Method of forming a curved composite structure are provided. In one embodiment, the method includes contacting at least one ply of preimpregnated material on a first surface of a curved mandrel. The first surface of the mandrel has a first radius of curvature. The mandrel further has at least one second surface that has a second radius of curvature. A tension gradient is introduced on the ply adjacent to the first radius of curvature and the ply is then pressed over the curved mandrel to form the curved composite structure.