Development of high-toughness aerospace composites through polyethersulfone composition optimization and mass production applicability evaluation

Abstract

Owing to the necessity of developing airframe materials for military unmanned aerial vehicles (UAVs), capable of operating in extreme environments, aerospace-grade composite materials were developed using a high-toughness epoxy-resin system, and were subsequently analyzed and evaluated. The phase transition behavior of a high- toughness epoxy-resin system was modeled and simulated as a function of the toughening agent, polyethersulfone (PES), and its content to optimize the resin system. Reliability was ensured through experimental validation. At the maximum PES content compatible with the base epoxy-resin and curing agent contents, the epoxy-resin system exhibited the highest tensile strength and toughness. However, results from preliminary tests performed using the pilot process revealed that an increase in viscosity beyond a certain level due to the addition of PES rendered it unsuitable for application in mass-production processes. The optimal composition of the high- toughness epoxy-resin system suitable for mass production was determined based on the results of the resin paper production using the pilot process. High-toughness carbon fiber-reinforced plastics (CFRPs) were then mass produced, and their characteristics were compared with those of conventionally toughened CFRPs and the pilot products. The results confirmed that compared with the conventionally toughened CFRPs, the massproduced CFRPs containing the high-toughness resin system showed 246%, 728%, 392% and 480% improvement in compression-after-impact strength, Mode-I interlaminar fracture toughness (ILFT), Mode-II ILFT for crack initiation, and Mode-II ILFT for crack propagation, respectively. In addition, these composites were used to manufacture UAV wings to evaluate their applicability in airframe structures.