The Effect of Plasma Treatment on the Cure Behavior of Out-Of-Life Prepregs and an Investigation of the Mechanical Properties of Composite Parts Manufactured from Plasma-Treated Prepregs

Many industries, including aircraft, automobiles, and marine, are using prepreg (pre-impregnated fibers and a partially cured polymer matrix) to manufacture composite parts to achieve optimum fiber and resin volume ratio and part repeatability. Since prepregs have a short out of life (i.e., the maximum storing time allowed at room temperature), they must be stored in refrigerators at low temperatures, which, if not maintained, have an unfavorable influence on the intended quality of the final product. For the present study, glass/epoxy prepregs (expired out-life) were plasmatreated before being used to make the composite part to compensate for the room temperature aging effect. Plasma treatments contribute to the conversion of low-energy surfaces to higher energy surfaces by attaching oxygen-containing species. After plasma treatment, the surface energy change has been measured by measuring the contact angles formed by a polar liquid (water) and a non-polar liquid (diiodomethane) using the Double Sessile Drop technique. The effect of plasma treatment on curing behavior was monitored in real-time using temperature-controlled Broadband dielectric spectroscopy and then compared to untreated prepreg curing. Using differential scanning calorimetry, the cure kinetics (change in activation energy) of plasma-treated prepreg has been studied. Furthermore, the shear and tensile strength of the final product have been investigated to observe how plasma treatment helps to improve the mechanical performance of the composite part made with plasma-treated prepreg. Overall, this study will provide a thorough understanding of how surface modifications using plasma treatment affects curing behavior and improve mechanical performance.