- Abstract The dynamic high-strain-rate behavior of boron carbide-based composites with similar phase composition yet different microstructural features, namely, amount of residual silicon, average grain size and morphology of the SiC particles, was investigated as a function of the planar impact strength. The composites consisted of boron carbide preforms (compacted or partly sintered powder) with or without free carbon addition, infiltrated with molten silicon. The dynamic response of the composites depends strongly on the amount of residual silicon, on the average size of the boron carbide grains, and on the morphology of the SiC particles. The preliminary sintering of the preforms exerts no effect on the dynamic properties of the composites. The deformation and failure mechanisms under dynamic loading are discussed.