Instability of Multiple Penny-Shape Delaminations in Composite Laminates Subjected to Quasi-Static Transverse Loading

Instability and propagation process of multiple penny-shape interlaminar delaminations in circular axi-symmetric plates subjected to a quasi static transverse load, which is an idealized problem of damage accumulation in composite laminates due to low velocity impact loading, is numerically studied through a finite element analysis. A special fracture element is proposed in order to simulate the crack propagation. Both failures due to maximum stress and fracture mechanical instability are possible to be considered by using the element when the failed surface is presumed beforehand. The convergence of the solution is discussed by studying the distribution of the expansion of the element ahead of crack tip. First, the element is applied to the problem of propagation of a penny shape crack in infinite body. The results agree well with the theoretically predicted results. Then, the element is used to simulate the propagation of multiple delaminations in a laminate. The finite element results are consistent with the failure process inferred from the energy release rate distribution theoretically and numerically obtained.