Influence of microporosity on the strength properties of SiC ceramic materials

A series of silicon carbide ceramic samples with variable characteristics of the microporosity and strength, such as the ballistic strength σ _B and the static strength σ _S , are investigated. The dependences of the strength on the integral porosity for ceramic materials are determined. It is established that the strength (both σ _B and σ _S ) is directly proportional to the average length of the bridges between micropores. The mechanism of the influence of microporosity on the strength of the ceramic materials is elucidated. According to this mechanism, interpore bridges are concentrators of stresses and, hence, are broken when a load is applied to the ceramic material. Numerous breakings of bridges bring about the failure of the ceramic body. The average stress concentration coefficient is estimated as a function of the integral porosity of the ceramic material. It is demonstrated that the static strength of the ceramic material is determined by the presence of large micropores (50–100 μm).