A Finite Element Analysis of Delamination Propagation in Composite Laminates

Abstract

Propagation of multiple circular 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 by a finite element analysis. A special fracture element is proposed for the analysis. The element, a nonlinear spring element, is characterized that the failure occurs at the stress equal to the maximum allowable stress of the material. The power form nonlinear property is defined so that the stored strain energy in the element becomes equal to the toughness of the material at moment of the failure. Then, both failures due to maximum stress and fracture mechanical instability are possible to be considered by using the element. Definitely, the failed surface must be presumed beforehand such as the case of delamination propagation in composite laminates when the present element is used. The element is applicable to the dynamic process accompanying damage accumulation, where the dissipated energy due to delamination propagation must be considered. The convergence of the solution with the element size is quite smooth and consistent with the theoretical results of fundamental problem of fracture mechanics. The propagation of the multiple delaminations in the circular laminate is well calculated.