The Study On Ultrasonic Evaluation Method Of The Porosity In Carbon Fiber Composite

Carbon fiber reinforced plastic that is superior performance and lower cost has been more and more widely used in the aerospace, aviation, automotive, nuclear power and other industrial areas. However, due to its special forming process, a quantity tiny pore often exists in CFRP more or less. The shear strength and flexural strength of CFPR will be influenced seriously and its life will be reduced. Consequently, we generally make use of NDE to detect the content of pore(namely porosity) to ensure that use the CFPR is used safely. Nonlinear ultrasonic testing technology is a new research in the field of ultrasonic nondestructive testing, its characteristics provide a new method of detection for porosity of the CFPR. According to practical needs and research status, in this paper the CFPR which is formed by hand-paste and hot pressing is the detection object, the ultrasonic attenuation and the nonlinear ultrasonic detect experiments is performed in the CFPR respectively, the characteristic parameters of ultrasonic detection are extracted, and the porosity of CFPR can be evaluated.Firstly, based on the traditional ultrasonic testing theory, the ultrasonic pulse echo reflection method is used. The signal form the region is collected and processed to achieve the attenuation coefficient.Secondly, from the nonlinear ultrasonic theory, some important ultrasound nonlinear effects are introduced. Based on this, discuss the relationship between the detection objectives and parameter of ultrasonic nonlinear, and point out that ultrasonic nonlinear parameters can be used as the characteristic parameters to evaluate the porosity of CFPR.Thirdly, according to the signal characteristics of the ultrasonic nonlinear response of the CFPR and the finite amplitude nonlinear ultrasonic testing method, design the experimental system of the nonlinear ultrasonic detection, and validate the performance of detection system, thereby the reliable and effective detection results can be ensured.Finally, by the experimental system of the nonlinear ultrasonic detection, the experiments are performed in the CFPR. The experimental results show that the ultrasonic nonlinear coefficient can evaluate the porosity of CFPR, which indicate the appropriate path to the nonlinear ultrasonic detection of the CFPR.Compared to the traditional ultrasonic attenuation detection technology, the nonlinear ultrasonic detection technology has the higher sensitivity and can obtain more effective detect information. Therefore, it is significant for the nonlinear ultrasonic detection technology to perform experiments, research the theory, explore its propagation rule and evolution characteristics and improve the experimental technology.