The effect of cracks interaction for transversely isotropic layered material under compressive loading.

Laminar composites due to their internal structure and manufacturing methods contain a number of inter- and intra-component defects whose size, dispersion and mutual interaction alter significantly the critical compression strain level. The current paper investigates crack interaction in transversely isotropic materials compressed in a static manner along inter- laminar defects. For laminated composites compressed along layers and, therefore, along the mentioned interfacial defects, the classical Griffith-Irvin criterion of fracture or its generalisation is inapplicable since all stresses intensity factors and crack opening displacements are equal to zero.
The statement of the problem is based on the most accurate approach, the model of piecewise-homogeneous medium. The moment of stability loss in the microstructure of material is treated as the onset of the fracture process. The behaviour of each constituent is described by the three-dimensional equations of solid mechanics, provided certain boundary conditions are satisfied at the interfaces. The complex non-classical fracture mechanics problem is solved by finite elements analysis, using a linear buckling model. The results are obtained for fibre volume fraction V-f = 0.1-0.73 for the typical dispositions of cracks. The model of classical cracks is utilised. It is found that the fibre volume fraction, the crack length and the mutual position of cracks influence the critical strain of the composite. (c) 2007 Elsevier B.V. All rights reserved.