the isolated element method.

Development of Efficient FEM Analysis Method using Equivalent 2D Model for Linear Friction Welding Analysis

Scipedia content — Wed, 06 Jul 2022 17:13:55 +0200

LFW(Linear Friction Welding) is the one of the smart industrial method matching to SDGs concept. It only needs a pair of blanks with no other assisting materials. This technique is now widely used in the Aeronautical, Automobile and other mechanical industries. In this paper we introduce an efficient LFW analysis method with 2D FEM model of LS-DYNA. In conclusion, analysis showed good correlation to the experimental results of the LFW process.

Development of a hybrid model for large-scale plant RUL prediction based on data and physical models

Scipedia content — Wed, 06 Jul 2022 17:13:39 +0200

Large plants in the process industry are monitored and maintained at regular intervals and repeatedly maintenance is either too early or too late. This causes unnecessary costs due to technicians, spare parts procurement as well as delivery issues and to high downtime costs due to unexpected shutdowns. In this context, the Remaining Useful Life (RUL) plays a major role, as it is an indicator of how long a machine or component can run without breakdown, repair or replacement. By predicting RUL using predictive maintenance, maintenance can be better planned, operational efficiency optimized, and unplanned downtime avoided. Optimizing the prediction accuracy should therefore always be in the foreground and is therefore the topic of this paper.

Development of a Fluid-Structure Interaction Method wiht Free Surface Using IGA

Scipedia content — Wed, 06 Jul 2022 17:13:24 +0200

The purpose of this study is to develop a fluid-structure interaction analysis method using IGA. For fluid analysis, the numerical method based on the VOF method is employed. The stabilized finite element method with IGA is applied as the spatial discretization method and the Crank-Nicolson method as the temporal discretization method. Several numerical examples are presented to demonstrate the promise and potential of the present method to solve the solid-fluid interaction problems with free surface(WCCM-APCOM 2022).

A Simple Test Case for Convergence Order in Time and Energy Conservation of Black-Box Coupling Schemes

Scipedia content — Wed, 06 Jul 2022 17:13:09 +0200

The most commonly used coupling schemes in partitioned multiphysics simulations suffer from a decrease in the order of convergence, specifically in the time domain; a phenomenon we call order degradation. This paper discusses when this issue arises and how it can be studied with a simple example. We present a simple mass-spring system of ordinary differential equations (ODEs) to analyze accuracy and energy conservation of different coupling schemes. The ability to restore higher order of convergence by using Strang splitting or waveform iterations is verified in the context of the presented example. This paper provides details on some aspects of the talk titled 'Design and evaluation of a waveform iterationbased approach for coupling heterogeneous time stepping methods via preCICE' given at WCCM-APCOM 2022.

Deformation Clustering Methods for Topologically Optimized Structures under Crash Load based on Displacement Time Series

Scipedia content — Wed, 06 Jul 2022 17:12:58 +0200

Multi-objective Topology Optimization has been receiving more and more attention in structural design recently. It attempts to maximize several performance objectives by redistributing the material in a design space for a given set of boundary conditions and constraints, yielding many Paretooptimal solutions. However, the high number of solutions makes it difficult to identify preferred designs. Therefore, an automatic way of summarizing solutions is needed for selecting interesting designs according to certain criteria, such as crashworthiness, deformation, and stress state. One approach for summarization is to cluster similar designs and obtain design representatives based on a suitable metric. For example, with Euclidean distance of the objective functions as the metric, design groups with similar performance can be identified and only the representative designs from different clusters may be analyzed. However, previous research has not dealt with the deformation-related time-series data of structures with different topologies. Since the non-linear dynamic behavior of designs is important in various fields such as vehicular crashworthiness, a clustering method based on time-dependent behavior of structures is proposed here. To compare the time-series displacement data of selected nodes in the structure and to create similarity matrices of those datasets, euclidean metrics and Dynamic Time Warping (DTW) are introduced. This is combined with clustering techniques such as k-medoids and Ordering Points To Identify the Clustering Structure (OPTICS), and we investigate the use of unsupervised learning methods to identify and group similar designs using the time series of nodal displacement data. In the first part, we create simple time-series datasets using a mass-spring system to validate the proposed methods. Each dataset has predefined clusters of data with distinct behavior such as different periods or modes. Then, we demonstrate that the combination of metrics for comparison of time series (Euclidean and DTW) and the clustering method (k-medoids and OPTICS) can identify the clusters of similar behavior accurately. In the second part, we apply these methods to a more realistic, engineering dataset of nodal displacement time series describing the crash behavior of topologically-optimized designs. We identify similar structures and obtain representative designs from each cluster. This reveals that the suggested method is useful in analyzing dynamic crash behavior and supports the designers in selecting representative structures based on deformation data at the early stages of the design process.

Data augmentation technique for construction engineering regression surrogate model

Scipedia content — Wed, 06 Jul 2022 17:12:45 +0200

The objective of this study is to predict the degree of danger to the human body from motion information such as acceleration, velocity and displacement during a collision between a car and a human body. As a preliminary step, the maximum bending moment that occurs in the leg was predicted using a convolutional neural network. The responses which are represented by learning data generated by 1D-CAE system. A number of training data sets are varied in order to show the enough number to predict. The predictor's accuracy is evaluated by the test data sets. We'd like to discuss necessisty of a total number of training data sets and effectiveness of data augmentation technique. In addition, the technique to utilize classification by the t-SNE method to improve accuracy is also examined. t-SNE is based on classification algorithm, however an engineering interpolation should be computed based on physical meanings and influential parameters.

Damaging Configurations in Arch Structures with Variable Curvature and Tapered Cross-section

Scipedia content — Wed, 06 Jul 2022 17:12:32 +0200

Arch structure is a widely used and important structure type all over the World. Due to its beautiful form and large spanning capacity, arch structure is widely used in bridges, tunnels and other buildings. Recently, the large span space arch structure has a stage of development. The defects of arch structure, such as connection, material, fatigue, stress concentration and welding, will directly affect the safety of these kind of structures. The study of the evolution of the damage in arches is a topic of interest since the antiquity. A well-done structural design should always account for the evolution of the damage in time, in particular if it can bring to a change in the static behaviour of the structure itself under different loading conditions. In this paper, a model for the calculation of localized damaged in arch structures is presented. In particular, using an analytical solution for the computation of the displacements field and the consequent internal actions of very general shapes with variable curvature and tapered cross-section, the damage is modelled by localized depletion of the cross-sectional properties (inertia) in the different points along the arch axis. Moreover, the depleted parameters are the crosssection and the bending stiffness of the arch. The model is applied to the study different configurations of the damage (localization of plastic hinges or different pattern of defects) and to consider the evolution of the damage in time.

DEEP LEARNING BASED SURROGATE MODELLING OF WAVE PROPAGATION AND DAMAGE DETECTION IN CRACKED ROD

Scipedia content — Wed, 06 Jul 2022 17:12:14 +0200

Guided wave-based Structural Health Monitoring (SHM) tools utilize the guided wave responses to interrogate damage in structures. This research demonstrates the use of various objective functions in single (mono) objective and multi-objective genetic algorithms for damage identification in isotropic 1D structures. The time domain spectral element method and a deep-learning-based surrogate is utilized for simulating wave propagation in an isotropic cracked rod. The genetic algorithms employ results ('numerical experiment') obtained from the spectral element model and the deep-learning-based surrogate to determine the optimized crack locations and crack depths as output parameters. The obtained optimized parameters from genetic algorithms are compared in terms of errors for various objective functions.

Critical Velocity and Instability of Inertial Objects Moving Uniformly on Layered Track Models

Scipedia content — Wed, 06 Jul 2022 17:11:57 +0200

In this contribution, a new form of semianalytical results related to inertial objects that are traversing homogeneous infinite structures, introduced in previous author's work, is used to analyze one-, twoand three-layer models of the railway track. The aim of these analyses is determination of the critical velocity of a moving force and of the onset of instability of moving masses or oscillators. As one of the most important conclusions, it will be shown that in the case of two moving proximate masses, damping can act in the opposite direction than expected and owing to the dynamic interaction, the onset of instability can be shifted deeply into the subcritical velocity range.

Coupled simulation of vibration of violint and sound radiation in concert hall

Scipedia content — Wed, 06 Jul 2022 17:11:44 +0200

The vibrations and the sound field around the body of an old violin made by Stradivari are studied in this paper, in which this violin is scanned using a micro-CT scanner to generate a highly precise geometric image. After the noise in the scanned data is eliminated using a computer-assisted design (CAD) software for post-processing, the geometric data are saved in the simulation software. Assuming the orthotropic properties of woods (spruce and maple), the major vibration modes of the violin, such as A0, center bout rotation, B1-, B1+, and the acoustic pressure level at the surface of the violin body are calculated using the finite element method. Next, using the sound pressure distribution at the surface of the instrument, the sound pressure spreading in a rectangular box simulating a concert hall is calculated with the open-source parallel acoustic analysis software: ADVENTURE Sound. It is concluded that the sound pressure from the violin is successfully simulated.

Construction of a surrogate model for crash box corruption

Scipedia content — Wed, 06 Jul 2022 17:11:30 +0200

The structural strength evaluation of crash boxes is predicted by machine learning in this study. The training data was obtained from the dynamic elastic plastic analysis of the crash box. The input physical quantities are barrier angle, box thickness, material properties and mass equivalent to vehicle weight. The output physical quantity is the reaction force. Buckling occurs in the analysis and different directions of corruptions are one of the most interesting phenomenon from a point of engineering view.

Constructing Machine-learned Interatomic Potentials for Covalent Bonding Materials and MD Analyses of Dislocation and Surface

Scipedia content — Wed, 06 Jul 2022 17:11:16 +0200

As machine learning potentials for molecular dynamics (MD) simulations, Spectral Neighbor Analysis Potential (SNAP) and quadratic SNAP (qSNAP) were constructed for silicon (Si) and silicon carbide (SiC). The reproducibility of the basic material properties about perfect crystal, free surface and dislocation cores in Si and 3C-SiC was investigated. The coefficients of SNAP and qSNAP were optimized using liner regression to present energy and force obtained by DFT. In addition, hyperparameters (cutoff length and weights for optimization, here) were determined using genetic algorithm to reproduce elastic moduli obtained by DFT. Lattice constant and elastic moduli of Si crystal by MD using our SNAP or qSNAP agree well with the values of DFT, and they have higher accuracy than those by any empirical potential. Additionally, melting point and specific heat at constant pressure were calculated by MD correctly. Especially in qSNAP of Si, the surface energy of {100} and {111} planes and the reconstructed {100} surface structure were almost reproduced. For 3C-SiC, SNAP reproduces lattice constant and elastic moduli of DFT. Furthermore, edge dislocation cores were generated successfully. However, the potentials we constructed have insufficient reproducibility in the plastic region, so it is necessary to continue development.

Considerations on the Updating Process in Density-based Topology Optimization Using the Modified Optimality Criteria Method

Scipedia content — Wed, 06 Jul 2022 17:11:00 +0200

In this study, we performed the density-based topology optimization in static problem using our modified optimality criteria method. In topology optimization based on the homogenization or density methods, the optimality criteria (OC) method is often employed as update equation for design variables. But the OC method needs to set the weighting factor and move limit. In the modified OC method, they are not necessary. However, in the international paper we have already reported, the performance function did not always go down in 3-dimensional static problems, thus we discuss the updating process in detail in this study. As a result, we confirmed that even the OC method was employed, the performance function increased significantly during the update process. The increase in the performance function when using the modified OC method is more supressed than when using the OC method.

Consideration of the Behaviour of a Wind Turbine Wake Using High-Fidelity CFD Simulations

Scipedia content — Wed, 06 Jul 2022 17:10:45 +0200

During operation of a wind turbine, wake flow occurs behind the wind turbine, reducing the amount of power generation and the life of the downwind wind turbine. To understand wind turbine wake flow, Computational Fluid Dynamics (CFD) simulations were conducted using 'RIAM-COMPACT' to reproduce wind turbine wake flow. There is no significant difference in the flow field of the wind turbine wake between upwind-type and downwind-type turbines. In the 5D downstream of the wind turbine, the vertical distribution of the mainstream velocity component is almost the same regardless of the power of the inflow profile in the swept area. When the inflow wind has a wind direction change of up to 10 degrees, the wind turbine wake is quite diffuse, and its vertical distribution is in good agreement with the field measurements made by the vertical profile lidar.

Concurrent Multiscale Topology Optimization for Designing Displacement Inverter

Scipedia content — Wed, 06 Jul 2022 17:10:31 +0200

Structural light-weighting is vital for increasing energy efficiency and reducing CO2 emissions. One of the mechanical structures that are used in numerous applications and can utilize light weighting is the displacement inverter. The displacement inverter is producing a mechanical reaction as the reverse of the input actuating action. In this research, multiscale topology optimization of compliance mechanism is used to design a lightweight displacement inverter. In this research, a hybrid topology optimization of SIMP for macroscale and ESO for microscale was used to obtain porous displacement inverter designs. Several numerical

examples were investigated, and an experimental case was conducted by printing the design displacement model using 3d printer.

