Two semi-crystalline polymers: polyethylene and polyamide 66 are selected for experiments over a wide range of strain rates (10⁻²–1 s⁻¹ and 1000–4000 s⁻¹) at indoor temperature. The Young modulus and yield stress of these two materials show a great strain-rate sensitivity, implying that the semi-crystalline polymers possess obviously viscous properties. Based on the mechanical response of the materials, a corporative viscoelastoplastic constitutive model is developed to describe the dynamic response of semi-crystalline polymers. In the elastic region, a modified Kelvin model is employed to represent the viscoelastic behavior. In the post-yield regime, combining the modified Eyring theory and the strain hardening model, a corporative model is built to characterize the viscoelastic and strain hardening properties. Comparing to the experimental results for compression at high strain rates, it shows that the constitutive model accurately describes the mechanical dynamic response of semi-crystalline polymers.

A tungsten fiber/Zr-based bulk metallic glass matrix composite (Wf/Zr-MG) is a potential penetrator material. To compare and analyze the penetration behavior of Wf/Zr-MG and a tungsten heavy alloy (WHA), a penetration experiment into the 30CrMnMo homogeneous armor target plate (RHA) is conducted in the present paper, by using a 37 mm smooth bore artillery with an impact velocity of 1550 ± 40 m/s. Unlike the penetrator made of WHA, the self-sharpening phenomenon was observed in the nose of the Wf/Zr-MG rod. The experimental results indicate that the penetration ability of Wf/Zr-MG rod is approximately 10% higher than that of the WHA rod when the impact velocity is 1550 ± 40 m/s. The combined findings on the microscopic morphology, composition, hardness distribution around the crater, and the macroscopic structure of the penetrator residual show that under this impact velocity, the Wf/Zr-MG material shows amorphous gasification. The Wfs outside the rod shows bending and backflow, resulting in the maintenance of the self-sharpening nose of the penetrator during the penetration process. Moreover, the hardness peak around the crater formed by the Wf/Zr-MG rod is lower, and the penetration crater is straighter, indicating that the Wf/Zr-MG rod has a stronger slag removal ability, lower penetration resistance, and higher penetration efficiency. It is an ideal penetrator material.

The dynamic behavior of a woven glass-fiber-reinforced polymer composite at different strain rates was investigated. Regarded as a transversely isotropic material, dynamic compression tests of the composite in the normal and tangent directions were conducted by Split-Hopkinson pressure-bar devices. The experimental results show: (1) This composite is a viscoelastic material, and the dynamic compression-failure stress of the material indicates a distinct strain-rate hardening effect. The compression-failure stress in the normal direction increases by almost 30% when the strain rate changes from 900/s to 2000/s. The failure stress in the tangent direction is enhanced by 34% when the strain rate increases from 700/s to 2000/s. The failure stresses of the composite depend linearly on the strain rates, and the corresponding strain-rate hardening factors are 0.14 and 0.046 for the normal and tangent directions, respectively. (2) The dynamic compression-failure stresses and failure strains in the normal direction are significantly larger than the corresponding values in the tangent direction at different strain rates. Based on these results, the modified ZWT viscoelastic model was adopted, and the constitutive relationships of the composite in two directions are presented for characterizing their dynamic compression response.