Elevated-Temperature Creep Buckling of Thermoplastic-Matrix Fiber Composites under Biaxial Loading

Abstract

An analytical study has been conducted to investigate the elevated- temperature creep buckling behavior of thermoplastic-matrix composite laminates sub jected to multiaxial loading. Anisotropic time-temperature dependent viscoelastic consti tutive equations of the composite are constructed first, using the experimental results and the modified Prony series expansion solution. Creep buckling loads and associated creep failure times are determined by a time-dependent bifurcation buckling analysis of the ther moplastic composite laminates under general loading in an elevated-temperature environ ment. Detailed solutions for high-temperature creep buckling and associated failure mode shapes of the AS4/J1 thermoplastic composite laminates with various fiber orientations are obtained. The creep buckling mode shape changes and the accompanying failure loads are studied for three commonly encountered loading modes: (1) pure shear, (2) biaxial compression with any arbitrary stress biaxiality ratios, and (3) combined axial compres sion and shear loading.