DEVELOPMENT OF AN OPEN INSTRUMENTATION SYSTEM FOR ULTRASONIC TESTING IN QUALITY CONTROL OF LABORATORY-SCALE LAMINATED COMPOSITE FABRICATION

• Main Author: Giri Wijaya, Yusuf
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/84038
• Institution: Institut Teknologi Bandung

Laminated composites are commonly used materials in the construction of unmanned aerial vehicle (UAV) structures across various research centers and small-scale industries. In laboratory-scale production, the fabrication of laminated composites still relies on manual methods, heavily dependent on the skill of the technicians. This reliance increases the susceptibility of laminated composites to manufacturing defects. Consequently, quality control is essential to ensure the integrity of the produced composites. One of the methods employed for quality control is Non-Destructive Testing (NDT), with ultrasonic testing being the most widely used technique. Ultrasonic testing is not only safe for the technicians but also provides accurate results. However, the application of ultrasonic NDT for quality control of laminated composite materials at the laboratory scale faces several challenges. The relatively high cost of commercial ultrasonic NDT systems poses a barrier for laboratories and small-scale UAV industries operating under budget constraints. Moreover, commercial ultrasonic NDT systems are generally closed systems, limiting access to raw testing data and reducing flexibility for modifications according to specimen or testing method requirements. This research aims to develop an ultrasonic NDT instrumentation system capable of detecting defects in laminated composites at a more affordable cost. The proposed system employs open-source hardware, allowing for further development and greater flexibility compared to commercial NDT systems. The NDT system is designed to identify defects by analyzing A-scan signal patterns and generating C-scan images that can predict the defect area. In this study, two types of specimens, carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP), were tested to evaluate the performance of the developed NDT system. Each specimen contained simulated inclusion defects, represented by Teflon layers of 0.17 mm thickness and 15 mm diameter. The specimens included two defects at varying depths to assess the detection capability of the proposed NDT system. The A-scan signals from the ultrasonic testing were processed into enveloped A-scan signals to facilitate defect detection within the specimens. The testing results were further converted into C-scan images based on the collection of enveloped A-scan signals, pre-arranged in a specific pattern before testing. The C-scan images were generated using the Pearson correlation coefficient method, which compares reference signals with measurement signals at each testing point. Defect areas were indicated by correlation coefficient values approaching 0, while defect-free areas showed values near 1. The testing results demonstrated that the developed NDT system successfully detected artificial defects in both CFRP and GFRP specimens. In the A-scan graph, defects were identified by the appearance of echoes resulting from the presence of defects within the specimens. Based on the generated C-scan images, the system effectively visualized the shape of the artificial defects, albeit not entirely circular as the original, but sufficiently accurate in estimating the defect area. The best accuracy was achieved with the CFRP specimen, showing an error (% deviation) of 0.14% at defect location 1 and 4.81% at defect location 2. Meanwhile, testing on the GFRP specimen showed higher error rates, with 0.28% at defect location 1 and 18.53% at defect location 2. These results underscore the significant potential of the developed ultrasonic NDT system for quality control applications in laminated composites at the laboratory scale. Keywords: Non-destructive test, Ultrasonic testing, Composite, A-scan, C-scan, Open-source hardware ?