Tailoring of AP-PLY composite laminates for improved performance in the presence of delaminations

A fibre placement architecture, Advanced Placed Ply (AP-PLY), has been shown to give significantly improved damage tolerance characteristics of composite structures. The behavior of delaminations resulting from low speed impact damage is of particular concern. Emphasis is placed on using developed methodology to expand current knowledge on the delamination response and optimization of simple AP-PLY composite structure. A proposed energy method to analyze the strain energy release rate (SERR) of an existing crack in a composite laminates, was applied to an AP-PLY beam structure. A step by step approach was developed to obtain the SERR of a crack that grows in regions of variable stiffness. The analytical SERR determined when two materials are used in sequence, sets the stage for optimization of AP-PLY composite laminates to tailor stiffness and minimize SERR. The results show promise in providing designs where the stiffness is altered so that delamination growth is delayed.