Code-Oriented Floor Acceleration Response Spectra of RC Framed Buildings Accounting for Nonlinear Response of Masonry Infills

Scipedia content — Wed, 06 Jul 2022 17:10:18 +0200

Modern code-oriented elastic floor response spectra formulations for RC framed structures do not take into account effects of non-negligible nonstructural components in terms of mass and stiffness, such as masonry infills (MIs). MIs nonlinear behaviour can be represented through the combination and mutual interaction between the in-plane (IP) and out-of-plane (OOP) responses. The present work is aimed at identifying the effect of IP and OOP nonlinear modelling assumptions on floor acceleration response spectra, consistently with the required seismic intensity level for simplified verification of life-threatening nonstructural elements. To this end, a spatial one-bay multi-storey shear-type model is considered as equivalent to infilled RC framed buildings with common double-leaf MIs. Additional variability of the following design parameters is considered: number of storeys (three, five and seven); behaviour factor (low, 1.5, medium, 3, and high, 4.5); OOP strength of MIs, with lower and upper bound values corresponding to oneand two-way arching mechanisms, respectively. A recently proposed computer code, that includes a five-element nonlinear infill macro-model comprising four diagonal OOP beams and one (horizontal) central IP truss, is considered for the numerical investigation. The proposed algorithm modifies stiffness and strength values of MIs in the OOP direction on the basis of simultaneous or prior IP damage and vice versa. Moreover, a lumped plasticity model describes the inelastic behaviour of RC frame members. Biaxial spectrum-compatible accelerograms are considered at life-safety limit state provided by the Italian seismic code. A simplified code-oriented formulation for the evaluation of floor response spectra of infilled RC framed structures is proposed. Nonstructural maximum acceleration is firstly evaluated by means of vertical and nonstructural amplification factors. Continuous wavelet transforms are used to calibrate parameters that define the resonance region width, accounting for moving resonance due to nonlinearity and higher modes effects. Parabolic and Gaussian curves are considered in order to reproduce preand post-resonance regions, respectively. Finally, a code-oriented proposal is compared to exact elastic and inelastic floor spectra of MIs evaluated over their common range of OOP vibration periods.

Clarification of the Damage Mechanism of the Long-Period Bridge System Damaged by the 2016 Kumamoto Earthquake

Scipedia content — Wed, 06 Jul 2022 17:10:03 +0200

This study aims to clarify the damage mechanism of a long-period bridge system-the Ohkirihata Bridge damaged in the 2016 Kumamoto earthquake-subjected to the combined effects of long-period pulsive ground motions and surface fault displacements. The target bridge's site-specific waveforms at abutment A1 were estimated using the finite difference method. Linear dynamic analysis with a three-dimensional finite element model of the bridge structure-underground interconnected system was performed to examine the effects of longperiod pulsive ground motions on the coupled responses of essential structural components: superstructure, rubber bearings, abutments, piers, foundations and underground.

Bayesian Optimization on Fifth-Order Targeted ENO Scheme for Compressible Flows

Scipedia content — Wed, 06 Jul 2022 17:09:48 +0200

Targeted ENO (TENO) has been proposed to overcome the shortcomings of WENO schemes, namely excessive dissipation of lower-order upwind-biased and degenerated schemes, and limited robustness of central-biased schemes. TENO offers a set of free parameters to shape the inherent effective local dissipation and dispersion. In the original formulation of TENO, these free parameters have been adjusting by means of the approximate dissipation-dispersion relation. Hence, the TENO formulation may be superior in this aspect, yet, it does not necessarily outperform other schemes in flows involving non-linear interaction of a broad range of scales. Data-driven methods enable optimizing these free parameters instead of adjusting them. In this work, we demonstrate the application of an iterative Bayesian optimization approach on designing fifth-order TENO (TENO5) schemes. Exploiting that Bayesian optimization efficiently and robustly finds an optimum of an expensive function with a low number of trials, we construct specific TENO5-schemes for compressible flows with gas dynamic discontinuities as well as for implicit large eddy simulation (ILES). For the former, we measure the error between under-resolved simulations of the Sod shock tube and its analytical solution for automatically generated TENO5 formulations as the objective. For the latter, under-resolved inviscid Taylor-Green vortex flows are evolved to their turbulent state, in which their kinetic energy spectrum in the inertial subrange is compared to the theoretical Kolmogorov-scaling solution to formulate its objective. We show that these two TENO5 formulations perform superior to the original formulation of TENO5 relevant to the specific types of flows. Also, a variety of benchmark test flows show that both specific TENO5 formulations outperform the original one in terms of phase speed, shock-preservation, as well as physical consistency of fluid-dynamic instabilities and turbulent flows.

Bayesian Model updating of Linear dynamic systems using complex modal data

Scipedia content — Wed, 06 Jul 2022 17:09:32 +0200

In the lifetime of structures, they may be exposed to damage that deviates their parameters to a new uncertain state. To predict these parameters, they must be updated using experimental data through various model updating methods. Among model updating methods, the Bayesian approach enables the exploration of all the probable models. Many approaches are available, like those that require the solution of the eigenvalue problem and those that do not require the resolution of the eigenvalue problem. Most existing studies have assumed proportional damping, which gives real modal data, which is not the case always. In this paper, a new Bayesian model updating methodology is proposed based on introducing system mode shapes, damping ratios and natural frequencies as additional uncertain parameters. A dynamic condensation technique is used to restrain the model updating problem to work on the observed degrees of freedom (DOF) field only. To decrease the number of uncertain parameters, system mode shapes are integrated out, and Transitional Monte Carlo Markov Chain (TMCMC) is used to sample from the posterior probability density function. The proposed approach has been applied to the 3-storey shear building model. Results show that the proposed methodology can predict the updated structural parameters in many cases, like the cases where the number of observed modes is greater than the number of observed DOF and if the observed modes are not the lowest-frequency modes.

Avalanching of variously shaped DEM particles

Scipedia content — Wed, 06 Jul 2022 16:54:16 +0200

Grains in most technically relevant granular materials are non-convex, while in discreteelement-simulations, convex particle shapes dominate. While differences in the physical behavior can be expected, the actual observables where these effects manifest are far from clear. In this research, we investigate how in a rotating two-dimensional drum, the physical behavior for rounded, irregular convex as well as non-convex shapes differs.

Assessment of Macro and Micro level Heterogeneities for Characterizing Mechanical Behavior of Sand in Biaxial Test employing DEM

Scipedia content — Wed, 06 Jul 2022 16:54:01 +0200

While characterizing the mechanical behavior of granular assemblies through DEM simulations, various macro and micro level heterogeneities are often encountered. Such macro level heterogeneities may arise due to stress and void concentration near the wall boundaries; whereas, the micro level heterogeneities are attributed to consideration of only limited number of particles within the representative volume element (RVE). The present study assesses these macro and micro level heterogeneities in reference to the mechanical characterization of sand in DEM-based biaxial test simulation with both rigid and flexible lateral boundaries. In this regard, stresses and strains have been calculated using a wall-based global estimation and a representative area element (RAE)-based local estimation. It has been suggested that the RAE should occupy a maximum of 90% area of the specimen in order to avoid any macro level heterogeneity and can still be able to capture its overall mechanical behavior. For obtaining the spatial variation of field variables, RAE of smaller diameters are often employed. In such cases, depending on the average particle size of the granular assembly and the specimen dimensions, the diameter of the RAE should be selected ensuring that it is small enough to aptly capture the local variation of field variables and at the same time, large enough to avoid any micro level heterogeneity.

Analysis of Combat Helmet Performance Integrating Blast Loading and Blunt Impact through Simulation

Scipedia content — Wed, 06 Jul 2022 16:53:48 +0200

The mild traumatic brain injury (mTBI) is one of the most common injuries to service members in recent conflicts. Combat helmets have been designed and evaluated to perform against ballistic and blunt impact threats, but not blast threats. An optimal design of combat helmet considering blunt, ballistic impacts and blast effects is a key requirement to improve the head protection against mTBI. Combat helmets are usually designed based on costly and time consuming laboratory tests. Computational models can offer insights in understanding the force transmission through the head-helmet system into the brain and underlying mechanism of brain injury, and help the development of effective protective design. We developed a design approach integrating the effect of both blast and blunt threats to a helmet system by utilizing multi-physics computational tools and representative human head and helmet models. The high-fidelity computational models were used to capture the dynamic response of the composite shell, suspension pads, retention straps and head. Multiple helmet system configurations subjected to blast and blunt loadings with a combination of loading magnitude and orientation were considered to quantify their influence on brain biomechanical response. Parametric studies were carried out to assess energy absorption for different suspension geometry and material morphology for different loadings. The resulting brain responses in terms of pressure, stress, strain, and strain rate as well as the head acceleration were used with published injury criteria to characterize the helmet system performance through a single metric for each threat type. Approaches to combine single-threat metrics to allow aggregating performance against multiple threats were discussed.

Analysis of Actuator Structure Using New Electro-Thermo-Mechanical Finite Element Derived for Functionally Graded Materials

Scipedia content — Wed, 06 Jul 2022 16:53:30 +0200

An Efficient Phase Field Model for Fatigue Fracture

Scipedia content — Wed, 06 Jul 2022 16:53:12 +0200

The fatigue phenomenon is difficult to be modeled and simulated because of its natural property, which does not happen imminently but rather after a larger number of cycles. Usually, the simulation of fatigue fracture behavior also requires a lot of computation effort which can be seen as very time-consuming. In this work, we represent an efficient phase field model aiming to handle the cyclic fatigue fracture.

An Alternative Approach for Inelastic Static Isogeometric Analysis and 3D Design with Advanced Spline Techniques with Geomiso TNL: a New Hybrid Cloud-based CAD/CAE Software

Scipedia content — Wed, 06 Jul 2022 16:52:54 +0200

The recently developed cloud-based platform www.geomiso.cloud is introduced to help engineers and industries make effective use of inelastic static isogeometric analysis and design with advanced spline techniques. The new Geomiso TNL software combines IGA and cloud computing, one of the fastest growing fields in IT industry. Cloud-based IGA represents the future of product engineering, soon to become an industry standard. This program fully integrates the industrial design with its computational real-time testing, while it is seen to handle demanding inelastic applications in structural mechanics remarkably well, as the numerical examples exhibit significantly improved accuracy with shortened computational time. It is argued that Geomiso TNL is a new, more efficient, alternative to FEA software packages. This is the first time ever such a cloud-based program has been developed.

Aerodynamic and Acoustic Design Optimization of a Multiple Propeller Combination for Distributed Electrical Propulsion

Scipedia content — Wed, 06 Jul 2022 16:52:38 +0200

This manuscript illustrates an optimization procedure carried out on a large-scale wind tunnel model conceived to investigate the aerodynamic and acoustic performance of a Distributed Electric Propulsion (DEP) system installed on the wings of a regional aircraft in high lift conditions. The aim of the optimization process is to obtain the best possible improvements in terms of noise and aerodynamic performance by modifying the propellers' layout of the Wing + DEP wind tunnel model. A multi-objective, multi-point design approach is adopted based on evolutionary computing. The research work is carried out in the framework of the VENUS EU-funded project GA-886019.

Adjoint-Based Shape Optimization for Industrial Heat Exchangers

Scipedia content — Wed, 06 Jul 2022 16:52:23 +0200

This paper showcases the multiphysics discrete adjoint solver of the open Source solver SU2 at the example of a pin-array heat exchanger, simulated via a simplified 2D unit cell to evaluate the pin-shapes performance. The shape derivatives of the utilized conjugate heat transfer case are validated against finite differences and show good agreement. In a constrained shape optimization, the presented workflow proves its robustness over a full optimization. The utilized mesh deformation setup for the investigated downstream periodic and internal flow is presented in detail, as retaining a valid mesh under deformation was found to be challenging.

