Initial elastic properties of unidirectional ceramic matrix composite fiber tows

The initial elastic properties of two unidirectional ceramic matrix composite tows, comprised of continuous, cylindrical fibers surrounded by one or more matrices, have been calculated using three different methods. The first uses finite element (FE) analysis of the tow to calculate values for elastic and shear moduli and Poisson's ratios in the three principal directions, and in the absence of confirmatory experimental data is regarded as the most accurate for a wide range of fiber/matrix geometries and materials. The other two models are (i) rule of mixtures, ROM/volume averaging and (ii) the approximate equations of Halpin-Tsai and analytical relations based on slab representation for composite materials that rely on the elastic properties and volume fractions of the constituent materials. Initial elastic properties of the tows determined by the FE method are presented, and they are compared with predictions made by the other two techniques.