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The material type for a spherical (isotropic) continuous fiber distribution is “spherical fiber distribution”. Since fibers can only sustain tension, this material is not stable on its own. It must be combined with a stable compressible material that acts as a ground matrix, using a “solid mixture” container as described in Section 4.1.3.22↑. The following material parameters need to be defined:

<material id="1" type="solid mixture">
  <solid type="neo-Hookean">
    <E>1000.0</E>
    <v>0.45</v>
  </solid>
  <solid type="spherical fiber distribution">
    <ksi>10</ksi>
    <alpha>0</alpha>
    <beta>2.5</beta>
  </solid>
</material>