Fabrication of defects in honeycomb specimens for ultrasonic analysis

• Main Author: Khairil Amirul Bin Ahmad
• Other Authors: Chai Gin Boay
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Materials::Material testing and characterization
• Online Access: https://hdl.handle.net/10356/167481
• Institution: Nanyang Technological University

Non-destructive testing (NDT) plays a critical role in ensuring the integrity and safety of aerospace and other high-performance composite structures. Honeycomb composites are widely used in these applications due to their high strength-to-weight ratio. Ultrasound NDT is a powerful technique for detecting defects in these complex materials. This abstract discusses the use of ultrasound NDT for the inspection of honeycomb composites, including the principles of ultrasonic testing, the types of defects that can be detected, and the factors that affect the accuracy and reliability of the inspection results. The results of recent studies in this area are presented, highlighting the potential of ultrasound NDT, specifically the A-Scan for the detection and characterization of defects in honeycomb composites. Initially, the specimens employed in the examination were created using Aluminum asthe honeycomb center and Carbon Fiber Reinforced Polymer for the exterior layers. The specimens were fabricated manually using an extensive method which would be described in more detail in the Appendixes. The mentioned flaws were subsequently introduced at different depths to imitate air gaps with the use of cut-out Teflon pieces. Afterwards, the assessment was conducted using both the Pulse Echo and Through Transmission methods. Essentially, the aim of this study is to find out if Pulse Echo can be used more widely in the industry to ease the method and produce faster turnaround time for aircrafts. It was discovered that contradictory to prior research, that the Pulse Echo method was able to detect defects to a depth of up to 50mm, and that the sound waves are able to traverse an extremely thin piece of honeycomb wall, a feat which was thought to be impossible. The studies conducted prove that the Pulse Echo method is much more reliable than what is initially thought, and it should be implemented more universally as this is an important discovery which can improve the overall quality of NDT methods.