Detection of impact damage of stiffened composite panels using embedded small-diameter optical fibers

摘要

It is well known that barely visible damage is often induced in composite structures subjected to out-of-plane impact, and the mechanical properties of the composites degrade markedly. The stiffened composite panels which are the representative structural elements of airplanes are characterized by impact damage different from that of coupon-level specimens. Therefore, the objective of this study is to apply small-diameter optical fiber sensors to stiffened composite panels for the detection of impact damage. In this study, both multi-mode optical fibers and fiber Bragg grating (FBG) sensors are used for detecting impact load and impact damage in stiffened composite panels. The fibers have polyimide coating with 40 mum cladding diameter which has no serious effect on the mechanical properties of composites. Impact tests are performed using stiffened composite panels with embedded optical fibers. The characteristics of impact damage are investigated. The impact load, the strain and the optical responses of the optical fibers are measured as a function of time. And we discuss the relationships among the optical responses, the impact load and the impact damage.