Macro-failure criterion for the theory of laminated composite structures with free edge delaminations

Free edge delamination is one of the basic types of failure for laminated composites. Edge delamination phenomena is usually treated as the problem of the onset of interlaminar crack near the flat boundary of a laminated composite structure. Micro-fracture criteria are usually treated with the use of stress intensity factors or energy release rates. Using this fundamental micromechanical information about the crack we formulate a so-called macro-failure criterion. This criterion is more convenient in applications than a micromechanical one because it is formulated using macro-quantity: mean value of normal, stress, acting along the edge of structure. Then this criterion is generalized and applied to the slightly curvilinear boundary of structure.