Layered Interphases in Ceramic Matrix Composites and Relation with Interfacial Behaviour
Unidirectional SiC/SiC minicomposites were produced by infiltration of a Hi-Nicalon fibre tow by using pulsed chemical vapour deposition (P-CVD). The sequence of precursor gazes inlet steps determines the structure of the Pyrocarbon/TiC layered interphase deposited first on the filaments. The SiC matrix is then deposited with a given thickness. The different interphase structures will be described. The interface behaviour was characterized by indentation method. The load is applied on the fibre-end at a polished cross-section of the composite, and 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-through test on thin composite slices gives directly access to sliding resistance because the fibre is less compressed. The load displacement curves obtained will be described and analysed. For example, sliding velocity jumps revealed a slight increase in sliding resistance with velocity. During push-back, a seating drop was recorded as the fibre returns in its initial position, illustrating a certain effect of roughness.
D. Rouby et al., "Layered Interphases in Ceramic Matrix Composites and Relation with Interfacial Behaviour", Advances in Science and Technology, Vol. 45, pp. 1475-1482, 2006