Damage Detection of Filament Wound Composite Cylinder Using Ultrasonic Waves

Abstract

This paper experimentally investigates the damage detection of filament-wound (FW) thick-wall composite cylinder using ultrasonic waves. The multi-layered cylinder has a 20 mm-thick steel liner with an inner radius of 421 mm, an 11 mm-thick layer of unidirectional carbon fiber reinforced composite that is wound on the steel liner, and a 2.15 mm-thick layer of coating over the composites. Damages are pre-manufactured in different wall depths of the cylinder. The main damages to be detected include the defects in the composite layer, the interface debonding between the composite layer and the steel liner, and the change of thickness of the steel liner due to corrosion. To interrogate above mentioned damages, the longitudinal waves are excited using an ultrasonic transducer in pulse-echo mode along the radial direction of the cylinder. The continuous wavelet transform (CWT) is used to analyze the reflected-ultrasonic signals in order to obtain the Time-of-Flight (ToF) and the amplitude ratio of different interfaces. Based on the ToF and amplitude ratios, the location and size of the damages are identified and the thickness of the steel liner is determined. Experimental results show that the ultrasonic pulse-echo technique combined with the CWT is feasible in damage detection of multi-layered filament-wound composite cylinder especially when a coating layer exists.