Reducing the Effect of Water on the Fatigue Properties of S-Glass Epoxy Composites

An epoxy resin composed of N,N-diglycidyl tribromoaniline (DGTBA) crosslinked with metaphenyline diamine (MPDA) has proven to be far superior to standard epoxy systems in reducing the effect of long-term water immersion on the fatigue life of epoxy-S glass composites. The results of experiments indicate up to a 20 to 30 percent improvement in fatigue life retention for the DGTBA/MPDA-S glass system over conventional bisphenol-A based epoxy-S glass systems. Copolymers of DGTBA and diglycidyl ether of bisphenol-A (DGEBA) containing over 50 percent DGTBA have essentially the same fatigue properties as those with pure DGTBA matrices. Copolymer results are explained in terms of a simple relationship between matrix water absorption and composite fatigue life.