Radiation-Curable Carbon-Fiber Prepreg Composites

Radiation processing is the utilization of ionizing radiation, usually photons or electron beams, to produce useful physical and chemical changes in a material. A potential application for electron beam processing for composite manufacturing is for curing carbon fiber prepregs. These prepregs, carbon fibers or fabrics preimpregnated with liquid polymer resin, are commonly used in the aircraft industry. Their use, however, can be time consuming and labor intensive. The advantages of radiation curing over thermal or chemical curing methods include improved rate control, reduced curing times, and curing at ambient temperature. There is no need for chemical initiators. A radiation-curable prepreg has been designed to meet the mechanical and physical property specifications of a leading aircraft manufacturing company. The resin is a mixture of an expoxy diacrylate, polybutadiene diacrylate, and a multifunctional monomer. This resin was used to impregnate a plain weave carbon fabric, at a loading of 35 percent (by mass), using a solvent process. Preliminary characterization studies show that the cured polymer produced by irradiation in air to a dose of 40 kGy is amorphous with a maximum gel fraction of 85 percent. The softening point of the polymer varied from 228°C (30-kGy sample) to 237°C (50-kGy sample). The linear thermal expansion coefficient of the polymer was 1.7 × 10−4 m/m°C from 25°C to 150°C and was unaffected by varying the applied dose from 30 to 50 kGy.