Characterizing multi mechanical behaviors for epoxy-like materials under wide strain rate range

Polymers, extensively used in aerospace and transport industries, mostly present distinct strain rate dependent. Their mechanical behaviors under dynamic loading conditions have not been well characterized by succinct formulations for practical engineering. In this work, the mechanical behaviors of a representative epoxy are investigated under strain rates from 0.001 s−1 to 5100 s−1 using Instron 5848 and split Hopkinson bar apparatus, for its constitutive behaviors and efficient formulation to characterize their multi-mechanical behaviors. The materials present high rate-dependence and share similar mechanical behaviors under wide strain rates including multiple characteristics: peak stress followed by post-yielding stress softening, plateau stress and strain hardening. The results from the strain-controlled experiments facilitate to analyze the damage degradation after peak stress formulated by a modified Weibull model. A succinct constitutive model containing only eight parameters is then constructed with three parallel components: Weibull model, Maxwell model and power function, which can capture well the multi-mechanical characteristics. It is easily further extended to other polymer and composites from literatures with stronger characterization capacity by less parameters.