Effects of Interfacial Conditions on Shear Strength of Interface and Critical Aspect Ratio in Tungsten-Copper Composites

Abstract

As part of fundamental studies on effects of interfacial conditions on stress transfer mechanisms, effects of irregularities on the fibre surface, sample preparation method, coating, interfacial reaction and thermal cycling on the shear strength of the interface and the critical aspect ratio were investigated by a pull-out test using a tungsten fibre-copper matrix composite system. The results of the pull-out test were checked with the appearances of the fracture surfaces of the composites with the identical interfacial conditions and compared with those of a multiple-fracture test.An appropriate preparation method or coating, and a favourable interfacial reaction produced high interfacial shear strength. Even when the tensile strength of the interface was nearly zero, the shear strength of the interface was not zero. This apparent inconsistency was explained in terms of the interlocking effect of the irregularities in the interface.In the pull-out test, the shear strength of the interface was measured. In the multiple-fracture test, the frictional shear stress at the interface was measured when the shear strength of the interface was so weak that debonding occurred at the interface, while the shear stress in the matrix was measured when the interfacial shear strength was higher than the shear stress in the matrix.