Actuation of concrete slabs under bending with integrated fluidic actuators

Scipedia content — Wed, 06 Jul 2022 16:52:07 +0200

Previous studies have shown that 33 % to 44 % of the mass embodied in residential and office buildings and up to 50 % in high-rise buildings is attributable to floor slabs. Floor slabs are typically bearing a bending load. Load-transfer through bending is not efficient because the material in the proximity of the neutral plane is practically unloaded thus resulting in a poor material utilization rate. Since bending stiffness is per se significantly lower than axial stiffness, the design of floor slabs is typically governed by deflection limits under out-of-plane loading, which causes significant oversizing. In addition, structures are typically oversized since they are designed to take extreme loading events, which in practice occur only for a small part of the service life. The ongoing climate crisis, the expected world population growth and associated resource scarcity call for new methods and solutions to build material-efficient structures that cause minimum greenhouse gas emissions. Employing adaptation strategies is a promising solution. By integrating structures with components such as sensors, actuators and control units stress and deformation caused by live loads can be reduced actively, which enables significant material savings. Previous work carried out at the University of Stuttgart within the Collaborative Research Center 1244 has demonstrated that it is possible to compensate deflections by integrating fluidic actuators in beam structures subjected to bending. However, it is not obvious how to transfer actuation concepts employed in beams to floor slabs due to multi-axial load-transfer behaviour. In this work, fluidic actuators are strategically integrated into floor slabs to employ multi-axial transfer to counteract the effect of out-of-plane loading. This research also addresses the choice of an optimal layout of the actuators. Numerical simulations of different actuation concepts, such as uniaxial and biaxial actuation have been carried out to derive influence surfaces. The relationship between principal moments and the effect of actuation is quantified numerically. Examples are provided to show how influence surfaces can be employed to select suitable actuation strategies. Results show that displacements can be efficiently compensated through a combination of uniaxial and biaxial actuation.

A wavelet-based three-dimensional Convolutional Neural Network for superresolution of turbulent vorticity

Scipedia content — Wed, 06 Jul 2022 16:51:51 +0200

We develop a wavelet-based three-dimensional convolutional neural network (WCNN3d) for superresolution of coarse-grained data of homogeneous isotropic turbulence. The turbulent flow data are computed by high resolution direct numerical simulation (DNS), while the coarse-grained data are obtained by applying a Gaussian filter to the DNS data. The CNNs are trained with the DNS data and the coarse-grained data. We compare vorticity- and velocity-based approaches and assess the proposed WCNN3d method in terms of flow visualization, enstrophy spectra and probability density functions. We show that orthogonal wavelets enhance the efficiency of the learning of CNN.

A Two-dimensional Bio-chemo-hydro-mechanical Model for In-situ Stabilization of Soils using Biochemical Processes

Scipedia content — Wed, 06 Jul 2022 16:51:37 +0200

Ground improvement techniques involving chemical additives are often energy-intensive and unsustainable due to the environmental distress caused by them. Sustainable biocementation processes such as microbially induced calcite precipitation (MICP) can overcome the drawbacks of traditional ground improvement techniques. Capturing the underlying coupled mechanisms in the biocementation process requires the knowledge of diverse fields of bio-chemo-hydro-mechanics. Modeling such a complex phenomenon is imperative for the successful implementation of the stabilisation technique in the field. The existing coupled models on biocementation are chiefly intended to validate the observed behavior of laboratory-scale biocemented specimens. This scenario demands the need to develop a coupled bio-chemo-hydro-mechanical (BCHM) model for field simulations. The BCHM model was developed with finite element and backward Euler finite difference approximations in space and time. The Galerkin weak formulations are derived for the mass balance equations of the coupled model. The advectivegoverned transport phenomena are accommodated with the Petrov-Galerkin formulation. An overall kinetically controlled reactive model is implemented to reproduce the urea hydrolysis and associated chemical kinetics. The reduced permeability of the biocemented soil is accounted in terms of its effective porosity, using the modified Kozeny-Carman equation. The fixed-point iteration scheme is implemented for bio-chemo-hydraulics to deal with the nonlinearity in the balance equations. The mechanical constitutive response of biocemented soil is simulated using a micromechanical framework. The von Mises and Drucker-Prager plasticity models were adopted for the biocement and soil particle phases, respectively. The integration of plasticity models was carried out using a return mapping algorithm. The Newton Raphson scheme is considered for the finite element implementation of elastoplastic models. The fully coupled nonlinear finite element problem is solved in a staggered approach using the developed MATLAB routine. The contour plots of biomass and chemical concentrations and precipitated calcite content are generated. The considered elastoplastic model predicted improvement in mechanical strength of biocemented specimen. A complete bio-chemo-hydro-mechanical behavior of the two-dimensional geometry is captured.

A Time Consistent Method by Preconditioning of the Diffusion Term for Unsteady Gas-Liquid Two-Phase Flows

Scipedia content — Wed, 06 Jul 2022 16:50:29 +0200

A time accurate and high resolution numerical method for gas-liquid two-phase flows is proposed. The artificial viscous terms in the flux splitting of upwinding are derived by using the preconditioner to enhance the stability of computation for compressible and incompressible combined flow with arbitrary void fractions. A homogeneous equilibrium gasliquid two-phase model taken account of the compressibility of mixed media is used. A finitedifference 4th-order Runge-Kutta method and a Roe-type flux splitting method with the MUSCL TVD scheme are employed. By this method, a one-dimensional two-phase shock tube problem was computed and confirmed the applicability to the unsteady and arbitrary Mach number flow problems. Detailed observations of shock and expansion wave propagations through the gasliquid two-phase media and comparisons of predicted results with exact solutions are made.

A study on Prediction of Water Discharge Performance for Showerhead Product Design

Scipedia content — Wed, 06 Jul 2022 16:44:19 +0200

LIXIL Co. handles a wide range of water-related products such as showers, toilets, baths, and kitchens. The fluid behavior control is a key technology for developing of these products. Therefore, the numerical simulation with CFD plays an important role in product and technical development. The flow of water in showers has been simulated with the finite volume method (FVM). However, the simulation with fine droplets such as in a shower needs a lot of computational cost. To deal with this problem, MPS particle method [1] has been introduced to take an advantage of enabling for simulating such as splashing, droplets, and mixing. In this paper, the MPS particle method is studied to simulate the shower head design because it is the first use case for simulating the spout, coupling with mechanism analysis. Because computational efficiency is also an important factor for the product development, the computational performance on GPU against multi-CPU for the MPS particle method is also discussed.

A numerical approach to the design of gridshells for WAAM

Scipedia content — Wed, 06 Jul 2022 16:40:03 +0200

A novel approach based on funicular analysis is investigated to cope with the design of spatial truss networks fabricated by Wire-and-Arc Additive Manufacturing (WAAM). The minimization of the horizontal thrusts of networks with fixed plan geometry is stated both in terms of any independent subset of the force densities and in terms of the height of the restrained nodes. Local enforcements are formulated to prescribe lower and upper bounds for the vertical coordinates of the nodes, and to control the stress regime in the branches. This allows also for a straightforward control of the length and maximum force magnitude in each branch. Constraints are such that sequential convex programming can be conveniently exploited to handle grids with general topology and boundary conditions. Optimal networks for WAAM are preliminary investigated, accounting for different sets of the above prescriptions.

A Novel Atomistic-Continuum Coupling Method for Amorphous Polymers at Finite Temperature

Scipedia content — Wed, 06 Jul 2022 16:32:22 +0200

A new simulation technique, based on the Arlequin framework and the Anchor Point method, is presented for concurrently coupling atomistic and continuum domains at finite temperatures with focus on all-atom molecular representations of thermosetting polymers. The method is derived and then benchmarked using a tensile test on a single graphene sheet. Next, the method is applied to simulate a uniaxial tensile test on a bar of thermosetting polymer (EPON-862 with crosslinking agent DETDA). For the polymer, the first case studied is at a temperature of 1 K in order to reduce thermal oscillation of atoms. Subsequently, results are obtained at 300K, showing large thermally induced oscillations in the system. Work is underway to mitigate this problem.

A New Mixed FE-Formulation for Liquid Crystal Elastomer Films

Scipedia content — Wed, 06 Jul 2022 16:28:40 +0200

Liquid crystal elastomers (LCEs) are soft materials, which are capable of large deformations induced by temperature changes and ultraviolet irradiation [1]. Therefore, since many years, these materials are under investigation in experimental researches as actuator materials. LCEs arise from a nematic polymer melt, consisting of long and flexible polymer chains as well as oriented and rigid rod-like molecules, the so-called mesogens, by crosslinking. After this process, the flow ability and the orientation of the mesogens is retained. To date, the alignment of LCEs is primarily achieved in thin films. When the orientational order in the film is lost due to temperature changes or ultraviolet irradiation, the LCE film is capable of length changes of 400 percent. In order to numerically simulate LCE materials as actuators in multibody system models by using the finite element method, a continuum formulation is necessary, which include in a thermo-viscoelastic material formulation of the polymer chains the orientation effects of the mesogens. This can be performed by introducing a normalized direction vector as an independent field, and deriving from additional (orientational) balance laws independent differential equations [2]. These differential equations describe the independent rotation of the rigid mesogens connected with the flexible polymer chains. The orientation-dependent stress law of LCEs arises from an anisotropic free energy, comparable with fibre-reinforced materials. But, the direction vector of a LCE model has to be independent. In contrast to [2], we apply a variational principle for deriving a new mixed finite element (FE) formulation, which is based on drilling degrees of freedom for describing the mesogens rotation [3]. This principle leads to balance laws, preserved by an energy-momentum scheme.

A new efficient methodology for the analysis of mechanical metamaterials with elastic instabilities

Scipedia content — Wed, 06 Jul 2022 16:18:52 +0200

This work addresses the analysis of mechanical metamaterials exhibiting, as a distinguishing feature, snap-through instabilities in the elastic regime. Among the various opportunities offered by this feature is the manipulation of the material deformation energy [1] that allows the conception of reusable energy-trapping or energy-dissipation devices [2]. As a task to reach this objective, we present a novel computational methodology for analysing microarchitectures displaying elastic snap-through instabilities. The strategy is based on the construction of a surrogate model that reduces the computational burden if compared with full high-fidelity models of non-linear volumetric finite elements or with nonlinear beam elements. The surrogate model opens the possibility to analyse a large number of unit cells of periodic metamaterials with instabilities. In addition, it permits an efficient assessment of different geometrical configurations proving a suitable tool for its use in microarchitecture topology optimization processes. Noting that, in general, existing designs of this class of metamaterials only achieve energy manipulation in a specific predefined loading direction, in this work, and based on the proposed computational technique, we aim at the analysis of reusable multidirectional isotropic energy manipulation. This objective agrees with more realistic uses of metamaterials in which general boundary conditions, typically the loading directions, are not established a priori.

A methodology for including suspension dynamics in a simple context of rail vehicle simulations

Scipedia content — Wed, 06 Jul 2022 16:15:57 +0200

The running behaviour of rail vehicles is highly influenced by suspension components. Dealing with ride comfort, secondary suspensions are adopted to reduce the vibrations transmitted to the carbody. In this context, the dynamics of the suspension elements themselves has to be properly included in multibody system. This paper proposes a strategy for modelling the passive vertical secondary suspension in the frequency domain. To this aim, a mathematical model is defined and its parameters are tuned to be representative of a real system. Then, a sensitivity analysis over the model parameters is proposed to discuss the suspension performances in terms of dynamic stiffness. Finally, a finite element model of the carbody is considered and coupled to the rear and front suspensions. The model is adopted to simulate the vehicle running on a rail track irregularity in the frequency domain, in the 0-30 Hz frequency range.

A Discrete Exterior Calculus Based Framework for CFD

Scipedia content — Wed, 06 Jul 2022 16:10:37 +0200

We present a framework for computing flows on surfaces based on a discrete exterior calculus (DEC) discretization of Navier-Stokes (N-S) equations on simplicial meshes. The framework incorporates primitive formulation of the N-S equations and allows for a time integration method which features energy conservation [1]. Other features of the framework consist of the inclusion of the Coriolis force term to investigate flows on rotating surfaces, and an interface tracking method for multiphase flows. The method is second order accurate on structured triangular meshes, and first order on otherwise unstructured meshes, and demonstrates the conservation of inviscid invariants such as kinetic energy and enstrophy over an extended period of time [2].

A Detailed Simulation Model to Evaluate the Crash Safety of a Li-Ion Pouch Battery Cell

Scipedia content — Wed, 06 Jul 2022 16:05:16 +0200

In crash situations with an electric vehicle, the integrity of the battery cells is critical for the consequences of the crash. A short circuit triggered by deformation and damage of the internal cell structure can cause overheating of the battery (thermal runaway) and may result in a vehicle fire or even an explosion. Thus, for assessing the crashworthiness of electric vehicles, evaluating the deformation states of potential crash situations with respect to the occurrence of a short circuit is crucial. A particular challenge for building a cell model with acceptable computational time lies in the very different spatial scales regarding the overall cell size and the thickness of individual layers. Cells installed in vehicles have dimensions of several centimeters, whereas the thickness of the individual layers is in the micrometer range. Much research has already been conducted based on homogenized cell models that do not explicitly account for the internal layer structure, and existing material models calibrated to experimental data (e.g. [1]-[3]), while explicitly considering the layered structure is just pursued more recently (e.g. [4]-[7]).

Within our contribution we introduce a detailed numerical model which, as a part of a multilevel simulation approach, can be used to evaluate the criticality of a deformation state. The model mimics the layered structure of the cell, whereby the constitutive properties were determined by in-house experiments on the respective materials. For validation, bending tests and indentation tests with different punch geometries along with CT-scans at selected indentation depths are available. Comparing the simulation results with the failure sequence and the force-displacement curve from the experiment, a closer view on critical deformations and on their respective stress states is obtained. The results indicate that in-depth understanding and modelling of the failure behavior is crucial for correctly modeling battery cells under crash loading scenarios.

