LAUSR

Abstract As a non-contact optical experimental method, caustic method is commonly employed in measuring stress intensity factor at the crack tips of different materials. Caustics theory is commonly used for solving stress intensity factor at crack tips in homogeneous isotropic materials, but it lacks the required accuracy for solving stress intensity factor in interfacial cracks in dissimilar materials. In this paper, we have deduced the theoretical equation of stress intensity factor at interfacial crack tips the orthotropic bi-materials and evaluated the effects of different crack propagation speeds, orthotropic bi-materials and other parameters on the initial curves of focal line and the shape of caustics. In addition, dynamic caustic experiments on composite/epoxy bi-materials under low velocity-impact loadings were performed and the evolution of dynamic interfacial cracks was captured by high-speed cameras which showed good agreements with theoretical results. Research results confirmed the usefulness of the application of caustic method in dissimilar isotropic and orthotropic materials, isotropic-orthotropic bi-materials and homogeneous isotropic and orthotropic materials under subsonic crack propagation velocities.