Finite Element Procedures for the Analysis of the Mechanical Behaviour of Damage in composite Plates Under Compression

In this work the delamination growth phenomenon in composite plates under compression has been investigated by using two different finite element models. In the first model the plate has been modelled with 20 node three-dimensional finite elements and initiation, growth and interaction of intralaminar and interlaminar damage have been analysed until the structural collapse condition is reached. Within the second model the composite plate with an embedded circular delamination has been discretized parametrically by adopting 8 node shell elements in order to perform fast evaluations of the delamination growth initiation load. Overlaps between the debonded sub-laminates have been prevented by introducing contact elements with different formulations and Strain energy Release Rate distribution at the delamination front has been computed by using the modified virtual crack closure technique (MVCCT). The 3D model has been enhanced by introducing a suitable propagation criterion, to follow the delamination growth phenomenon, and an iterative numerical procedure, to simulate the progressive matrix and fibre breakage by adopting respectively the Hashin’s failure criteria to check the stress state and instantaneous degradation rules for reduction of the damaged material properties. The analysis of the mechanical behaviour of a composite plate with a circular embedded delamination has been performed by using the two developed models and results have been compared with experimental data