Design and testing of kinematic electromagnetic induction heating system for manufacturing of high-performance carbon fiber composites

The present paper reports development of a novel concept of electromagnetic induction heating system for manufacturing of high-performance carbon fiber reinforced polymer (CFRP) composites. The proposed induction heating system consists of several key parts such as medium-to-high frequency generator, induction coil with 3 degrees of freedom movement controlled by a CNC software, high-resolution thermal imaging camera with live workpiece temperature distribution data processing algorithm. The proposed system allows for mitigation of highly non-uniform temperature distribution associated with induction heating such as formation of cold spots, skin and corner effects, which are further amplified due to high material anisotropy of CFRPs caused by difference in mechanical and physical properties in longitudinal and transverse direction of the fibers. In the present work, movement of the induction coil during induction heating was set to simple cyclic rectangular paths which resulted in a more uniform temperature distribution and a significantly larger area of composite subjected to sufficient curing temperature compared to static coil systems. Efficiency of induction curing of the designed system was evaluated by experimental measurement of temperature distribution in dry fabrics and pre-preg laminates. Validation of induction heating system efficiency was performed by mechanical and degree-of-cure experimental tests of different configurations of carbon/epoxy prepreg laminates. Additionally, challenges in air void entrapment in the material due to non-uniform distribution of soft and solid resin regions during the curing process were encountered and potential mechanisms of their entrapment were analyzed.