Silva et al 2022a - Revision history

Materiales.Compuestos at 18:42, 10 December 2022

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Materiales.Compuestos at 18:41, 10 December 2022

2022-12-10T18:41:52Z

Materiales.Compuestos: Materiales.Compuestos moved page Review 575365408416 to Silva et al 2022a

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Materiales.Compuestos moved page Review 575365408416 to Silva et al 2022a

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Materiales.Compuestos moved page Draft Compuestos 661203933 to Review 575365408416

Materiales.Compuestos at 08:00, 16 June 2022

2022-06-16T08:00:45Z

Materiales.Compuestos: Created page with "
Jorge Nuno Silva^a, Luís Pina^a, Susana Sousa^a

2022-06-16T07:56:16Z

Created page with " <div class="center" style="width: auto; margin-left: auto; margin-right: auto;"> Jorge Nuno Silva<sup>a</sup>, Luís Pina<sup>a</sup>, Susana Sousa<sup>a</sup> </div> <div..."

New page

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
Jorge Nuno Silva<sup>a</sup>, Luís Pina<sup>a</sup>, Susana Sousa<sup>a</sup> </div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;"><sup>a</sup> INEGI – Pólo FEUP, Rua Dr. Roberto Frias, 400, 4200-465 Porto, Portugal</span></div>

{| style="width: 87%;border-collapse: collapse;"
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| colspan='2' style="vertical-align: top;"|<big>Proceso de hibridación del moldeo con hoja de compuesto de fibra de carbono con preimpregnados de fibra de carbono: un estudio de caso</big>
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| style="border-bottom: 1pt solid black;vertical-align: top;"|<span style="text-align: center; font-size: 75%;"> [[Image:Draft_Compuestos_661203933-image1.png|54px]] </span>
| style="vertical-align: top;"|
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| style="border-top: 1pt solid black;border-bottom: 1pt solid black;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Historia del artículo:</span>

<span style="text-align: center; font-size: 75%;">Recibido 7 de Junio de 2019</span>

<span style="text-align: center; font-size: 75%;">En la versión revisada 20 de Junio de 2019</span>

<span style="text-align: center; font-size: 75%;">Aceptado 5 de Julio de 2019</span>

<span style="text-align: center; font-size: 75%;">Accesible online 19 de Julio de 2021</span>
| rowspan='4' style="vertical-align: top;"|<span style="text-align: center; font-size: 75%;">El objetivo principal de este trabajo fue mostrar la viabilidad técnica de un proceso tradicional de Moldeo con Hoja de Compuesto hibridado con refuerzos pre impregnados de fibra de Carbono, en una estructura demostrativa de asientos para automóviles. El nuevo asiento reforzado es más liviano, tiene mejor resistencia mecánica al impacto y el típico aspecto visual de fibra de carbono en las áreas reforzadas. Actualmente, la estructura del asiento está compuesta por la solución híbrida y las matrices de ambos materiales son de material epoxi, por lo </span><span style="text-align: center; font-size: 75%;">tanto, compatibles, lo que promueve una buena adherencia en las condiciones de procesamiento correctas. Para garantizar la viabilidad de esta hibridación, se llevó a cabo una extensa campaña de pruebas de laboratorio en una prensa de placas calientes, a nivel de laboratorio, para estudiar la dinámica del flujo del compuesto de moldeo de hojas durante el proceso y cómo interactúa con las preformas pre impregnadas. El proceso de curado de ambos materiales también se analizó para establecer los perfiles de temperatura óptimos. Finalmente, las pruebas mecánicas se realizaron de acuerdo con la norma ASTM D 5868-01 para evaluar las propiedades mecánicas de la unión entre los dos materiales.</span><span style="text-align: center; font-size: 75%;">El prototipo de asiento de automóvil reforzado se validó de acuerdo con las pruebas de impacto ECE-R17 y FMVSS202a en el reposacabezas y se logró una reducción del 25% en el peso total. Se espera que el costo del ciclo de vida y los beneficios del aspecto visual compensen el costo de fabricación ligeramente más alto en relación con la pieza original debido al costo del material pre impregnado. Se requerirá investigación adicional en términos de automatización de procesos para garantizar la calidad de proceso requerida</span><span style="text-align: center; font-size: 75%;">. </span>

