Bond Line Monitoring Technology for Aircraft CFRP Structure Using Lamb Wave

Abstract

We have been developing a Structural Health Monitoring (SHM) System for Carbon Fiber Reinforced Plastic (CFRP) structure of aircraft. This system can diagnose structural integrity of the composite and metal aircraft structure by analyzing a Lamb wave which is a type of ultrasonic wave. Our SHM system consists of Macro Fiber Composite (MFC) piezoelectric actuators, Fiber Bragg Grating (FBG) optical fiber sensors, interrogation unit and control/analysis software. The MFC actuators and the FBG sensors are worked as source and detector of the Lamb wave, respectively. The Lamb wave propagates into aircraft structures and if there are some damages and defects in the structures, measured waveform will be changed. The analysis software of the SHM system can calculate degree of the damages and the defects by evaluation of the waveform change. The SHM system has been developed as an inspection and maintenance support system for the composite aircraft structure and it will reduce operation cost and improve flight safety. In the previous study, we had shown that the SHM system could diagnose debonding length quantitatively in the edge of the skin/stringer bonding region, generally called Hot-Spot. And Probability of Detection (PoD) of the system was also evaluated. In this study, the SHM system is enhanced to be able to diagnose more widely region and its damage detection ability is evaluated. Test results show that the SHM system can diagnose structural integrity precisely not only in the HotSpot region but also entire bond-line of the composite aircraft structure. doi: 10.12783/SHM2015/25