Research on the dynamic mechanical properties of polymethacrylimide foam sandwich structure

Abstract

Polymethacrylimide foam is fully closed-cell isotropic foam which possesses high stiffness and strength to weight ratios. The paper reports the findings of an experimental study developing to investigate the quasi-static and dynamic response of sandwich panels based on polymethacrylimide foam using compression tests and Split Hopkinson Pressure Bar, respectively. The effect of thickness of aluminum face sheet, thickness and density of the polymethacrylimide core on the mechanical properties of the sandwich structures are studied respectively. It is shown that core density has the greatest effect on compressive strength of sandwich structure. The elasticity modulus and compressive strength of sandwich decreased by 40% under quasi-static compressive when the density of the core reduced by 28%. Secondly, dynamic compressive experiment results show that when the density of the core reduced by 28%, at the strain rate of 150 s−1, compressive strength decreased by 45%; strain rate 310 s−1, compressive strength reduced by 42%. When the strain rate increased from 7.6 × 10−4 s−1 to 150 s−1, compressive strength increased by 26%; strain rate increases from 7.6 × 10−4 s−1 to 310 s−1, compressive strength increased by 43%. The dynamic mechanical properties of polymethacrylimide foam sandwich panels accompanied with the increase of strain rate. Finally, dynamic constitutive relation of Cowper-Symonds function is fitted.