CRITICAL MATRIX YIELDING STRESS AND INTERFACIAL FRACTURE IN FORMING OF METAL-MATRIX COMPOSITE WIRES

Effective manufacturing processes are vital in large-scale use of comp osite materials. Metal matrix composites have the potential to be form ed into parts. To analyze the forming process, some yield criteria hav e been proposed assuming perfect bonding between fiber and matrix. The present paper provides a concise calculation of the yield condition t aking into consideration the limited interfacial fracture strength to ensure swaging of a bundle of composite wires without fiber-matrix deb onding. The yielding stress of the matrix must be constantly kept belo w a limit, most feasibly by heating. In the present analysis, Timoshen ko's model is used to calculate the apparent stress distribution in a wire cross section under symmetric lateral loading. The yield function of Dvorak and Bahei-El-Din is applied to predict the initial yield. T he stress concentration at the interface is determined by Goodier's me thod. Using the interface fracture strength as a criterion, the matrix yielding stress is limited to a critical value, beyond which interfac ial bonding fails during the forming process. This concept and the ens uing results can be applied in the industrial forming of metal matrix composites.