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| style="border-top: 1pt solid black;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Palabras clave:</span>

<span style="text-align: center; font-size: 75%;">Compuesto</span>

<span style="text-align: center; font-size: 75%;">Estructura del asiento de automóvil</span>

<span style="text-align: center; font-size: 75%;">Automatización </span>

<span style="text-align: center; font-size: 75%;">SMC</span>

<span style="text-align: center; font-size: 75%;">Prepreg de fibra de carbono</span>
|-
| style="border-top: 1pt solid black;vertical-align: top;"|
|-
| colspan='2' style="vertical-align: top;"|<big>Hybridization Process of Carbon Fibre Sheet Moulding Compound with Carbon Fibre Prepregs: a Case Study </big>
|-
| style="border-bottom: 1pt solid black;vertical-align: top;"|<span style="text-align: center; font-size: 75%;"> [[Image:Draft_Compuestos_661203933-image2.png|54px]] </span>
| style="vertical-align: top;"|
|-
| style="border-top: 1pt solid black;border-bottom: 1pt solid black;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">Keywords:</span>

<span style="text-align: center; font-size: 75%;">Composite</span>

<span style="text-align: center; font-size: 75%;">Car Seat Structure</span>

<span style="text-align: center; font-size: 75%;">Automation </span>

<span style="text-align: center; font-size: 75%;">SMC</span>

<span style="text-align: center; font-size: 75%;">Carbon-fibre prepreg</span>
| rowspan='2' style="vertical-align: top;"|<span style="text-align: center; font-size: 75%;">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.</span>
|-
| style="border-top: 1pt solid black;vertical-align: top;"|
|}

==1 Introduction==

The modern automobile industry is constantly facing with new requirements associated to recyclable, fuel-efficient, safety, and low-emission vehicles. In order to give answers to these issues, vehicle manufacturers have been focusing in developing lightweight advanced materials in order to reduce the overall vehicle mass and decrease the negative environmental impacts during use phase. Although, reducing the overall weight of modern automobiles with a decrease processing time and cost, ensuring the affordability of the vehicles is a challenge. Affordability is essential since it will allow for larger portion of the vehicle manufacturers to adopt specific light weighting solutions [1, 2].

Sheet moulding compound (SMC), is a widely used process of the automotive sector, due to its capability to produce thermoset based components with discontinuous glass fibre reinforced composites with an acceptable specific stiffness and strength, combined with a cost-efficient manufacturing process and high formability. To continue to enhance material properties of SMC products and to meet the increasing interest in this material class, different approaches recently focused on combining this process with carbon fibres, particular in aerospace applications. However, the combination of oriented, continuous carbon fibres prepregs with traditional SMC represents a new technology approach for automobile production and automotive engineering [3-6].

Therefore, with this hybrid composite technology would be possible to guarantee a very high productivity, excellent part reproducibility, cost efficiency, and produce lighter/stronger components with complex geometries and integrated functions. With this knowledge, the main objective of this work is to show the technical viability of a traditional SMC process, hybridized with carbon fibre prepreg, in a demonstrative car seat structure (<span id='cite-_Ref10466472'></span>[[#_Ref10466472|Figure 1]]).

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
[[Image:Draft_Compuestos_661203933-image5-c.png|348px]] </div>

<div id="_Ref10466472" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 1. '''Back view of the headrest structure</span></div>

Mechanical properties were analysed and quantified by lap shear adhesion and impact tests. The visual aspect of the final prototype was also studied in this research work.

==2 <br/>Materials and Methods==

==='''2.1''' Raw materials and manufacturing procedures===

A commercially available carbon prepreg, with trade name Pyrofil™, and an epoxy matrix were used to produce the headrest structure.

Unidirectional carbon prepreg (30 wt. % of resin content) was used as reinforcement and woven fabric (40 wt. % of resin content) was the last layer added to give a good visual finishing.

