Development of the tensioned push-out test for study of fibre/matrix interfaces

Abstract

Finite element modelling has been used to explore the basic single-fibre push-out test and a variant in which in-plane tension is simultaneously applied. Comparison with experimental photoelastic data has shown that shear-lag based analytical models of the test are unreliable, even for the simplest cases. It has been shown that the loading geometry and, particularly, the presence of thermal residual stresses can affect the interfacial stress state, which often tends to vary significantly along the length of the fibre. For a metal-matrix composite, the peak shear stress is predicted to occur near the bottom of the fibre, which is where debonding is expected to initiate. The proportion of normal and shear stresses at the interface can be altered by the application of in-plane tension. Some previously published experimental tensioned push-out data for the SiC/Ti system have been interpreted in the light of finite element modelling, allowing an estimate to be made of the interfacial coefficient of friction.