Abstract: The invention is a process for forming a preform for use in a structure having at least one curved portion of a specific length, including the steps of: 1) providing a preform having cable of expanding in length threads in rows parallel to the direction of curvature over a length equal to the length requiring curvature, such that the gaps between each thread row are spaced from the gaps in the adjacent tread rows; and 2) stretching the portions of the preform requiring curvature in a sine-wave pattern.

Abstract: The invention is a process for forming a 3D woven PI shaped cross-section preform having a first and second bottom foot portions and first and second upstanding leg portions for use in a structure having at least one curved portion of a specific length. In detail, the process includes the steps of: 1) cutting the treads parallel to the direction of curvature into over a length equal to the length, such that the cuts in each thread are spaced from the cuts in the adjacent treads; 2) stretching the portions of the preform requiring curvature; and 3) forming the curvature in the preform.