High Strain Rate Performance of Thermoset Epoxy Resins

Fiber reinforced thermoset resins make up an important part of armor packages for ballistics applications.  While a significant amount of work has been done understanding fiber and composite performance, relatively little has been done to understand or improve thermoset matrix energy absorption during high strain rate impact.  Furthermore, the mechanical performance of epoxy resins is well understood at quasi-static to low impact velocity strain rates, but has not been extensively explored for regimes above about 10² s^-1.   In the present work, we explore the high strain rate performance of diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) cured with a large variety of amine-based agents, representing a range in glass transition temperature of greater than 150^oC.  Samples were investigated using differential scanning calorimetry, dynamic mechanical analysis, rheological measurements and ballistic testing at temperatures below the glass transition with a view toward obtaining a fundamental understanding of the dissipative influence of molecular relaxations and, more broadly, molecular structure.  Correlations between temperature and V50 (velocity at which 50% of samples are penetrated during the impact test) are presented and interpreted in light of dynamic mechanical analysis relaxation data.