The prototype was produced in two phases:

:1. Prepreg compression moulding (PCM) manufacturing process

:2. Hybrid composite manufacture

In the first phase, the prepreg layers were stacked up and formed to a pre-shape, which was similar to the final one. This phase can be summarized in the following steps (Figure 2):

:1. Cut the desired shape - Cutting the layers of prepreg, from the prepreg rolls, to the desired shape and orientation;

:2. Stacking the prepreg and mould positioning - Stacking the prepreg layers to the desired combination and positioning on the proper position on the mould;

:3. Heating - Has a purpose to soften the material for the pressing step;

:4. Compression - The different prepreg layers are compressed together, cooled down and shapped to a close to the final shape;

:<span style="text-align: center; font-size: 75%;">5.
[[Image:Draft_Compuestos_661203933-image6.png|center|600px]]
</span>Vacuum - A vacuum membrane is lowered on top of the post-compression PCM part and, after membrane is fully lowered, it is applied vacuum to the PCM, where the void concentration/percentage is reduced and the PCM parts are demoulded.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 2.''' Preparation of the PCM</span></div>

After obtaining the PCM, the carbon fibre sheet moulding compound (CF-SMC) composites are combined together to obtain the desired hybrid headrest structure. This 2<sup>nd</sup> phase can be synthesised in the subsequent steps (Figure 3):

:1. PCM + CF-SMC placement - Placement PCM headrest structure on the mould and the CF-SMC charges;

:2. Compression - The upper and lower moulds are set to a specific temperature that allows for the proper CF-SMC flow within the mould, fill the part correctly and ensure the bonding of the two composite materials. The temperature combined with pressure and time, will ensure the cure of the resin and give the part its final shape;

:3. Demoulding - Demoulding the compound in its final shape and in an advanced cure state;

:4. Trimming - After demoulding the part there are some sharp edges and excess material that needs trimming afterwards in order to be able to deliver a finished part.

<div id="_Ref10474034" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">''' [[Image:Draft_Compuestos_661203933-image7.png|600px]] '''</span></div>

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 3. '''Hybrid composite manufacture</span></div>

During the manufacturing process, there are a few defects that can occur and that should be taken into consideration when optimizing the parameters, mould special characteristics, shapes, material placement and quantities.

==='''2.2''' Tests procedures===

In order to test and validate the resistance of the bonding areas, it were used the principles according to the test procedure described in standard ASTM D 5868-01 [7]. Three specimens with an overlay of 25 x 25 mm, for each bonding condition (<span id='cite-_Ref10531697'></span>[[#_Ref10531697|Table 1]]), were tested at a constant loading rate of 1,3 mm/min. These tests were carried out in a universal mechanical testing machine (INSTRON 4208), equipped with a 100 kN load cell (<span id='cite-_Ref10477065'></span>[[#_Ref10477065|Figure 4]]). All specimens were previously conditioned at 23°C/50% RH for 24 hours before testing.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 1. '''Tested specimens</span></div>

{| style="width: 100%;border-collapse: collapse;"
|-
| style="border: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Type'''</span>
| style="border: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Standard '''</span>
| style="border: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Hybrid '''</span>
|-
| style="border: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Material combination'''</span>
| style="border: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">CF-SMC</span>
| style="border: 1pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">CF-SMC + CF-prepregs</span>
|}

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
[[Image:Draft_Compuestos_661203933-image8.png|258px]] </div>

<div id="_Ref10477065" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 4. '''Set-up used for the lap-shear test analysis</span></div>

Visual inspection of the prototype has been performed to ensure that it was free from the unacceptable defects according to ASTM D 2563-08, beaning the most relevant visual defects are porosity, wash and wrinkles [8].

Impact tests were performed in the prototype (<span id='cite-_Ref10534417'></span>[[#_Ref10534417|Figure 5]]) to ensure that it follows the requirements of ECE-R17 and FMVSS202a [9, 10].

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">

{|
|-
| [[Image:Draft_Compuestos_661203933-image9-c.jpeg|150px]]
| [[Image:Draft_Compuestos_661203933-image10-c.jpeg|center|420px]]
|}
</div>

<div id="_Ref10534417" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 5. '''Set-up used for the impact test analysis</span></div>

==3 Experimental Results and Discussion==

==='''3.1''' Data test results===

Lap-shear test results, in terms of maximum strength (F<sub>max</sub>), maximum deflection (d<sub>max</sub>) and maximum stress (σ<sub>max</sub>) are summarized in Table 2. Presented values represent the average values obtained for 3 specimens of each trial formulation and correspondent standard deviations.

