Through-thickness crystallinity gradient controls warpage reduction in CF/PAEK via in-situ consolidation automated fiber placement

Aiming at reducing the warpage that occurs during in-situ consolidation automated fiber placement (ISC-AFP) of thermoplastic composites, this article explores, for the first time, the through-thickness crystallinity distribution characteristics of laminate and its effect on warpage. A tool-temperature-compensation isothermal consolidation (TTC-IC) technology is proposed to achieve warpage suppression. The research results indicate that laminate crystallinity decreases gradually from the bottom to the top layer. At a fixed initial consolidation temperature, higher tool temperatures (T_tool) reduce the through-thickness temperature gradient during consolidation. However, as T_tool increases, the through-thickness crystallinity gradient of the laminate also increases, resulting in greater warpage. This indicates that crystallinity gradient dominates the warpage. Via the proposed TTC-IC technology, the through-thickness crystallization gradient of the laminate was reduced, achieving a reduction of 33.33% in warpage and 46.1% in porosity. This study addresses the knowledge gap in warpage formation mechanisms for laminates fabricated via ISC-AFP and introduces a novel in-situ technological approach for warpage control.