The mechanical behaviour of interfacial cracks and dislocations in composite materials was investigated. The stress intensity factor at a crack tip along a perfectly bonded interface, arising from a screw dislocation, was found to yield the same expression as that for a single-phase medium if the shear modulus of the latter was replaced by the harmonic mean of the shear moduli of the media making up the composite. The mode-I stress intensity factor at a crack tip along a sliding interface, arising from an edge dislocation, was the same as that for a single-phase medium if the elastic constant, E(1-υ2), of the single-phase medium was replaced by the harmonic mean of the E(1-υ2) of the media making up the composite. However, the mode-II and mode-III stress intensity factors at a sliding interfacial crack, arising from edge and screw dislocations, were zero. The mode-III stress intensity factor at a crack tip along a perfectly bonded interface, and the mode-I stress intensity factor at a crack tip along a sliding interface, arising from an applied load, yielded the same expression as the single-phase medium counterparts. This was because these expressions did not contain any elastic constants. Under high-temperature creep conditions, the expression for the stress in composite materials had the same form as that for a single-phase material if E(1-υ2) for the single-phase medium was replaced by the harmonic mean of the E(1-υ2) of the media in the composite. The stress intensity factors at a crack tip along a perfect bonded interface, arising from an edge dislocation and a mode-I applied load, were mixed and could not be obtained from solutions for single-phase media.

Micromechanics of Composite Materials - Interfacial Crack and Dislocations. S.Lee: Proceedings of the National Science Council of the Republic of China A, 1998, 22[6], 734-50