Effect of defects in laying process of carbon fiber prepreg on the properties of sample

Defects such as gaps and overlaps introduced during automated fiber placement (AFP) can significantly affect the mechanical performance of carbon fiber-reinforced polymer (CFRP) laminates. This study systematically investigates the influence of different defect types and layout strategies on the tensile, compressive, and bending properties of CFRP laminates. Six defect configurations were designed, including three gap widths and two overlap widths introduced between specific laminate plies. Theoretical analysis of resin squeeze flow was conducted to understand the contact behavior between prepreg layers. Finite element simulations were used to model resin deformation under compaction, validating the theoretical predictions. Experimental testing was performed on specimens prepared using T700/G06 unidirectional prepreg, with detailed measurements of mechanical strength and variability. The results show that small overlaps can improve mechanical performance due to enhanced fiber continuity, while gaps consistently reduce strength by introducing discontinuities and local porosity. These findings highlight the critical role of defect arrangement strategy in AFP processes and offer practical guidelines for defect management in composite manufacturing.