Effect of line-focused infrared heating-assisted CF/PEEK in-situ consolidation compaction force on interlayer shear strength

Line-focused infrared (LFIR) heating technology is an emerging heating method with high heat flux density/fast response rate, which can meet the demand of automatic placement of thermoplastic composites. Interlaminar performance is an important indicator of the overall quality of composites, and compaction force is a key factor affecting the quality of in-situ consolidated interlaminates. In this study, line-focused infrared heating-assisted in-situ consolidation experiments under different compaction forces were designed to investigate the law and mechanism of compaction force effects on the interlayer bonding properties. The results show that the interlayer shear strength (ILSS) increases nonlinearly with compaction force in the compaction force range of 100-400N, and the average ILSS strength of the 400N specimen increases by 17.27 MPa compared with that of 100N, which is an increase of 85.9%. The micro-morphological analysis showed that the effect of porosity on the interlayer bond strength was particularly prominent. At high compaction forces, the porosity decreased, the pure interlayer separation section of the specimen was flatter, and the interlayer contact was tighter. In addition, pressure analysis of the pressure-sensitive paper showed that the effect of the surface morphology of the raw Prepreg tows on the initial close contact between the layers was weakened as the compaction force increased, and the effective contact area increased. Finally, thermal history analysis shows that higher compaction force can reduce the interlayer contact thermal resistance and increase the temperature of 2-3 layers by 15 °C–30 °C. This paper reveals the mechanism of compaction force on key factors such as porosity and surface morphology, as well as the effect of compaction force on the temperature history, which provides a theoretical basis for optimizing the manufacturing process of composites.