Anisotropy degree

Typically, one sees normahzed principal axes, a mean shape factor, and a mean anisotropy degree specihed for an elhpsoid. Often, the elhpsoid is characterized by its overall shape with respect to its three radii. Oblate elhpsoids (disk-shaped) have a = b> c prolate elhpsoids (cigar-shaped) have a = b < c and scalene elhpsoids have three unequal sides (a > h > c). In a sphere, of course, a = b = c. 

Figure 6. Variation of strength anisotropy degree with confining pressure.

If the variation of anisotropy degree with confining pressure is known, it is advisable to select the mean anisotropy degree over the confining pressure range of the application (e.g. deep tunnels) when using equation 6, which yields more accurate results. 

This kind of feature, i.e., the dependence on direction, will be generally called as anisotropy, while the isotropy corresponds to the particular case of uniformity, by the direction non-dependency. Therefore, based on the directionality of a physical system (crystalline in this case) and based on the type of the existing elements of symmetry one will determine the anisotropy degree, the homogeneity or the lack in homogeneity and the distribution of the physical properties of that system. Figure 2.53. 

It has been shown that oiganoclay platelets aggregation in packets (tactoids) results in laige-scale disorder intensification that reduces nanofiller anisotropy degree. In its turn, this factor decreases essentially... 

FIGURE 5.2 The dependence of organoclay anisotropy degree a on its platelets number per one tactoid Npl for nanocomposites PVC-MMT. 

Theoretical method of parameter a (a estimation can be obtained as follows. Organoclay aggregates (tactoids) anisotropy degree can be determined aeeording to the equation ... 

FIGURE 5.3 The comparison of experimental a and calculated according to the Eq. (13) oF organoclay anisotropy degree for nanocomposites PVC-MMT. 

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