3 infrared thermal imaging technology
Infrared thermal imaging is a technique for non-contact measurement of the temperature distribution and isotherm profile of a surface of a workpiece to be inspected by means of a thermal imager. It can detect defects such as delamination, impact damage, debonding and core debonding and water intrusion in the sandwich structure. Due to its advantages of non-contact, rapid film detection, application to external field and in-situ detection, it has received extensive attention in recent years.
According to the different thermal excitation methods, it is divided into pulse heating method, modulation heating method and ultrasonic excitation heating method. Among them, the American infrared heat wave detection (TWI) company's pulse flash infrared thermal imaging detection system has been applied to the in-service aircraft inspection by the US military, mainly to detect the impact damage of the honeycomb structure into the water, debonding and laminate structure. And stratified damage.
Infrared thermal imaging detection technology is also used by Airbus as one of the detection methods of its A300 series aircraft. Its thermal excitation includes not only thermal excitation methods such as incubators, infrared lamps, hot air guns, arc lamps, but also cold air guns. Cooling methods such as low temperature fluids and refrigerators. The types of damage detected include lamination of layers, degumming and inclusion, degumming and liquid infiltration of sandwich structures, degumming and corrosion of metal joints, and the like.
Conclusion
The proportion of composite structures used in aircraft structures is increasing, and the increase in the amount of application brings about an increase in damage in applications. It is necessary to ensure the aircraft's attendance rate and ensure the flight safety of the aircraft. This means that the non-destructive testing time of the external field can not be too long, it is best to carry it in place without disassembly, and the detection speed is faster; the reliability of the test must be guaranteed, and the defect exceeding the standard cannot be missed. Many of the above-mentioned advanced detection methods have been applied abroad for many years. They are still new in China. It is necessary to further study the advanced technology of non-destructive testing of foreign composite materials and improve the non-destructive testing level of composite materials in China.
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