Cavity expansion resistance of brittle materials obeying a two-curve pressure-shear behavior

We derived a closed-form solution for the pressure required to open a spher ical or a cylindrical cavity in brittle materials which demonstrate a two-c urve pressure-shear behavior. The material is allowed to crack under tensio n and fail under shear; only both failure modes result in comminution. Sinc e the cavity expansion pressure is closely related to the penetration resis tance of a target material, this solution identifies the material parameter s that are important in impact and penetration problems. It is found that c racking and comminution can be prevented when a large enough confinement pr essure is present, and the resulting high cavity expansion resistance could explain the intriguing phenomenon of interface defeat. The effects of dila tancy, and shear strength of comminuted ceramic on cavity expansion pressur e are explicitly revealed. (C) 2000 American Institute of Physics. [S0021-8 979(00)01518-8].