Elastic-viscoplastic constitutive model for capturing the mechanical response of polymer composite at various strain rates

Recently, polymer composites, consisting of hard segments and soft segments blend, attract a broad research interest because of the high flow stress and large deformation under a high rate loading. They display an outstanding energy absorption capability for impact resistant engineering. In this paper, a physics-based elastic-viscoplastic constitutive model is developed which accounts the activation of molecular chains motion at different segments upon an applied stress as well as the rate dependency of mechanical properties. Accordingly, finite element simulations are conducted to derive the mechanical performance at various strain rates. It involves the linearly elastic deformation to yielding, softening behavior with a slight decrease of stress, plastic flow at a plateau stress accompanied by a considerable straining, densification with a fast increase of stress. The results achieved from model simulations match well with these obtained by experiments and the mechanical response in the strain rate range from 0.0001 s⁻¹ to 8000 s⁻¹ can be captured by this model. Finally, energy absorption capability of the polymer composite is discussed, and the physical mechanisms in material science are addressed by post-loading analysis. This work is full of interest to develop the constitutive model for designing the impact-resistant polymers and illustrating the dynamic mechanical response, which will promote the application of light-weight transparent protection structure against a high-speed impact.