Accelerating sensitivity analysis in structural topology optimization using deep neural network

Scipedia content — Wed, 06 Jul 2022 15:59:04 +0200

In recent years, Topology Optimization (TO) has been increasingly gaining attention with the development of new constructing techniques. In the optimization process of a density-based TO method, the sensitivities of the design variables are often computed using numerical methods like Finite Element Method (FEM). Such operation is performed repetitively for tens or hundreds of iteration steps, therefore generating huge computational cost for large scale design scenarios. This paper proposes to accelerate TO by replacing the full-scale sensitivity analysis of FEM with a reduced-scale case, and adopting a deep neural network to map the reduced-scale sensitivity field back to fine scale. Three neural network models are trained and tested using training data generated by structures of three difference scales. The results show that the proposed network successfully reduced the time cost to a large extent, while preserving the topology of the optimized design.

A Comparison Study between Isogeometric Analysis and Finite Element Analysis for Nonlinear Inelastic Dynamic Problems with Geomiso DNL Software

Scipedia content — Wed, 06 Jul 2022 15:52:54 +0200

The new Geomiso DNL software is proposed to facilitate the use of isogeometric analysis for nonlinear inelastic dynamic applications. This hybrid software solution combines isogeometric analysis and 3D design with advanced spline techniques, such as NURBS and Tsplines. Its dual nature satisfies the rising industrial need for unification of the fields of computer-aided design (CAD) and computer-aided analysis (CAE), as it eliminates geometric errors by merging geometry design with mesh generation into a single procedure. This paper presents sample nonlinear applications in structural dynamics. Geomiso DNL is seen to handle these situations remarkably well, as the numerical examples exhibit significantly improved accuracy of the results, and reduced computational cost, when compared with finite element software packages. It is argued that Geomiso DNL is a new, more efficient, alternative to FEA software packages. This is the first time ever such a cloud-based program has been developed.

The nature of the power of attorney and the role of ethical considerations

saeeid bigdeli — Wed, 06 Jul 2022 08:04:03 +0200

'''Background''': Jurisprudence is a science whose basis is moral and the word of any legal institution, especially the power of attorney is based on representation and permission of a person is based on morality. It is shown in the history of civilization, history and the evolution of peoples and nations that there have always been people have taken on the task of defending and realizing the right for another and in another name, where the person did not have the help and ability. Therefore, in according to this ethical issue, attorney representation is considered irreplaceable and permissible. '''Conclusion''': The attorney representation is usually known through two faces, which both of them are based on ethics and its continuity is also based on ethics. Its main face is the "attorney representation" that is the subject of the civil law, whose general rules are defined in terms of definition and conditions of its conclusion and its effects in this law. The other face is "judicial representation of attorney" which is mainly viewed with the same principles of civil advocacy. Advocacy, as well as close to civil advocacy contains a special nature of independent contractual representation influenced by the help of the people and the defense of the oppressed as a matter of ethics under the guise of observing the interests of the client.

Eco Sustainable Rail: production of sustainable railway sleepers from mixed plastics waste

Materiales Compuestos — Mon, 04 Jul 2022 01:32:03 +0200

Mixed plastics waste (MPW) constitute a material of extreme recycling difficulty due to their heterogeneity and contamination level. As a consequence, a large fraction of MPW is landfilled. It is imperative to find new applications for MPW that bring new value as a raw material, with application in high added-value products. The restrictions on the marketing and application of biocidal products such as the creosote treatment performed on wood railway sleepers, introduced by Directive 98/8/EC, triggered the replacement of several products traditionally produced in wood. Currently, there is a global need to find solutions for replacement of wood railway sleepers for specific railway applications. The present study investigates the application requirements and proposes a new solution based on MPW composites for the production of eco-friendly railway sleepers. The composites are mostly based on MPW and glass fibers. The prototype composite sleepers were produced by intrusion processing and tested in simulated mechanical and environmental operating conditions. Overall this new circularity approach will largely contribute to reduce the deposition of MPW in landfills, responding to a current need of the railway sector, and will contribute to implement circular economy and resource efficiency.

Fiber reclamation from composite materials by thermal treatment: experimental and mathematical optimization of operating parameters

Materiales Compuestos — Mon, 04 Jul 2022 01:19:03 +0200

Las fibras de carbono y de vidrio que se encuentran en los residuos que se generan en los sectores industriales que fabrican o utilizan materiales compuestos reforzados con fibra pueden recuperarse a través del tratamiento térmico. Este tratamiento consiste en el calentamiento del material en atmósfera inerte (pirólisis) hasta la temperatura suficiente para que se descomponga la resina polimérica y la posterior oxidación de los productos carbonosos generados en esta descomposición en presencia de aire. El resultado de este tratamiento es la eliminación completa de la resina y la recuperación de las fibras, que mantienen buenas propiedades físico-químicas. En este trabajo se ha utilizado el diseño estadístico de experimentos para determinar la influencia que tienen las tres variables de operación principales involucradas en la recuperación de fibras por tratamiento térmico (temperatura de pirólisis, temperatura de oxidación y tiempo de oxidación) sobre el rendimiento de eliminación de resina polimérica. La estrategia experimental utilizada ha sido el diseño factorial completo 2k, donde k=3, las variables de operación estudiadas. El método se ha aplicado a residuos procedentes del sector eólico y del sector aeronáutico, tanto de piezas curadas como pre-pregs caducados, y reforzadas con fibra de carbono y fibra de vidrio. Con los resultados obtenidos en la experimentación con termobalanza se ha determinado la importancia relativa de las variables estudiadas para cada una de las muestras y se han definido las ecuaciones matemáticas que permiten predecir el rendimiento de eliminación de resina en función del valor que tomen estas variables.

Study of the rheological behavior of polymer-modified asphalts

Materiales Compuestos — Mon, 04 Jul 2022 01:05:04 +0200

Nowadays asphalts modified with polymers (PMA) are used in a wide range of applications, for example, as waterproofing, pavements and membranes, and are being object of a great amount of publications and patents. The processes of modification of asphalt with polymers are widely used to achieve the use of asphalts for some applications where the use of non-modified asphalt is not suitable due to their high thermal susceptibility, their tendency to oxidize or their high content of saturated and aromatic compounds. In this work, milled rubber has been used as an asphalt modifier for the manufacture of waterproofing covers. The use of milled rubber makes it possible to find a viable outlet for the large quantities of discarded tires that accumulate in the tanks and achieve an ecological benefit. Therefore, the rheological study of new compositions with different percentages of polymer addition have been carried out. As main results, it is observed that the asphalt without polymer (MA) at 30º C behaves practically like a Newtonian liquid, while the PMA samples behave as non-Newtonian fluids. On the other hand, the addition of rubber leads to an increase in two orders of magnitude of the elastic and viscous modulus, as does the complex viscosity. The yield stress is greater in the PMA samples, and both the maximum force and the adhesion work increase. The addition of elastomer increases the viscosity of the product, but further increases its elastic component. In MA, the viscous component is greater than the elastic component whereas in the PMAs this behavior is reversed.

The nature of the power of attorney and the role of ethical considerations in it

University of Cincinnati Law Review — Sun, 03 Jul 2022 15:21:02 +0200

Background: Jurisprudence is a science whose basis is moral and the word of any legal institution, especially the power of attorney is based on representation and permission of a person is based on morality. It is shown in the history of civilization, history and the evolution of peoples and nations that there have always been people have taken on the task of defending and realizing the right for another and in another name, where the person did not have the help and ability. Therefore, in according to this ethical issue, attorney representation is considered irreplaceable and permissible.

Conclusion: The attorney representation is usually known through two faces, which both of them are based on ethics and its continuity is also based on ethics. Its main face is the "attorney representation" that is the subject of the civil law, whose general rules are defined in terms of definition and conditions of its conclusion and its effects in this law. The other face is "judicial representation of attorney" which is mainly viewed with the same principles of civil advocacy. Advocacy, as well as close to civil advocacy contains a special nature of independent contractual representation influenced by the help of the people and the defense of the oppressed as a matter of ethics under the guise of observing the interests of the client.

Cell geopolymers: development of ecological light concrete without cement (GEOCEL project)

Materiales Compuestos — Sat, 02 Jul 2022 23:08:04 +0200

Cement is the most used construction material in the world (3670 MT/year are generated), being highly polluting, emitting aproximately one ton of CO2 per ton of cement. In this sector, in which the search for more sustainable materials becomes essential, the geopolymers or alkaline cements are introduced as an ecological alternative, resulting in 80% less polluting and requiring 50% less of energy comsumption in the manufacturing process.

In this context, GeoCel project is oriented to the developing of ecological construction materials to get concretes and mortars (without Portland cement) of cellular structure. Different constructive solutions were proposed for these inovative materials as wall cladding and insulation panels and continous and draining pavements.The caracterization of the different solutions was carried out bymechanical resistance, fire resistance and thermal conductivity tests, among others, based on the requiremens imposed at the industrial level, in order to evaluate the technical viability of the new materials. The results obtained have been promising, getting mechanical strengths superior to conventional materials in case of mortars , as well as classification of reaction to fire A1.

Softwood kraft lignin characterization and melt extrusion of blends with two bioderived polyesters

Materiales Compuestos — Sat, 02 Jul 2022 22:58:03 +0200

Lignin is one of the three major polymeric constituents of wood. It is a natural and renewable resource, and due to its structure it is the most abundant aromatic polymer on Earth. The present work reports the thermal and chemical characterization of a kraft lignin and the study of it’s mixing ability with two bioderived polyesters, namely PLA and PHB, to test their suitability for the production of green fibre.

Surface modification of carbon fibres for its use as supercapacitors in electric vehicles

Materiales Compuestos — Sat, 02 Jul 2022 22:48:03 +0200

Carbon fibre reinforced composite materials show potential as energy storage components, due to the high electric conductivity of the carbon fibre. Supercapacitors store electrostatic energy over the electrode surface. Increasing the surface area of electrodes based on carbon fibre could lead to an increase in storage capacitance.

Different methods to increase surface area of carbon fibre are studied with the aim of increasing energy storage capacitance of the fibres working as electrodes for structural electrochemical capacitors. Surface modification was carried out by the deposition of carbon nanoparticles (GNP) and porous carbon (CAG). Effectiveness of the different methods was analysed by measurements of BET surface area and microscopy characterisation. The effect on mechanical properties of individual fibres was analysed and storage capacitance was measured by electrochemical characterisation.

Comparative of mechanical properties of tensile, compression and in plane shear strength of natural composite materials

Materiales Compuestos — Sat, 02 Jul 2022 19:59:04 +0200

Developing a sustainable industry based on respectable materials with the environment, through optimal processes with low impact is a fundamental aim, but it remains a considerable challenge to achieve. Despite the large amount of research on composite materials in natural fibers, the limitations in the results have been obtained, being usual to find mechanical results with a wide coefficient of variation and values much lower than expected. The industry of products with bamboo fiber has increased in decorative applications because it is one of the lowest cost raw materials. However, there are limited structural applications, due to the low mechanical properties. A study of the methodology and the extraction area has been carried out in order to maximize the Young's modulus, doubling the value with respect to the E-type and epoxy glass material. Once, continuous networks such as linen, sisal, silk and cotton have been reduced, to develop a unidirectional tape semi-impregnated by a winding process, which allows the fabrication of structures with curvature, with comparable shear values in the plane with the reference material. Finally, in addition to the extensive campaign of mechanical tests, three demonstrators have been manufactured with their respective respect to show the capacity of use and the limitations of the materials. Environmental terms, industrial sectors such as wind or automotive.

Vol4 num3-15 Two-component epoxy sel-healing adhesive throught the incorporation of smart microcapsules

Materiales Compuestos — Sat, 02 Jul 2022 01:13:02 +0200

In this work, the effect of the localization of the catalyst in a self-repairing system based on the microencapsulation technology in a bi-component epoxy adhesive has been studied. The efficiency of a conventional self-healing system (microcapsules + catalyst) has been compared with a system in which the curing agent and the catalyst are in the same microcapsule but isolated from each other. This system has been called "All in one" and has shown to be more efficient than the conventional one, achieving efficiencies of up to 116%.

Prediction of fiber orientation in thermoplastic composites

Materiales Compuestos — Sat, 02 Jul 2022 00:58:04 +0200

The prediction of the fiber orientation in thermoplastic composites, manufactured by the injection moulding process, allows the determination of the mechanical behaviour with greater precision.

In the present work, the prediction of the fibre orientation made by the Autodesk Moldflow Insight program has been analysed through the ARD-RSC model.

This model presents six coefficients that can be modified and according to which values take the result of the prediction of the orientation of the fiber will be different. That is why the response surface method has been applied to know the relationship between the coefficients of the ARD-RSC model and its prediction of fibre orientation.

