Static and Impact Shear Strength Estimation of a Continuous Carbon Fiber-Reinforced Silicon Nitride Using Double Notched Specimens

Abstract

Finite element analysis was performed to investigate the shear stress distribution in double notched isotropic and orthotropic specimens under compressive loading. The shear stress distribution between the notches in the orthotropic material was found to be relatively uniform except at the notch roots where a distinct stress concentration was predicted at both for the isotropic and the orthotropic materials. In brittle orthotropic materials, microcracks initiate in the adjacent regions to the notch roots and may relax stress concentration. Static and dynamic tests were performed on double notched specimens of continuous carbon fiber-reinforced silicon nitride ceramics. The shear strength in the fiber direction is much lower on the perpendicular plane than on the parallel plane to the hot pressing direction. The strain rate dependencies of the shear strength were clarified through the present method. It is found that the shear strength evaluated by this method was much lower than that evaluated by conventional tests, such as the short beam or the compression tests.