Curing multidirectional carbon fiber reinforced polymer composites with indirect microwave heating

Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, multidirectional carbon fiber reinforced polymer composites can hardly be penetrated and heated by microwave directly, which has become a major obstacle in industrial application worldwide. In this paper, an indirect microwave curing method was proposed to solve this problem. The microwave absorption performance of the indirect microwave heating medium was systematically optimized by evaluating its dielectric properties and reflection loss according to the transmission line theory. On this basis, the microwave susceptive mold was carefully designed and manufactured. Subsequently, the multidirectional carbon fiber/epoxy composite was successfully cured with indirect microwave heating, which was demonstrated by the observation of the curing process with infrared thermal imager and differential scanning calorimetry analysis of the final products. Compared with the traditional thermal curing method, the curing cycle and energy consumption were reduced by 42.1% and 75.9% respectively. Results of further characterization experiments indicated that the mechanical properties of indirect microwave cured specimens were slightly higher than those of the thermally cured counterparts.