Electromagnetic acoustic transducer inspection of composites

Abstract

Composites have seen an increase in utilization across all industries due to their desirable mechanical properties. Defects may form in composite components during manufacturing or in-service. If left undetected and untreated, these flaws may lead to catastrophic failure of the component. As a result, there is a need for effective non-destructive methods to monitor and detect flaws in composite parts and components. In this study, the use of electromagnetic acoustic transducers (EMAT) to inspect carbon fiber reinforced polymer (CFRP) samples was explored. Given that ultrasonic immersion testing (UT) is presently widely used across different industries to inspect composite materials, the same samples were also tested using UT to set a baseline for comparison. The EMAT scan results vis-à-vis the UT scan results were then analyzed.

Three CFRP samples with different thicknesses were prepared for this study. Side-drilled holes (SDH) and flat-bottomed holes (FBH) of varying sizes were drilled into the samples as artificial defects. Using an automated immersion UT system, B and C-scan images of the samples were produced. Due to equipment limitations, point testing was conducted on the same samples using the EMAT system. The A-scans obtained from UT and EMAT were then compared. The overall capability of the two systems to detect, size and locate defects was also discussed.

Based on the results obtained, it was found that EMAT is a viable method to detect defects in the CFRP samples. However, determining the size and location of defect was not possible with the experimental setup that was used, unlike UT. Regardless, there is potential for the use of EMAT to inspect composites, especially in terms of non-contact inspection.