The precision and correlation of this calculated fiber orientation has been analysed in two ways. The first of them using tomographic analysis with which you can visualize and compare with the actual arrangement of the fibre in the thermoplastic composite and the second moving the orientation calculated by Autodesk Moldflow Insight to the Digimat program and comparing its prediction of mechanical properties with the real properties that the thermoplastic composite presents in the mechanical tests carried out.

Taking into account the modification of the coefficients, the improvement of the correlation between the experimental test and the structural simulation has been observed in the analyzed component.

Fabricación mediante laminación automática en un paso con materiales termoplásticos de una estructura altamente integrada

Materiales Compuestos — Sat, 02 Jul 2022 00:49:03 +0200

During the last years, the benefits of using carbon reinforced thermoplastic composite materials (CRTP) have been questioned and defended (higher fatigue resistance, greater toughness, better durability, reprocesability, recyclability and so on), they are considered as a future innovative technology allowing highly integrated structures, impacting in weight reduction and reducing energetic costs by using out of autoclave processes. Therefore, (CRTP) could be considered as a future substitute of metallic materials and composite materials with thermoset matrices for aerospace applications, automotive and other industries.

Under the frame of the OUTCOME project (Clean Sky II), the design and analysis of the Upper Skin (upper coverage of a stiffened wing) for the militar aircraft C295 is developed, a medium tactical transport aircraft of ADS.

The selected material for the work is the unidirectional composite material APC2/AS4, supplied by Solvay, with PEEK as the thermoplastic matrix and carbon fibre as the reinforcement. Flat panels, detailed elementals and subelementals have been manufactured, all of them have been widely characterized attempting to obtain the required design allowables.

Moreover, with the goal of cost reduction, productivity increases and environmental impact control, the manufacturing selected processes have been: a) Hot-forming in oven and/or self heated toolings for stringers manufacturing and b) Automatic lamination in one step for the co-consolidation (full-integration) of the skin with the stringers.

The main goal of this review is showing the different steps in the manufacturing of a detailed element for a later structural test.

Development and characterization of polypropylene nano-composites

Materiales Compuestos — Sat, 02 Jul 2022 00:31:03 +0200

Modification of polymer matrices has a great insterest in the field of new materials, based on the possibilities offered by the additivation, being able to modulate the properties of the base material depending on the incorporated aggregates. Among the improvements searched include the increase in the mechanical strength of the material or the improvement in the interaction with other materials (adhesion), in addition to providing multifunctionality, combining properties of materials separately in order to obtain a composite with improved properties.

This study focuses on the modification of a polypropylene-ethylene co-polymer by the incorporation of nanoclays and carbon nanotubes (MWCNTs) in low concentrations (0.1% by weight). In order to facilitate the dispersion of the nanomaterials in the matrix by mixing and extrusion, maleic anhydride was used as a compatibilizer. The behavior of these composites was characterized by studying the variation of torque during the compounding, in addition to analize the melt flow index (MFI) and perform an analysis by DSC, TGA and TEM of the composites obtained. Based on the low polarity of polypropylene, the introduction into the matrix of maleic anhydride provides a certain polarity in the composite, so the increase in the surface energy of the different formulations is studied by contact angle measurements (using the OWRK/Fowkes method). The increase in surface energy involves a greater affinity for polar materials, such as polyurethane (PU) or other foams.

Mechanical Stimuli in Prediction of Trabecular Bone Adaptation: Numerical Comparison

Scipedia content — Thu, 30 Jun 2022 14:33:39 +0200

Adaptation is the process, with which bone responds to changes in loading environment and modifies its properties and organisation to meet the mechanical demands. Trabecular bone undergoes significant adaptation when subjected to external forces, accomplished through resorption of old and fractured bone and formation of a new bone material. These processes are assumed to be driven by mechanical stimuli of bone-matrix deformation sensed by bone mechanosensory cells. Although numerous in vivo and in vitro experimental evidence of trabecular bone morphology adaptation was obtained, the exact nature of mechanical stimuli triggering biological responses (i.e., osteoclastic resorption and osteoblastic formation) is still debated. This study aims to compare different mechanical stimuli with regard to their ability to initiate the load-induced adaptation in trabecular bone. For this purpose, a 2D model of two trabeculae, connected at their basement, with bone marrow in the intertrabecular space was developed. The finite-element method was implemented for the model loaded in compression to calculate magnitudes of several candidates of the bone-adaptation stimuli. A user material subroutine was developed to relate a magnitude of each candidate to changes in the shape of trabeculae.

Hybrid laser joining of thermoplastic composites with stainless steel

Materiales Compuestos — Thu, 30 Jun 2022 13:55:02 +0200

There is an increasing interest in the use of multi-materials in the transport sector in order to reduce the weight of vehicles and the fuel consumption for a clean mobility towards the goal of zero CO2 emissions, as defined the European directive (EU) 2019/1161.

The use of hybrid materials has promoted the research on dissimilar joints (metal-polymer) in order to solve the drawbacks related to the traditional joining techniques such as stress concentration, large repairs area and emissions harmful to the environment.

In this work, the behavior of hybrid joints between steel and GRFC with thermoplastic matrix by laser technology has been analyzed. This study is framed to the European project RECOTRANS, focused on the manufacturing of composites (RTM and pultrusion) with new MW accelerated curing acrylic resins and their joining to metal inserts using LAMP technology (laser assisted metal polymer joining).

Laser technology for metal-polymer joining is an alternative to other conventional processes offering relevant advantages over these techniques since it is a single-stage instantaneous automated process, with localized heating and low residual stresses.

In this study, the shear behavior of laser assisted joints between AISI304 steel samples and composites with different acrylic resin formulations has been analyzed. The effect that different variables have on these joints has been evaluated, such as the topography of the metallic surface, the temperature generated during the joining process or the laser interaction time. The results obtained show a mechanical resistance similar or even higher than that obtained in adhesive joining.

Thermomechanical characterization of biolaminates epoxy/sisal

Materiales Compuestos — Thu, 30 Jun 2022 13:40:05 +0200

One of the most common materials to be used as cores of sandwich structures is polymeric foam. Due to an increasing effort to reduce the environmental impact of industrial processes, there is a great interest in the incorporation of natural materials from renewable sources to facilitate the reusing and recycling of the structures. One of the possibilities for replacing polymeric foams in sandwich structures is agglomerated cork, due to its good mechanical properties. However, for this material to be used as a core, it is necessary to know its behaviour under impact loads, both at low and high velocities.

In this work, the behaviour of a commercial PVC foam is compared with agglomerated corks of several densities. The force, displacement, absorbed energy and perforation velocity have been analysed. The behaviour of the agglomerated cork can be similar to that of a conventional polymeric foam, although with an increase in weight. However, it has been shown that agglomerated cork can be a better alternative to polymeric foams in those applications that may be subjected to several successive impacts.

Optimización Instalación Térmica (vs) Sistema de Producción: Caso Práctico “Hot-forming"

Materiales Compuestos — Wed, 29 Jun 2022 21:16:04 +0200

Productividad y reducción de costes, son actualmente dos de los principales “drivers” que motivan nuevas formas de parámetros de control en los procesos de fabricación de materiales compuestos. El sector aeronáutico no es propiamente conocido como de producción en masa, sin embargo, por la naturaleza y requisitos de autoridades certificadoras, requiere que todos los pasos del proceso estén controlados y documentados. Esto supone la ventaja de ser una fuente de generación de datos de control que analizados correctamente, creando las correlaciones pertinentes y con un objetivo claro pueden permitirnos establecer otras formas alternativas de control que cumplan con los requerimientos y nos conduzcan a un aumento de la productividad y ahorro de costes.

Uno de los procesos de mejora es el de Hot-forming. Este es un proceso utilizado para proporcionar, a laminados de espesor considerable, una pre-forma antes del proceso de curado, garantizando una mejor calidad del conformado de detalles intrincados de pieza, que en caso de no realizarse producirían defectos no aceptables, como ejemplo, en zonas de radios.

Después de varios años trabajando con plantas de fabricación de materiales compuestos, se han definido los parámetros claves del proceso en un medio industrial (medio de calentamiento, materiales auxiliares, construcción de piezas, parámetros de control, limitaciones de equipamiento y de material, posible envejecimiento de material). Esta es la base de la presentación sobre la cual se expondrá el método experimental seguido para justificar la correlación de datos de control del proceso de Hot-forming por membrana en vez de control en pieza.

Vol4 num2-20 Monitoring of multi-material structures for offshore applications with fiber optic sensors

Materiales Compuestos — Wed, 29 Jun 2022 17:18:03 +0200

The development of renewable energies is a fundamental need to meet the ambitious energy targets demanded by industry and the European Union in the coming years. In the case of offshore wind energy, it has certain limitations due to its relative youth and associated costs, especially in the maintenance, operation and repair operations. Within the project, that includes this work, has developed a new multi-material component with high structural requirements for the offshore wind sector. A combination of steel and composite, manufactured by filament winding, with a system of protection of biofouling and corrosion, will be validated in a real conditions test in the experimental zone of INEGA (A Coruña), by a demonstrator to scale 1:5.

For real-time monitoring of the multi-material structure, a monitoring system has been developed based on fiber optics sensors type Bragg Grating (FBG), integrated in this structure. This monitoring system includes sensors of corrosion, temperature and deformation. This paper shows the development and characterization of these sensors at the laboratory level against mechanical, thermal tests and study durability in marine environment. In addition, it describes the integration of the monitoring system in the demonstrator and its response during the validation phase.

Adhesive Film Carriers Effect on Adhesive Function

Materiales Compuestos — Mon, 27 Jun 2022 22:04:05 +0200

One of the main "drivers" in the development of aeronautical structures in composite material is the development of more integrated structures that are manufactured in a single step ("One-Shot") to optimize times. The adhesive materials in film format are one of the main variables to take into consideration to achieve the aforementioned integration. This need has promoted creativity at the level of use / parameterization of new adhesives in the form of a film.

Film adhesives are used in the integration of composite, sandwich or monolithic structures. Regarding sandwich structures, the adhesive film is used to ensure a good adhesion between the core and the prepreg, through the formation of a meniscus of adhesive material in the core cell. This function is fulfilled depending on the type of "carrier". For Monolithic structures, the adhesive film is used to ensure a good adhesion in co-bonding processes (bonding of cured laminate with fresh prepreg) and secondary bonding (bonding between 2 previously cured laminates), interleaved between materials to achieve optimum thickness, guaranteeing the best mechanical properties of the element at interlaminar level. This, without forgetting, the repair processes that are within the processes of co-bonding, with all its specificities and operational limitations, either in manufacturing or in service.

The market options, qualified by OEMs or not, are wide, having developed different support materials, or variants of the same material, with the aim of achieving the best mechanical properties of the elements where they are used.

Influence of surface topography parameters on the structural adhesive of aluminum 7075 polishing by robot and TEPEX®

Materiales Compuestos — Sun, 26 Jun 2022 13:17:04 +0200

In the process of continuous improvement of manufacturing processes in the field of the automotive sector comes this study developed within the framework of the Ecovoss project. Its objective is based on substitution of aluminum welding operations with the option of adhesive operations with other types of materials such as polyamides or, in this case, a TEPEX® composite material (dynalite 202-c200 / 50% TYP 13). In this work we try to test the best texturing in the union of 7075 aluminum specimens manufactured by robotized polishing with ABB 6640 robot, with specimens in TEPEX® material cutted in order to have a surface for application of the adhesive product. It uses a structural adhesive film AF-163-2 from 3M, which must be applied with determined pressure and temperature. The tests carried out are based on the topographic measurement of the surfaces to be adhesively bonded with the Alicona interferometer and in the tests for cutting the adhesive bond. The expected results must provide the state conditions of the surfaces to optimize the adhesiveness of the materials studied.

CFRP advanced surface characterization prior to adhesive bonding. Peel ply treatment vs UV laser

Materiales Compuestos — Sun, 26 Jun 2022 12:58:23 +0200

Surface treatment is one of the most important issues for obtaining high quality adhesive bonding. The main objective of this treatment is the removal of surface contaminants, the modification of surface roughness and the increase of surface free energy, without damaging the surface of the composite material.

Nowadays, the treatments which are approved by the aeronautical sector for the surface preparation of CFRP prior to adhesive bonding are manual and some of them depend on the skills of the operator. Because of this, different automatable alternatives are being studied in order to substitute these traditional methods. One of these alternatives is the use of UV laser radiation.

In this work the advanced surface characterization of CFRP surfaces treated with peel ply and processed with UV laser have been performed. Advanced techniques have been used in order to evaluate the changes that occur in the surface and which can be related to adhesiveness. Thus, techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), surface free energy determination and 3D optical confocal profilometry have been used to evaluate chemical and physical properties of treated surfaces.

Obtained results show that UV laser radiation leads to surface changes which would improve the adhesiveness of the surfaces, although these changes suggest that the mechanism by which adhesion happens is different from the one which is related to peel ply.

