Fabrication of an isogrid fan containment case

Despite having demonstrated he design potential to save significant weight on airplane engines, acceptance of an all-composite isogrid fan containment case (FCC) has been hampered by the lack of a demonstrated and inexpensive fabrication method. The isogrid geometry employed on the current metal "so ft-catch" FCC is the most efficient structure known for strengthening this component. Redundant load paths allow the structure to maintain design stif fness after a fan blade loss has occurred. In the past, fabricating this is ogrid structure in composite materials has been an expensive and difficult task. Tooling approaches that maintain tight tolerances, consolidate the ma terial, and bring cost-effective automation to the process has, to date, el uded composite manufacturers. Alliant Techsystems has demonstrated, under the Affordable Composites for P ropulsion (ACP) program, a tooling method that, when coupled with the advan tages of Automated Fiber Placement, can produce a composite fan containment case lighter in weight and cost competitive in comparison to its aluminum counterpart. Forty-five degree arc segments of a full-scale, 2.8 m diameter FCC have been successfully demonstrated and tested. Unique approaches have been demonstrated for both an internal and external isogrid, thus allowing greater design flexibility. A full-scale demonstration article was complet ed in October 1998. This automated composite isogrid manufacturing process also opens up design possibilities in numerous aerospace areas: for example , engine firewalls, shrouds, wing skins, fuselage panels, itc. The technolo gy can be transferred to nonaerospace technologies as well.