Studies On Laser Shearographic NDT Of Honeycombsandwich Structure

Honeycomb sandwich composites have many advantages, such as the low density,the high specific strength and specific stiffness, the low thermal expansion coefficient,high impact resistance,the good stability, the high loading capacity.It has graduallyreplaced metallic materials in aireraft and has a very extensive application in theaerospace field. Honeycomb sandwich structure inevitably exsit defects and damageswhich are brought during processing and operation, it affect the structural performanceand may lead to security risks. In order to ensure the security applications of materials,itis particularly important to use nondestructive test method to control the quality. Thispaper take the honeycomb sandwich sample with artificial defects in according toHB5461-1990as the object for study, the auther researched on the application of lasershearography, optimized technological parameter, simulated and calculated thedeformation of the defects by abaqus. And explored the method to test kissing bonddefects which the conventional NDT methods can not detect.Aluminum honeycomb sample with artificial defects was nondestructivelyinspected with LTI-5100laser shearographic system in this paper. High qualityinspection images were obtained by optimization of technological parameter such asshearing direction, shearing amount, loading method, loading amount. The results whichis got from the comparition between the ultrasonic C-scan test and shearography testcan be mutually validated. It is shown that defect detection and defect sizing of thermalshearography are all reliable,and parameter control is an important Factor onshearographic images. The results also show that Shearography has great advantages ondetection speed,and it is much faster than ultrasonic C-scan.C-type honeycomb structure sample with artificial defects was inspected byportable vacuum shearography system. The auther established finite element model byabaqus,calculated the deformation of the defects under vacuum loading and comparewith shearography results. It is shown that surface deformation of the defects is differentfrom the normal position, when this deformation reaches2μm, shearography canidentify and determine the defect.It reliaze the feasibility of shearography on kissingbond defect of honeycomb sandwich structure,and obtain the rule of loading selection.The results also show that the finite element model is effective, and provide a reference for the practical application of vacuum shearography.By comparing the finite element analysis and experimental results in this paper,itproved that shearography is suitable for rapid NDT of large composite honeycombstructures which used in the aerospace field.The results of this study also provide areference for the Further development and practical application of laser shearography.