Material#

PreVABS uses the keyword material for the physical properties attached to any materials, while lamina for material plus thickness, which in a sense is fixed by manufacturers. This can be thought as the basic commercially available “material”, such as a composite preprag. A layer is a stack of laminae with the same fiber orientation. The thickness of a layer can only be a multiplier of the lamina thickness. Layup is several layers stacked together in a specific order. This relationship is illustrated as: fig-layup

Both materials and laminae are stored in one XML file (or directly in the main cross-section file under a <materials> block). Each material must have a name and type. Under each <material> element, there are a <density> element and an <elastic> element. If failure analysis is wanted, users need to provide extra data including <strength> and <failure_criterion>.

A template of this file is shown below:

<materials>
  ...
  <material name="..." type="...">
    <density>...</density>
    <elastic>...</elastic>
    <strength>...</strength>
    <failure_criterion>...</failure_criterion>
  </material>
  ...
</materials>

Specification

  • <material> - Root element for each material.

    • name - Name of the material.

    • type - Material symmetry class. Choose one from isotropic, transversely isotropic, orthotropic (alias engineering), and anisotropic.

    • <density> - Density of the material. Default is 1.0.

    • <elastic> - Elastic properties of the material. Specifications are different for different types.

    • <strength> - Strength properties of the material. Specifications are different for different types and different failure criterion.

    • <failure_criterion> - Failure criterion of the material. Options are different for different types.

Note

Note type="lamina" is no longer accepted as a material symmetry type. Use type="transversely isotropic" for a material with transverse isotropy (the four engineering constants \(E_1\), \(E_2\), \(\nu_{12}\), \(G_{12}\) are required, the rest are derived as described below). The <lamina> element is now used only to bind a material to a thickness, see the Lamina section.

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