Real composite materials are seldom single-layer uniaxial systems. Frequently, random chopped fibers, woven fiber fabrics, or oriented uniaxial layers are used to form the final composite material. The photograph shows a plan and cross-section of the fibers used

in a woven fiber fabric for composite reinforcement. A fabric of this type will be impregnated with a polymer (an epoxy resin) and the resin cured to form the multilayer material. In this material, fiber-fiber damage can occur and reduce the fracture stress of the fibers.

The behavior of the composite can be made more isotropic by making several layers with this orthogonal fiber structure, and then laminating them with different fabric angles in adjacent layers. For the best thermal and mechanical behavior, the layup design should be symmetrical about a center lamina.

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