Effects of heat treatment on the microstructure and flexural mechanical properties of carbon fiber reinforced composite cured by electron beam

Carbon fiber (CF)-reinforced composite materials are attracting attention in the automobile and aerospace industries based on their light weight and excellent mechanical properties. Electron beam curing technology is replacing the thermal curing process and can improve productivity by shortening the curing time of CF-reinforced composite materials to minutes. However, the electron beam-cured CF-reinforced composite materials have weak flexural strength. We have found that the deterioration of flexural strength of electron beam-cured CF-reinforced composites can be solved by heat treatment in a vacuum bag prior to the electron beam curing process. Through heat treatment under vacuum, the viscosity of the matrix resin was lowered, and voids between the laminated surfaces of the CF prepregs could be removed. Through this approach, the flexural strength of the electron beam cured composite material reached 1.6 GPa, which was approximately 65% improved compared to the non-heat treated material. In addition, the energy distribution transmitted when the composite material is irradiated with an electron beam was simulated using the Geant4 code. It was confirmed that the nonlinear distribution of energy transmitted to the inside of the specimen according to the electron beam energy should be carefully considered in the design of the product shape and when setting the electron beam irradiation conditions.