Process induced stress for woven fabric thick section composite structures

Abstract

A semi-numerical model was developed to simulate processing induced stress for woven fabric composite material structures. The approach consists three main parts. The first part was the simulation of resin chemical kinetic cure behavior and micromechanics for cure dependent resin and glass fiber. The second was the analytical extension of TEXCAD woven fabric micromechanics model (Naik RA. TEXCAD-Textile Composite Analysis for Design. NASA report 4639, December 1994) to cure dependent textile unit cell model. The last was the introducing of the effective unit cell properties to finite element structure modeling. Cure dependent material response includes thermoset resin hardening and volumetric shrinkage during cure. The approach was incrementally employed whereby the model predicts the composite fabric unit cell effective modulus, processing-induced strains and stresses (thermal expansion and chemical shrinkage) during cure. Case studies were presented which illustrate the effective modulus and processing stress/strain development during cure for a plain weave S2-glass/vinyl–ester composite laminate. An understanding of the complex relationships between cure, modulus and processing-induced stress/strain development represents a significant step towards optimizing processing strategies for thick-section woven fabric composite structures.