Orthotropic material

The variation of a material's properties with direction. Fibre-reinforced composites are strongly anisotropic, with much higher stiffness and strength along the fibre direction than across it, so ply orientations must be matched to the expected load paths.

The condition in which a material has the same properties in every direction, as with most metals, unreinforced plastics and glass. Isotropic behaviour simplifies design because a single set of property values applies regardless of load direction.

A composite element built up from multiple bonded layers (plies) of reinforcement and matrix, consolidated and cured so that they act as a single structural material. Its stiffness and strength depend on the fibre orientations and stacking sequence of the plies.