A design concept is introduced to address the need for a significant improvement in strength and toughness of composites through control of the fiber architecture. A three-dimensional (3-D) braided structure is used to illustrate the approach. The mechanical properties of the 3-D braid metal matrix and ceramic matrix composites are compared with composites reinforced by various fiber architecture. In order to provide a rational means for the design and control of the microstructure of the fiber architecture, a processing science base has been established by means of a fabric geometry model (FGM) relating material properties, microstructure, fiber architecture, processing parameters, and composite properties.