A novel noise-resistant method for damage identification in Composite plates using equivalent mode shape derivatives

This paper proposes a novel non-destructive testing method for damage identification in composite plates, which is based on Frequency Response Functions (FRFs)-integrated Equivalent Mode Shape Derivatives (FEMSD), to address the critical challenge of measurement noise degrading the accuracy of vibration-based methods. The proposed method constructs noise-robust equivalent mode shape derivatives by leveraging FRFs within adaptively optimized frequency bands. Its core innovation lies in uniquely determining these optimal frequency bands by minimizing the equivalent mode shape's mean curvature. This strategy autonomously balances noise suppression with modal fidelity without any prior knowledge of the uncontaminated mode shape. Validation via numerical simulations and experiments on composite plates with matrix cracks and delamination shows that the proposed method establishes a robust and noise-resistant framework, outperforming the conventional Mode Shape Derivative Based Damage Identification (MSDBDI) method in accuracy, noise robustness, and reliability. It achieves accurate identification of a 112-mm crack at 10 % noise and 40 × 40 mm delamination at 15 % noise, whereas the MSDBDI method possesses 0 % noise tolerance for accurate identification. Experimental validations further confirm the method's practicality, demonstrating that it eliminates false positives generated by MSDBDI and yields identification results consistent with ultrasonic C -scans.