Abstract

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.

Abstract

Lightening vehicles has been and continues to be one of the main objectives of the automotive industry. On one hand, to reduce fuel consumption in internal combustion vehicles, and, on the other hand, to try to maximize the autonomy of electric vehicles. In this aspect, composite polymeric materials, such as Sheet Molding Compound (SMC) materials, play a decisive role; however, their use in structural parts requires appropriate design and simulation techniques. In order to maximize design possibilities, in the conceptualization phases of the product development process, topology optimization tools open many possibilities. Nevertheless, the use of this technique in SMC materials generates certain uncertainties due to the nature of the material.

In this context, in this work a metal part has been replaced by a version of it in SMC and topological optimization tools have been used in the conceptual design stage. The possible variants have been analyzed when entering the mechanical data of the material, due to its anisotropic nature, as well as the influence of temperature on them, due to the fact that in the working environment the piece is subjected to 130 ºC. To do this, samples of material have been molded and a mechanical characterization has been carried out to understand the behavior of the material with respect to fiber orientation and temperature. Then, using the PTC Creo design tool, a topological optimization and subsequent adaptation were carried out to improve the processability of the component. The most promising versions have been virtually validated using finite elements with Abaqus software.

In conclusion, this work has demonstrated the viability of using topology optimization techniques in the conceptual design of components with SMC materials. Furthermore, in combination with simulation techniques using finite elements, they have proven to be tools that reduce and perfect product development in composite materials.