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Abstract

Due to good thermal insulation properties combined with high mechanical strength and damage tolerance, fibre-reinforded ceramics with porous matrices are being considered as suitable candidates for refractory materials in high temperature applications such as burners of stationary gas turbines. The microstructure of the porous matrix of the fiber-reinforced composite commonly consists of sintered ceramic particles that form a porous material. The mechanical properties of porous materials are typically related to microstructure characteristics such as porosity and the size distributions of pores and solid particles. However, it has been shown that the mechanical properties can vary by a large degree for a given porosity. This indicates that, besides porosity, there must be further parameters influencing mechanical properties. To investigate microstructural influences on the elastic properties of porous ceramics with a typical sintered microstructure a combination of stochastic and mechanical modeling is applied. Quasi-2D representative volume elements (RVE) are generated employing methods from stochastic geometry and graph theory. These RVEs consist of complex microstructures with two phases (pores and solid) and are designed to mimic the real microstructure topologically. The stochastic model is capable of controlling quantities like porosity, the degree of particle overlap and connectivity (coordination number of sintered particles) such that the model can represent a variety of microstructures. In the next step the mechanical properties of the RVEs are characterized by means of the finite element method and homogenization techniques, which yield the effective Young's modulus as a function of the microstructure. The results clearly demonstrate that the connectivity in terms of the average coordination number of sintered particles is strongly related with the elastic properties, whereas the influence of the porosity is only a minor factor for a given average coordination number.