Molecular dynamics simulations on cyclic deformation of an epoxy thermoset

We use molecular dynamics simulations to study the thermo-mechanical response of a thermosetting polymer (diglycidyl ether of bisphenol A with 3,3′diamino-Diphenylsulfone) subject to cyclic loading for a family of tri-axial deformation paths and two different load levels and strain rates. We focus on how the relative amount of deviatoric and volumetric deformation affects strain accumulation and energy dissipation and find that uniaxial stress conditions lead to the highest rate of strain accumulation and dissipation. A characterization of the molecular-level processes responsible for strain accumulation provides insight into the observed role of volumetric and deviatoric deformations and explains the relatively low strain accumulation for purely deviatoric or volumetric loads. These results may help the design of polymer matrix composites with improved performance under cyclic loading conditions.