EFFECT OF TEMPERATURE ON DELAYED YIELD AND FAILURE OF PLASTICIZED EPOXY RESIN

Epoxy‐Versamid specimens were loaded in tension up to failure at different constant strain‐rates and temperatures. Results revealed three modes of behavior prevailing at different temperature‐strain‐rate regions and associated with brittle, ductile and rubbery failure modes. The ductile region was found to be confined within a narrow band on the temperature‐strain‐rate plane, and is characterized by a yield plateau in the stress‐strain curve and by linear dependence of yield stress on log strain rate and temperature. Yield strain seems to be almost unaffected by strain‐rate, but decreases slightly with temperature rise. Analysis indicated that experimental data within the ductile region are consistent with Eyring's formulation for non‐Newtonian viscoplastic flows. It leads to the evaluation of the “apparent activation energy” and activation volume for the two epoxy systems tested. Comparison with previous work indicates that the above parameters as well as yield stress and elastic modulus tend to increase with the decrease of the Versamid content in the resin. Copyright © 1969 Society of Plastics Engineers, Inc.