Post-joining thermal characteristics and repair integrity of carbon fiber-reinforced thermoplastic composites during ultrasonic reconsolidation at 20 kHz

Ultrasonic reconsolidation offers significant potential to replace traditional adhesive bonding techniques used in the aerospace industries for bonding repair patches to damaged composite structures without resin additives. Temperature, a characteristic variable, is a key factor influencing the quality of joints in ultrasonic welding of thermoplastic composites. In this study, instead of measuring temperature during the joining process, the focus was on post-joining analysis on temperature at various hold times and holding forces. The findings revealed that an average hold time of 5 s and a holding force of 750 N produced higher-quality joints with minimal damages to fiber bundles and residual matrix. Additionally, it was recommended that repair patches should only undergo a maximum of two reconsolidation cycles. Beyond this point, the fibers and matrix begins to degrade, leading to a 35% reduction in mechanical performance after the fourth cycle.