Veil binder morphology and interfacial performance of carbon fiber preforms: Resin spreading, impregnation, and interlaminar shear strength

초록

In carbon fiber-reinforced polymer composite manufacturing, preforming stabilizes fiber arrangement before resin impregnation and improves the reproducibility of final composite properties. Polyamide (PA) veils are effective binders for fixing carbon fiber tows; however, their molten morphology can affect resin impregnation and interfacial formation in the final composite. In this study, PA veil-based carbon fiber preforms were fabricated by infrared heating, and the effects of heat-source distance and processing speed on veil morphology, preform bonding, resin impregnation, and interlaminar properties were investigated. Resin flow behavior was further analyzed using simultaneous optical observation and top- and bottom-electrode electrical resistance (ER) responses as spreading- and impregnation-related indices. Processing speed was the dominant factor controlling veil melting and preform bonding. Localized melted veil domains balanced preform stability and resin impregnation by allowing freer resin progression, whereas thin, widely spread veil layers retained resin on the surface and restricted internal resin flow. The combined optical and ER results confirmed that localized veil domains produced a delayed bottom ER response while resin continued to progress into the preform. These results demonstrate that veil morphology governs preform bonding and resin impregnation, and that ER monitoring is an effective in situ method for evaluating resin flow in veil binder-based carbon fiber preforms. © 2026 Elsevier Ltd

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