Damage Detection Via Electrical Impedance Tomography in a Filament Wound Glass Fiber/Epoxy Composite Tube with Carbon Black Filler

Abstract

Fiber reinforced polymer composites are increasingly being used in the automotive, aerospace, and many other sectors owing to their superior specific stiffness and strength. Filament winding provides means to manufacture cylindrical fibrous composites finding applications in building stronger pressure vessels and corrosion-resistant piping systems. With the expanding use of composites to build vital structural components, there arises the need to monitor the health of these structures. The primary challenge in health monitoring of composites involves the detection of nonvisible and sub-surface damage. Current methods to address this issue in filament wound composites include embedding optical fiber or piezoelectric sensors during the manufacturing process. Apart from introducing weak spots in the structure, embedding these sensors make the manufacturing process difficult and time consuming. Nanofiller modified matrix composites impart conductive properties to the composite which can be leveraged for health monitoring with minimal changes to the manufacturing process. The self-sensing capability of these composites can be combined with conductivity imaging modalities such as electrical impedance tomography (EIT) for damage identification and localization. EIT is a low-cost, real-time imaging technique in which the electrical conductivity of the body is inferred from boundary voltage measurements. To date, however, EIT has been primarily used on planar geometries such as rectangular composite coupons. Therefore, this work demonstrates the potential of EIT for damage detection in non-planar, multiply connected domains – a carbon black (CB)-modified glass fiber/epoxy filament wound composite tube. The results show that multiple through holes as small as 7.94 mm can be detected for tubes with a diameter-to-length ratio of 1:2. It was also observed that the sensitivity of this method improved as the aspect ratio of the tube decreased. These preliminary findings strongly indicate the potential of using EIT for damage detection in more complex geometries such as self-sensing filament wound composite tubes.