Processing Science of Epoxy Resin Composites

The Processing Science of Epoxy Resin Composites program investigated the interrelationships between the resin and prepreg physical and chemical properties of 177C 350F curing epoxy resin systems and how these properties ultimately affected the processing characteristics of the material. The primary influence in affecting laminate quality was determined to be the volatiles in the resin. The major volatile was determined to be water. The situation, however, was more complicated than just the quantity of volatiles that were in a resin or prepreg. Rather, the point of volatile release and local concentrations played a significant role in void formation. Associated also with void formation was vacuum application during processing. Mathematical models have been developed to describe the collective effects of diffusivity, solubility, surface tension, resin flow, and pressure on the removal of volatile material and entrapped air within a laminate. Two techniques were developed to insure pressure translation into the resin during processing, i.e., 1 bagless curing of consolidated parts and 2 internal bag pressurization. These processes have proven to be quite successful in part fabrication, if prior processing cycles were employed.