This mid-term monitoring of the progress of the prodPhD project shows that the implemented activities thus far meet their corresponding KPIs. In addition, this deliverable also provides an overall assessment of each Work Package (WP). Both the KPI monitoring and the overall assessment of each WP show the activities completed thus far meet their targets and, hence, the prodPhD project is on track to deliver optimal outcomes to meet its aims.

Once the fibers are obtained through pyrolysis, with a high retention of mechanical properties, the next step is the manufacturing process by injection using a thermoplastic polymeric matrix of polypropylene, a polymer widely used in the composite industry. For that purpose, a study of the compatibility of the fiber with the maleic anhydride polypropylene at different relations -10, 20 and 30%- has been carried out.

In order to enhance the mechanical properties, a combination of homopolymer polypropylene, maleic anhydride polypropylene and recycled carbon fibers is studied through the production of a masterbach composed of maleic anhydride polypropylene and carbon fibers, followed by the addition of the homopolymer polypropylene.

Once the pellets are obtained, they are injected. The samples injected are analyzed in terms of fiber distribution by scanning electron microscopy and tomography, thus the mechanical properties are evaluated through tensile, impact and bending tests, to determine the optimum fiber/resin ratio.

On the other hand, the recyclability is another important point, since the directives on the end of the useful life of the vehicles, stipulates that will be obligatory the recycling of 85% of the vehicle, not contemplating the "recovery of energy" of polymers as a means for its recycling.

Composites, although they are lightweight and have a high resistance, have the disadvantage of their recyclability, and the reality is that environmental legislation is becoming increasingly restrictive, and it is urgent to find solutions to landfill. This is one of the reasons why the pyrolysis of carbon composites for the recovery of carbon fiber, and its reuse in the form of non-woven MAT, and the thermostable resins that can be recycled and reprocessed, can lead to a new generation of sustainable and recyclable composites in the automotive sector.

Among its remarkable combination of properties, we can find a hyperelastic behaviour, low thermal conductivity, low permeability, and good energy absorption and vibration damping properties. Additionally agglomerated cork is produced from the waste of the cork industry, being a renewable and biodegradable material that is environmentally sustainable.

The aim of this work is to address the quasi-static and dynamic compression testing of two types of agglomerated cork of different densities, using a servo-hydraulic testing machine and drop weight tower. The mechanical behaviour and energy absorption properties at different strain rates are evaluated from the contact force measurements and estimations of impact kinetic energy. Additionally, Digital Image Correlation (DIC) is used to estimate the variability in the local strain through the test specimen.

The compound is chemically composed of anhydrous calcium sulfate that could be activated through catalysts, hydrating and turning itself into dehydrate calcium sulphate (gypsum). The aforementioned material presents great aptitudes for self-levelling screeds due to its good reology and little shrinkage. Generally, they are used in building industry once the building envelope is finished and water tight as its water solubility restricts its use in damp environments.

The current paper presents improvements in the resistance against water presence by dosing damp-proof product as siloxan derivatives and zinc stearate. There have been obtained important improvements in the reduction of superficial absorption and capilarity absortion. Also the effect of these aditives on the mechanical properties of the self-levelling compound have been studied in this paper.

The printing filaments are developed from a PA 6,6 matrix obtained from vacuum bags used for the manufacture of pre-impregnated composites and by means of a reinforcement of short carbon fiber obtained from the residues of pieces of composite material or uncured fibre.

The printing trials as well as the specimens for tests and demonstrators have been produced in an open printing system allowing to obtain the optimal process parameters for this type of materials.

The application of these materials and technologies within the aerospace field in flying parts as well as in production jigs and tools as well as in other industries such as automotive, sporting goods or accessories constitutes a key element to align the use of composite materials with the objectives of eco-efficiency that society demands for the immediate future.

Currently, the most used polymers in FFF process are the polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). However, their mechanical properties and service temperature are not good enough to be used in applications where high technical demands are recquired. Due to these shortcomings, scientists have focused on other technical polymers such polyether ether ketone (PEEK) and polyetherimide (PEI). Other approach to improve mechanical performance of traditional materials is the use of fibers or nanofibers, which allows printed parts with new functionalities and/or improved properties.

