Monitoring the repair process of internal microdamages in thermoplastic composites using optical coherence tomography

The reliability of composite structures critically depends on effective damage repair. This study employs optical coherence tomography (OCT), a non-destructive imaging technique capable of generating cross-sectional images of translucent materials, to investigate the repair of early-stage microdamage in thermoplastic composites. Using electrical resistance heating, the healing of a microscale void in a carbon fiber-reinforced ethylene-vinyl acetate (EVA) polymer sample was monitored through OCT-derived scattered light intensity and phase difference measurements. Firstly, the void healing process was observed using a self-developed OCT system. Repair parameters, including initiation and completion times, were then estimated from the scattered light intensity changes in the defective region. Additionally, phase-contrast imaging was utilized to analyze phase difference patterns, enabling the computation of displacement fields across the defective cross-section and providing quantitative insights into the healing dynamics. The findings demonstrate the efficacy of OCT in monitoring and characterizing the repair processes of composite materials, highlighting its potential as a valuable tool in structural health assessment.