Weibull parameter effects on tensile strength in continuous fiber-reinforced ceramic matrix composites

초록

A model to predict ultimate strength of continuous fiber-reinforced brittle matrix composites is developed. A statistical theory for the strength of a uniaxially fiber-reinforced brittle matrix composite is presented. A material of matrix is assumed to be homogeneous and isotropic, so that the strength of material is anywhere constant, whilst that of fiber is considered to show Weibull statistical distribution. They may be utilized to optimize the biaxial and multidirectional tensile strength properties of the laminated materials. The composite strength is estimated for assuming no interacting matrix cracks. The frictional shear stress caused by bridging fibers is involved in the strength computation. The predicted result is compared to experimental results on LAS-Glass/Nicalon fiber composite. The major purpose in nonceramic matrix composites is to have the fiber bear greater proportion of the applied load. This load sharing depends on the ratio of fiber and matrix elastic moduli. In polymeric matrix composites, this ratio is very high, while in ceramic matrix composites, it is rather low and can be as low as unity. In the ceramic matrix composites, the purpose of reinforcing is mainly to enhance toughness by utilizing fiber/matrix interfacial characteristics. Thus, the mechanism of ultimate tensile strength should be understood on the basis of frictional resistance along the interface as well as fracture strength of constituents.