X-ray and ultrasonic testing techniques for defect inspection in composite

• Main Author: Zhou, David Yutian.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/53629
• Institution: Nanyang Technological University

Composite materials are increasingly used in the construction of modern commercial aircraft, to reduce weight and improve structural strength. In manufacturing composites for aircraft, one other consideration would be its ability to withstand extreme temperatures. This is crucial as the body of the aircraft must be able to withstand adverse conditions while in operation (e.g. overheating near the engine, lightning strikes). Such conditions could alter the integrity of the material in the long run. Therefore, the study of Non Destructive Testing (NDT) on composites is vital in order to maximize the airworthiness and flight safety of aircrafts. This project is an industrial collaboration between Nanyang Technological University and the Singapore Institute of Manufacturing Technology (SIMTech). The various experiments performed seek to explore the effectiveness of different ultrasonic techniques in detecting both volumetric and non-volumetric defects arising from heat treatment. Specimens used in the experiment include one honeycomb composite (CHRS) and three other heat-treated composite laminates. Special attention was directed at studying if non-volumetric (incipient) heat damage in composite material can be detected before it escalates into physical deformation. Five different ultrasonic testing techniques, as well as one 2D X-ray inspection, were performed on the aforementioned specimens. The X-ray scan, BondMaster 1000e+ Inspection (Pitch-catch swept mode)) and SIMTech Sonic Inspections were carried out in the SIMTech laboratory. Other experiments (A scan, C scan and Through Transmission Testing) were carried out in the NTU Material Lab 2. The SIMTech Sonic NDT System, which is a technique new to the industry (currently still under testing), was also used during the course of the experiments. Its feasibility and usefulness in NDT are examined, together with the other available methods in the industry. From the results tabulated, we can see that the new SIMTech Sonic NDT System is highly effective in picking up heat induced delamination as well as common defects in honeycomb structure (CHRS). However, its ability in picking up incipient heat damage (Specimen A, B and C) is uncertain and requires further confirmation. In addition, the SIMTech System is more versatile in terms of defect recognition and has a higher sensitivity to smaller delamination than the BondMaster 1000e+. Through Transmission, A scan and C scan are equally good in detecting delamination but provide no useful information on defects in the honeycomb structure. The detailed experimental results and the evaluation of the various NDT methods are discussed in chapter 6 of the report.