A study of using the thermography testing techniques to inspect defects of CFRP Structure

• Main Authors: Ching-Tang Liu, 劉慶堂
• Other Authors: MIN-JUI HUANG
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/56875486482752287652

博士 === 國立中興大學 === 機械工程學系所 === 100 === For researching the thermography testing technology used to detect the defects of composite material structure, this study developed a set of thermal testing equipment which is low-cost and efficient for using to detect the defects in composite material structural of aircraft. In order to simplify the testing instruments, easy to carry and to provide efficiency heating source, the pulse heating and the step heating method were chosen as an active heat source in our developing test system. First at all, This research used the finite element method to calculate the impact on the thermal conductivity of the composite structure with flaw, which result in the temperature difference between the defective area and normal area, and then to estimate the flux and time of exposure of heating and infrared camera performance of resolution and wavelength. This result is valuable information for designing the specimen and experimental method. For verification the performance of development thermography testing equipment, this research used standard composite material specimen with artificial defects for evaluation. In the same time, these specimens were evaluated by other non-destructive testing laboratories. The test results verified that developed thermography testing equipment has the same performance of other test lab’s thermography equipment. In addition, this research also refer to the different non-destructive testing methods results, such as air-coupled ultrasound, Back reflective X-Ray, to compare the inspection capability among these methods. Test results were confirmed that defects, in shallower position (less than 2.0 mm) and the minimum area 3x3 mm2, can be effectively identified by developed thermography testing equipment. The defects, in structure deeper zone and smaller dimension, can not be identified. The drawback of this system which is only showed the defects on two-dimensional. It does not identify effectively the flaw for depth location and precise position in space, so the defects in deeper space need using other non-destructive testing methods to inspect. Also, the uniformity of heat source and surface of specimen affect inspecting capability of thermography testing equipment. In addition, developed thermography testing equipment was used to detect the composite material structure which is a thin laminated construction of unmanned aircraft control surfaces. The test result shows the defects of adhesive bounding problem can be identified effectively. This thermography testing equipment has advantage of easy to operate, rapid detection and on-side supporting test, which can save measurement time and enhance the efficiency.