Influence of strain rate on the deformation and fracture response of a 6061-T6 Al–50 vol.% Al 2O 3 continuous-reinforced composite

Abstract

The compressive mechanical properties of an aluminum–matrix composite unidirectionally reinforced with Al 2O 3 fibers have been measured and characterized as a function of loading orientation. The influence of strain rate and fiber orientation on the deformation and fracture response of a 6061 Al–50 vol.% Al 2O 3 continuous fiber-reinforced metal–matrix composite (MMC) aged to a T6 condition is reported. The stress–strain response of this composite was found to vary substantially as a function of loading orientation; the quasi-static yield changing from nominally 250 MPa transverse to the fibers to ∼1.7 GPa parallel to the fibers under ideal conditions. Increasing the strain rate to 2000 s −1 was observed to only slightly increase the yield strength of the composite for both orientations. The main failure mechanism has been identified to be kinking, although an upper bound seems to be attained when the fibers reach their compressive strength. The experimental results are consistent with a plastic kinking model for strain hardening composites. The failure response of the composite transverse to the fibers, under both uniaxial stress (quasi-static and dynamic) and uniaxial strain loading, displays a protracted but substantial load drop after yield followed by continued degradation in load carrying capacity. Lack of ideal parallel fiber construction was found to lead to systematic buckling failure of the alumina fibers through the sample under uniaxial loading.