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Table 2. '''Lap-shear test results</span></div>

{| style="width: 100%;border-collapse: collapse;"
|-
| style="border-bottom: 1pt solid black;border-right: 1pt solid black;text-align: center;"|
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">'''Standard'''</span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">'''Hybrid'''</span>
|-
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">'''F<sub>max</sub>'''</span><span style="text-align: center; font-size: 75%;">''' [N]'''</span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">1485.28 ± 104.07 </span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">4096.69 ± 159.99</span>
|-
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">'''d<sub>max</sub>'''</span><span style="text-align: center; font-size: 75%;">'''[mm]'''</span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">4.01 ± 0.98</span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">1.39 ± 0.19</span>
|-
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">'''σ<sub>max</sub>'''</span><span style="text-align: center; font-size: 75%;">'''[N/mm<sup>2</sup>'''</span><span style="text-align: center; font-size: 75%;">''']'''</span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">1.28 ± 0.04 </span>
| style="border: 1pt solid black;text-align: center;"|<span style="text-align: center; font-size: 75%;">6.73 ± 1.21</span>
|}

The detected visual defects in the final prototype are shown in <span id='cite-_Ref10538346'></span>[[#_Ref10538346|<span style="text-align: center; font-size: 75%;">Figure 6</span>]].

[[Image:Draft_Compuestos_661203933-image11-c.png|600px]]

<div id="_Ref10538346" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 6. '''Visual defects</span></div>

In the impact tests, it was verified that the headrest have accomplish the standard requirements.

==='''3.2''' Analysis and discussion===

The hybrid solution leads to an increase on peak load of approximately 176%, when compared with the standard solution. The hybrid materials lead to a lower axial displacement (-65%), which may indicate a higher specific stiffness around the bonded area (<span id='cite-_Ref10540707'></span>[[#_Ref10540707|Figure 7]]).

{| style="width: 48%;margin: 1em auto 0.1em auto;border-collapse: collapse;"
|-
| style="text-align: center;vertical-align: top;width: 0%;"|[[Image:Draft_Compuestos_661203933-image12-c.jpeg|96px]]
| style="text-align: center;vertical-align: top;"|
| style="text-align: center;vertical-align: top;"|
| style="text-align: center;vertical-align: top;width: 0%;"|[[Image:Draft_Compuestos_661203933-image13-c.jpeg|90px]]
|-
| style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Standard'''</span>
| style="text-align: center;vertical-align: top;"|
| style="text-align: center;vertical-align: top;"|
| style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Hybrid'''</span>
|}

<div id="_Ref10540707" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 7. '''Typical fracture/damage of the tested specimens</span></div>

It was observed that most relevant visual defects indicated in the ASTM D 2563-08 were not detected in the prototype. Although it was observed three defects:

:1. Weave distortion - Most likely due to wrong CF-SMC charges placement and poor PCM shape design.

:2. Bonding – Probably several parameters lead to this defect, such as setup of the machines, CF-SMC placement, PCM shape or fault on the compression area.

:3. Resin concentration spots – Is mainly caused by the CF-SMC placement and flow.

Overall, it can be considered that the visual aspect requirement it was achieved. In Figure 8 can be observed the standard and the hybrid headrest structure. Although the visual quality of the developed prototype can be improved.

{| style="width: 100%;border-collapse: collapse;"
|-
| style="text-align: center;vertical-align: top;width: 51%;"|[[Image:Draft_Compuestos_661203933-image14-c.png|276px]]
| style="text-align: center;vertical-align: top;width: 48%;"|[[Image:Draft_Compuestos_661203933-image15-c.png|264px]]
|-
| style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Standard'''</span>

| colspan='2' style="text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">'''Hybrid'''</span>

|}

<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<span style="text-align: center; font-size: 75%;">'''Figure 8. '''Headrest structures</span></div>

After the impact tests it was observed that the standard solutions and the hybrid prototype were undamaged. Although, the hybrid solution is 25% lighter that the standard one but is three times more expensive due to the new materials used and an increase on the more processes that need to take place to produce the hybrid prototype.

