Inspection of GFRP composites using capacitive imaging

• Main Author: Toh, Choon Hong
• Other Authors: Fan Zheng, David
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Manufacturing::Quality control
• Online Access: https://hdl.handle.net/10356/163686
• Institution: Nanyang Technological University

Various defects, most notably delamination and debonding can form on Glass-Fibre Reinforced Plastics, during manufacturing processes and during a components’ service life, which could severely limit its capabilities. Current widespread methods used to inspect GFRP include Ultrasonic Testing (UT) and Eddy current testing, but they have long processing times, expensive equipment and are limited by some inconveniences, such as requiring a coupling medium for Ultrasound Testing. Hence, a low-cost, high-speed non-destructive testing (NDT) method able to reliably detect and locate the presence of defects on GFRP is required. As such, this Final Year Project (FYP) aims to explore Capacitive Imaging (CI), a low-cost non-destructive inspection technique that utilises an electrical approach based on the capacitance of co-planar electrodes to detect irregularities on a material, and its effectiveness on GFRP. Ultrasound Testing, a well-established NDT method proven to work on GFRP, was compared with the CI result to ascertain its effectiveness. Both NDT methods are applied on various GFRP samples with planted defects. Results have shown that CI is generally unable to detect planted defects on CSM GFRP. Although it roughly locates surface and subsurface defects for unidirectional GFRP and woven GFRP, it is unable to measure the defect size precisely. It has also shown that higher scanning speed could enhance CI’s ability to pinpoint the location of defects on woven samples. This makes CI a good complementary NDT method together with Ultrasound Testing in identifying defects. Future work would involve translating the proof-of-concept into a preliminary prototype using low-cost electronics and explore the possibility of a multiplexed sensor array to reduce scanning time.