Electron beam cure of fiberglass/epoxy prepregs

Recently developed epoxy resin prepregs were electron beam cured and experimentally explored to determine their suitability for use in an aerospace-quality aircraft component. There were two major goals for this program. The first was to determine whether the electron beam-curable prepregs were capable of meeting the requirements of the U.S. Air Force T-38 supersonic jet trainer composite windshield frame. The T-38 windshield frame is currently manufactured using an aerospace-grade prepreg composed of 6781 S-2 woven fiberglass and various 250 °F thermally-cured epoxies. The second goal was to develop the lowest cost hand layup and debulk process that could be used to produce laminates with acceptable properties. The laminate properties examined to determine prepreg suitability include laminate mechanical and analytical properties at room and elevated temperatures, prepreg tackiness, prepreg out-time capability, and the debulk requirements needed to achieve these properties. Four resins and three fiber sizings were experimentally examined using this criteria. One epoxy and one fiber sizing were found to have suitable characteristics in each of these categories and were later chosen for the manufacture of the T-38 windshield frame. This experimental study shows that by using low-cost debulk and layup processes, the electron beam-cured prepreg mechanical and analytical properties are in the range of comparable thermally-cured prepregs.