ROUGHNESS TOUGHNESS CORRELATIONS IN METAL MATRIX COMPOSITE

The crack growth mechanism in metals containing inclusions is usually due to the nucleation growth and final coalescence of micron sized voids. The dissipation of energy is thus related to both the plasticity in the material and the size of the process zone. However, it is not clear what is the relation, if any, between a material`s crack growth resistance (i.e. energy dissipation) and the roughness of the corresponding fracture surface (dictated by the underlying microstructure). Since the pioneering work of Mandelbrot fracture surfaces are known to be self-affine fractals. Moreover it was shown that the fractal dimension of fracture surfaces is universal and does not depend on the loading scenario or the material. Here, we present an experimental study, where the statistical characteristics are explored beyond the universality of the fractal dimension. The fracture toughness of Aluminium diamond MMC is probed for different diamond densities/sizes, using single edge notched tensile specimens (SENT). A correlation between the measured fracture toughness and some of the statistical parameters of the fracture surface will be discussed and analysed as a function of particle spacing and size. Our results will be discussed with relation to numerical observations in the literature where a linear correlation was shown to exist between the fracture toughness and fracture surface roughness of ductile materials.