Microwave heating and curing of metal-like CFRP laminates through ultrathin and flexible resonance structures

Abstract

Since 1980, microwave has been used to cure carbon fiber reinforced polymer (CFRP) composites with high efficiency and low energy consumption. However, for 40 years, this good vision has not been realized because microwave will be reflected by the preformed components, as multidirectional carbon fibers give CFRP laminates metal-like electromagnetic properties in-plane. Here, for the first time, we propose an idea to make the highly reflective CFRP laminates perfectly absorptive by introducing ultrathin and flexible metallic resonance structures supported by a dielectric spacer. We find that the metal-insulator-CFRP configuration can couple powerfully to the magnetic field of microwave. As a result, strong currents can be induced inside the multidirectional CFRP laminate, converting microwave energy to Joule heat. In this way, rapid energy-efficient heating of metal-like CFRP laminates has been realized, with an improvement of 36.3 times in heating efficiency and a reduction of 99.2% in energy consumption compared with autoclaves. A patterned heating process has also been demonstrated by adjusting the arrangement of resonance structures. Experimental results indicate that the mechanical properties of multidirectional CFRP laminates cured by high-pressure microwave are comparable or even higher than those of the autoclave processed counterparts. Our work not only paves the way for microwave curing technology but can also be promoted to other applications associated with electromagnetic waves and CFRP composites.