Unraveling the distinct dynamic mechanical responses and damage mechanisms of two typical polymers across wide strain-rate and temperature ranges

Rigid-chain and flexible-chain polymers are both widely employed in protective engineering, yet their mechanical responses under dynamic loading differ substantially. A comprehensive understanding of these differences is essential for developing high-performance materials. In this study, we comparatively investigate the dynamic mechanical responses and damage mechanisms of two typical polymers—polyimide (PI) and Ultra-High Molecular Weight Polyethylene (UHMWPE)—across a wide strain-rate range (10 -3 –10 4 s -1 ), using a Split Hopkinson Pressure Bar (SHPB) system and scanning electron microscopy (SEM). The results reveal that UHMWPE undergoes two distinct strain-rate-dependent damage stages under dynamic loading: (i) a wrinkle-dominated stage, where dense wrinkle structures facilitate stress transmission and the stress–strain response transform from smooth yielding to stress plateau, and (ii) a crack-dominated stage, where microcrack formation produces opaque fibrous morphologies, leading to strength degradation and overlapping stress–strain curves of different strain rate within the 0–0.2 strain range. In contrast, PI consistently exhibits microcrack-driven failure across all loading conditions, with stress–strain curves characteristic of brittle polymers, including high modulus and yield strength. Temperature effects further distinguish the two polymers: PI maintains remarkable thermal stability at elevated temperatures (>473 K), showing negligible variation in mechanical response and damage mode, whereas UHMWPE demonstrates pronounced temperature sensitivity, with significantly reduced yield strength and more prominent wrinkle morphologies at elevated temperatures. To quantitatively capture these behaviors, we establish a modified G’Sell–Jonas constitutive model, enabling accurate description of the dynamic responses of both polymers. This work provides new mechanistic insights into the contrasting strain-rate and temperature-dependent behaviors of rigid-chain and flexible-chain polymers, offering a scientific basis for the design and optimization of high-performance polymers. • UHMWPE exhibits two strain-rate-dependent damage stages under dynamic loading. • Wrinkle structure of UHMWPE appears in the wrinkled-dominated stage. • Crack in UHMWPE cause strength degradation and overlapping stress–strain curves. • PI consistently exhibits microcrack-driven failure across all loading conditions. • The difference stems from the distinct molecular chain mobility of these materials.