In this study a needle-like nanoclay has been used for obtaining bio-polyamide nanocomposites, specially prepared for FFF application. The final printed parts showed good dimensional stability and good mechanical properties, which place them between the conventional (PLA and ABS) and the technical materials (PEEK and PEI).

In this context, the addition of nanoparticles, such as carbon nanotubes (CNTs), is arousing much interest. More specifically, CNTs have a vast potential in Structural Health Monitoring (SHM) applications, due to their piezoresistive behaviour and tunnelling conduction mechanisms providing a great electrical sensitivity under strain.

The present study aims to exploit those CNT capabilities for SHM purposes, combining them with the 3D printing manufacturing technology. To achieve this, Digital Light Processing (DLP) 3D printing technique has been used to obtain composite materials based on a commercial resin doped with CNTs, by varying the nanoparticles content.

First results obtained for tensile and flexural tests show an electrical sensitivity slightly higher to the typical values of metallic gauges, thus, proving a high potential for strain monitoring applications.

With the aim of improving the mechanical properties, chemical crosslinking of the Polyvinyl alcohol base was induced prior to lyophilization by immersing the material in a sodium borate solution. It was found that the mechanical response under compression was enhanced in regards to the non-crosslinked systems. A highly retardant composite material was fabricated by superposing an alginate/MMT at the external layer as the most promising system for fire protection

The graphene concept studied for anti-icing application is an electro-thermal system, where heat is generated by applying electrical voltage by Joule effect. Key work performed in this study was focused on following aspects: identification of use cases and requirements, selection of graphene based related material, integration concepts within carbon fiber reinforced polymers (CFRP), demonstration or proof of concept through manufacturing and functionality tests, and, finally, preliminary value and risk assessment of solution.

As per work performed, it can be concluded that the potential of proposed innovative graphene based electro-thermal system for composite aeronautical part anti-icing function has been preliminary proven and demonstrated. However, there is still a long way to increase the maturity, scale-up the concept, demonstrate cost saving and benefits versus other solutions, as well as to overcome the identified risks.

In this framework, ECOFUNEL project was launched by Liebherr Aerospace SAS with the consortium formed by FIDAMC, CTAG and CANOE, and with the financial support of the European Commission under the Clean Sky 2 initiative. The work aims to giving alternatives to current metal valve bodies of air conditioning systems for aircraft, by investigating the use of thermoplastic while addressing the challenge of keeping sufficient electrical conductivity and mechanical properties of the part.

The research line put the focus on the development of new functionalized material formulations based on high performance injection molding thermoplastic compounds with enhanced electrical feature. New formulations are designed, produced and studied systematically within ECOFUNEL and a final prototype element will be created employing the ad-hoc own-designed materials.

This work is base on the development of a methodology to control the impregnation process. It has demonstrated a substantial improvement in the mechanical properties when the flow velocity is controlled and kept around the optimum value.The methodology aims to identify the optimum impregnation velocity value through experimentation, and then, this value is applied during during the whole infusion process. For this purpose, an artificial vision system has been used, which allows keeping the flow velocity constant and near to the optimum value which optimize the mechanical properties.

Its experimental application in both conventional and stitched laminates has shown an increase in the tensile and impact mechanical properties. At the same time, level of control of the infusion process has been enhanced.

In the present study, a thermosetting matrix composed of UV-curable acrylic monomers and UV-transparent aluminium trihydrate (ATH) flame retardant fillers have been added to UV-transparent polyester resin for the manufacture of flame retardant composites. An in-depth study of the most suitable types of ATH-based flame retardant additives and possible synergistic combinations to improve the fire performance of the UV-curable composite has been carried out. Not only has the type of flame retardant been studied, but also the most suitable additive percentage to comply with railway sector regulations.

The compatibility between the fillers and the matrix has been analysed by means of dielectric analysis, as well as the properties of the matrix and final composites against fire and mechanical properties.

This work comprises the design, manufacturing and validation of a novel anti-buckling device for compression after impact thin specimens. For that purpose, a study of the specification toolings along with a review of the already developed anti-buckling tooling literature has been carried. As part of the validation process three series of impacted specimens of 3mm thickness.

