Improving the Sensitivity of the Mechanoluminescence Composite through Functionalization for Structural Health Monitoring

particles functionalized with (3-aminopropyl)triethoxysilane. We performed a tensile test on an epoxy/ML composite specimen to investigate the effect of surface modification of ML particles on the luminescent sensitivity. A series of characterization analyses were performed on the modified surface to investigate the interfacial bonding. In addition, we applied the modified ML/epoxy paint to one side of the tensile specimen with an artificial invisible notch on the other side to visualize the stress field via light intensity (LI) distribution and then compared the results through a finite-element analysis (FEA). Surface modification of ML particles increased the sensitivity and introduced new chemical bonds, corresponding to a larger stress transfer through interfacial bonding rather than mere mechanical locking. In addition, the applied ML film on the notched specimen could visualize the specific pattern of LI reflecting the presence of a crack, which was confirmed by the FEA simulation. This implies that the proposed method of enhancing the ML film is promising for nondestructively predicting the presence, shape, and residual life of a crack in a specimen.