Symmetric laminate

A laminate that contains, for every angled ply, a matching ply at the equal and opposite angle, eliminating coupling between in-plane extension and shear. Balanced, symmetric laminates are the default choice where predictable, distortion-free behaviour is required.

The specified order and orientation of the plies through the thickness of a laminate, usually written as a shorthand code of ply angles. It governs the laminate's stiffness, strength and coupling behaviour, and is fixed on the drawing as part of the laminate schedule.

A laminate with equal numbers of plies in three or more equally spaced orientations, giving in-plane stiffness that is effectively the same in every direction. It is the standard conservative layup where load directions are uncertain or vary in service.