Characterization and modeling of the uniaxial thermo-mechanical compressive behavior of polymethacrylimide (PMI) foam at different temperatures

This paper investigates the uniaxial compressive failure behavior of polymethacrylimide (PMI) foam across a range of temperatures (20 °C–200 °C), at both macro- and microscales. The investigation includes dynamic mechanical analysis and dimensional stability tests to evaluate the material’s heat resistance. The stress–strain curve of PMI foam under varying compressive failure mechanisms was analyzed, utilizing the Liu–Subhash model for accurate prediction of the material’s stress–strain constitutive relationship at different temperatures. The results indicate that between 20 °C and 180 °C, PMI foam behaves as an elastoplastic material, displaying a “three-stage” pattern in its stress–strain curve. At 200 °C, the material transitions to a hyperelastic incompressible state, evidenced by a “two-stage” stress–strain pattern. The paper also determines how temperature affects yield strength and elastic modulus, as well as the influence of strain rate at different temperatures. A quasi-static compression constitutive model for PMI foam, considering temperature effects, was modified from the Liu–Subhash model. These findings offer crucial theoretical support and data for understanding the thermo-mechanical bearing mechanism in composite sandwich structures.