This activity is developed as part of the project CERES, which is framed under Clean Sky 2, and has the main objective of validating the manufactured anti-buckling tooling. This tooling has been developed as an innovative solution for its application in compression after impact thin specimens. 

Initially, the displacements and bending moments produced in plates of isotropic material have been analysed by means of numerical simulation and analytical approach. The results obtained have been corroborated with other works published in the scientific literature.

Subsequently, the numerical models and the analytical development have been applied to plates formed with orthotropic material, in the configuration of the two-plane bending test. For this purpose, rectangular plates with different aspect ratio have been analysed in order to obtain different stress ratios along the fibre and perpendicular to it.

Finally, the results obtained both by numerical simulation and by the analytical approach have been compared with experimental tests carried out on unidirectional composite specimens made of epoxy matrix and carbon fibre.

In the current context in which it is essential to reduce the carbon footprint of each component, the reduction in the energy needed and in the cycle times to obtain competitive processes is fundamental. In this context, Tecnalia has developed an advanced preforming cell for the manufacture of dry fibre preforms for RTM or infusion components by applying direct resistive heating. The application of a current directly on the material to be processed has the advantage of avoiding the heating and cooling of molds and obtaining results in a much faster and more efficient way than with the methods traditionally used until now. The application of heating only to the preform guarantees the obtaining of much shorter cycle times, and a reduction in energy consumption of up to 90%. This results in a reduction in the cost of the process associated with lower energy consumption and shorter cycle time.

The resistive preforming offers results of a quality of the preforms similar to that of conventional hot drape forming technology, being also a repetitive process, which has been validated by impregnating preforms tested under flight conditions.

This study has allowed the integration of unconventional technologies, such as AFP, within conventional production systems, such as VIP, which is the key to developing sustainable units, overcoming the common difficulties associated with processing and achieving the modularity of the manufacturing process and the reduction of the weight of the final rail structure. For this reason, a comparison of the manufacture of both monolithic composites and sandwich structures have been obtained through the VIP process, manufactured in an automated and manual way.

Several automated approaches have been studied, with the choice of the robotized lay up of bindered dry fibers. An out of autoclave manufacturing was assisted through different monitoring technologies such as resin arrival sensors and thermography in order to ensure high quality components.

Volume fraction of voids (pores), resin and fibre is part of the set of properties that must be verified, especially in novel and/or low cost manufacturing processess that can affect the structural behaviour. The ability to obtain results depending on the technique used for testing becomes very important at this point.

This study proposes a comparative analysis of the measurement of voids, fibre and resin percentage on carbon fibre reinforced polymers by automated image analysis technique and acid digestion method, varying parameters of the test procedure with the purpose of evaluating their influence in the correct determination of volume fractions. The use of different methods and parameters allows to analyze comparatively the different results obtained and shows advantages and disadvantages of both methods as well as provides valuable information on the best practices for correct test execution following each procedure.

The main problem to implement composite materials within the railway sector is that each component and assembly in the complete train needs to fulfil the Fire, Smoke and Toxicity (FST) requirements described in standard EN 45545-2. At present, there are very few resins that comply with this regulation, due to the recent incorporation of this normative which was approved in 2013 and the resins that manage to comply with it are highly doped that it is difficult to obtain good manufacturing results with them.

A preliminary selection of the materials validated by the railway industry will be carried out. Moreover, it will be necessary to develop a study and characterization of the different options in order to find the best possible choice according to the different applications. This way, materials will be evaluated in terms of processability, physical-chemical and mechanical properties.

For preimpregnated materials, the properties obtained with different curing processes will be analyzed: Oven Cure and Autoclave (only as a comparative reference). The objective is to get a preliminary evaluation and compare the different materials between each other.

This work has been focussed on studying an emerging technology such as Pultrusion for stiffeners manufacturing. For this, it has been used a demonstrator based on a common airframe structure, panels stiffened with profiles. This time, the classic stiffener manufactured using prepreg and autoclave cured has been replaced by stiffeners manufactured by Pultrusion. For that purpose, it was manufactured flat panels using prepegs and autoclave curing, for subsequently bond L shaped high resistance carbon fibre profiles manufactured by Pultrusion.

