EFFECTS OF MATRIX CRACKING AND HYGROTHERMAL STRESSES ON THE STRAIN-ENERGY RELEASE RATE FOR EDGE DELAMINATION IN COMPOSITE LAMINATES

A simple theoretical model based upon the equivalent constraint model( 1,2) and a sublaminate approach(3) is used to determine the strain ene rgy release rate, G(ed), in [+/-theta(m)/90(n)](s) carbon/epoxy lamina tes loaded in tension. The analysis provides closed-form expressions f or the reduced stiffness due to edge delamination and matrix cracking and the total strain energy release rate. The parameters controlling t he behaviour are identified. The effect of laminate stacking sequence, matrix crack density and hygrothermal stresses on G(ed) is examined. Results show that the available energy for edge delamination is increa sed notably due to transverse ply cracking. Also, residual thermal str esses increase substantially the strain energy release rate and this e ffect is magnified by the presence of matrix cracking. Finally, predic tions for the edge delamination onset strain are in acceptable agreeme nt with experimental measurements.