EVALUATION OF STRAIN ENERGY RELEASE RATES IN DELAMINATED LAMINATES UNDER COMPRESSION

摘要

Various approaches to the determination of the energy release rates of copressively loaded composite laminates are critically reviewed. These are the J integral, crack-closure integrals, and the direct method, which involves integration of the load-end compression relationship. The J integral is found to be a reliable approximation for the total energy release rate. The use of the crack tip stress field for the determination of modal contributions is explored for cracks between plies of same and differing material properties, respectively. The assumptions on which this technique is based are critically examined. Finally, a new displacement based method for the computation of modal contributions to G is proposed. This approach is found to be very reliable and provides values of G_I and G_II with a relatively coarse mesh. This new technique is expected to supplant the currently used stress-based mode separation technique.