Furthermore, FEM simulations were conducted over these coupons for three different mechanical testing conditions, tensile, compression and shear, aiming to determine the capability of these methods for simulating reliably the mechanical performance of pultruded materials on such above-mentioned structures.

The results obtained in this work have been used for model parameter adjustments to obtain reasonable correlation levels, enabling the future usage of Pultrusion technology in the stiffener profiles manufacturing.

In order to improve interlaminar crack propagation, some works were already carried out using interleaved thin veils between laminate layers to enhance the interlaminar Mode I and II fracture toughness. In this work, a study was carried out on the distribution of stresses across the thickness of a carbon/epoxide laminate typically used in structural aircraft components, to define between which specific layers would be better to interleave thin veils made from four different materials (glass, carbon, aramid and polyester) to achieve better LVI damage tolerance. Samples made from the selected structural carbon/epoxy laminate were then produced by vacuum bag infusion with those thin veils located between their most appropriated layers to be submitted experimental testing and compare their mechanical and LVI performances with those without using interleaved veils. All studied laminates were observed under scanning electron microscopes (SEM) for assessing their processing quality and submitted to interlaminar shear strength (ILSS) and LVI tests to evaluate their delamination resistance and impact response, respectively.

With this objective and thanks to the contribution of the Spanish goverment trough CDTI, a very effective collaboration was organized between Airbus, pushed by the initiative of the spanish comercial part, FIDAMC, the Technology center linked to Airbus in Spain, MTorres, a recognized supplier of composite industrial equipment and Hexcel, one of the lead suppliers of high performance composite materials. The Project, known as HDPREG, has allowed, trough a complete test pyramid, the development of a material, a new automatic lamination head and a manufacturing process, all adapted for the production of large lifting surface parts for aircraft use and compatible with the mentioned requirements.

As a final exercise, beyond the scope of the project, FIDAMC, MTORRES and HEXCEL, funded the manufacture of an 18 m real-scale component, demonstrating the very high lamination productivity, as well as the feasibility of the application of the new material and the innovative manufacturing processes to meet the demands in terms of cost, weight, and industrial robustness.

This article describes the process of designing and optimizing an elastic-hinge, for a telecommunication satellite considering both structural and frequency requirements using finite element analysis, manufacturing and experimental testing. Furthermore, the paper details the sequence of optimization algorithms that were used to produce a solution capable of meeting the original design specifications.

The structural assessment consists of the elastic-hinge numerical modelling during the folding process, by means of an explicit formulation. This model correlates well to the experimental test data and was used to evaluate the damage installed in the hinge using a pletfora of damage criteria.

The frequency analysis considers the numerical modelling of a system constituted by the elastic-hinge and a telecommunication satellite antenna. This model was used to estimate the natural frequency of the system.

Results show that a design methodology which uses a genetic algorithm (GA) for a global search, followed by a particle swarm optimization (PSO) method for a local search provides a good approach to the optimization problem. It is also shown that the efficiency of these algorithms can be maximized by tailoring their architecture and internal parameters.

The melt mixing method and vulcanization procees was followed for the manufacture of the composites.Composite materials with natural magnetite and synthetic magnetite have been considered separately. Reinforcements fillers were added in different ratios. The morphological analysis carried out by FESEM demonstrates the differences in size and shape of the fillers.Through the Raman and XPS spectroscopy the  interface matrix-fillers was studied. The magnetite content, as well as its source, directly affect the magnetic behavior of the composites. The electromagnetic shielding properties were evaluated in the X band of frequency (8-12 GHz) and K band (18-27 GHz), with attenuations greater than 34 dB for the composites with the highest amount of magnetite. 

The development of more reactive formulations for processes that allow to increase production rates and reduce process times to a few minutes are arousing great interest, such as the HP-RTM (high pressure RTM) and the HP-CRTM (RTM compression).

In the case of RTM resins, ultra-fast (2-5min) and low viscosity curing formulations are sought to optimize the curing and injection cycles to the maximum. The technology based on polyurethane resins (PUR) offers against other alternatives the advantage of having great tenacity and resistance to fatigue which makes it especially attractive for elements subject to impacts or cyclic loads such as suspension elements.

