Abstract
Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation.
Highlights
Composite materials are prime candidates for structural applications, such as aerospace, marine, automotive and infrastructure industries, because of their specific strength and stiffness but are expensive to maintain
This work was devoted to debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures by using the fiber optic Doppler (FOD) sensor
The FOD sensors can be embedded in composite structures, instead of mounted on surface of structure, to protect them from damage in practical applications. Both the He-Ne-laser-based and the infrared-semiconductor-laser-based interferometers were proposed for the purpose of guided wave detection using fiber optic Doppler (FOD) sensor
Summary
Composite materials are prime candidates for structural applications, such as aerospace, marine, automotive and infrastructure industries, because of their specific strength and stiffness but are expensive to maintain. A questionnaire based end-user requirements [2,3], performed under the Brite Euram project monitor, demonstrates that the major causes of in-service damage to composites structures in aerospace industry are low velocity impacts such as bird strike, runway stones and tool-drop (hangar rash) during maintenance and standby. These events lead to BVID (barely visible impact damage) which are prime sources of delamination and fiber cracking in composites structures. This work was devoted to debonding damage detection of lap splice joints in CFRP structures by using the FOD sensor. Debonding damages are assessed by using characteristics of guided wave signals
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