Dynamic hysteresis brittle behavior and temperature–strain rate-coupled damage modeling: A multiscale study of poly(phthalazinone ether sulfone ketone) under extreme service conditions

Poly (phthalazinone ether sulfone ketone) (PPESK) is a new-generation high-performance thermoplastic resin that exhibits excellent thermal stability and mechanical properties. However, its damage and failure mechanisms under high-temperature and high-strain-rate coupling conditions remain unclear, significantly limiting the engineering applications of PPESK-based composites in extreme environments such as aerospace. To address this issue, in this study, a temperature-controlled split Hopkinson pressure bar experimental platform was developed for dynamic tensile/compressive loading scenarios. Combined with scanning electron microscopy and molecular dynamics simulations, the thermomechanical behavior and failure mechanisms of PPESK were systematically investigated over the temperature range of 293–473 K. The study revealed a novel "dynamic hysteresis brittle behavior" and its underlying "segmental activation–response lag antagonistic mechanism". The results showed that the strain-rate-induced response lag of polymer chain segments significantly weakened the viscous dissipation capacity activated by thermal energy at elevated temperatures. Although high-strain-rate conditions led to notable enhancement in the dynamic strength of the material (with an increase of 8%–233%, reaching 130%–330% at elevated temperatures), the fracture surface morphology tended to become smoother, and brittle fracture characteristics became more pronounced. Based on these findings, a temperature–strain rate hysteresis antagonistic function was constructed, which effectively captured the competitive relationship between temperature-driven relaxation behavior and strain-rate-induced hysteresis in thermoplastic resins. A multiscale damage evolution constitutive model with temperature–rate coupling was subsequently established and numerically implemented via the VUMAT user subroutine. This study not only unveils the nonlinear damage mechanisms of PPESK under combined service temperatures and dynamic/static loading conditions, but also provides a strong theoretical foundation and engineering guidance for the constitutive modeling and parametric design of thermoplastic resin-based materials.