==4 Conclusions==

There is a huge world concern with the environment sustainability and European legislation has been changing tending to restrict levels of pollution in industry and the mobility of automobiles. With this knowledge, automotive industry has been absorbed the lighter advanced composite materials and technologies from aeronautic sector to improve the performance of the components.

Experiments were performed in order to demonstrate the technical viability of a traditional SMC process hybridized with Carbon fibre prepreg reinforcements (typical aeronautical solution), in a demonstrative car seat structure. The SMC process presented within this study enabled the manufacturing of hybrid carbon fibre SMC sheets based on two-steps. The developed solution was compared with the conventional one. The key findings of the developed testing programme are as follows:

:* Properties in terms of maximum adhesion force as well as failure evolution were investigated. The developed hybrid solution leads, in general, to significant increase of the adhesion properties and a higher specific stiffness around the bonded area;

:* Few visual defects that were observed are likely related to the mould, which causes small distortions on the twill. It can be considered that the visual aspect requirements were achieved;

:* Both standard and hybrid headrest structures accomplish the impact requirements;

:* The hybrid solution is 25% lighter and 3 times more expensive that the standard one.

Therefore, with the results obtained in this research is possible to verify that the development of the combination of SMC and pre-impregnated, orientated carbon fibre fabrics is auspicious referring to an improvement of adhesion properties. Besides, this technology promises optimised lightweight and load-bearing properties in connection with complex shapes and design freedom. However, for automotive applications there does not exist a one special SMC hybrid technology. Consequently, each material combination has to be developed and adapted to the requirements for each particular application.

However, for now, the process is very time consuming due to the preparation required per each moulding. 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. Although there are many open questions regarding this innovative, hybrid SMC technology. Further research will be needed to in terms of process automation to ensure the required process quality.

==Acknowledgements==

This work was performed under the AEROCAR project, co-financed by the Interreg Sudoe Program through the European Regional Development Fund (ERDF).

“Authors gratefully acknowledge the funding of Project NORTE-01-0145-FEDER-000022 - SciTech - Science and Technology for Competitive and Sustainable Industries, cofinanced by Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER)”.

==References==

[1] D. Mayer, T. Bein, H. Buff, B. Gotz, O. Schwarzhaupt, and D. Spancken, "Enhanced lightweight design by composites - Results of the EU project ENLIGHT," ''Journal of Reinforced Plastics and Composites'', Article '''37''', no. 19, pp. 1217-1224. (2018).

[2] V. K. Soo, P. Compston, and M. Doolan, "Interaction between New Car Design and Recycling Impact on Life Cycle Assessment," ''Procedia CIRP'', '''29''', pp. 426-431. (2015).

[3] S. B. Visweswaraiah, M. Selezneva, L. Lessard, and P. Hubert, "Mechanical characterisation and modelling of randomly oriented strand architecture and their hybrids - A general review," ''Journal of Reinforced Plastics and Composites'', Review '''37''', no. 8, pp. 548-580. (2018).

[4] A. Trauth, K. A. Weidenmann, and W. Altenhof, "Puncture properties of a hybrid continuous-discontinuous sheet moulding compound for structural applications," ''Composites Part B-Engineering'', Article '''158''', pp. 46-54. (2019).

[5] J. Wulfsberg, A. Herrmann, G. Ziegmann, G. Lonsdorfer, N. Stoss, and M. Fette, "Combination of carbon fibre sheet moulding compound and prepreg compression moulding in aerospace industry," in ''11<sup>th</sup> International Conference on Technology of Plasticity'', Ictp 2014, '''81''', T. Ishikawa and K. I. Mori, Eds. (Procedia Engineering, Amsterdam: Elsevier Science Bv, pp. 1601-1607. (2014).

[6] W. White Salmon, A. L. SpA, and I. Sant’Agata Bolognese, "Lamborghini “forged composite®” technology for the suspension arms of the sesto elemento,". (2011).

[7] ASTM D5868-01(2014), Standard Test Method for Lap Shear Adhesion for Fiber Reinforced Plastic (FRP) Bonding, ''ASTM International'', West Conshohocken, PA. (2014).

