Quantitative Detection Research On Hole Defect Volume Of Carbon Fiber Composites Based On Infrared Testing

Industrial production requires more and more comprehensive properties of materials,in order to produce high quality products,researchers pay more and more attention to the use of carbon fiber composites with high specific modulus,stable chemical properties and fatigue resistance.Carbon fiber composites will inevitably produce a certain amount of damage in large-scale preparation and practical application.When these damages increased to a sufficient amount,the comprehensive performance of carbon fiber composites may be greatly reduced,which will significantly reduce the safety of carbon fiber composites.Therefore,it is necessary and significant to inspect and evaluate the quality of carbon fiber composites during manufacturing,processing and practical application.For the quality inspection of carbon fiber sheet,the pulsed infrared nondestructive testing method has been paid attention by experts and scholars for its high sensitivity,wide detection range and high safety.Previously,in the research of pulsed infrared nondestructive testing of hole defect in carbon fiber sheet,many researchers have studied round flat bottom hole defect,but from the real situation,when hole defect appear in sheet,the shape of the defect is often irregular.In order to make the research closer to the reality,this dissertation creatively designs a four leaf clover-shaped flat bottom hole defect,the surface and bottom of which are the union parts of two identical ellipses after orthogonalization.In this dissertation,an infrared nondestructive testing model of four leaf clover-shaped flat bottom hole defect in carbon fiber composites was constructed by using COMSOL software,the heat conduction process of carbon fiber sheet under the condition of pulse heating was simulated.The temperature field variation law of the simulated sheet surface and the factors affecting infrared NDT were expored under the conditions of different defect bottom areas,different depths and different defect structures.With the help of the simulation study,the principle of pulsed infrared NDT is elaborated to provide theoretical support for the quantitative detection of defect volume in four leaf clover-shaped flat bottom holes.In infrared nondestructive testing,it is generally needed to perform necessary image processing on the original infrared thermogram.The acquired original infrared thermogram is sequentially filtered and noise reduced,image enhanced,and image segmented to greatly improve the image quality and facilitate the identification of defective image features and their volume analysis and calculation.Therefore,the way to choose the best image processing method,improve the SINR and information entropy of the image,and highlight the contour and edge features of each defect is the focus of quantitative detection of defect volume of four leaf clover-shaped flat bottom holes of carbon fiber sheet.By analyzing and calculating infrared thermograms which have been image processed,the depth measurements and equivalent area measurements of each defect are obtained,and the volume measurements of each defect is then obtained to accomplish the pre-defined objectives of the project.By comparing the volume measurements of each defect with the real volume values,the error magnitude was analyzed.The test results show that for the four-leaf clover-shaped flat bottom hole defect of carbon fiber sheet,the hole defect volume measurement method of carbon fiber composites based on infrared nondestructive testing technology proposed in this dissertation has certain reliability and provides a new idea for nondestructive testing of carbon fiber sheets.For the four leaf clover-shaped flat-bottomed hole defect with the same bottom area and surface area and shallow defect depth,when the bottom area of the hole defect is large,the defect volume measurement method proposed in this dissertation has high accuracy.