The effect of cracks interaction on the critical strain in orthotropic heterogeneous material under compressive static loading

Laminar composites due to their internal structure and manufacturing methods contain a number of inter- and intra-component defects which size, dispersion and mutual interaction alter significantly the critical compression strain level. The current paper is one of the first attempts to study the crack interaction in orthotropic materials compressed in a static manner along interlaminar defects. For laminated composites compressed along layers and, therefore, along the mentioned interfacial defects, the classical Griffith - Irvin criterion of fracture or its generalization are inapplicable and all stresses intensity factors and crack opening displacements are equal to zero. This fact emphasises the importance and the necessity of the most careful investigation of fracture due to specific mechanisms inherent to heterogeneous materials. The statement of the problem is based on the most accurate approach, the model of piecewise-homogenous 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 linear buckling model. Numerical analysis is aided by the advanced FE analysis software -Abaqus 6.5. The results were obtained for particular cases of real composites for the typical dispositions of cracks. It was found that both cracks length and mutual position of cracks influence the critical strain of the composite.