The Brittle Strength of Orthotropic Materials

A phenomenological fracture condition is proposed for ortho tropic brittle materials. It contains nine material parameters and can account for widely differing compressive and tensile strengths in various directions. The proposed fracture condition is devel oped, purely on formal grounds, by borrowing features of the Mises-Schleicher isotropic yield condition and Hill's orthotropic yield condition. Comparison with experimental data on a fiber- reinforced composite material shows good agreement. The reader is reminded repeatedly that, despite formal similarities, yield conditions and brittle-fracture conditions pertain to unrelated physical phenomena.