A two-phase integrated flow-stress process model for composites with application to highly compressible phases

A new methodology is presented to integrate the simulation of flow and stress development into a unified computational modelling framework for processing of two-phase composite materials. The governing equations are developed for the general case of a composite material system that, as a consequence of curing, undergoes a transition from a fluid-like state into an elastic solid. The constitutive equations employed are such that they provide a continuous representation of the evolving material behaviour while maintaining consistency with the formulations that are typically used to represent the material at each of the two extremes. The formulation is capable of handling highly compressible phases, which is an important consideration when extending the model to a three-phase model that includes gas as a distinct phase. The model is implemented in a 2D plane strain u-v-P finite element code developed in MATLAB. Numerical examples are presented to demonstrate the capability of the integrated flow-stress model to predict the flow-compaction and stress development throughout the curing process of thermoset composite materials. The interactive effects of resin flow and stress development under various representative boundary conditions are investigated and comparisons are made with the predicted results obtained from the application of the stress model alone.