This study contains three components: measurement, modeling, and inverse modeling to get the fiber elastic constants. The studied composite consisted of 70 volthinsp;percnt; continuous uniaxial graphite fibers in a magnesium matrix. By ultrasonichyphen;velocity methods, we measured the compositersquo;s complete orthotropichyphen;symmetry (ninehyphen;independenthyphen;component) elastichyphen;constant tensor:Cijin Voigt contracted notation. Approximately, the composite shows transversehyphen;isotropic symmetry. For a model, we used a wavehyphen;scattering method in the longhyphen;wavelength limit. The model requires two inputs: the two isotropic matrix elastic constants and the five anisotropic fiber elastic constants. We measured the first and guessed the second based on graphitehyphen;fiber elastic constants reported by others. This guess gave good measurementhyphen;model agreement only forC11,C22, andC33. Especially, the shear moduliCii(i=4,5,6) agreed poorly (a 20percnt; difference). Using inverse modelingmdash;calculating fiber properties from measured matrix properties and measured composite propertiesmdash;we estimated the anisotropic fiber elastic constants. For the fiber we predict a Younghyphen;modulus anisotropy of 12 and a principal Poisson ratio range of 0.03ndash;0.37.
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