Forming predictions of UD reinforced thermoplastic laminates

Abstract

A preliminary study was made of the thermoforming process of UD fibre reinforced thermoplastic laminates. Deformation mechanisms of the ply and the laminate were identified. Forming experiments were performed with a single dome to support this study. The experiments were also used to validate the forming predictions with finite element analyses. The laminates were modelled with Discrete Kirchoff Triangles combined with multiple membrane elements to describe the in-plane behaviour. The Ideal Fibre Reinforced Newtonian fluid Model was employed for the membrane terms, involving transverse and longitudinal viscosities. Different characterisation methods show large variations in magnitude of the measured viscosities. The effect of these variations on the forming predictions has been examined. A large effect was observed for cross-ply laminates, whereas the differences for the quasi-isotropic laminates were smaller. Moreover, wrinkling predictions show good agreement with the experiments.