Prediction For Coefficient Of Thermal Expansion Of Ceramic Matrix Composites Based On XCT Technology

Ceramic matrix composites(CMCs)have been widely applied to aerospace engineering on account of properties of low density,high intensity and superior high temperature performance.Coefficient of thermal expansion(CTE),reflects the hot deformation behavior in high temperature of CMCs,is the basic parameter in thermal analysis of CMCs.The coefficient of thermal expansion of CMCs is closely related to the mesoscopic structure which is very complicated as there are many random shape,size and location of the hole.In addition,as a result of the limitation of the preparation process,reinforcing fibers are not strictly distributed periodically.So it's extremely hard to accurately calculating the coefficient of thermal expansion of CMCs.To predict the thermal expansion behavior of CMCs,researchers at home and abroad have developed kinds of mechanical models which were based on the ideal structure of CMCs.However,these models couldn't represent the real microscopic structure of materials and the results were not ideal.Thus,it's required to predict the CTE based on geometrical models that can truthfully reflect the microscopic structure of CMCs.Elastic moduli and coefficients of thermal expansion of composites of 2.5D C/SiC composites,C/SiC mini-composites and needled 2D composites from 100 to 1500? were measured by nanoidentation and thermal expansion experiments.Thesis in a numerical method based on X-ray computed tomography(XCT),using an independent developed pattern recognition program,has realized the automatic component identification of 2.5D C/SiC composites and developed a micro geometrical structural modeling method of 2.5D composites.And the finite element models of C/SiC mini-composites and needled 2D composites were also built.The coefficients of thermal expansion of these composites from 100 to 1500? were calculated.The models based on XCT slices identified with actual micro structural of composites and the numerical results of XCT model coincided with the experimental results as a whole.It's verified that the predicting method by finite elements calculation is practicable.Otherwise,the influence of parameters of components and volume fraction on the CTE of CMCs was also discussed.