Components of the carbon fiber-reinforced SiC-matrix composites,or C/SiC composites,are mapped with scanning electron microscope(SEM)and X-ray computed tomography,including C fibers and fiber bundles,SiC matrix,and inter-and intrabundle voids.Dynamic loading is applied by split Hopkinson pressure bar,gas gun and electrical gun at strain rates of 102-103 s-1,and the recovered specimens are examinated by SEM.A microstructure-based modeling is developed to simulate micro damage evolution with finite element method.For the in-plane compressive loading,two dynamic fracture modes illustrated by high-speed photography are actually induced by inhomogeneous micro-structures.One fracture mode promoting the toughness significantly(increase of 35%),mostly without strength decrease,provides a promising way for micro-structure optimization of C/SiC composites.For the out-of-plane tensile loading,failure involves delamination,fiber pullout and fiber breaking.In contrary to normal solids,dynamic tensile or spall strength decreases with increasing impact velocities,owing to compression-induced pre-damage before subsequent tensile loading.For hypervelocity impact loading,the distribution of debris clouds shows "three zones" mode,forming with different mechanisms,and demonstrates that there is a high-energy powdering column in the entre zone.Furthermore,the damage induced by hypervelocity impact significantly reduces the strength of C/SiC composites.