Numerical Modeling of Micro-Mechanical Residual Stresses in Carbon-Epoxy Composites During the Curing Process.

Abstract

This article analyzes the residual stresses generated during the curing process of thermoset composites. Specifically, a numerical procedure is developed and implemented in Ansys 18.0 to evaluate, at the micromechanical level, the residual stresses in a carbon epoxy composite that undergoes the process of curing. The viscoelastic behavior of the epoxy material is modeled using a formulation recently published by the same authors. It accounts for the concurrent effect of curing and structural relaxation on epoxy's relaxation times, assuming thermo-rheological and thermo-chemical simplicities. The model validated for the neat epoxy matrix is now tested against the composite application. Various representative volume element (RVE) arrangements and fiber fractions are examined. The proposed procedure can predict the evolution of mechanical properties (apparent stiffness and creep compliance) and the residual stresses that develop in each composite constituent during the cure. It demonstrates that the residual stresses in the matrix are a consistent fraction of an epoxy's nominal strength and significantly influence the transverse mechanical properties of the composite.