Micromechanical analysis of strain rate-dependent deformation and failure in composite microstructures under dynamic loading conditions

This paper is intended to study the effect of microstructural morphology and loading characteristics on micromechanical stress-wave propagation leading to different damage mechanisms, energy absorption and dissipation characteristics. The composite material microstructure is represented by brittle fibers in a ductile matrix in different arrangements. The matrix material behavior is modeled using a strain-rate dependent elastic-viscoplastic constitutive model with damage evolution based on the Gurson-Tvergaard-Needleman model with a Johnson-Cook type hardening law. Damage in the fiber is modeled by an isotropic continuum damage mechanics (CDM) model. The microstructural failure modes and energy absorption and dissipation properties show strong dependence on the load types, volume fractions and microstructures, with relatively lower dependence on strain rates. The studies show that for the SiC fiber/Al7075-T6 composites, the microstructures with 15-20% unidirectional hexagonal arrangement of fibers are good designs for energy absorption and dissipation.