Stress intensity factors from reflected caustics in birefringent plates with cracks

Abstract

In the present paper the method of reflected caustics is used for the evaluation of stress intensity factors in plates made of birefringent materials with a crack submitted to the opening mode of loading. It has already been established that due to the optical anisotropy of the material the rays reflected from the rear face of the plate form a double caustic. In this paper the influence of the optical anisotropy factor ξ of the material on the relative position and sizes of the two constituent branches of the caustic is studied. Nomograms are given for the accurate evaluation of mode I stress intensity factors from the geometrical characteristics of the two branches of the caustic. A series of tests, undertaken on plates made of polycarbonate of bisphenol A with ξ_r = 0.153, showed that the accuracy of evaluation of κ_I is the same as with the same method applied to optically inert materials.