Numerical modelling of thermoplastic resin behaviour for thermoforming of laminates composed of non-crimp fabrics

Abstract

Although composite materials have been used for many years in aeronautic and defense industries, the interest in the automotive industry has grown only recently. However, since they are expensive, aeronautic materials cannot be directly used for automotive and new woven fiber composites are being developed such as Non-Crimp Fabrics (NCF) with thermoplastic resin. Woven fiber composite material properties depend on many parameters such as non-linearity of tensile stiffness in yarn direction, shearing effect between fibers, temperature and strain rate dependency. Numerical simulation becomes a helpful tool which can be used to estimate the risk of defects after forming. A reliable characterization of resin behavior with respect to the process temperature and speed will allow users to optimize the process and reduce development cycles. In this study, we investigate a method to model a NCF thermoplastic composite taking into account both thermal and strain rate dependency using the non-linear finite element solver RADIOSS®. A new multi-layer property is used to model the NCF resin and fabric components. Fibers are modeled with a hyper-elastic anisotropic fabric material model available in RADIOSS, and the resin is modelled as an elastoplastic thermal and strain-rate dependent material. The laminate behavior is characterized using data from Bias tests in two different directions and validated process simulation. A numerical study is used to show the influence of process temperature and speed on the final shape and presence of defects. The first section in your paper.