Effect of Defects on the Mechanical Properties of Virtually Cured Composite Structures

Abstract

This paper addresses the effects of defects occurring during the manufacturing process on mechanical performance of Polymer Matrix Composites (PMCs). Damage accumulation during cure and subsequent in-service performance are studied by using randomly packed Repeating Unit Cell (RUC) representative of unidirectional fiber ply material or a textile fiber tow, at the microstructural level. Computations are carried out using the Finite Element (FE) method within the commercial code ABAQUS in which constitutive models are implemented via user-written subroutines. The transition from a continuum to damage and failure is determined by using the Bažant-Oh crack band model. Results are presented for RUCs that are first subjected to curing and subsequently to mechanical loading in the transverse direction. The analysis shows the differences in both the cured RUC transverse strength, S , and stiffness, E , when cure induced damage and imperfections such as presence of voids, fiber contact, imperfect fiber/matrix bonding and presence of matrix pockets are considered.