Composite materials are used as a vital material in aerospace structures because of their excellent strength-to-weight ratios. In recent years, the fiber reinforced composite laminates, for example, carbon fiber reinforced plastics (CFRP), have already been used in many fields besides in aerospace structures, and the increasing applications are expected for this kind of materials now. On the other hand, composite laminated plates are vulnerable to external impacts and internal damages such as delamination, fiber breakage and matrix cracks can be caused easily. These internal damages might extremely reduce the mechanical properties of laminates such as their compressive strength. Therefore, it is necessary to monitor structural conditions and to detect impact damages in real-time by nondestructive inspection. However, some existing nondestructive inspection methods, such as ultrasonic wave, X-ray and thermography, need to suspend the operation of structures, and have the possibility of human carelessness. Therefore, it is difficult to guarantee the integrity of structures with high reliability in real-time. Accordingly, the concept called as structural health monitoring is drawing much attention recently. Structural health monitoring is a technology that automatically monitors structural conditions from sensor information, by equipping sensor network into structures and implementing diagnosis software into computers. Besides direct detection of damages, generally the information of applied external force is also very important and useful in assessment of integrity of structures. As a part of health monitoring studies for composite structures, an experimental identification method of impact force is presented in this study.
edited by Hideaki MIYAZAWA