TRIAIXIAL OVERBRAIDING OF COMPLEX COMPOSITE STRUCTURES USING MELT-OUT MANDRELS

A serpentine inlet duct for a 30-foot unmanned combat aircraft was designed as part of the Air Force Research Lab (AFRL)-funded Manufacturing for Affordable Sustainable Composites (MASC) program at Wichita State University (WSU). This manufacturing demonstrator aimed to develop a cost model based on manufacturing data, including various materials, processes, and assembly methods. The goal was to enable the industry to leverage this information for on-demand, flexible manufacturing and assembly of composite structures tailored to specific volume, cost, weight, and mission requirements. The inlet duct’s complex curvature necessitated a novel manufacturing approach. Automated tape-laying for tow placement was constrained by the part's minimum radius of curvature, and hand placement of prepreg would have led to excessive cutting and splicing. To address this challenge, the overbraiding technology developed by A&P Technology in Cincinnati, Ohio was employed to demonstrate high-rate production for this aircraft component. The demonstrator inlet duct measures approximately eight feet in length, with perimeters ranging from 56.5 to 96.6 inches. The melt-out mandrel for the tool was created using Fiber Dynamics' Lost Core Tooling System. A&P Technology then used this system to overbraid five layers of triaxial braid at a constant thickness, achieving bias angle changes along the part's length from ±55° to ±71°. The process was executed without any cuts or splices, and the precise control of fiber angles ensured consistently high part-to-part repeatability. These research findings will provide valuable insights for the design, manufacturing, and certification of over-braided structures for complex geometries.