This study presents a pointwise ultrasonic A-scan method for detecting interfacial debonding in co-cured CFRP/PVC foam core sandwich composites. A 10 × 10 grid-based measurement was performed on specimens with and without adhesive film, acquiring A-scan signals from 100 discrete points per sample. The collected waveforms were averaged and analyzed in both time and frequency domains. Key indicators such as tensile test, waveform amplitude, weighted root mean square (RMS) energy, and spectral amplitude were extracted to distinguish bonded and debonded regions. Results showed consistent differences in tensile test and weighted RMS energy difference (ΔE%), primarily attributed to variations in resin distribution and interfacial bonding quality. Energy-based imaging and normalization techniques further enhanced the analysis of resin distribution and visual differentiation between sound and defective areas. The proposed method demonstrates that pointwise A-scan acquisition, combined with signal averaging and energy analysis, offers a practical and non-destructive approach for assessing hidden debonding in composite sandwich structures.

Keywords: Ultrasonic A-scan, CFRP sandwich composite, Non-destructive evaluation (NDE)