力致荧光传感技术在复合材料结构健康检测中的应用

Composite materials have the advantages of high strength and light weight, being widely used in aerospace, automotive, medical, etc. However, due to their complex structure, conventional detection methods cannot achieve real-time monitoring of damage and failure in composites structures. Mechanoluminescence refers to a phenomenon that a solid emits light emission under mechanical activation. This effect could convert mechanical energy into a sensitive optical signal, acting as a bridge linking the microscopic molecular level and macroscopic material properties. It is expected to be used in the development of high-sensitivity structural health monitoring technologies and plays an important role in the detection of structure damage detection and failure mechanisms. The project includes the following parts: (1) Systematic study of the synthesis conditions for the preparation of mechanical responsive phosphors EuD4TEA and SrAl2O4: Eu2+ to improve luminescent properties; (2) The in-depth development of force-induced fluorescence theoretical models and establishment of the relationship between luminescent performance and structure; (3) Fabrication of epoxy and phosphor powder compositing coating with stress-sensing capability using spray curing technology, and adjustment of the elasticity and tensile strength of composite surface to optimize sensitivity. Examination of fluorescence under the mechanical action (Three-point bending, reciprocating stretching, quasi-static compression) using the spectrometer and high-speed camera, and investigation of the relationship between the fluorescence intensity and the loading force / mechanical strain energy / strain. (4) Model building with ABAQUS finite element analysis for composite structures, validating the pressure sensitive properties of mechanoluminescent coating; (5) Development of a distributed detection system with force-induced fluorescent particles and optical fibers, which are embedded uniformly in carbon/glass fiber based composite materials. Photomultiplier tubes (PMT) are used to detect the optical signal to monitor the interface delamination and matrix crack damage of the composite materials. The accuracy, response speed, and sensitivity of the detection technology are verified on composite components and assembly for aerospace and the influence of the embedded detection system on mechanical properties of composites is evaluated.

复合材料由于结构复杂，常规检测手段无法实现损伤信息实时监测。力致荧光是在机械作用下固体产生荧光的现象，该效应将机械能转换成灵敏的光信号，是连接微观分子水平与宏观材料性能的桥梁，有望用于发展高灵敏度的结构健康监测技术，在结构损伤探测与失效机理研究方面发挥重要作用。本项目包括：（1）改进荧光粉EuD4TEA及SrAl2O4:Eu2+的合成工艺，提高力致发光性能；（2）深入发展力致荧光理论模型；（3）环氧聚合物和荧光粉共混液喷涂固化在复合材料表面，调控弹性模量及拉伸强度，采用光谱仪和高速摄像机获取在机械作用（三点弯曲，往复拉伸，准静态压缩）下的荧光释放，建立荧光强度和加载力/机械应变能/应变的关系；（4）运用ABAQUS有限元分析，与实验结果对比，论证力致荧光型压感涂层的精确度；（5）开发力致荧光+光纤+光信号探测以及力致荧光+光伏传感+电信号探测的复合分布式结构健康监测系统。

力致荧光/变色是指在机械力(变形、力致、碰撞、振动等)作用下材料产生光释放或者颜色变化的现象。本项目合成了具有力致变色功能的自感知形状记忆聚氨酯薄膜，改善了物理填充分散不均匀，易结晶析出的问题，制备的螺吡喃接枝聚氨酯材料在应力传感器、损伤预警等方面具有潜在的应用价值。优化了机械荧光环氧聚合物的合成工艺研究及力学响应功能，利用形状记忆高分子的变刚度特性，用于不同形状构件的结构健康监测，建立了机械发光强度和分布与荧光粉含量和负载条件的关系。开发基于力致荧光+光纤+光检测器以的结构健康监测传感系统，实时监测动态应力变化，对应力集中具有很高的敏感性，能有效识别冲击等载荷作用。开展形状记忆大变形复合结构的有限元模拟，验证制力致荧光/变色无损监测技术的识别可靠性。. 本项目通过分子改性，提高力致荧光粉在不同温度湿度下的稳定性差的问题。本项目深入讨论机械力诱导荧光的普遍性发光机理，通过预固化环氧，增加溶液粘度等一系列手段，提高粒子在聚合物中的均匀分散度。本项目采用大直径分布式聚合物光纤，通过间隔刻蚀外层，提高信号噪声比，解决荧光信号不稳定信号采集效率低，采集难的问题，实现高效无损伤的结构内部健康监测。优化机械荧光环氧涂层技术，提高涂层在复合材料结构表面的结合力，解决了形状记聚合物及复合结构的应力分布可视化的难题。