[8] ASTM D2563-08(2015), Standard Practice for Classifying Visual Defects in Glass-Reinforced Plastic Laminate Parts, ''ASTM International'', West Conshohocken, PA. (2015).

[9] Agreement Concerning the Adoption of Uniform Technical Prescriptions for Wheeled Vehicles, Uniform Provisions Concerning the Approval of Vehicles with Regard to the Seats, their Anchorages and Any Head Restraints. (2014).

[10] H. A. Kaleto, H. W. Mangum, P. Lee, and M. Schick, "Overview of Federal Motor Vehicle Safety Standard (FMVSS) 202A-Head Restraints: Methodology and Equipment for the Dynamic Test," ''SAE Technical Paper'' 0148-7191. (2007).

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−	~~\| colspan='2' style="vertical-align: top;"\|<big>Proceso de hibridación del moldeo con hoja de compuesto de fibra de carbono con preimpregnados de fibra de carbono: un estudio de caso</big>~~
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−	~~\| style="border-bottom: 1pt solid black;vertical-align: top;"\|<span style="text-align: center; font-size: 75%;"> [[Image:Draft_Compuestos_661203933-image1.png\|54px]] </span>~~
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−	~~\| style="border-top: 1pt solid black;border-bottom: 1pt solid black;vertical-align: top;"\|<span style="text-align: center; font-size: 75%;">Historia del artículo:</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Recibido 7 de Junio de 2019</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">En la versión revisada 20 de Junio de 2019</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Aceptado 5 de Julio de 2019</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Accesible online 19 de Julio de 2021</span>~~
−	\| rowspan='4' style="vertical-align: top;"\|<span style="text-align: center; font-size: 75%;">El objetivo principal de este trabajo fue mostrar la viabilidad técnica de un proceso tradicional de Moldeo con Hoja de Compuesto hibridado con refuerzos pre impregnados de fibra de Carbono, en una estructura demostrativa de asientos para automóviles. El nuevo asiento reforzado es más liviano, tiene mejor resistencia mecánica al impacto y el típico aspecto visual de fibra de carbono en las áreas reforzadas. Actualmente, la estructura del asiento está compuesta por la solución híbrida y las matrices de ambos materiales son de material epoxi, por lo </span><span style="text-align: center; font-size: 75%;">tanto, compatibles, lo que promueve una buena adherencia en las condiciones de procesamiento correctas. Para garantizar la viabilidad de esta hibridación, se llevó a cabo una extensa campaña de pruebas de laboratorio en una prensa de placas calientes, a nivel de laboratorio, para estudiar la dinámica del flujo del compuesto de moldeo de hojas durante el proceso y cómo interactúa con las preformas pre impregnadas. El proceso de curado de ambos materiales también se analizó para establecer los perfiles de temperatura óptimos. Finalmente, las pruebas mecánicas se realizaron de acuerdo con la norma ASTM D 5868-01 para evaluar las propiedades mecánicas de la unión entre los dos materiales.</span><span style="text-align: center; font-size: 75%;">El prototipo de asiento de automóvil reforzado se validó de acuerdo con las pruebas de impacto ECE-R17 y FMVSS202a en el reposacabezas y se logró una reducción del 25% en el peso total. Se espera que el costo del ciclo de vida y los beneficios del aspecto visual compensen el costo de fabricación ligeramente más alto en relación con la pieza original debido al costo del material pre impregnado. Se requerirá investigación adicional en términos de automatización de procesos para garantizar la calidad de proceso requerida</span><span style="text-align: center; font-size: 75%;">. </span>
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−	~~\| style="border-top: 1pt solid black;vertical-align: top;"\|<span style="text-align: center; font-size: 75%;">Palabras clave:</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Compuesto</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Estructura del asiento de automóvil</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Automatización </span>~~
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−	~~<span style="text-align: center; font-size: 75%;">SMC</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Prepreg de fibra de carbono</span>~~
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−	~~\| style="border-top: 1pt solid black;vertical-align: top;"\|~~
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−	~~\| colspan='2' style="vertical-align: top;"\|<big>Hybridization Process of Carbon Fibre Sheet Moulding Compound with Carbon Fibre Prepregs: a Case Study </big>~~
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−	~~\| style="border-bottom: 1pt solid black;vertical-align: top;"\|<span style="text-align: center; font-size: 75%;"> [[Image:Draft_Compuestos_661203933-image2.png\|54px]] </span>~~
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−	~~\| style="border-top: 1pt solid black;border-bottom: 1pt solid black;vertical-align: top;"\|<span style="text-align: center; font-size: 75%;">Keywords:</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Composite</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Car Seat Structure</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Automation </span>~~
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−	~~<span style="text-align: center; font-size: 75%;">SMC</span>~~
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−	~~<span style="text-align: center; font-size: 75%;">Carbon-fibre prepreg</span>~~
−	\| rowspan='2' style="vertical-align: top;"\|<span style="text-align: center; font-size: 75%;">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.</span>
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−	~~\| style="border-top: 1pt solid black;vertical-align: top;"\|~~
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	==1 Introduction==		==1 Introduction==

