US Patent 7712488 Fiber architecture for Pi-preforms

A woven preform for a reinforces composite material, which may be woven flat and folded into a shape. The preform has a three-dimensional weave architecture with fill fibers woven to provide layer-to-layer interlocking of layers of warp fiber as well as interlocking of fibers within each layer. At least two legs extend from a base, the base and legs each having at least two layers of warp fibers. The legs can be connected at a symmetrical or asymmetrical, distributed-column intersection, with an even or odd number of columns of warp fibers being located between the legs. The outer ends of the base and/or legs preferably have tapers formed from terminating layers of warp fibers in a stepped pattern.