Investigation of laser thermography of composite materials

• Main Author: Hong, Ping Ting.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Materials::Composite materials
• Online Access: http://hdl.handle.net/10356/16181
• Institution: Nanyang Technological University

This report discusses the feasibility of carrying out NDT method infrared thermography by laser as thermal heating source instead of conventional halogen lamp, on composite materials such as CFRC and graphite honeycomb which are chosen as the specimens. The optimal experimental parameters are developed by varying the different variables such as the distance between the specimen and thermal source and the heating time. The objective is to find the peak contrast for both the infrared and laser thermography for best result achievable. The results lead to an experimental parameter of 30cm test distance for both the specimen and the thermal sources. For heating time, the highest contrast for laser is observed at 8s of heating time and for halogen lamp, 60s of heating time is employed. Laser thermograhy technique has proven to have a high sensitivity in detecting the defects. In some of the defect, it has shown a capability of producing a temperature contrast that is four times of that demonstrated by halogen lamp, i.e., four times the sensitivity. This is especially so in the graphite honeycomb where no conclusions on the existence of defects could be drawn through the thermographic images. However, laser thermography demonstrates a success by an edge, in which a peak contrast of 20°C for adhesive disbond and 7°C for graphite ply disbond were observed. Also, due to the distinct temperature gradient at the edge of the defect, the defect shape and length are predictable from the results.Overall, Laser thermography has demonstrated its feasibility in becoming a NDT method to be widely used in the industry, and also, it has shown its significance for any further research and investigation.