Abstract: The delamination problem of composite laminates is investigated. This problem is one of the most important problems affecting the use of structure composite laminates. Here, the delamination damage in composite laminates is regarded as the line-crack and the fracture mechanics method is used. Due to the existence of the interlaminar stresses in the free-edge in composite laminates, the delamination crack is generally mixed-mode. Thus, the mixed-mode fracture criterion of the delamination onset for composite laminates is presented in this paper. Using this criterion, it is expected that the failures of various composite laminates whose major failure model is delamina ted can be analysed.

Key words: composites, delamination, fracture, criterion