Machining of Hybrid Composite Materials

Materiales Compuestos — Sat, 25 Jun 2022 21:22:08 +0200

Composite materials have been having an increasing importance in the industry. Their high specific properties and their high flexibility that allows tailoring materials that suit the needs of practically every project, have been leading to a growth in the demand of this kind of materials. Fiber-Metal Laminates have an established usage on the aeronautic industry and lately have been subject of research by the automotive industry.

Since composite manufacturing methods allow the obtention of components with their final geometry, drilling is the most used machining operation in the machining of composites. Drilling of composites is very demanding from the tools point of view, with very high wear rates and several defects can occur to the workpiece like delamination, fiber pull-outs, burrs and matrix degradation. When combined with a metal, additional challenges appear in drilling these materials such as loads of different magnitudes during a single operation and surface defects on the interface because of chip removal. Orbital drilling is seen as a promising alternative to conventional drilling, presenting several advantages that result in holes with higher quality.

Given the interest the automotive industry has been showing in fiber-metal laminates constituted by steel and carbon fiber reinforced plastics (CFRP) and due to the lack of information regarding drilling of this combination of materials, the aim of this work was to evaluate the influence of the machining parameters in the quality of holes obtained by orbital drilling. A full factorial design of experiments was done and the influence of the parameters was then evaluated by means of an Analysis of Variance (ANOVA).

Estudio topográfico y dimensional de material poliuretano termoestable mecanizado mediante mecanizado robotizado

Materiales Compuestos — Sat, 25 Jun 2022 20:30:03 +0200

El poliuretano termoestable es un material utilizado en el sector de modelizado y actualmente está sustituyendo a piezas estructurales en maquetas de control del sector del automóvil y aeronáutico, por su facilidad de mecanizado, además de aportar unas buenas propiedades mecánicas. En este trabajo se ha experimentado el mecanizado robotizado de un material poliuretano comercial tipo Necuron® 651.

El mecanizado robotizado ofrece una amplia posibilidad de mecanizar y modelar materiales con la ventaja de aumentar la accesibilidad a las piezas, en comparación con los centros de mecanizado convencionales de tres o más ejes. El mecanizado se ha llevado a cabo con una instalación consistente en un robot ABB® 6640-235 con un cabezal de alta velocidad Peroni® y mesa rotativa ABB. La desventaja del mecanizado robotizado, causado por la falta de rigidez de la morfología del robot, son los errores macro y micro dimensionales. Se han realizado geometrías sencillas con herramientas enterizas de acero rápido. La programación CAM se ha obtenido con el software Powermill® de la compañía DELCAM, teniendo en cuenta dos tipos de estrategias de limitación de grados de libertad del robot, para verificar resultados geométricos. Finalmente se ha medido y analizado la superficie generada mediante interferómetro autofocus Alicona y se ha medido la macrogeometría de las muestras en máquina de medición por coordenadas. Los resultados muestran que los errores tanto micro como macro disminuyen significativamente si se hacen fijos alguno de los siete ejes, del sistema robotizado.

Automatic 3D cutting of dry CFRP preforms based on computer vision

Materiales Compuestos — Sat, 25 Jun 2022 20:20:04 +0200

Cutting preforms in complex 3D geometries is one of the challeges of carbon fiber manufacturing for both prepreg and dry fibre parts. Even after cutting layer by layer, a subsequent process is still necessary due to possitioning tolerances and the need of trimming of the edges. Nowadays, this process is carried out by hand. These manual cuts are performed on cutting mats and employ specific tooling to keep the preform in a fixed position and shape. Moreover, often it is necessary to move the preform into several cutting positions leading to poor ergonomics, specially for very thick preforms.

The process presented here attempts to solve this problem by introducing an automatic cut without any cutting mat nor complex and expensive fixing jig. The greatest difficulty of this approach lies on the flexibility of the preforms as they are not rigid enough to maintain their shape and position during the cut.

The solution combines a computer vision system withan ultrasound cutting system embedded on a robotic arm. This may lead to improvements in productivity as well as in quality (Regarding cut tolerances and finish) as well as increased repeatability compared to manual processes, enabling the deveolpment of net preform cutting technologies. Templates are not required and tooling is simpler, so recurring costs plummet as well as set up times. This is specially useful for prototyping and short production series as cutting lines may be easily modified without making new templates since the system is able to identify the new cutting path.

Classical Hodgkin's lymphoma with cutaneous involvement in an adolescent male: A case study

Sumon Ghosh — Sat, 25 Jun 2022 16:20:02 +0200

Background: Hodgkin's lymphoma (HL) with skin involvement is reasonably rare. It typically occurs late in the course and is associated with a poor prognosis; however, it may also be indolent in some cases. Case: We report a case of a 15-year-old previously healthy male with Hodgkin's lymphoma who presented with multiple lymphadenopathies of axilla and serpiginous ulcerative nodular lesions involving pectoral skin. A lymph node biopsy was performed following an initial diagnostic workup for a suspected active infectious disease, which revealed a neoplastic invasion from a mixed cellularity classical HL with skin involvement. A total of six cycles of ABVD (doxorubicin, bleomycin, vinblastine, and dacarbazine) chemotherapy regimen was administered to the patient. Conclusion: In comparison to other studies, this case demonstrates that a good response is possible with standard ABVD chemotherapy.

Specimens manufacturing by infusion for the ”Outcome Lower Skin” structural tests pyramid (Clean Sky 2)

Materiales Compuestos — Fri, 24 Jun 2022 19:56:10 +0200

The aim of this project had been the infusion specimens manufacturing to support design, analysis and qualification for the “Outcome Lower Skin” pyramid structural tests inside the Clean Sky 2 programm. It is the reinforcement lower skin structural tests pyramid for the C295 military aircraft from Airbus Defence & Space.

Along the project UD dry fiber manufacturing process had been developed until to obtain an automatic, robust and efficiency process in order to be able to manufacture a lower skin with stringers and spars integrated and that will be able to compete with the typical prepreg process with regard to fabricability, ratio, performance and cost.

The manufacturing process includes the dry fiber pre-forms automatic lay-up by AFP (Automated Fiber Placement), a hot-forming process for the stringers and finally a process infusion by VAP (Vacuum Assisted Process). To achive this goal, the AFP has been set up to optimize the laying parameters for the processing of the material to be used (½” Hexcel Hi-Tape fiber) and RTM6 resin. On the other hand, several tests of hot forming had been carried out modifying process variables, and several infusion bags configurations had been used to stringers and skin integration by infusion (VAP) until to find the key process parameters to obtain valid parts for the structural test pyramid.

Simulation strategy to compensate spring-in deformations in aeronautical panel made by liquid resin infusion

Materiales Compuestos — Fri, 24 Jun 2022 19:44:03 +0200

Spring-in in composite manufacturing is a relevant non desired effect that complicates the industrialization process of new composite parts. Geometrical deviations of the part with regard to the nominal dimensions hinders posterior assembly operations or even can cause unconformities (part rejection). Although some correction operations may be introduced in the assembly method to absorb these deviations, a preferred approach is to compensate the tool geometry to produce the part within tolerances.

This contribution presents a methodology that, in an iterative process, links a MEF simulation workflow for the prediction of process induced distortions, a routine to compute deviations and updating tool cavity surface, till the deviations are within a target tolerance. The spring-in calculation engine is implemented in Abaqus Standard with specific subroutines to model resin curing kinetics, heat generation, cure dependent mechanical constitutive model with consideration of thermal expansion and cure shrinkage, and specific strategies to simulate the tool/part interactions. The spring-in engine is incorporated in an external Python manager in charge of post-processing results, updating the mesh and launching the executions. This methodology aims at proposing a modified tool surface geometry that could be used to build a compensated tool at first, reducing industrialization time and cost.

Influencia de la compactación en las propiedades de compuestos poliméricos reforzados con fibra de carbono

Materiales Compuestos — Fri, 24 Jun 2022 19:36:05 +0200

La infusión de resina es un proceso de moldeo por vía líquida, comúnmente utilizado para consolidar preformas de tejidos non-crimp fabrics (NCFs) empleados en la fabricación de piezas composites poliméricos reforzados con fibra de carbono. Las propiedades de estos composites dependen de la relación fibra/resina y de la porosidad del producto final. Para la obtención de unos valores adecuados de dichos parámetros, es de vital importancia controlar el grado de compactación de la preforma justo antes de la infiltración de la resina. Por esta razón, el estudio del comportamiento de la compactación de los NCFs es esencial para la optimización de los procesos de fabricación de materiales compuestos en términos de tiempo y coste.

En este trabajo, se muestran los resultados del comportamiento de los NCFs en la compactación y en la infusión. El comportamiento en la compactación incluye la influencia de la composición de los NCFs, como por ejemplo la presencia de un adhesivo orgánico o el número compactaciones. El proceso de infusión se caracterizó por medio de análisis dieléctrico (DEA). La calidad de los laminados infusionados se analizó en términos del contenido de poro en la pieza final, por medio de métodos no destructivos (NDT), y de la relación fibra/resina, cuantificada por medio de digestión ácida de la matriz.

Study of resin velocity and voids in LCM processes by means of fast X-ray Computed Tomography

Materiales Compuestos — Fri, 24 Jun 2022 19:27:03 +0200

In this work, experiments of RTM processes have been carried out. The composite manufacturing have been visualized using Synchrotron X-ray Computed Tomography (S-XCT) in the Swiss Light Source (SLS) facilities (Villigen, Switzerland). The main goal of these tests is to study the behaviour of the resin in a porous medium such as a dry fibre fabrics at different capillary numbers, i.e. resin velocity. According to the theory, the capillary number of a process is an indicator that shows whether the resin flows preferably the fibre bundles or the channels between the bundles and, therefore, where the voids are mainly generated. To study this relation, a characterized (viscosity, surface tension and contact angle) epoxy resin has been injected into a closed mould containing six layers of dry E glass fibres at constant and controlled flow using a commercial syringe pump. Due to the high resolution and the low acquisition time of the tomograms, the movement of resin between and within the bundles, the void formation and the void transport have been captured in the images. In this article, it is shown the effect on these phenomena depending on the resin velocity.

Reliability-Based Criterion for Evaluating Explicit Approximations of Colebrook Equation

Dejan Brkić — Fri, 24 Jun 2022 02:58:02 +0200

Numerous explicit approximations of the Colebrook equation have been developed and evaluated based on two criteria: prediction accuracy and computational efficiency. This paper introduces a new evaluation criterion based on the reliability of each equation. The reliability is defined by the coefficient of variation (CV) of the explicit friction factor that is a function of the variabilities of component random variables (roughness height of the internal pipe surface and kinematic viscosity of the fluid). The coefficient of variation of the friction factor depends on its first derivative for roughness height of the inner pipe surface and kinematic viscosity of the fluid and their correlation. Seven explicit approximations were evaluated using the new reliability-based criterion. The results show that all explicit approximations are very reliable, but variations exist regarding the reliability level. The reliabilities of the seven approximations is very close for the rough-flow regime and when the CV of the viscosity is minimal. However, for the smooth-flow regime, and when the CV of the roughness is minimal, various approximations showed substantially different reliabilities. The novelty of the proposed criterion is that it addresses an evaluation dimension that complements the accuracy and efficiency criteria.

Analysis of uncertainty using stochastic flow simulation of LCM at constant thickness

Materiales Compuestos — Thu, 23 Jun 2022 19:58:03 +0200

Liquid Composite Moulding (LCM) process design requires that the resin impregnation minimizes both mould filling time, as well as the probability of occurrence of dry, unsaturated zones. This can be challenging, as the degree of variability present in material properties and the manufacturing process itself, can be substantial.

The main purpose of this study is to understand and quantify how the different sources of variability, present in LCM, may affect the performance of the mould filling process, creating defects and to quantify how lower scale interactions may affect macro-scale flow. In order to transfer the meso-scale stochastic behaviour towards a complete macro-scale model, an uncertainty propagation model is proposed, whereby local statistical properties are used to predict the upscaled flow behaviour. This is done by means of flow simulation, using stochastic models for the input process variables. Local fabric distortions, combined with fabric permeability, pressure and race-tracking serving as inputs to estimate the joint probability distribution that characterizes the global uncertainty in flow performance.

Preliminary uncertainty analyses investigating individual sources of variability are available in the literature, however, a complete framework combining the different variables into a mould filling scenario, was not found. Therefore, this study tries to develop a new multi-variable aggregating concept that is applied to mould filling simulation. The individual contribution of each source of variability used in this work is quantified, providing a better understanding of the reliability of alternative process designs.

