Effect of irradiation swelling on the mechanical properties of unidirectional SiC/SiC composites: A numerical investigation at microstructural level

Abstract

In order to apply SiC/SiC composites in nuclear systems, it is essential to understand the potential effects of dimensional changes induced by neutron irradiation on property degradation. A microscale model has been developed to predict the mechanical behaviour of irradiated fibre composites, including matrix cracking and interface debonding. The present work investigated the states of residual stresses and damage that may be induced by swelling mismatch between fibres and matrix, and their subsequent effects on the transverse and longitudinal tensile mechanical properties of composites. Unidirectional (UD) composites with various fibre contents and porosities were subject to different swelling mismatch to simulate irradiation-induced dimensional changes. The composites were then virtually tested in tension to determine the modulus and strength. The focus of the present work is the transverse properties, and some illustrative results for the longitudinal behaviour are also presented. The sensitivity of the composites’ properties to irradiation swelling was affected by the fibre volume fraction, and not by the pore volume fraction, though the porosity dramatically affected the initial unirradiated properties. The model correctly describes experimental trends reported in the literature, and a simple optimisation of the model parameters is demonstrated by the successful simulation of experimental data for tensile loading of a mini composite specimen.