The left-hand diagram shows the ordering of uni-axial lamina required to produce a composite material with approximately isotropic mechanical and thermal properties.

The right-hand diagram illustrates the effect of heating a two ply composite (non-symmetric). The originally planar material twists on heating (or cooling from an elevated curing temperature).

The bottom diagram also illustrates thermal effects on a two layer composite with orthogonal fiber directions in the layers. Again this type of distortion may arise at room temperature if the polymer matrix is cured above room temperature.

From: Hull, "An Introduction to Composite Materials,"
Cambridge (1992)