Compression yielding of epoxy: Strain rate and temperature effect

The response to compressive mechanical loading of the thermosetting system epoxy polymer based on diglycidyl ether of bisphenol A (DGEBA) and an aromatic amine hardener, 4,4′-methylenedianiline (DDM) has been experimentally investigated as a function of strain rate and temperature, ranging from 0.0025 to 2500 s−1 and from room temperature to 100 °C, all below the glass transition temperature. Results showed that both the elastic modulus and the compression strength of the material significantly increased with strain rate and decreased with temperature. Quasi-static tests, performed in electromechanical machines, and dynamic tests, carried out in a Hopkinson bar, were compared and simultaneously analyzed to generate a master curve representative of the material yielding, assuming the strain rate-temperature superposition principle. Experimental data were fitted to equations based on thermally activated models for polymers.

► Compressive yield stress at high strain rates is much higher than at quasi-static.
► Increasing the strain rate up to 2200 s−1 increased 2–3 times the yield stress.
► The strain rate-temperature superposition principle can be applied to epoxy resins.
► The Eyring linear model for yield stress can only be applied at low strain rates.
► Equations based on the cooperative model have been used to fit experimental data.