Prediction of low velocity impact damage in carbon–epoxy laminates

It is well known that composite laminates are easily damaged by low velocity impact. This event causes internal delaminations that can drastically reduce the compressive strength of laminates. In this study, numerical and experimental analyses for predicting the damage in carbon–epoxy laminates, subjected to low velocity impact, were performed. Two different laminates (04,904)s and (02,±452,902)s were tested using a drop weight testing machine. Damage characterisation was carried out using X-rays radiography and the deply technique. The developed numerical model is based on a special shell finite element that guarantees interlaminar shear stresses continuity between different oriented layers, which was considered fundamental to predict delaminations. In order to predict the occurrence of matrix failure and the delaminated areas, a new failure criterion based on experimental observations and on other developed criteria, is included. A good agreement between experimental and numerical analysis for shape and orientation of delaminations was obtained. For delaminated areas, reasonable agreement was obtained.