@@ Line 39: / Line 39: @@
 :4. Compression - The different prepreg layers are compressed together, cooled down and shapped to a close to the final shape;
-:<span style="text-align: center; font-size: 75%;">5.
+:5. Vacuum - A vacuum membrane is lowered on top of the post-compression PCM part and, after membrane is fully lowered, it is applied vacuum to the PCM, where the void concentration/percentage is reduced and the PCM parts are demoulded.
 [[Image:Draft_Compuestos_661203933-image6.png|center|600px]]
 <div class="center" style="width: auto; margin-left: auto; margin-right: auto;">

@@ Line 11: / Line 11: @@
 <div id="_Ref10466472" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 1. '''Back view of the headrest structure</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 1. '''Back view of the headrest structure.</span></div>
 Mechanical properties were analysed and quantified by lap shear adhesion and impact tests. The visual aspect of the final prototype was also studied in this research work.
@@ Line 44: / Line 44: @@
 <div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 2.''' Preparation of the PCM</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 2.''' Preparation of the PCM.</span></div>
 After obtaining the PCM, the carbon fibre sheet moulding compound (CF-SMC) composites are combined together to obtain the desired hybrid headrest structure. This 2<sup>nd</sup> phase can be synthesised in the subsequent steps (Figure 3):
@@ Line 60: / Line 60: @@
 <div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 3. '''Hybrid composite manufacture</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 3. '''Hybrid composite manufacture.</span></div>
 During the manufacturing process, there are a few defects that can occur and that should be taken into consideration when optimizing the parameters, mould special characteristics, shapes, material placement and quantities.
@@ Line 87: / Line 87: @@
 <div id="_Ref10477065" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 4. '''Set-up used for the lap-shear test analysis</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 4. '''Set-up used for the lap-shear test analysis.</span></div>
 Visual inspection of the prototype has been performed to ensure that it was free from the unacceptable defects according to ASTM D 2563-08, beaning the most relevant visual defects are porosity, wash and wrinkles [8].
@@ Line 103: / Line 103: @@
 <div id="_Ref10534417" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 5. '''Set-up used for the impact test analysis</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 5. '''Set-up used for the impact test analysis.</span></div>
 ==3 Experimental Results and Discussion==
@@ Line 139: / Line 139: @@
 <div id="_Ref10538346" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 6. '''Visual defects</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 6. '''Visual defects.</span></div>
 In the impact tests, it was verified that the headrest have accomplish the standard requirements.
@@ Line 162: / Line 162: @@
 <div id="_Ref10540707" class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 7. '''Typical fracture/damage of the tested specimens</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 7. '''Typical fracture/damage of the tested specimens.</span></div>
 It was observed that most relevant visual defects indicated in the ASTM D 2563-08 were not detected in the prototype. Although it was observed three defects:
@@ Line 189: / Line 189: @@
 <div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
-<span style="text-align: center; font-size: 75%;">'''Figure 8. '''Headrest structures</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 8. '''Headrest structures.</span></div>
 After the impact tests it was observed that the standard solutions and the hybrid prototype were undamaged. Although, the hybrid solution is 25% lighter that the standard one but is three times more expensive due to the new materials used and an increase on the more processes that need to take place to produce the hybrid prototype.

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