IMPACT DAMAGE MONITORING OF AIRCRAFT COMPOSITE STRUCTURES WITH PIEZOELECTRIC SENSORS

为了提高复合材料智能结构的可靠性和安全性，本文提出了一种基于应变传感器的复合材料智能结构实时自动健康监测方法。本研究的主要结论如下：1.提出了一种基于实验传递矩阵的力识别方法，并从复合材料层合板的动态应变响应中识别了冲击力的位置和历史。通过对CFRP加筋板的冲击试验验证了该方法的有效性，在冲击后几秒钟内可以准确地识别出冲击力的位置和历史.一个实时的损伤监测方法已经开发出使用识别的冲击力的历史。结果表明，损伤发生可以很容易地从识别的力历史的形状预测，其中的力历史的形状是光滑的没有损伤，而有一个尖锐的振荡与损伤.在落锤试验中，得到了冲击能量与最大冲击力、最大冲击力与损伤尺寸的实验关系，与有限元分析的预测值吻合较好。由有限元分析预测的脱层尺寸也有一个很好的协议与实验观察到的超声C扫描图像。

In the present research, we have developed a real-time and automatic health monitoring method for smart composite structures with strain sensors, in order to improve the reliability and safety of composite structures. The conclusions obtained by the present study are summarized as follows:1. We have proposed a force identification method using an experimental transfer matrix, and identified the location and history of impact force from dynamic strain responses in composite laminates. The validity of the present method is verified through an impact test of CFRP stiffened panels with impulse hummer, and the location and history of impact force can be identified precisely in a few seconds after impact.2. A real-time damage monitoring method has been developed using the identified impact force history. It is shown that the damage occurrence can be predicted easily from the shape of the identified force history, where the shape of force history is smooth without damage while that has a sharp oscillation with damage.3. The experimental relationships between the impact energy and the maximum force, and between the maximum force and the damage size have been obtained in drop-weight test, which have a good agreement with predicted ones based on the finite element analysis. Delamination size predicted by the finite element analysis has also a good agreement with that observed experimentally by the ultrasonic C-scan image.