Research On Composite Materials Defect Detection By Low-power Ultrasonic Infrared Thermography

With the development of global manufacturing industry and materials science,composites are widely used in civil equipment,aerospace and other fields because of their excellent performance.It is particularly important to realize the rapid and effective detection of various damage defects of composite materials.In this thesis,a set of low-power ultrasonic infrared thermography defect detection system is built.The system avoids the disadvantages of the commonly used high-power ultrasonic infrared thermography detection system,such as large volume,heavy weight and so on,which can make the ultrasonic infrared thermography defect detection technology more convenient and faster.Then,on the basis of the low-power ultrasonic infrared thermography defect detection system,the flat bottom hole defects of composite materials,cavity defects of coating materials and impact damage defects of composite materials were detected by using the built system.For the flat bottom hole defects of composite materials,low-power ultrasonic infrared thermography detection system is used to detect and analyze flat bottom hole defects with the same defect diameter and different thickness.The results show that the low-power ultrasonic infrared thermography defect detection system can detect the flat bottom hole defects of composite materials.After the detection,the principal component analysis algorithm(PCA),independent component analysis algorithm(ICA)and Fast Fourier Transform algorithm(FFT)are applied to process the detection data,and the evaluation method based on information entropy is used to analyze the processing results.The results of PCA and ICA have better processing effect.For the cavity defects of coating materials,low-power ultrasonic infrared thermography defect detection system is used to detect and analyze cavity defects with the same defect thickness,different coating thickness and different defect diameter.The experimental results show that the low-power ultrasonic infrared thermography detection system has the ability to detect the cavity defects of coating materials.The ICA and FFT have better processing effect.For the impact damage defects of composite materials,low-power ultrasonic infrared thermography defect detection system is used to detect and analyze the visible impact defects formed by 5J,15 J and 25 J energy impact and the invisible impact defects formed by 12 J and 16 J energy impact,and the nonlinear acoustic response signal generated by ultrasonic excitation is detected by acoustic emission instrument.The experimental results show that the low-power ultrasonic infrared thermography detection system can detect different impact defects of composite materials.The results of PCA and FFT have better processing effect.In this thesis,the low-power ultrasonic infrared thermography defect detection system is built,and the detection ability of the system for flat bottom hole defects of composite materials,cavity defects of coating materials and impact defects composite materials is verified through experimental research.The PCA,ICA and FFT algorithms are applied to the processing of ultrasonic infrared thermography defect detection data.The evaluation method based on information entropy is used to evaluate and analyze the results of the algorithm.