Fatigue Crack Initiation And Microstructural Research Of Carbon/Carbon Composites After Laser Irradiation

This paper uses ANSYS finite element analysis software to simulate the macroscopictemperature field of the sample and the microscopic stress field’s distribution law in theC/C composites’irradiating process with laser, And then the laser thermal fatigue test isdone, On the basis of the laser thermal fatigue test, Using polarized light microscopy,scanning electron microscope, laser Raman, X ray diffraction and nano indentation andother modern analysis method, studies the C/C composites after laser irradiation fatiguecrack initiation and microstructure evolution systematically, clarifing C/C composites’thermal fatigue mechanism to provides theory basis.The numerical simulation of the micro-stress field with ANSYS shows that: after thelaser irradiation of the C/C composites, the needle area’s greatest stress appeared in thefiber and matrix interface place. With the increase of the fiber volume (V%), tensile stressincreased and pressure stress decreased. The parts by the fiber’ volume influence the stressdistribution, hence affect the crack initiation and growth, applied tensile load maininfluencing stress distribution. The maximum of the tensile stress of the cloth area locatedon the second floor of the interface between fiber and matrix.Laser thermal fatigue experiments of the C/C composites show that: fatigue crackinitiation interface place of the fiber and matrix in needle area. Crack propagated along theinterface of fiber and matrix or matrix, fiber "squeeze out" phenomenon accompanied, theresult is consistent with the simulation of The ANSYS microscopic stress field. Elasticmodulus(Er) is reduced in the needle fiber, meanwhile, hardness (H) declined, and thematrix’s elastic modulus in the needle area declined unobviously, structure’s defectionincreased, graphitization degree declined, and crystallite size reduced.