Non-linear mechanical behavior of amorphous glassy polymers: An experimental review

This review provides an overview of the non-linear mechanical behavior of amorphous glassy polymers under constant strain rate (CSR) testing. These materials exhibit complex responses to mechanical loading, including yielding, strain softening, and strain hardening, arising from the interplay between their out-of-equilibrium structure and the applied deformation. While many studies have addressed isolated aspects of glassy polymer behavior, a unified examination centered specifically on CSR tests remains limited. We first discuss the fundamental origins of non-linearity, including geometric effects and intrinsic mechanisms. Key features of the mechanical response, such as stress–strain curves, volume changes, molecular mobility, and ductile–brittle behavior, are then described. Finally, the effects of critical experimental variables, including strain rate, temperature, hydrostatic pressure, and thermal history (e.g., aging and annealing), are systematically reviewed. By consolidating findings across diverse studies, this review aims to clarify the characteristic mechanical behavior of amorphous glassy polymers in CSR tests and provide a foundation for future experimental and modeling efforts.