基于光纤光栅传感的CFRP胶接接头损伤监测与识别研究

Carbon fiber reinforced plastic (CFRP) has advantages of light-weight, high-strength, low thermal expansion coefficient, corrosion resistance, excellent fatigue and high designable, etc. It has become an indispensable key material of aircraft design, and the design of adhesive joints has become an essential step in structure designing. However, due to the lack of empirical research and validation on damage monitoring and identification of CFRP adhesive joints in the service environment, the structural design and damage analysis rely on theoretical analysis and finite element simulation, which leads to the difficulties of accurately determining and predicting the damages and failures. Therefore, this project named “Research on carbon fiber reinforced plastic adhesive joints damage monitoring and identification based on fiber bragg grating sensing" is proposed, aiming at building the strain fields characteristics of the damage on CFRP adhesive joints, putting forward the reconstruction method of Fiber Gratings of CFRP adhesive joints under inhomogeneous strain fields, constructing distributed FBG sensing network of CFRP adhesive joints, establishing the model of mapping relationship between the strain field characteristics and damage, building the system of damage online monitoring of CFRP adhesive joints under typical load, putting forward the theory and method of damage identification on CFRP adhesive joints based on strain field. These studies establish the theoretical foundation for the optimal design of CFRP adhesive joints and the application of FBG sensors on damage monitoring of CFRP adhesive joints.

碳纤维复合材料（CFRP）具有轻质高强、热膨胀系数小、耐腐蚀、抗疲劳和材料可设计性强等优点，已成为飞行器设计中不可或缺的关键材料，其胶接连接接头的设计也成为结构设计中必不可少的关键环节。然而，由于缺乏CFRP胶接接头在服役环境下损伤的监测与识别的实证研究，其结构设计和损伤分析主要依赖理论分析和有限元仿真，导致其损伤与失效很难准确判别和预测。为此，本项目提出基于光纤光栅传感的CFRP胶接接头损伤监测与识别研究，旨在建立CFRP胶接接头损伤的应变场表征，提出CFRP胶接接头在非均匀应变下的光纤光栅光谱重构方法，构建CFRP胶接接头的光纤光栅应变分布式传感网络，建立应变场特征与损伤之间的映射关系模型，搭建在典型载荷下CFRP胶接接头的光纤光栅损伤监测系统，提出基于应变场的CFRP胶接接头损伤识别的原理与方法，为CFRP胶接接头的优化设计及光纤光栅在胶接接头损伤监测与识别中的应用奠定理论基础。

碳纤维复合材料（CFRP）胶接连接接头的设计也成为结构设计中必不可少的关键环节。本项目针对各类型CFRP胶接接头提出基于光纤光栅传感的损伤在线监测与识别问题进行研究，根据CFRP胶接接头的类型，主要从平面搭接和正交连接两类对象展开研究。. 在平面搭接胶接接头损伤监测与识别研究方向主要成果有：（1）对基于非均匀应变重构方法对CFRP单搭接胶接接头的内聚损伤演化过程监测进行了研究，提出了一种基于遗传算法的FBG传感区域非均匀应变重构方法。对不同载荷下的单搭接胶接接头被粘件的应变分布进行了重构，重构的应变分布曲线与理想应变分布曲线的最大误差不超过7.43%。（2）分析胶层内聚损伤对CFRP被胶接件应变的变化情况，判断不同载荷作用下胶接接头的损伤状况，构建具备可靠性特点的分布式FBG应变传感网络系统实现了CFRP双搭接胶接接头的内聚损伤监测。实现了CFRP双搭接胶接接头载荷作用下胶层的内聚渐进损伤过程的监测。. 在正交连接胶接接头损伤监测与识别研究方向主要成果有：（1）分析了L形CFRP胶接接头胶层的内聚损伤演化过程，得到了被胶接件胶接区域的层间应变分布的变化与胶层损伤演化间的映射关系，构建了基于FBG传感的L形CFRP胶接接头的内聚损伤监测实验系统，验证了仿真映射关系模型的准确性，最大误差不超过8.5%。（2）基于损伤力学确定了碳纤维复合材料π型胶接接头的损伤判定准则，仿真分析了拉伸载荷作用下碳纤维复合材料π型胶接接头的损伤过程，得到了损伤演化过程与应力应变分布变化的映射关系。在接头损伤部位埋置FBG传感器对CFRPπ型胶接接头进行了拉伸实验，利用传输矩阵法对FBG传感区的反射光谱进行了计算，并运用粒子群算法在理论上对碳纤维复合材料π型胶接接头FBG传感区的非均匀剥离应力分布进行了重构研究，重构误差不超过5.46%。. 本项目利用光纤光栅传感在非均匀应变作用下的光谱特性对CFRP胶接接头损伤监测展开研究，为CFRP胶接接头的优化设计及光纤光栅传感技术在飞行器CFRP胶接接头损伤监测中的应用奠定理论基础。