面向复合材料薄壁结构健康监测的层合微元动态响应理论

Damage occurence and propagation in thin-walled aerospace composite structures seriously jeopardize the safety and reliability structures in service. Thus the developement of structural health monitoring and damage identification methods becomes of highly improtance in recent years. Most existing vibration-based damage identificaiton methods are dependent on the establishment of structural global models and baseline signals. The effectiveness of such methods is limited by factors such as boundary condition. Moreover, existing methods focus intensively on mathematical analysis rather than investigations of physical essence, which hampers the precision and reliability of damage identificaiton. The proposed project aims at developing a new damage identificaiton approach relying on the dynamic response of infinitesimal laminate element. With an explict physical implication, the approach is independent of global modelling and baseline signals; and the damage detection strategy is straightforward and reliable, able to adapt the variation of enviromental factors in engineering applications. The theoretical model of damage indicator is to be derived based on dynamic equilibrium of laminate element; and the detection method is to be established without knowledge of structural baseline parameters; the noise influence of detection result is to be estimated quantitatively; and the damage indicator is to be reconstructed experimentally based on displacement/strain measurement. The achivement of the project is expected to eliminate the limitation of vibration theory in the application of damage identification, and the proposed method is also expected to contribute to the improvement of the safety of structural service and the effeciency of health maintenence.

航空航天复合材料薄壁结构内部损伤的产生和扩展对飞行器运行的安全性与可靠性构成严重威胁。因此，针对该类结构的在线健康监测与损伤识别成为近年来的研究热点。目前振动理论框架下的损伤检测方法大多依赖结构整体建模与基准信号采集，其有效性受到边界条件等因素制约。另外，现有方法过多偏重数学分析而忽略了对物理本质的研究，使损伤识别精度与可靠性无法得到保障。该项目以复合材料层合微元动态平衡为出发点，提出了基于微元动态响应的损伤检测理论。该理论物理意义明确，摆脱了对基准信号与整体建模的依赖；且损伤识别方法简单可靠，能够适应实际工况下环境因素的变化。拟通过理论推导构建层合微元损伤因子理论模型；建立未知基准参数下的损伤检测机制；完善探伤信号信噪比水平定量评估；采用分布式位移/应变测量技术实现损伤因子实验重构。预期成果有望突破振动理论应用于损伤检测领域的固有局限，并在提高结构安全性，降低检修成本等方面做出贡献。

本项目针对复合材料薄壁结构内部损伤的高精度监测，提出了新型的微元动态平衡理论。开展了层合微元动态响应与复合材料薄壁结构局部损伤的关联性分析，着重推导了基于复合材料板结构动态平衡方程的损伤因子理论模型；建立了未知基准参数下损伤检测机制，以实测动态响应为已知量对基准参数进行反向估算，使损伤识别在未知基准参数环境下进行；开展了损伤因子分布特征的统计学分析与量化 ，以数值仿真为主要手段，从统计学角度建立损伤识别精度与测点密度、测量噪音等影响因素的相互关 系，为设置实验参数和发展滤波技术提供依据；开展了含分层损伤复合材料加筋层合结构损伤识别的可靠性研究； 实现了基于分布式应变传感信号的损伤定量识别，基于应变信号构建动态位移信号，进而完成损伤的定量识别。同时着重开发新型柔性传感器网络，进一步提高损伤识别的可行性。.本项目基于复合材料层合结构的微元动态关系建立了损伤因子理论模型，并通过实验与数值分析，验证了基于该模型的损伤识别有效性与精度。从原理方面分析，该方法将复合材料动态平衡与损伤进行了有效关联，是对现有损伤识别理论的延伸，具有一定科学意义。从应用角度分析，该方法可以基于先进传感网络实现结构损伤的在线定量监测，对航空航天等结构的服役安全性与可靠性提供保障。除此之外，项目还建立了基于应变测量的位移分布重构方法，以及新型的纳米复合材料传感器制备方法，在相关理论与工程应用领域做出了贡献。