Abstract: Fiber materials of unidirectional, parallel filaments are fully impregnated with highly viscous resins such as polymers having linear, long chain molecular structures, by heat softening the resin, applying it to opposite sides of the fiber material, subjecting it to low pressure (e.g. 4 psi) and generating shear stresses in a boundary layer of the pressurized resin immediately adjacent the faces of the fiber material to align the long chain molecules in the vicinity of the filaments substantially parallel to the filaments. Shear is generated by moving the material, including the applied resin, through a restricted passageway which defines a shear zone. While the resin is subjected to shear its viscosity is reduced to such an extent that it penetrates into the fiber material and substantially fully encapsulates the fibers with the resin.