Multiscale computational model for polymer matrix composites under impact loading, including adiabatic heating effects

It is well known that significant heat generation often accompanies the high rate inelastic deformation of polymers. As the rate of deformation increases, the thermodynamic condition transitions from isothermal to adiabatic. Adiabatic conditions can be assumed for polymer matrix composites under ballistic impact loading, where local matrix temperature rises have been experimentally observed to exceed the matrix glass transition temperature. In this work, a multiscale modeling approach is used to provide insight into the effects of matrix adiabatic heating on the impact response of a triaxially braided polymer matrix composite. Unified thermo-viscoplastic constitutive equations, recently extended by the authors to i) more accurately account for tension-compression asymmetry, ii) ensure physically realistic plastic flow, and iii) ensure thermodynamic consistency, are applied at the microscale to describe the nonlinear deformation of the thermoset polymer matrix. The thermo-viscoplastic constitutive equations are implemented into the doubly-periodic generalized method of cells micromechanics framework, which is subsequently implemented into LS-DYNA as a user defined material subroutine. Local temperature rises in the matrix due to plastic dissipation are computed via the heat energy equation. The user routine, in conjunction with a subcell-based approach to approximate the mesoscale composite braid architecture as an assemblage of laminated composite subcells, is utilized to conduct simulations of quasi-static coupon tests and flat panel impact experiments conducted on a T700/Epon 862 [0°/60°/-60°] triaxially braided composite. Available experimental data is used for model characterization and validation. Impact simulation results indicate significant local temperature rises in resin rich regions in an impact event, which are expected to play a major role in the prediction of progressive damage and failure in polymer matrix composites under impact loading.