DEVELOPMENT OF THE TENSIONED PUSH-OUT TEST FOR STUDY OF FIBER-MATRIX INTERFACES

Finite element modelling has been used to explore the basic single-fib re push-out test and a variant in which in-plane tension is simultaneo usly applied. Comparison with experimental photoelastic data has shown that shear-lag based analytical models of the test are unreliable, ev en for the simplest cases. It has been shown that the loading geometry and, particularly, the presence of thermal residual stresses can affe ct the interfacial stress state, which often tends to vary significant ly along the length of the fibre. For a metal-matrix composite, the pe ak shear stress is predicted to occur near the bottom of the fibre, wh ich is where debonding is expected to initiate. The proportion of norm al and shear stresses at the interface can be altered by the applicati on of in-plane tension. Some previously published experimental tension ed push-out data for the SiC/Ti system have been interpreted in the li ght of finite element modelling, allowing an estimate to be made of th e interfacial coefficient of friction.