Measurement and Modeling of the Effect of Aging on the Compressive Yield of Epoxy

Cylindrical specimens of a bisphenol A epoxy resin and polyetheramine curative were made following standard procedures and tested in compression over a range of temperatures and strain rates. The resin and curative were reacted to completion, annealed above Tg, and cooled at a controlled rate in order to define a known thermal history. The resulting stress-strain curves were analyzed for the yield stress. The yield stress is a highly non-linear property and is challenging for constitutive modeling to predict. The sensitivity of the yield stress to physical aging is probed by aging at temperatures 5 to 10 $^{\circ}$C below the Tg before applying the compressive load. Yield stresses under the experimental conditions are predicted by the activated-process based Ree-Eyring theory as well as by the SPEC constitutive mode and compared to the experimental results. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.