On the energy release rate and mode mix of delaminated shear deformable composite plates

A first-order shear deformable plate theory-based method is developed to calculate the strain energy release rate and stress intensity factor of a non-homogeneous delaminated composite plate under a general three-dimensional (3-D) loading condition. By modeling the delaminated plate as two shear deformable sub-laminates on either side of the delaminated plane, the strain energy release rate is expressed in terms of three concentrated forces at the crack tip and their corresponding compliance coefficients. The simple expression of strain energy release rate makes the mode decomposition under complicated loading situation possible with the aid of two supplementary continuum analyses. To illustrate the present method, a plain strain delamination. problem of laminates is examined, and the closed-form expressions of strain energy release rate and stress intensity factor are obtained. It is found that the available solutions, such as the ones based on the classical plate theory, can be recovered from the present solutions by simply neglecting the transverse shear force. The relationship between the global and local decompositions is further established, and the accuracy of the present solutions is examined by comparing with numerical results of boundary element method. With inclusion of transverse shear deformation in the formulation, more accurate and explicit predictions of the strain energy release rate and stress intensity factor of delaminated composite plate are achieved by the present method, especially when a laminate has a relatively low. transverse shear modulus or moderate thickness. (C) 2003 Elsevier Ltd. All rights reserved.