In-Plane Shear Characterisation of Uni-Directionally Reinforced Thermoplastic Melts

Intra-ply shear is an important mechanism in hot stamp forming processes of UD fibre reinforced thermoplastic laminates. Various methods have been developed to characterise this shear mechanism, but measured properties may differ for several orders of magnitude. Therefore, an alternative method to characterise the longitudinal shearing viscosity is presented. Straight fibre reinforced thermoplastic bars with a rectangular cross section are subjected to torsional loadings. The specimens' response can be used to characterise the shear properties of the fibre reinforced polymer melt. Different geometries and clamping conditions were modelled to show the sensitivity of the measured viscosity. Based on this, experiments were performed with thick bars with a PEI-AS4 and PEEK-AS4 composition. Frequency sweeps were applied at different temperatures. All measurements showed a clear shear thinning behaviour, which can conveniently be described with a power law model