In-situ crystallization process monitoring of thermoplastic composites by dielectric sensing during laser-assisted automated fiber placement

Abstract

The crystallization process during the laser-assisted automated fiber placement (LAFP) is important for the mechanical performance and process-induced deformation of fiber reinforced thermoplastic composites. However, there is lack of method for in-situ crystallization process monitoring of thermoplastic composites during the LAFP process with rapid cooling and multiple heating. Here we present a novel dielectric method for in-situ measurement of crystallization development of glass fiber reinforced polypropylene (PP) during the LAFP process using interdigital electrodes for the first time. The accuracy of the dielectric method was verified by standard XRD and DSC methods at different cooling rates. Furthermore, the effect of laser power on crystallinity was analyzed by the proposed method. The feasibility of this method for monitoring crystallinity development during continuous LAFP process was performed. We anticipate that the dielectric method offers considerable potential for quality monitoring for the LAFP process and other additive manufacturing processes for thermoplastic composites.