Strain energy release rate associated with local delamination in cracked composite laminates

Abstract

In the present paper the total strain energy release rate G T associated with delaminations that initiate from a matrix crack in a symmetric composite laminate is calculated using the potential energy approach in elastic fracture mechanics and a two-dimensional finite element analysis. Two laminate stacking sequences, [ 0 2 90 4 ] s and [ ±25 90 4 ] s , are examined with a matrix crack in the 90° plies and delaminations growing uniformly from the matrix crack tip in the 0 90 and − 25 90 interfaces, respectively. The finite element analysis indicates that the G l component (opening mode delamination) is reduced to zero for delamination length greater than one ply thickness; the shear mode (Mode II) dominates the growth of delamination. The total G T increases with increasing delamination length, but eventually approaches a constant asymptotic value, which is close to the G T result calculated from the analytical model. Finally, the analytical and numerical calculations show that G for local delamination decreases notably with increasing matrix cracking.