Mixed-Mode Subcritical Crack Growth in Orthotropic Polymers.

The article presents a semi-empirical model of mixed-mode sub-critical crack propagation for orthotropic polymers subjected to continuous loading. A combination of opening and shearing propagation modes are considered by the model. Crack propagation in an orthotropic liquid crystalline polymer film for orientation angles of 45 and 90 degrees are measured optically to provide empirical constants. Comparison of predicted and measured crack propagation at 30, 60, and 75 degrees is used to validate the model. Identification of a critical angle at which the crack propagation rates for the opening and shearing modes are equivalent are presented.