The stability of tensile deformation of single ductile fibre-ductile matrix composites with weak interfaces

Abstract

The embedded molybdenum fibre in a copper matrix composite was elongated apparently uniformly although the interface was so weak that necking in the fibre could not be suppressed by the matrix. To explain this result, a possible mechanism was suggested where suppression of necking in the fibre is caused by strain hardening of the composite as a whole and by an increment in strain rate in the cross-section where the fibre starts necking, but the incremental deformation amount and the incremental strain rate of the cross-section are small. On the basis of this mechanism, and with the aid of Hart's criterion, a new instability approach to tensile behaviour of the composite is presented. It was found that the stability of the composite is determined mainly by the strain-hardening exponent of the composite, which is determined by the modified rule of mixtures. The present derived condition of instability of the composite is in good agreement with that proposed by Mileiko.