STRAIN-ENERGY DENSITY RATIO CRITERION FOR FRACTURE OF COMPOSITE-MATERIALS

The strain energy density ratio (SEDR) criterion for fracture of fibre reinforced composite materials is proposed. The definition and expression of the SEDR are presented first, then its function of predicting crack growth direction in the materials is demonstrated through the comparison of the experimental and predicted results. In the tests, the crack directions, both in initiation stage and in the pre-fracture propagation stage, were recorded with Moire's fringe method and the ordinary photography. Finally, the function of SEDR criterion for predicting failure strength of fibre composites was illustrated through the comparison of the predicted results of SEDR and Tsai-Hill criteria. © 1990.