Energy release rate and stress intensity factors for delaminated composite laminates

A procedure of total energy release rate and stress intensity factors is developed for general non-homogeneous laminated composite laminates. The total energy release rate is obtained by using the J-integral for a one dimensional model of plane stress, plane strain and cylindrical bending. Decomposition of it into mode I and mode II, by which the mode mixity calculation is carried out, is based on the assumption of equivalent orthotropic properties through the laminate thickness. The process is straightforward and can be used as a criterion for delamination onset and growth of one dimensional structural model under general loading in the pre- and post-buckling states.