Accelerated aging of an epoxy glass under elevated temperatures and compressive stresses

The aging of the diglycidyl ether of bisphenol-A (DGEBA) cured with diethanolamine was studied both in its "neat" state and filled (at 50 vol%) with glass microballoons (D32-4500, 3M). Cylindrical test samples were compressed uniaxially and the stress-strain curves were analyzed for materials properties (principally the maximum,or yield, stress). Samples were oven-aged at five sub-Tg temperatures for extended times before testing at their aging temperatures and a range of strain rates. As the glass densifies during aging, the yield stress increases. The effect of applying uniaxial stress to the samples during aging is also studied. The samples are held at ~70% of the yield stress over periods of time (up to 24 hrs.), unloaded and then reloaded through yield. The recovery strain and yield stress are found. The yield stress is found to increase and the recovery strain to decrease as aging time increases. The rate of increase of the yield stress is compared to the oven-aged tests.