DESIGN, ANALYSIS AND APPLICATION OF AN IMPROVED PUSH-THROUGH TEST FOR THE MEASUREMENT OF INTERFACE PROPERTIES IN COMPOSITES

An improved fiber push-through test has been designed and used to obtain new information about interfaces in composites consisting of matrices of a Ti alloy and a borosilicate glass, both reinforced with SiC fibers. Interpretation of these results is accomplished through an analysis of coupled debonding and push-through, followed by push-back. The sliding stress is found to vary with push-out distance and to be substantially reduced in the vicinity of a fatigue crack in the Ti matrix composite. These effects are attributed to asperity wear, matrix plasticity and fragmentation of the fiber coating around the debonded interface. Reseating effects on push-back have been demonstrated, but have been found to diminish as the relative fiber-matrix displacement increases. Fiber roughness has been identified as an important aspect of interface sliding.