Dictionary:Stiffness

The ratio of stress to strain, each with specified directions. Stiffness constitutes a tensor of rank 4, which is the inverse of the compliance tensor. It is also expressible as a 6×6 matrix, using Voigt notation :

$\{c_{IJ}\}={\begin{pmatrix}c_{11}&c_{12}&c_{13}&c_{14}&c_{15}&c_{16}\\c_{12}&c_{22}&c_{23}&c_{24}&c_{25}&c_{26}\\c_{13}&c_{23}&c_{33}&c_{34}&c_{35}&c_{36}\\c_{14}&c_{24}&c_{34}&c_{44}&c_{45}&c_{46}\\c_{15}&c_{25}&c_{35}&c_{45}&c_{55}&c_{56}\\c_{16}&c_{26}&c_{36}&c_{46}&c_{56}&c_{66}\\\end{pmatrix}}$

See Figure E-5.

See elastic constants