The effect of preloaded on delamination of composite laminate subjected to low energy impact

Abstract

Abstract The CFRP laminate composite is used widely especially in aerospace industry. The design concern of this type of structure is on its strength under impact loading even under low energy impact. Under low impact loading, delamination occurs and reduce the residual strength of laminate, therefore the necessity to predict this phenomena prior to its utilization. In practice the aircraft structure is subjected to pre-stress loading such as due to aerodynamics loading while in the same time loaded under impact loading due to, for example, birds impact. This paper deals with the investigation on the delamination trend of pre-stressed CFRP composite laminate subjected to low energy and low speed impact. A FE model is proposed and validated using published data. After validation confirmation, 2 types of pre-stressed; compression and tension are used to vary the pre-stress parameter. The pre-stress is modelled by prescribe displacement at both edge of the laminate with 5 different values of −0.01, −0.05, −0.1, −0.15, −0.2 mm for compression and 0.01, 0.05, 0.1, 0.3, 0.5 mm for tension. The FE shows that maximum force during impact increases with pre-stress in compression and decreases in tension. The contact time between impactor and laminate remains constant for pre-stress in tension and increases in compression. The impactor displacement during impact is lower for tension and higher for compression. Delamination area increases regardless whether in pre-stress tension or compression. The same trend of delamination shape evolution during impact is observed both for compression and tension; ellipse evolution in transverse or perpendicular direction to the prestress direction.