The surface and through crack problems in orthotropic plates

Abstract

The general mode I crack problem for orthotropic plates under bending and membrane loading is considered. First the bending problem for a series of coplanar through cracks is formulated and the effect of material orthotropy on the stress intensity factors is studied. By varying the six independent material constants one at a time it is shown that, with the exception of Poisson's ratio, all other material constants may have a considerable effect on the stress intensity factors. The surface crack problem is then formulated by using the line spring model with a transverse shear theory of plate bonding. Examples are given for composite laminates and crystalline plates containing one or two semielliptic surface cracks and subjected to membrane loading or bending. Here. too. by comparing the results with the isotropic plate solution, it is shown that for severely orthotropic materials such as composite laminates the effect of material orthotropy on the stress intensity factors could be rather significant.