A 3-D Finite Deformation Anisotropic Visco-Plasticity Model for Fiber Composites

Abstract

A 3-D finite deformation anisotropic visco-plasticity model is presented for fiber composites in total Lagrangian co-ordinates. The plastic potential function is given by a quadratic function in stresses in the local co-ordinates system of the lamina. The model is used to derive the anisotropic plastic constitutive relation of a woven composite made of S-2 glass fibers embedded in polyester resinwith approximately 60% by weight of fibers. The coefficients of the constitutive model are experimentally determined through off-axis tension tests and out-of-plane shear tests. Off-axis tension tests are carried out by varying the angle between the fiber orientation and loading direction. The measured stress-strain curves are used to derive a master effective stress–effective plastic strain curve, which is described by two power laws. Amodified Arcan fixture is used to carry out pure shear tests to determine the out-of-plane shear coefficient. Compression tests are carried out to establish the material compressive response in the plane of the lamina and along the fiber direction. The anisotropic plasticity model is integrated into the in-house finite element code FEAP98. Numerical analyses are carried out for the off-axis tension tests and compression tests. These analyses show that the model reasonably predicts the constitutive response of wovenGRPcomposites in confirmation with the experimental data. The model further incorporates strain rate and temperature dependence on the anisotropic plastic flow constitutive law. Ballistic penetration simulations are carried out using the integrated code. The velocity at the back surface of the composite target, obtained by analyses, is compared with the data measured experimentally using interferometry. Insight into the failure process is obtained through analysis of different energy dissipation mechanisms.