MICROMECHANICS OF IMPERFECT INTERFACES IN HETEROGENEOUS MATERIALS

In the design of strong engineered materials containing fibres or part iculates to be used for impact and abrasive wear, one important proble m is the magnitude of the stress concentration around these second-pha se constituents. Analytical solutions for cylindrical and spherical in clusions embedded within infinite matrices are reviewed and assessed f or their value in predicting the constitutive behaviour of heterogeneo us materials. Solutions for two distinct interfacial behaviours are fo und in the literature: (1 ) radial displacement and stress continuity with zero shear stress across the interface (i.e. frictionless); and ( 2) an elastic interface (modelled as a very thin interfacial elastic l ayer) capable of supporting both normal and tangential displacements a nd stresses. However, both of these approaches incorporate constitutiv e behaviour that would be considered incompatible for real materials ( e.g. interpenetration between reinforcement and matrix). In this study , finite element models are developed without these limitations and th eir results (stress concentration factors) are compared with analytica lly derived solutions. It is shown that for certain load cases analyti cal solutions inadequately model the idealized micromechanical behavio ur of heterogeneous materials.