This work, based on simulations, has determined an optimal value of the PUR viscosity for RTM. In addition, a preliminary analysis of the curing kinetics of a commercial PUR resin has been carried out. The results indicate that the resin evaluated is not viable for the process due to its high reactivity at the beginning of curing, so that work will continue on the search for more latent PUR solutions for RTM.

Normalized tensile and three-point bending tests were performed and it was observed that the oak wood laminates in the outer layers give a great aesthetic finish and the tensile stiffness is also increased a 2% compared to the flax reinforced biocomposite. Regarding the results of three-point bending, the oak laminates in the core provide a greater flexure breaking strength, which is a 10% higher than the flax reinforced biocomposite. SEM micrographs show both the accuracy of the infusion process and the good adhesion of the different natural fibres and bioresin.

Finite Element simulations (FEM) were carried out at different pressures generated by three wind velocities (V_wind= 3, 8 and 11m/s). Both tension and deformation results show that the structural integrity of the biocomposite wind blades is not compromised. Finally, the real tests in the wind tunnel have validated the use of the developed biomaterials in manufacturing blades for small wind turbines.

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.

This work, developed within the framework of the European COMMUNION project (GA680567), addresses the optimization of the direct joining process between different high-performance metals and thermoplastic composite cintas. The study deals with surface preparation using laser texturing, the study of different joining strategies and the characterization of joints using different techniques and Single-Lap Shear tests.

Depending on the texture, type of materials or manufacturing strategy, the strength of the joint is improved by 50-200%, achieving structural strength values (> 10MPa) in the optimized joints.

Nevertheless, these materials can also be obtained from the valorisation of different residues generated in local agroforestry crops, which besides it have a low level of exploitation. They are evaluated to the Galicia Euroregion North Portugal, the different natural sources of these materials and its analysed the availability that exists and the technology available to its collection.

They are analysed too, the different phases and processes required to do the preparation of these materials to its use in injection, extrusion and rotomolding composites and, especially, in relation to material moisture content and its morphological characteristics.

In most of the cases, these residues present difficulties to be valorised so that, in many cases it is resorted to its direct burning, generating environmental problems.

Even though, the most part of these materials are susceptibles too to be energy valorised, it is possible to combine in the same industrial process the combined production of natural fibres and material to energy production. 

The physical process, corona treatment, was applied in the kraft paper with different discharge dosages, while the chemical treatment was performed through the use of several alkali solutions with different concentrations of NaOH. The obtained results from the performed tests shows that the alkali solution treatments improved, up to 57%, the mechanical properties of tensile strength and Young Modulus of the composite material, comparatively with the effect of corona treatment on its surface. These results induce an increase of interface compatibility between the matrix and kraft paper.

En este trabajo se compara el comportamiento de una espuma de PVC comercial con corchos aglomerados de diferentes densidades. Se ha analizado la fuerza, desplazamiento, energía absorbida y velocidad de perforación. Se ha observado que el comportamiento del corcho aglomerado puede ser similar al de una espuma polimérica convencional, aunque con un incremento de peso. Adicionalmente se ha puesto de manifiesto que el corcho aglomerado puede ser una alternativa mejor a las espumas poliméricas en aquellas aplicaciones que puedan verse sometidas a varios impactos sucesivos.

Current bus structures present serious problems of fatigue due to their rigidity, resulting in unexpected failures in certain nodes where stresses are concentrated. This work is part of a project that it is trying to provide more elasticity to the structure through the use of a new CFRP node joined by adhesives to the bus structure using polyurethane.

The complex design of the node has caused numerous manufacturing problems. PLA node was manufactured using 3D printing for being used as a core. PLA node was covered layer by layer with CFRP by hand lay-up. In order to know the behavior of the whole set (CFRP node, adhesive and steel beams), four prototypes were manufactured and tested. Four point flexural test was carried out on the prototypes to validate the assembly. Results show the suitability and capacity of this new node concept to be used in bus structures.

