DYNAMIC COMPRESSIVE STRENGTH AND FAILURE OF CARBON FIBER REINFORCED ALUMINIUM METAL MATRIX COMPOSITE

Dynamic compressive behaviour of 5~15 Vf % carbon fiber reinforced 7075 Al metal matrix composite has been studied at room temperature at strain rates from about 10-1 s-1 to 3.5_103 s-1. The low rate tests were performed using a Saginomiya 100 metal forming machine, while a compressive split Hopkinson bar was used for high strain rate tests. In addition to the determination of dynamic properties, the influence of strain rate and fiber volume fraction on the microstructure and fracture mechanisms 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.