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Subsubsection 4.1.3.21: Porous Neo-Hookean Up Subsection 4.1.3: Unconstrained Materials Subsubsection 4.1.3.23: Spherical Fiber Distribution

#### 4.1.3.22 Solid Mixture

This material describes a mixture of unconstrained elastic solids. It is a container for any combination of the materials described in Section 4.1.3↑.
 Container tag for unconstrained solid material
The mixture may consist of any number of solids. The stress tensor for the solid mixture is the sum of the stresses for all the solids.
Material axes may be optionally specified within the <material> level, as well as within each <solid>. Within the <material> level, these represent the local element axes relative to the global coordinate system. Within the <solid>, they represent local material axes relative to the element. If material axes are specified at both levels, they are properly compounded to produce local material axes relative to the global coordinate system. Material axes specified in the <ElementData> section are equivalent to a specification at the <material> level: they correspond to local element axes relative to the global system.
Example:
<material id="1" type="solid mixture">
<solid type="neo-Hookean">
<E>1000.0</E>
<v>0.45</v>
</solid>
<solid type="ellipsoidal fiber distribution">
<mat_axis type="vector">
<a>0.8660254, 0.5, 0</a>
<d>0,0,1</d>
</mat_axis>
<ksi>5, 1, 1</ksi>
<beta>2.5, 3, 3</beta>
</solid>
<solid type="ellipsoidal fiber distribution">
<mat_axis type="vector">
<a>0.8660254,-0.5, 0</a>
<d>0,0,1</d>
</mat_axis>
<ksi>5, 1, 1</ksi>
<beta>2.5, 3, 3</beta>
</solid>
</material>


Subsubsection 4.1.3.21: Porous Neo-Hookean Up Subsection 4.1.3: Unconstrained Materials Subsubsection 4.1.3.23: Spherical Fiber Distribution