Mechanical optimization of a pultruded thermoplastic composite profile
Résumé
The context of this study is a French national research program called Defi Composite (Airbus-France-led consortium) which aims to develop carbon fibre based composites structures. By providing research and development facilities, the CEMCAT (French technical center dedicated to the improvement of advanced composite materials) participate to a work package dedicated to the enhancement of thermoplastic pultrusion process. This process offers recyclability and productivity advantages over its conventional thermoset counterpart. In this paper, a numerical contribution to this project is presented. Pultrusion technology basically consists of pulling a number of impregnated fibre tows through a heated die; it is simple in concept but complex in detail. Indeed, nature doesn't use solid homogeneous materials and this is the very essence of composite materials: put stiff fibres in the right place with the right orientation and volume fraction. Taking advantage of such a process and through a closed optimization loop, the study aimed at finding the best fibre distribution for a composite profile; the latter exhibiting antagonistic flexural stiffness and flexibility in torsion. We use anisotropic elasticity theory, finite element analysis and genetic algorithms to design an optimal structure with respect to performances, manufacturability and costs. This means that making the composite material at the microscale, we also make the final engineering component. Such an optimization process is always multi-objective but succeeds to guide us towards the specified requirements with originality in fibre distribution.