Simultaneous modelling of impact-induced intra- and interlaminar damage in CFRP laminates

An effort is made to increase the accuracy and reliability of explicit Finite Element Method numerical procedures for the structural behaviour of Carbon Fibre Reinforced Polymer (CFRP) composite materials, especially focused on impact loadings. This was done by development of a joint, interactive material model with the capability to assess both intralaminar (intra-ply) and interlaminar (interface damage, delamination) damage initiation and progressive evolution, and their mutual interaction. This enabled additional improvements such as removal of free-floating and non-physical residual cohesive interface elements, as well as inclusion of strain rate effects on the interlaminar behaviour. This study is a continuation of the authors’ previous work in which intralaminar and interlaminar material models were developed and tested separately. Developed interlaminar material model is presented, along its validation by recreating the dynamic Double Cantilever Beam experiments reported in literature. The strategy and the general scheme of the comprehensive, joint, interactive material model along with its key features are described. Testing of the new numerical material model was done by recreating the experimental impact investigation on the AS4/8552 carbon/epoxy laminates with the layups [+-45/0/452/-452/90]s and [+-45/0/+-45/90/(+-45)2]s at various energy levels. The results have shown major improvement regarding the prediction of the delamination extent and the shape of the delaminated areas compared to the default Cohesive Zone Model available in Abaqus. The significance of inclusion of the strain rate effects on interlaminar behaviour has also been proven. Additionally, improvements regarding the prediction of the peak displacement and contact force values were achieved as well.