Comportamiento a compresión de non-crimp fabrics impregnados

Materiales Compuestos — Thu, 23 Jun 2022 19:47:02 +0200

Muchas industrias, como la del automovil están haciendo un gran esfuerzo para reducir costes y aumentar la productividad de los procesos de fabricación de composites. Aunque todas estas tecnologías aún están emergiendo, parece que los procesos de Moldeo de Compuestos por Vía Líquida (LCM) en los que hay una fase de compresión, como el Moldeo de impregnación por Compresión (WCM) o el Moldeo por Transferencia de Resina de Compresión (CRTM), son los mejor posicionados. En estos casos, dado que la preforma de fibra impregnada se comprime durante el proceso, es imprescindible conocer el comportamiento de compresión de estos materiales para seleccionar y optimizar el proceso de fabricación mediante herramientas de simulación.

Cuando se trata del proceso de compresión, se ha considerado que las preformas presentan un comportamiento elástico-lineal. Sin embargo, las últimas publicaciones han demostrado que este comportamiento es principalmente viscoelástico.

En este trabajo se ha caracterizado la relajación de un Non-Crimp Fabric (NCF) impregnado de 50k, bajo presión, para 3 velocidades de compresión diferentes. Para ello, el comportamiento viscoelástico se ha descrito mediante modelos fraccionarios, que en comparación con los modelos clásicos exponenciales, son capaces de reproducir correctamente la relajación del material durante la fase de máxima compresión

Fabricación de piezas de geometría compleja mediante infusión empleando tecnología de impresión 3D para la generacion de utillaje

Materiales Compuestos — Thu, 23 Jun 2022 19:35:03 +0200

Los procesos de fabricación con materiales compuestos fuera de autoclave están actualmente en auge, debido a la flexibilidad y la reducción de costes asociados. Entre estos métodos de fabricación destaca el proceso de infusión por vacío modificada, el cual permite obtener geometrías relativamente complejas, de grandes dimensiones y con un mayor nivel de integración, mediante el apilado de tejido seco y la posterior inyección de resina líquida. Uno de los principales costes de este método es el de la fabricación de los útiles necesarios, que se incrementa considerablemente al aumentar la complejidad de la geometría de la pieza a fabricar.

En este trabajo se presentan los resultados obtenidos en la fabricación de piezas complejas mediante infusión, empleando útiles fabricados con tecnología de impresión 3D de plástico.En concreto, se fabricó un perfil alar de dimensiones aproximadas 500 x 340 mm con capacidad sustentadora (psu-90-125wl-il), empleando un conjunto de 12 moldes fabricados en PLA mediante impresión 3D. Para ello, se diseñó el útil necesario con herramientas CAD a partir de la geometría del perfil a fabricar, para posteriormente dividirlo en secciones fabricables usando los medios de impresión 3D disponibles en TITANIA. Se estudiaron los métodos de relleno de y encolado de las secciones, a fin de lograr un único molde con la geometría requerida. Así mismo, se estudió el sistema de sellado de la superficie del útil que permitiese la generación y mantenimiento del vacío requerido para infusionar la pieza, logrando finalmente su fabricación.

De este trabajo práctico se han extraído una serie de conclusiones y limitaciones a considerar en el futuro desarrollo de esta técnica de fabricación de utillaje, la cual puede resultar de interés para la fabricación de piezas mediante infusión a bajo coste.

Vol4 num2-4 Development of multi-material components for the automotive sector

Materiales Compuestos — Thu, 23 Jun 2022 19:09:03 +0200

The present work addresses different aspects of the manufacturing process optimization of structural components for the automotive sector. More precisley the development of a novel bumper beam is being pursued by combining steel and composite to achieve, ultimatly, a weight reduction of the current component. For this it has been fundamental to consider not only the requirements of the part, specially from the safety prespective, but also manufacturing criteria.

The study carried out has included everything from the design of the component up to the evaluation of a wide range of composite materials, both of thermostable and thermoplastic nature. Thus, different manufacturing technologies together with their process window and tooling desing has been accomplished in this work. In addition, several surface treatment technologies including cutting-edge ones such as laser texturing, have been combined with different strategies to ensure, in this way, the optimal performance of the solution.

Finally, the development of ad-hoc demonstrators has allowed identifying the most suitable design and materials. Also, it has been possible to quantify the performance of the components, process times and final cost. Finally, a 25% weight reduction has been achieved, maintaining the mechanical properties and cycle times down to 5 minutes.

Evolución del proceso de fabricación de un mamparo rigidizado con diferentes opciones tecnológicas

Materiales Compuestos — Thu, 23 Jun 2022 18:59:04 +0200

La solución clásica para la fabricación de un mamparo rigidizado, consiste en un panel plano monolítico de CFRP rigidizado por una o ambas caras mediante elementales metálicas y de CFRP a través de uniones convencionales de remachado, resultando un componente de alto coste debido al número de operaciones y elementos individuales implicados.

El objetivo de este proyecto es dar una visión de la evolución del desarrollo de este componente usando diferentes alternativas tecnológicas con objeto de obtener una estructura altamente integrada que represente una ventaja de ahorro de costes y peso.

Se presentan el recorrido por dos soluciones adicionales. Inicialmente una “solución cocurada en autoclave” mediante un proceso innovador de rigidizadores de geometrías en “Ω” y “T” cocurados por ambas caras del panel en material pre-preg y en segundo lugar, una “solución de curado fuera de autoclave-OoA” mediante un panel completamente integrado con una estructura reticular de larguerillos fabricados con diferentes materiales de fibra seca y tecnología de infusión.

Los resultados obtenidos mediantes estos desarrollos tecnológicos garantizan la fabricabilidad y requerimientos de la estructura y no sólo reportan una reducción de costes mediante la disminución de tiempos de fabricación y eliminación de operaciones de montaje, adicionalmente suponen una oportunidad de aplicación a futuros componentes.

Estilos de comunicación en parejas conyugales del Centro Poblado de Mallaritos-Sullana: Un estudio descriptivo-comparativo Rev. PAIAN julio – diciembre 2021.Vol.12/Nº2

Revista Científica PAIAN — Wed, 22 Jun 2022 03:58:03 +0200

Biaxial testings with fiber optic sensors based in Bragg gratings

Materiales Compuestos — Tue, 21 Jun 2022 18:46:02 +0200

Bragg Grating based optical fibre sensors are widely used for structural monitoring. Its operation is theoretical well known when deformations are measured along the fibre axes. Nevertheless, transverse deformations of the optical fibre have an effect that affects the performance of the sensors. This transverse effect has not been so deeply studied as the longitudinal and it is less known. When a sensor is embedded in a composite structure, its deformation is rarely unidirectional because of the presence of complex loads cases and/or the Poisson module effect on the deformation of the lamination.

A test campaign of biaxial composite material specimens with embedded fibre optic sensors is going to be performed. The work pursues to create controlled deformation cases to the sensor in the two main axes of its plane, by means of perpendicular loads in each axis. Following this test methodology in the plane, it will be observed the influence of the transverse deformations on the values of the longitudinal deformation measured by the sensors.

To carry out the biaxial tests it has been used equipment that allows the control of the applied load in the three coordinate axes independently. It also been used a digital image correlation (DIC) equipment for measuring the deformations. Characterization of the sensors will be carried out with different load case tests.

Additive manufacturing of continuous fibre reinforced thermoplastic composites using fused deposition modelling: Effect of process parameters on mechanical properties

Materiales Compuestos — Tue, 21 Jun 2022 18:36:04 +0200

Continuous Fibre Reinforced Thermoplastic Composites (CFRTPCs) are becoming alternative materials to replace the conventional thermosetting polymers and metals due to excellent mechanical performance, recycling and potential used in lightweight structures. Fused deposition modelling (FDM) is a promising additive manufacturing technology and an alternative of conventional processes for the fabrication of CFRTPCs due to its ability to build functional parts having complex geometries. The mechanical properties of a built part depend on several process parameters. The aim of this study is to characterize the effect of build orientation, layer thickness and fibre volume content on the mechanical performance of 3D printed continuous fibre reinforced composites components manufactured by a desktop 3D printer. Tensile and three-point bending tests are carried out to determine the mechanical response of the printed specimens. SEM images of fractured surfaces are evaluated to determine the effects of process parameters on failure modes.

It is observed that the effect of layer thickness of nylon samples on the mechanical performance is marginally significant. In addition, continuous fibre reinforced samples show higher strength and stiffness values than unreinforced ones. The results show that carbon fibre reinforced composites exhibit the best mechanical performance with higher stiffness and flat samples exhibit higher values of strength and stiffness than on-edge samples. Additionally, the results show that strength and stiffness increase as fibre volume content increases in most cases but, conversely, the level of increment in mechanical performance is moderate with continued rise in fibre content, particularly in the case of Kevlar® and glass fibres, due to weak bonding between the fibre/nylon layers as well as the presence of increased levels of defects.

Monitoring of Freeze-Thaw Cycles in concrete using an embedded micro-Sensor and Strain gauges

Materiales Compuestos — Mon, 20 Jun 2022 11:41:04 +0200

This paper deals with the study of internal stress produced during freeze-thaw (F-T) cycles using two non-destructive measurement approaches: the first approach devoted to continuous and internal monitoring using an embedded sensor based on amorphous ferromagnetic microwire during the cycles, and the second one, measuring the strain variations at the surface of the specimens by means of strain gauges. Also, measurements of ultrasonic pulse velocity through the concrete specimens were taken simultaneously during the freeze-thaw cycles. The objectives of this paper are to investigate the internal strain of freeze-thaw exposure providing a new way of measurement. These inspections may provide great reference for further research on the development of a calculation modelling of deterioration process in concrete structures under a freeze-thaw environment.

Study of acelerated agening under concentrated solar radiation of silicon oxycarbide glases as high temperature solar receivers

Materiales Compuestos — Sun, 19 Jun 2022 14:44:04 +0200

Solar energy and especially concentrated solar power systems (CSP) need materials that can tolerate the demanding working conditions. In this sense, the receivers are exposed to large fluxes of solar radiation that produce very high temperatures. In addition, due to the operational conditions of receivers large temperature variations occur during day and night, or on cloudy days being these the main aging factors. However, other factors such as humidity, salines environments or pollutans in industrial zones can not be ruled out. Silicon oxycarbide glasses (SiOC) are composite materials formed by a SiOC glass phase (matrix phase) and a C phase (reinforcing phase) homogeneously dispersed and they can be very promising candidates for this type of applications due to their excellent intrinsic properties like their high resistante against to both oxidation and very aggressive environments, good mechanical properties, etc.

In this work we have focused in the evaluation of the composite materials (SiOC porous and dense) against thermal shock produced by Frenel lens that concentrated solar radiation more than 2600 times. In every cycle materials they have been heated (32 ºC s-1) an cooled (27 ºC s-1) at very high rates from room temperature to 1000 ºC. This process has been repeated 100 times or lesser in the case of catastrophic material damage. The evolution of material surface during thermal shock cycles has been followed by several techniques such confocal and electronic microscopies and Raman, Infrarred and UV-Visible spectroscopies. Porous silicon oxycarbide materials experiencied a rapid and severe degradation during the first cycles but dense one tolerates quite well the exposure againts concentrated solar radiation.

Laminados aeronáuticos multifuncionales y multiesclares con diferentes contenidos en grafeno obtenido por un proceso mecano-químico

Materiales Compuestos — Sun, 19 Jun 2022 14:20:04 +0200

Este trabajo presenta los resultados obtenidos en la caracterización de laminados de material compuesto epoxi/fibra de carbono que presentan dos peculiaridades: se ha utilizado un tejido de fibra de carbono con formato non-crimp fabric (NCF) y se ha dopado la resina con diferentes contenidos de grafeno obtenidos mediante un proceso mecano-químico a partir de nanofibras de carbono.

Debido a la utilización de grafeno de pequeño tamaño lateral se espera evitar el efecto de filtrado durante la fabricación de laminados mediante RTM. Los paneles fabricados presentan baja porosidad y en el caso del panel con un 0,2 % de grafeno en la resina se ha obtenido una distribución homogénea de resina y fibra en diferentes zonas a lo largo del recorrido de la resina por el panel durante la inyección.

Los resultados obtenidos en el estudio de curado revelan un ligero adelanto en la reacción de curado de la resina epoxi utilizada causado por la presencia de las partículas de grafeno. Sin embargo, el grado de curado y la temperatura de transición vítrea de los paneles es muy similar. Con respecto a la caracterización mecánica, se ha obtenido un incremento del 9 % en la resistencia a cortadura interlaminar.

Study of multifunctional composites of epoxy matrix with ceramic nanoparticles

Materiales Compuestos — Sun, 19 Jun 2022 14:08:03 +0200

The research about multifunctional materials has gained special relevance in recent years. In this sense, properties such as hydrophobicity, due to their potential applications (water repellent surfaces, self-cleaning, anti-icing, protective against corrosion, etc.) in combination with others, such as thermal conductivity or electrical insulation, can lead to new materials and coatings suitable for use in the field of energy and electronics.

