ACOUSTIC MICROSCOPY OF CERAMIC-FIBER COMPOSITES

A variety of ceramic-fibre composites has been studied by acoustic microscopy, at 1.9 GHz with a resolution of 0.8 mum. The materials studied were Nicalon-reinforced borosilicate glass, SiC fibres in a magnesium-aluminosilicate matrix and a calcium-aluminosilicate matrix, and SiC monofilaments in a Ti-6Al-4V matrix. In all the specimens the contrast was dominated by strong excitation of Rayleigh waves in the surface. This gave strong contrast from different phases, and revealed interfaces and cracks by characteristic crack patterns. Quantitative agreement between observed and calculated fringe patterns was found, and values of shear and Young's modulus were measured. In the SiC monofilament specimens, various stages of progressive deterioration as a result of thermal ageing treatments were observed.