Papers by Keyword: Transformation Particle

Abstract: The composite ceramics is composed of fiber-eutectics, transformation particles and matrix particles. First, the recessive expression between the effective stress in fiber-eutectic and the flexibility increment tensor is obtained according to the four-phase model. Second, the analytical formula which contains elastic constant of the fiber-eutectic is obtained applying Taylor’s formula. The eutectic is transverse isotropy, so there are five elastic constants. Third, the effective elastic constants of composite ceramics are predicted. The result shows that the elastic modulus of composite ceramic is reduced with the increase of fibers fraction and fibers diameter.

Abstract: Based on the microstructure of fiber eutectics and transformation particles composite ceramic, the bridging stress of the fiber eutectic is determined. The bridging load that makes crack closure to reduce the stress concentration of crack tip is calculated. The energy dissipative value of the bridging load is obtained by considering the random orientation of the fiber eutectic. Finally, according to the relationship of the fracture toughness and energy dissipation, the bridging toughening mechanism is established. Analysis shows that the bridging toughening value is enhanced with the increasing of volume fraction and fracture strength of fiber eutectic, and enhanced with the decreasing of interface bonding strength and length-diameter ratio.

Abstract: This paper presents on the cracking mechanisms of fiber-eutectics and transformation particles composite ceramic. First, supposing that the tensile stress among fiber eutectics is transmitted by means of shear stress along the interfaces of fiber eutectics, based on fiber eutectics having lengths smaller than the critical length, the force acting along the fiber eutectic can be determined by the shear stress. Then, the probability of ending fiber eutectics and bridging fiber eutectics can be gotten by defining a critical district. Finally, according to the random orientations and the lengths of the fiber eutectics, composite ceramics will crack by slip incompatibility among bridging fiber eutectics. The cracking stress of the composite ceramics is built.

Abstract: The composite ceramics that contains nano-fibers and transformation particles, fabricated through SHS process, is performed with high fracture toughness and high plasticity. The matrix of composite ceramics was mainly composed of fiber eutectics with nano-fibers. The transformation particles were distributed along boundaries of the fiber eutectic structures. First, Mori-Tanaka method was used to predict the stiffness of the fiber eutectic. The fiber eutectic is transverse isotropy and has five independent elastic constants. Then considering random orientation of the fiber eutectic, the Young’s modulus and Poisson’s ratio of the matrix is determined by even strain. The matrix is isotropy. Finely, assuming the transformation particles as spheres distributed in the matrix, the effective stiffness for composite ceramics was computed. When the volume fraction of fibers and particles increase, the Young’s modulus of composite ceramics decrease and are little smaller than the volume average value, the Poisson’s ratio of composite ceramics decrease and are little bigger than the volume average value.