Identification of Impact Force on Stiffened Composite Panels

The use of composite panels in spacecrafts is increasing due to their high specific strength and specific stiffness. Since composite panels are susceptible to transverse impact forces, external impacts by foreign objects may induce damage in the composite structures and cause a catastrophic fracture. In order to expand the application of composite structures to the primary structures of spacecrafts, damage prediction and assessment of structural integrity in real time is required to assure its safety. The locations and force histories of impact forces are significant information that could be used for damage prediction. Therefore, impact force identificaton is important for and has been investigated by many researchers. Most of the impact force identification methods reported so far are modelbased identification methods, which require an analytical model of the structure. For instance, Yen and Wu1) reported the identification results of the location and force history of impact force acting on a rectangular plate. Seydel and Chang2) identified the location and force history of impact force acting on a stiffened composite panel. Zhang et al.3) conducted load reconstruction of low velocity impact load on an advanced grid-stiffened composite plate. Onozaki and Sekine4,5) proposed methods for identifying multiple point impacts using acceleration reponses. The authors6,7) proposed a method to identify the location and force history of impact force based on the finite element method. Recently, the authors8) have proposed an experimental impact force identification method, which does not require an analytical model of the structure, and verified its effectiveness. In this paper, identification of an impact force acting on a CFRP stiffened panel is conducted by two different impact force identificaton methods, i.e. the model-based identification method and the experimental identification method. First, the relations between the impact force and strain responses at measurement positions are determined. By employing the relations, the location and force history of the impact force are identified by adjusting the corresponding strain responses to the measured strain responses. 2. Identification Method of Impact Force