Out of Plane (Z') Strain Tensor Components

Out of plane (Z') strain tensor components

Thin shells do not integrate the through thickness strain ( _ZZ' ), but this value may nevertheless be reported as non-zero. This is because the shell thickness may change, leading to a strain: its stiffness in this direction is based on volume preservation, but there is no stress associated with this.

Therefore principal strains also may not be confined to the plane of the element.