Quantitative stiffness evaluation and damage mechanism investigation in open-hole composites via multi-modal SHM data fusion

Accurate assessment of stiffness in composite laminates remains a critical challenge for structural integrity evaluation. This study develops a novel multi-modal structural health monitoring (SHM) framework that synergistically integrates ultrasonic guided wave (UGW) and acoustic emission (AE) technologies, capitalizing on their complementary strengths: UGW’s sensitivity to mechanical property variations and AE’s damage-mode classification capacity. The methodology proposes an UGW propagation characteristic-based numerical model to establish quantitative correlations between UGW phase velocity variation and stiffness reduction across distinct damage modes, with inputs derived from AE signal analysis. Initially, to acquire the damage ratios across different damage stages and understand the damage process, we perform clustering analysis on AE signal features, dividing the damage process into different stages and identifying primary mechanisms contributing to stiffness degradation. Additionally, the finite element method (FEM) simulation is conducted to further validate the damage mechanism, in conjunction with DIC results and fractographic analysis. Key findings reveal that abrupt stiffness reductions (quantified through UGW phase velocity shifts) exhibit a strong temporal correlation with high-energy AE events, indicating the feasibility and sensitivity of UGW-based stiffness monitoring. Finally, we employ AE events number as input for the UGW-based stiffness/velocity model, thereby integrating the complementary information from UGW and AE to establish a quantitative relationship between damage severity and actual stiffness variation. Comparative analysis demonstrates a < 2.3 % deviation between numerical predictions and experimental AE cumulative counts across all damage stages. This integrated approach provides a novel method in composite damage monitoring that enables quantitative mapping between non-destructive evaluation metrics and mechanical property evolution.