The present work focuses on the development of multifunctional materials of epoxy resins with inorganic nanoparticles with hydrophobic properties and better heat transfer capacity. To achieve this goal, nano-reinforcements of zinc and titanium oxides of different sizes and morphologies have been selected to obtain hydrophobicity, in addition to boron nitride platelets to improve the thermal conductivity of the nanocomposites coating.

Among the possible applications of these coatings would be their use as electrical insulators for high voltage applications, such as self-cleaning surfaces, scratch resistance, etc. The addition of hydrophobic coatings, which also achieve a remarkable mechanical and thermal stability, could lead to new designs of greater reliability and durability in their functions.

Modification of carbon fibre/epoxy composites properties by the incorporation of nanoparticles functionalized electrospun PA6 veils

Materiales Compuestos — Sun, 19 Jun 2022 13:41:10 +0200

Epoxy resin composites inherent brittleness and poor crack resistance make necessary some form of toughening. Recently, several types of nanoparticles are being incorporated due to their theoretical high stiffness and strength. However, the addition of tougheners to the entire matrix resin could lead to a decrease in in-plane mechanical properties and to an increased viscosity of the system, being reduced the processing ability of matrix resin. Moreover, a homogeneous dispersion of these nanoparticles is still a problem. Thermoplastic nanofibrous structures can tackle these problems. They offer a solution for the dispersion issue, since they can be readily embedded in the resin and incorporate a nanosized phase in the composite. These nanofibres also do not increase the viscosity of the resin. Moreover, due to their macro scale length, no health hazards are involved in the production and use of these nanofibres.

This paper investigates the effect of electrospun nanofibrous veils made of polyamide 6 modified with TiO2 nanoparticles on the properties of a carbon fibre/epoxy composite. The nanofibres were incorporated in the carbon fibre/epoxy composite as stand-alone interlayered structure during a vacuum infusion process. The effect of positioning these veils in different composite positions has been investigated. Incorporation of polyamide nanofibers increases the stress at failure and the Young’s modulus. Furthermore, mode I tests showed a slight improvement. When TiO2 modified veils are incorporated in the composite, similar mechanical properties were obtained, but new antibacterial properties were achieved when irradiated with UV light widening the application area of these composites.

Technological challenges of the injection moulding implementation for aeronautical parts

Materiales Compuestos — Sat, 18 Jun 2022 18:58:03 +0200

The potential implementation in the aeronautical industry of the injection moulding manufacturing process with short fiber reinforced plastics was studied on different parts with low structural responsability within horizontal and vertical stabilizers thanks to the atractive recurent cost and hi-rate production widely demostrated within automotive industry. The present work shows the different activities performed in the frame of engineering and manufacturing with the aim to assess the feseability for the aplication of the technology. These activities go from design, stress and mechanical testing, study of the different injection strategies and the implications in the mold design to evolve from conventional plastic to reinforced mateials mainly due to the high temperatures and anisotropy of the material

Previous developments are included in the project FACTORIA, funded by the Ministerio de Economía y Competitividad, by means of the Centro Tecnológico Industrial (CDTI), in the Strategic Programme CIEN 2018

Preform development of dry fabrics for manufacturing of large dimensions structural components by RTM for aeronautical industry

Materiales Compuestos — Sat, 18 Jun 2022 18:51:04 +0200

Resin Transfer Moulding Technology (RTM) is gaining attention on developing composite structural components for aeronautical industry, due to its high-cadence production, and as a consequence, a significant manufacturing cost reduction. This document describes the manufacturing of a composite fuselage frame oriented in dry reinforcement preform construction that, it’s one of the main factors that intervene in RTM process and has a direct influence on the component structural quality.

It’s exposed the definition of an overlap strategy for dry Non-Crimp Fabric adaption on structural aeronautical components of large dimensions and implementation of such strategy for manufacture a real-scale demonstrator, exposing process time reduction base on a tooling design that facilitate the cycle time reduction. Simultaneously, it’s described a procedure to study the overlap influence at a dimensional and structural level and defects generation. Also, it’s exposed different overlap strategies for preform consolidation by commercial adhesives incorporation for fabrics and thermoplastic binders.

Fast preforming for automotive applications through flexible and automated facilities

Materiales Compuestos — Sat, 18 Jun 2022 18:41:04 +0200

The use of polymer matrix composites and, in particular, based on carbon fiber, is awakening more and more interest in the automotive sector, due to the great weight reduction potential they offer for the lightening of vehicle structures. The case of the BMW (with the i3, i8 and 7 Series) and some other manufacturers, represent the first cases of use of "large scale production" with these materials, with a growth perspective provided by the electric vehicle. To achieve a mass implementation of these new materials it is a key factor the development of processes and equipment that allow manufacturing with very short cycle times.

Preforming is the key stage where the fiber stacking takes the form of the injection mold in which it will be introduced later. This stage of the process is the one that has a greater impact on the cost of the overall process, so it is especially necessary to develop optimization and automation techniques for rapid preforming.

In this context, Fagor Arrasate, with the aim of offering its customers a competitive installation, has created and led a project in which it has collaborated with Tecnalia to develop pre-forming installations for the automotive sector.. A fast preforming process based on preheating and cold stamping has been developed combined with an automatic material feeding based on a transfer system and also completed with the automation of the initial stacking and the trimming of the final preform. The capabilities of this installation have been validated for an automotive demonstrator.

Use of tough matrices to improve the adhesive bonding between carbon fiber laminate layers

Materiales Compuestos — Sat, 18 Jun 2022 10:36:03 +0200

In recent years, the use of carbon fiber reinforced epoxi (CFRP) for the automotive industry has taken a great deal of development; whether in the manufacture of bodyworks, chassis or in interior parts with low mechanical responsibility. These structures in their normal life, will be continually subjected to external exertions of small intensity. These efforts will be able to lead to fractures in the matrix of the composite material if it presents high stiffness.

For this reason, the aim of this work is to replace epoxy matrices, which are usually used to manufacture CFRP by another with large toughness like modified acrylics or epoxies. In this work, characteristics of two epoxies are compared, one of them traditionally used for high modulus composites with low deformation capacity and another that has large toughness. For that purpose, thermal and mechanical properties of the composites manufactured with them are determined.

Hybridization Process of Carbon Fibre Sheet Moulding Compound with Carbon Fibre Prepregs: a Case Study

Materiales Compuestos — Thu, 16 Jun 2022 09:56:04 +0200

The main objective of this work was to show the technical viability of a traditional Sheet Moulding Compound process hybridized with Carbon fibre prepreg reinforcements, in a demonstrative car seat structure. The new reinforced seat is lighter, has better mechanical resistance to impact and the typical carbon fibre visual aspect in the reinforced areas. Currently, the seat structure is composed by the hybrid solution with the matrixes of both materials being epoxy, therefore compatible which promotes a good adhesion under the correct processing conditions. To ensure the viability of this hybridization, an extensive laboratorial test campaign was conducted in a laboratorial hot plate press to study the Sheet Moulding Compound flow dynamics during the moulding process and how it interacts with the prepreg preforms. The cure process of both materials was also analysed to establish the optimal temperature profiles. Finally, mechanical tests were performed according to ASTM D 5868-01 to evaluate the mechanical properties of the bonding between the two materials. The reinforced car seat prototype was validated according to the ECE-R17 and FMVSS202a impact tests on the head rest and a 25% reduction in overall weight was achieved. The life-cycle cost and the visual aspect benefits are expected to compensate the slightly higher manufacturing cost in relation to the original part due to the cost of the prepreg material. Further research will be needed to in terms of process automation to ensure the required process quality.

New Materials in Automotive. Adhesive Solutions and their Processes

Materiales Compuestos — Thu, 16 Jun 2022 09:41:03 +0200

Composite introduction to automotive industry create new joining requirements and associated technologies, where adhesives are a key technology to acheive this challenges. This circumstances introduces new parameters onto adhesive solution sorting and characterization.

Work completed it is focused onto two diferent areas, first one analyze compatibility of different chemistries available at 3M portfolio (epoxy, polyurethane, acrylic), and how they answer to different question marks created in structural bonding at automotive, several substrates has been considered like: TEPEX^®, CFRP or Alumimun with minimal to none surface preparation.Test completed include shear strength before and after different agging cycles with different adhesives and substrates.

Second piece of work complete is focus on different induccion/lockup cycles, either for liquid and fillm structrual adhesives, which the goal to create cycle times lower than 90s, and keep line manufacturing process.

Research complete is partially covered under ECOVOSS project, which goal is to develop lightweigth structures for automotive, and it also include different 3M researches and experiences bonding composites structures in Automotive.

FIBRE4YARDS_MARTECH2022_Presentation_WP2_INEGI_20220525

Jesús Sánchez Pinedo — Tue, 07 Jun 2022 10:10:02 +0200

The main objective of the FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced.

This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement N° 101006860.

FIBRE4YARDS_MARTECH2022_Presentation_Project_Overview_CIMNE_20220525

Jesús Sánchez Pinedo — Tue, 07 Jun 2022 10:06:03 +0200

This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement N° 101006860.

TRAFFIC CRASH INJURIES OCCURRENCE VARIETIES ACROSS BARCELONA DISTRICTS

Benjamin Colucci — Fri, 03 Jun 2022 17:57:48 +0200

Barcelona (Spain) had a total population of 1,636,762 in 2019 that are distributed on 10 districts across the city. These districts have different characteristics in size and population density. As a result, this can lead to different traffic crashes injuries occurrences and numbers in these areas. Therefore, this study is attempting to determine the conditional probabilities for each district in order to identify the district that has highest number of injuries compared to other areas. A Bayesian network approach is utilized to analyze the dataset and identify the high-risk district alongside analyzing the varieties of traffic crashes during four-year intervals. The results have shown that the district that has the highest population, highest usage of private transport mode, and highest density of passenger cars per km2 (compared to all other districts), has the highest risk of having all types of injuries resulting from traffic crashes. For the temporal factor represented by the four years interval, traffic crashes occurrences varied from district to district based on the level of injury.

LESSONS LEARNED FROM THE VIRGINIA REFLECTIVE CRACKING STUDY UNDER ACCELERATED PAVEMENT TESTING

Benjamin Colucci — Fri, 03 Jun 2022 17:46:46 +0200

Road administrators encounter situations where they must make decisions regarding the maintenance and rehabilitation of a road network without knowing the outcome of those decisions until years later. The Heavy Vehicle Simulator has been widely used as an accelerated testing tool to study pavement performance in a shorter period and under more controlled conditions than in the field. The Virginia Department of Transportation, in conjunction with the Virginia Tech Transportation Institute and the Virginia Transportation Research Council, has initiated a research project to study the behavior and performance of different pavement materials and structures under accelerated load through a Heavy Vehicle Simulator. Six pavement sections with different structures were built and instrumented with strain gauges, load cells, temperature gauges, and linear vertical displacement transducers. Two lanes were dedicated to study reflection cracking. They included a concrete pavement with joints 9.5 mm (3/8 inch) wide to reflect cracks in the surface. These lanes were covered with two 1.5-inch (38.1-mm) layers of a control SMA mix asphalt and a similar mix

modified with a synthetic fiber. This article presents the results of this reflection cracking study. The article describes the characterization of the asphalt mixtures used, the pavement structure, the construction design, the Heavy Vehicle Simulator used and the installed instrumentation. The paper also presents some of the lessons learned, experimental changes, and study results in terms of cracking and rutting performance.

VULNERABILITY OF SCHOOLS IN PUERTO RICO TO TSUNAMIS

Benjamin Colucci — Fri, 03 Jun 2022 17:37:48 +0200

The archipelago of Puerto Rico is a region of high danger to tsunamis (ATC, 2019).

Recognizing that the school population in Puerto Rico is around 600,000 people (including students and

teachers, according to 2016 data), and that schools are essential facilities to safeguard against extreme events,

the objective of the research has been to evaluate if the Puerto Rican schools are vulnerable to tsunamis. In the

first instance, a comprehensive database of schools in Puerto Rico that could be affected by tsunami events

was developed and critical municipalities were identified. The municipalities of San Juan and Cataño were

selected as case studies in which a more detailed evaluation was carried out. This evaluation included the

analysis of the evacuation time required to move from each schoolyard to a safe place as the main vulnerability

factor. The shortest route and several alternative routes were evaluated for each school. The analysis included

as a complementary factor the status of the critical school evacuation route in each of the two municipalities.

In addition, a survey form was developed and administered to collect data on school evacuation preparedness.

The study found that the most vulnerable schools in each study municipality present excessive evacuation

times and unsafe and inadequate evacuation routes for the evacuation process. Several additional study areas

have been identified to improve the vulnerability assessment of schools. Therefore, a second phase of the

research is being developed to obtain better estimates of evacuation times, including all stages of the evacuation

process (evacuation timeline), analyzing the factors that affect pedestrian dynamics and simulation of each of

these phases and integrating data from evacuation drills. The results of these investigations are expected to

contribute to the rehabilitation processes of coastal schools by providing refined tools to decide if vertical

evacuation is required.