Microwave Assisted Curing of CFRP Composite Laminates for Aerospace Applications

Microwave curing of glass–epoxy composites is a well-known processing technique for rapid curing of aerospace and allied structural components. However, microwave assisted curing of unidirectional (UD) and bidirectional (BD) carbon-epoxy composites has some associated challenges such as arcing and possible damage to the microwave sources. The presence of continuous carbon fibers affects the penetration of microwave radiation, because of the electrical conductivity and electromagnetic reflection of carbon fiber bundles. These limitations affect the full-fledged utilization of this rapid and energy-efficient processing technique. In the present work, vacuum assisted microwave curing of 2 ± 0.5 mm thick UD-CFRP and BD-CFRP laminates has been successfully achieved using a custom-developed dual frequency microwave cure facility. In order to circumvent arcing and its detrimental effects, process refinements were made such as use of special microwave amenable molds, bagging, and consumable arrangements, which resulted in the microwave cured CFRP laminates exhibiting physical, thermal and mechanical properties similar to or exceeding those of equivalent oven-cured ones. Application of vacuum resulted in good compaction of the plies while the use of microwave amenable molds resulted in rapid and uniform curing of the composite as determined using a thermal imaging camera.