Quantitative evaluation by fractal analysis of indentation crack paths in Si3N4-SiCW composites

The crack paths, generated by Vickers indentation in Si3N4-SiCw composites, were analysed from a quantitative point of view, in order to distinguish b etween the possible toughening mechanisms involved. It was found that the r oughness parameter R-L and the fractal dimension D describe the geometrical features of the cracks and evidence the anisotropy of the microstructure, due to the whisker and Si(3)N(4)beta-grain orientation. The relationships f ound between fracture toughness and these geometrical parameters emphasise the importance of the crack deflection mechanism in improving toughness and provide information on the role played by microstructure in determining th e mechanical properties of a composite. (C) 1999 Elsevier Science Limited. All rights reserved.