<p>Coda waves have been shown to be sensitive to lab-controlled defects such as very small holes in fibrous composite material. In the real world, damages are subtler and more irregular. Higer sensitivity of coda waves to such subtle changes is an advantage for health monitoring complex structures like composites. The main objective of this work is to investigate coda wave sensitivity to low-velocity impact damages. The emphasis is to detect the presence of barely visible impact damage using ultrasonic waves. The estimation of the size of the damage is not the objective. This incipient damage state can grow into bigger flaws over the structure life and hence is the objective of interest. Five differential features, previously used in similar work, have been utilized to detect realistic impact damages on carbon fiber composites. Quasi-isotropic composite laminates were subjected to low-velocity impact energy ranging from 2J to 4.5J. Not all differential features have shown promising results, but some features could detect the presence of damage. It is observed that ply orientation can be a deterministic factor for indicating damages. The size and shape of the impact damage have been characterized using ultrasonic c-scans. Results indicate that coda waves are sensitive to small impact damages.</p>

Coda Waves for the Health Monitoring of Composites Under Low-Velocity Impact

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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