Abstract
In the fibre-reinforced ceramic-matrix composites, the fibre-matrix interface plays an important role. Tailoring the interfacial bond strength improves mechanical properties of the materials. Micro-mechanical experiments indicate that the sliding surface of fibre/matrix interface is rough. The interface roughness plays an important role on the frictional slid and hence on the interfacial shear stress (ISS). The interfacial properties of SiCf/SiC mini-composites with different interphase structures have been determined by indentation, with pushes the top of a selected fibre on a polished cross section. The displacement of that fibre-end is measured. The push-in test on thick specimens shows that the fibre debonds at a given fibre stress and then slides under a certain frictional shear stress. Both parameters increase when the TiC layers become discontinuous, like aligned TiC clusters in a Pyrocarbon matrix. The load-displacement behaviour is in very good agreement with theory when the interfacial shear stress is kept constant, non depending on relative slip displacement. The push-out test on thin composite slices gives directly access to the force which is directly related to the interfacial shear stress associated to slip, without taking into account the elastic compression of the fibre (generally is very small). During push-back, a seating drop was recorded as the fibre returns in its initial position, illustrating a certain effect of roughness. The results obtained by push in on thick specimens are higher than of those of push-out on thin films.
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