Abstract
An elastic-plastic material model for simulating the crush behaviour of random fibre reinforced thermoset composites is presented. The model is intended to allow efficient simulation of the crash behaviour of thin walled composite structures. It is implemented for shell elements where a single shell represents the entire laminate. The model consists of three parts: an elastic model, a failure criterion, and a post-failure behaviour. The elastic portion is linear elastic orthotropic and uses the plane stress assumption. Failure is predicted using the Tsai-Hill criterion which is implemented in such a way that independent failure strengths can be used in tension, compression and shear. Post-failure behaviour is modelled with piecewise linear plastic yielding. The model allows the user to input three independent curves, one each for tension, compression and shear, with hardening, softening or perfectly plastic behaviour. Finally elements can be eliminated using a strain based elimination criterion. This model is implemented in the ABAQUS/Explicit finite element package using the VUMAT user defined subroutine.
The model was compared to experimental results. Tubes were crushed at quasi-static rates onto plug type initiators with different fillet radii. These tests were then modelled using the user-defined material. The deformed shape and load-displacement responses matched experimental results well. A sensitivity study was performed using the model and showed that the tensile post failure behaviour had the strongest influence on the crush response.