> For the complete documentation index, see [llms.txt](https://alpaca4d.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alpaca4d.gitbook.io/docs/basics/materials.md).

# Materials

There are two families of material that you can define in Alpaca4d: **UniaxialMaterial** and **NDMaterial**.

**UniaxialMaterial** is used to construct a material object which represents uniaxial stress-strain relationships. The implemented relationship is Linear Elastic.

**NDMaterial** is used to construct a material object which represents the stress-strain relationship at the gauss-point of a continuum element. The behaviour is an Elastic Isotropic or Elastic Orthotropic.


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