THE FRACTURE ENERGY OF BIMATERIAL INTERFACES

This article describes a framework applicable to the measurement and interpretation of the fracture energy of bimaterial interfaces. A major conclusion of this study is that the fracture energy and usually exhibits values substantially larger than the thermodynamic "work of adhesion". The non-uniqueness is related to the mode mixity (shear and opening) effects experienced by interface cracks, as characterized by the phase angle ψ of loading; typically, Γi is found to increase as ψ increases. These trends are attributed to crack shielding caused by roughness of the interface fracture surface, to material non-linearity etc. The phase angle is, in turn, influenced by the choice of test specimen, resulting in values of Γi that differ between specimens in a manner attributed to the locus of Γi with ψ. Preliminary models that relate Γi to roughness, plasticity, segregation, etc. are described, leading to insights concerning microstructural aspects of "weak" and "strong" interfaces. © 1990.