Finite Element Simulation Of Laser Ultrasonic Testing Of Unidirectional Fiber Reinforced Composites

Due to its excellent functional properties,fiber-reinforced composite materials are gradually being used in national defense construction and scientific research.During the preparation and service process,however,components are vulnerable to damage and faults.Affect its mechanical properties and increase the risk of early failure of the structure in service.Therefore,to ensure the safety of the components,wo need to test the fiber-reinforced composite materials during the production process or before use.Laser ultrasound as a new form of non-destructive testing technology has wide frequency range of excited ultrasonic waves,for example,it can tested the samples with no contact it,and detected tiny defects.Unidirectional fiber-reinforced composites are the basic material units that constitute other fiber-reinforced composites.Summarizing the echo law of displacement waveforms in such media can lay a foundation for the quantitative analysis of defects in fiber-reinforced composites.Therefore,based on the propagation principle of laser ultrasound on the surface and inside of the structure and the law of echo signals,This study used a numerical model to investigate the mechanism of laser ultrasonic testing of unidirectional fiber reinforced composite materials,as well as assess the size,kind,and defect of flaws.The influence of depth on acoustic waves provides some theoretical guidance for laser ultrasound in defect detection of fiber-reinforced composites.Aiming at the transverse isotropic properties of unidirectional fiber reinforced composites,the paper establishes a laser ultrasonic excitation model of pulsed laser in unidirectional fiber reinforced composites,and studies the transient temperature field,According to the lamb wave propagation mechanism of laser ultrasound,the research on the propagation characteristics of laser ultrasound and the detection of defects by using characteristic echoes was carried out,and the influence of factors such as grid profile size,time step and spot radius on the generation of acoustic waves was analyzed;The established defect detection mode examined the relationship between defect dimensions such as surface crack depth and width and echo signal;the signal change of reflected transverse wave of laser ultrasound inside the workpiece was studied by the time domain analysis method,revealing the law of the influence of internal defects on the path of ultrasound,and achieving accurate detection of material defect information.The signal variation of the reflected transverse wave of laser ultrasound inside the workpiece is studied by the time domain analysis method,which reveals the law of the influence of internal defects on the ultrasound propagation path,and the signal characteristics of different types of defect echoes are studied to achieve the accurate detection of material defect information.It provides a theoretical basis for further realization of the identification and quantitative analysis of defects in composite materials.