Apparent fracture toughness master curve of a zirconia-alumina composite

Recently, the existence of specimen-size-independent Weibull master curves characterizing strength and failure of macroscopically homogeneous, brittle materials, if the Weibull modulus m > 1, has been demonstrated by the present author. Furthermore, an apparent fracture toughness master curve M(a) has been derived from experimental Weibull master curves, which can even be applied to materials undergoing an amount of stable crack growth prior to failure. The objective of the present paper is to show that another type of specimen-size-independent Weibull master curves K(y,m), which is obtained by scaling the cumulative failure probability distribution function P(sigma) with the physically, highly significant mean stress = integral(0)(1) sigma dP, can be constructed for every Weibull modulus m > 0. Moreover, an apparent fracture toughness master curve T(b), being physically highly significant and evident, can be derived from the Weibull master curves K(y, m) for every m > 0. T(b) provides characteristic magnitudes, which facilitate a thorough comprehension of the fracture toughness of the investigated solids. Therefore the apparent fracture toughness master curve T(b) of an 8 wt% yttria partially stabilized zirconia-20vol.% beta-alumina composite has been evaluated, using data from three-point bend tests performed at room temperature.