STRENGTH VERSUS GAUGE LENGTH IN CERAMIC-MATRIX COMPOSITES

The strength of ceramic-matrix composites as a function of sample gauge length is derived as a function of the composite constituent material properties. Within the context of a global load-sharing assumption for how load is transferred from broken to unbroken fibers, the analysis shows that, for samples shorter than 0.8delta(c) (where delta(c) is the characteristic slip length determining composite pullout), the composite ultimate strength increases with decreasing gauge length. For samples longer than 0.8delta(c), the strength is independent of gauge length. Implications of these results on the performance of composites with small-scale stress concentrators is briefly discussed.