Research on a novel annealing strategy for AFP of thermoplastic composites

In laser-assisted in-situ consolidation technology, the products are subjected to highly rapid cooling due to the relatively narrow heating zone and fast layup speed, resulting in reduced crystallinity, insufficient interlayer bonding, and warpage deformation. This study developed a line-focused infrared heater (LFIH) that is easy to integrate with automated fiber placement (AFP) equipment and validated its effectiveness in annealing thermoplastic composites (TPCs). A comprehensive mathematical model was developed to correlate the structural characteristics of the LFIH with the heat flow field, coupling it with a 3D finite element model utilizing the DFLUX subroutine to predict the evolution of the temperature field distribution. The results indicate that the LFIH effectively achieves strong focusing characteristics, fulfilling the requirements for the annealing treatment of TPCs. Furthermore, the simulation and experimental results exhibit close agreement, with peak annealing temperature discrepancies among layers maintained within 7 %. After annealing treatment with the LFIH, the crystallinity and interlayer properties of the layup products were improved, while the porosity and warpage deformation of the layup products were reduced. This novel, high-energy-density annealing strategy effectively enhances the quality of laminates.