Over the past few years, considerable effort has been directed toward the development and improvement of mechanoluminescence (ML)-based stress sensing as an efficient nondestructive inspection technique. One of the challenges in ML stress sensing is the limited luminescent intensity and sensitivity of the ML-epoxy composite film to the local stress field. Herein, we present a novel approach for increasing the sensitivity of ML composites made of an epoxy resin matrix and SrAl₂O₄:Eu²⁺, Dy³⁺ 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.

中文翻译：

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通过结构健康监测的功能化提高机械发光复合材料的灵敏度

在过去的几年里，作为一种有效的无损检测技术，人们已经做出了相当大的努力来开发和改进基于机械发光 (ML) 的应力传感。ML 应力传感的挑战之一是 ML-环氧树脂复合膜对局部应力场的发光强度和敏感性有限。在此，我们提出了一种提高由环氧树脂基体和 SrAl ₂ O ₄ :Eu ²⁺ , Dy ^{3+制成的 ML 复合材料的灵敏度的新方法。}用（3-氨基丙基）三乙氧基硅烷功能化的颗粒。我们对环氧树脂/ML 复合材料样品进行了拉伸试验，以研究 ML 颗粒的表面改性对发光灵敏度的影响。对改性表面进行了一系列表征分析以研究界面结合。此外，我们将改性的 ML/环氧树脂涂料涂在拉伸试样的一侧，在另一侧设置人工隐形缺口，通过光强度 (LI) 分布可视化应力场，然后通过有限元分析比较结果（有限元分析）。ML 颗粒的表面改性提高了灵敏度并引入了新的化学键，对应于通过界面键合而不是仅仅机械锁定的更大应力转移。此外，在缺口试样上应用的 ML 薄膜可以显示 LI 的特定图案，反映了裂纹的存在，这已通过 FEA 模拟得到证实。这意味着所提出的增强 ML 薄膜的方法有望用于无损预测试样中裂纹的存在、形状和剩余寿命。