Tension–compression asymmetry in viscoelastic mechanical behavior and micro–mesoscale coupling mechanisms of composite propellant

Solid propellants are particle-filled polymeric materials exhibiting nonlinear viscoelastic properties. In this study, viscoelastic compression tests are conducted on solid propellants. The compression nominal stress–strain curves exhibit a J shaped. Relaxation time and viscous stress increase with increasing deformation. The Tension–compression asymmetry in viscoelastic behavior is analyzed. Compared with tension, compression induces higher stress, longer relaxation time, and a larger viscous part. The mechanisms of nonlinear relaxation and Tension–compression asymmetry are analyzed through free volume theory and mesoscale simulations. At the microscopic scale, the limited free volume hinders the rearrangement of molecular networks and chain segments under large deformations. Less free volume and more coiled chain segments under compression lead to higher stress and longer relaxation time. At the mesoscopic scale, the patterns of interface debonding and damage evolution differ under tension and compression. The strength disparity between interfaces and particles leads to distinct tension and compression modulus. The micro–mesoscale coupling mechanisms result in Tension–compression asymmetry in the macroscopic viscoelastic mechanical behavior. The methodology and findings provide insights for multiscale investigations of other particle-filled composites.