Rapid Manufacture of Thin Composites via Infrared-Assisted Frontal Polymerization

Abstract

State-of-the-art technologies for manufacture of fiber-reinforced polymer composites (FRPCs) rely on bulk polymerization of matrix thermoset resins at elevated temperatures for several hours (up to 24 h) in an autoclave or oven. This process is energy- and time-intensive, generates a significant carbon footprint, and requires expensive equipment. In recent years, frontal polymerization (FP) has emerged as an alternative approach for rapid and energy-efficient curing of FRPCs. However, widespread and practical adoption of this curing technique at industrial scale is limited by the low front velocities (<10 cm min-1), the need for using highly thermally insulating tooling materials (e.g., polymer foams), and low degree of cure of resin in produced composites. In addition, frontal curing of thin composite laminates is quite challenging even on highly thermally insulating tooling materials due to the high rate of heat loss through boundaries compared to the generated heat, resulting in quenching of reaction and incomplete cure. Here, we present a new approach for rapid curing (~50 cm min-1) of FRPC panels via FP by supporting the underlying thermal curing reaction using a moving infrared heating source. In our approach, following the infusion of a carbon fiber composite layup by an FP resin system, an infrared heating source is linearly moved along the length of the layup to not only initiate the FP reaction via photothermal energy conversion effect but also locally pre-heat the resin and increase its frontal reactivity and front velocity. We successfully cure a 5 Å~ 15 cm2 composite panel on a glass tool plate within 24 s with a total energy consumption of 8.3 kJ as a proof of concept. Differential scanning calorimetry measurements are also conducted on produced laminates to determine the degree of cure of produced FRPCs. Finally, a thin laminate, consisting of a single ply of carbon fabric is fabricated as a proof-of-concept to further demonstrate the capability of our technique for rapid manufacturing of thin composites, which is promising for use in space and aerospace applications.