Stress Field Simmulation And Microstructure Research Of Carbon/Carbon Composites By Laser Irradiation

The ANSYS Thermal Analysis software, Transmission Electron Microscopy andScanning Electron Microscope have been used to simulate stress distribution andmicrostructure of Carbon/Carbon composites irradiated by laser. Results have been given:The distance between two carbon planes has been reduced after laser irradiation, andtensile load applied to the C/C composites at the same time has more influence onreducing the distance. The maximum thermal stress appeared in the interfacial arearesulted from the difference of elasticity modulus and coefficient of thermal expansionbetween carbon fiber and matrix indicates that the graphitization degree of the interfacialarea has been improved, stress induced graphitization occurred in the interfacial area. Theresult of using ANSYS indicated that the maximum stress in the radial, circumferentialand axial direction appeared in the interfacial area of carbon fiber and matrix, all of thesestress are relevant to graphitization of material, thus high degree graphitization after laserirradiation has been explained.Before laser irradiation, the skin-core structure of carbon fiber has been observed, theorientation angle of carbon plane in the core area is higher than in the skin area of whichthe carbon plane distribute at random. The skin-core structure disappeared after laserirradiation.After laser irradiation, cracks are mainly occurred in the interfacial area of carbonfiber and matrix, accompanied by fiber pull and squeeze, when the laser irradiationtemperature load up to1900℃,the matrix interlaminar crack has occured. The result ofthe maximum of the first principal stress appeared in the interfacial area of carbon fiberand matrix based on the first strength theory indicated that cracks are more likely occurredin the interfacial area of carbon fiber and matrix, which can be used to explain the result ofSEM.