Investigation of push-out delamination using cohesive zone modelling and acoustic emission technique

Push-out delamination is a serious concern in the drilling of fibre-reinforced composite materials. This damage occurs as the drill reaches the exit side of the material and can reduce the strength and stiffness of the structure. In this paper, a three-point bending test is performed on glass/epoxy-laminated composites to simulate the push-out delamination induced by thrust force during drilling. Cohesive zone modelling and acoustic emission monitoring are utilized to investigate the push-out delamination. Initially, double cantilever beam and end-notched flexure tests were performed to calibrate the cohesive zone modelling model. Following that, the actual loading condition is simulated using cohesive zone modelling-based finite element modelling. Energy of the acoustic emission signals is also used to detect the initiation of the delamination. The results obtained from cohesive zone modelling and acoustic emission showed that the applied methods can be used to understand and predict the initiation of push-out delamination and its progression. Finally, it is concluded that the proposed cohesive zone modelling and acoustic emission techniques can be used in the design stage as well as during the drilling process of laminated composite structures to avoid delamination.