Dynamic Impact and Fracture Behaviour of Carbon Fiber Reinforced 7075 Aluminum Metal Matrix Composite

Abstract

The aim of this work is to study the effect of strain rate and fiber volume fraction on the dynamic impact of response and fracture behaviour of carbon fiber reinforced 7075 Al metal matrix composite under room temperature. Cylindrical specimens containing 5-15 V _f % carbon fiber were deformed at strain rates ranging from 10⁻¹s⁻¹ to 3.5 x 10³s⁻¹ by means of a Saginomiya 100 metal forming machine and a compressive split-Hopkinson bar. Fracture phenomena and variation of microstructure were investigated using optical and scanning electron microscopy. The resulting data indicate that impact response of the tested composite is affected both by applied strain rate and fiber volume fraction, resulting in variations of work hardening rate, strain rate sensitivity and activation volume. The deformed microstructure at both low and high strain rates displayed extensive unstable plastic flow of Al matrix associated with catastrophic fiber fragmentation. Fiber breakage is dominated mostly by shearing and tension, and a relatively shorter fiber fragment length is found at high rate conditions. Fracture behaviour and the damage process of the tested composite depend quite strongly on the strain rate.