In recent years exponential increase in the use of adhesives in industrial processes is observed. Nowadays these materials are used in applications as diverse as aerospace industry, automotive industry, railway industry or even civil construction. In the same way, the use of composite materials has grown enormously, especially in the aerospace industry, thanks to the benefits that this type of materials are able to provide, even as reinforcement.

Current bus structures present serious problems of fatigue due to their rigidity, resulting in unexpected failures in certain nodes where stresses are concentrated. This work is part of a project that it is trying to provide more elasticity to the structure through the use of a new CFRP node joined by adhesives to the bus structure using polyurethane.

The complex design of the node has caused numerous manufacturing problems. PLA node was manufactured using 3D printing for being used as a core. PLA node was covered layer by layer with CFRP by hand lay-up. In order to know the behavior of the whole set (CFRP node, adhesive and steel beams), four prototypes were manufactured and tested. Four point flexural test was carried out on the prototypes to validate the assembly. Results show the suitability and capacity of this new node concept to be used in bus structures.

In this last group, at least, three failure mechanisms must be taken into account: tension, shear and bearing. In each of these failure mechanisms, it must be verified that the component of the stress state responsible for the failure does not exceed a certain critical value that causes the failure.

In the case of riveted joints with composite materials, the task is doubly complex. On the one hand, the stress state in the neighbourhood of the hole is complex, not only because of the non-linearity of the problem (the contact of the rivet with the walls of the hole) but also because of the non-isotropic nature of the material. This makes the stresses to have a strong dependence on the type of fiber, stacking sequence, and in general, on the mechanical properties (non-isotropic) of the laminate. On the other hand, the determination of the critical values, associated with each component of the stress state, responsible for each failure mechanism, is difficult to obtain, due to the fact that these strength values also depend on the particular orientation along the hole contour, where they are evaluated.

In the present work, the stress state in the neighbourhood of the hole is evaluated in riveted joints with composite materials, analyzing different types of laminates, to serve as a basis for the prediction of the different failure mechanisms potentially acting.

From the in-plane displacement measurements, the in-plane strain tensor components and the corresponding CTE are determined. Results show that the presented technique is capable of determining these CTE with high accuracy.

Displacement measurements in the direction normal to the face, enables determining the rotation of the face and consequently the difference between the CTE in the thickness direction and the CTE in the in-plane direction affected by the curvature.

Results obtained for the CTE in the thickness direction show, first, values significantly higher than the CTE of the material in the in-plane direction normal to the fibres and, second, a high dispersion from one stacking sequence to another. These discrepancies were expected and are caused by the misalignment of the fibres in the corner zone of the samples.

For this reason, the objective is to replace lead or other heavy materials by boron PMCs with lower densities for the manufacture of radiological shields. For this purpose, low density polyethylene films and LDPE composite films with 15-30 and 60% wt. of boron were made. Films have been manufactured by hot extrusion and compression. The test that has been carried out is to calculate the shielding effect on the aluminum of these films using X-rays provided by a laboratory equipment used for the characterization of materials. The results have shown a greater shielding for a multilayer system, than a single one with the same thickness.

A numerical multiscale homogenization will be shown where the behavior of the whole composite is obtained by a micromechanical study of the material components and their interaction within of the composite microstructure through an RVE model. The proposed formulation uses a non-linear activation function in the structural scale and its task is to predict if a material point in the structure is in linear or non-linear range. Because of this, the developed strategy only solves the microscopic Boundary Value Problem using the RVE for the non-linear integration points found.

The procedure will be used in the nonlinear numerical simulaction of an eco-composite sanwich panel subjected to a four point bending test.

In the present study, a thermosetting matrix composed of UV-curable acrylic monomers and UV-transparent aluminium trihydrate (ATH) flame retardant fillers has been added to UV-transparent polyester resin for the manufacture of flame retardant composites. An in-depth study of the most suitable types of ATH-based flame retardant additives and possible synergistic combinations to improve the fire performance of the UV-curable composite has been carried out. Not only has the type of flame retardant been studied, but also the most suitable additive percentage to comply with railway sector regulations.

The compatibility between the fillers and the matrix has been analysed by means of dielectric analysis, as well as the properties of the matrix and final composites against fire and mechanical properties.