Simulation And Verification Of The Stress-Strain Responding Of Needle C/SiC Composites

Needle ceramic matrix composites is an extremely high development potential structuralcomposites materials which improves the braided ceramic matrix composites layer strength, at thesame time also is low cost disadvantage and the simply process than3D woven ceramic matrixcomposites. Both at home and abroad, a lot of research has been carried out on the preparation ofneedle ceramic matrix composites and static strength tests. But the material’s constitutive andappropriate model is less. Therefore, it has a positive meaning and application of value engineering toresearch for the material’s constitutive and appropriate model.According to the microstructure photographs of Needle C/SiC composites, we establish thestructure analysis model. Using finite element method to predict the macro properties of needle C/SiCcomposites and in good agreement with experimental data. For the porosity, using the metallographicmethod and the drainage method to measurement the holes porosity, and using the density method tocalculated the total porosity. The pores will be reducted to the corresponding modulus of matrix.Finally, we use the modulus after reducting to predict the elastic properties.On the basis of the micro-structural analysis model, the stress-strain curve of needle C/SiCcomposites was predicted under tensile and was researched on testing. The micro-mechanics, theinitial matrix cracking model and the fiber failure statistical model and the shear-lag were integratedwith the relevant failure criterions and the stiffness reduction criterions to analyze the progressivedamage of the matrix and fiber bundles. And analysising of the evolution of the loading process of thefailure, at the sme time geting stress-strain curve of the material. The results predicted agreed wellwith experimental curve.Based on the continuum damage mechanics theory and the experimental curve, establishing theconstitutive equations of a suitable needle C/SiC composite damage evolution. Firstly, the constitutiveequations and damage evolution equations were derived base on the theory. And then, on the basis ofthe elastic properties calculated the micro-mechanical model and the experimental curve, determinedthe parameters of equations. The model will be verificated through the matlab and the seconddevelopment of ansys(UPFs). Finally, according to the established constitutive model, analysising ofthe complex structures by the finite element.