Uniaxial quasi-static compression performance of PMI foam at different temperatures and constitutive model establishment

Abstract

Abstract The uniaxial compression failure mode of polymethacrylimide (PMI) foam under the combined action of heat and load was investigated from the macro and micro perspectives. Moreover, the heat resistance of the material was analyzed by dynamic mechanical analysis and dimensional stability tests. The stress-strain curve of the PMI foam in the range of 20℃–200℃ at different stages of compression failure mechanism was revealed, and the Liu-Subhash model was used to accurately predict the stress-strain constitutive relationship of PMI at different temperatures. The results showed that, in the range of 20℃–180℃, the material is an elastoplastic material, and the stress-strain curve exhibits a typical 'three-stage' pattern. When the temperature is 200℃, the material is transformed completely into a hyperelastic incompressible material, and the stress-strain curve exhibits a 'two-stage' pattern. In addition, the temperature effect on the yield strength and elastic modulus of the material and the strain rate effect at different temperatures were also discussed. Finally, based on the Liu-Subhash model, a PMI quasi-static compression constitutive model considering the temperature effect was established. This conclusion provides theoretical support and data input for the study of the thermo-mechanical combined bearing mechanism of composite sandwich structures.