| Dynamic loading response is an important design parameter, which is critical in severe applications where impact loading occurs, but which has been little investigated to date for MMCs. Those MMCs which have been tested at high strain-rates so far have been diverse in terms of matrix alloy and reinforcement type, size and shape, making comparisons difficult. In this study, four different MMCs, SiC particulate and whisker reinforced, {dollar}rm Alsb2Osb3{dollar} short and long fiber reinforced, representing currently available MMC groups, have been compression tested at quasi-static and high strain rates {dollar}rm({lcub}sim{rcub}10sp3 ssp{lcub}-1{rcub}).{dollar}; It has been shown that the strain rate sensitivity of the composite is very similar to that of the corresponding unreinforced alloy for the following composites: SiC{dollar}rmsb{lcub}p{rcub}{dollar}/2024 Al MMC, SiC{dollar}rmsb{lcub}w{rcub}{dollar}/2124-T6 Al MMC, {dollar}rm Alsb2Osb3{dollar} (Saffil) short fiber reinforced Al-1.2wt%Cu in a direction normal to the Planar Random Fiber Plane, and {dollar}rm Alsb2Osb3{dollar} (FP) long fiber reinforced Al-3wt%Li MMC tested in the transverse direction.; In {dollar}rm Alsb2Osb3{dollar} Saffil short fiber reinforced Al-1.2wt%Cu MMC tested in a direction parallel to the Planar Random Fiber Plane and FP-{dollar}rm Alsb2Osb3{dollar} long fiber MMC in the longitudinal direction, the strain rate sensitivities of the flow stress or maximum stress were found to be higher than those of the monolithic alloy. The increased strain rate sensitivity in Saffil short fiber reinforced MMC was found to be a combined effect of matrix rate sensitivity and load carried by fiber until about 5% strains. The increased rate sensitivity of FP reinforced MMC in the longitudinal direction was due to the increased fiber buckling stress which scaled with matrix shear stress.; Microscopic observations have shown that, in SiC whisker reinforced MMC, the failure was controlled by thermal softening and strain localization at high strain rates. In Saffil reinforced MMC, the reduced fiber fragment size at high strain rates and increased extent of matrix voiding were the dominant deformation mechanism at high strain rates. The failure in FP reinforced MMC in the longitudinal direction was due to microbuckling leading to kink formation. |
