Mechanical Behavior of Repaired Multi-Layered Woven Lattice Sandwich Composites Using Acoustic Emission

Acoustic emission (AE) was employed to characterize the mechanical behavior of repaired multi-layered woven lattice sandwich composite (MWLSC) in this paper. A patch repair strategy was adopted, in which damaged cores were reconstructed with polyurethane foam and fractured face sheets were restored using fiber fabric. Mechanical recovery was evaluated through mechanical testing, and AE monitoring was used to analyze damage evolution before and after repair. The repaired double-layered and triple-layered warp specimens recovered 123% and 104% of their original peak load, respectively, while the triple-layered weft specimen recovered 83%. Compared with pristine specimens, repaired MWLSC exhibited reduced cumulative AE counts and lower proportions of high-energy events. Continuous wavelet transform analysis revealed that the high-frequency components associated with interfacial delamination were significantly diminished after repair. These results indicate that repair modifies the dominant failure mechanism, shifting from delamination-dominated fracture toward core-related damage. The study demonstrates the effectiveness of AE techniques in capturing changes in damage evolution and mechanical response in repaired MWLSC.