Bonded Composite Wing Surpasses All Expectations Published Dec. 13, 2006 By Plans and Programs Directorate AFRL/XP WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- AFRL researchers successfully demonstrated the ultimate load-carrying capacity of a bonded fighter aircraft wing constructed mostly of composite materials. Developed under the Composites Affordability Initiative (CAI) X-45C Technology Transition project, the bonded composite wing surpassed engineering expectations despite undergoing intentional damage, along with simulated stresses and wear representing two aircraft lifetimes of fatigue, during the tests. The CAI is a focused effort to develop the technologies and tools necessary for reducing the acquisition cost of composite structures used in airframe structures and transition these capabilities to future weapons systems. The CAI team includes members from AFRL, Navy Manufacturing Technology, Bell Helicopter Textron, Boeing, Lockheed Martin, and Northrop Grumman. The CAI team designed, fabricated, and conducted extensive testing of the bonded composite X-45C wing, which demonstrated exceptional performance. Boeing designed the wing as an alternative to the aircraft's baseline, mechanically fastened wing to meet or exceed X-45C performance requirements. The team constructed the 26-foot-long wing, which was projected to cost 29% less than the baseline wing, using standard layup techniques for the skins and a bonded pi-joint structure. The team's fully matured, bonded pi-joint design improves the original manufacturing method, which entails drilling holes and using fasteners to assemble the X-45C aircraft. By bonding the wing, the team completed the assembly effort in days as opposed to the weeks needed for conventional construction. The new design eliminates about 2,000 fasteners with respect to the baseline wing design. The bonded structure could reduce life-cycle costs, which dominate total ownership costs for weapon systems, approximately 75% as compared to fastened structures. The CAI team's lengthy test series--which included efforts ranging from coupon testing for the effects of defects to ballistic survivability--corroborated the robustness of the pi-joint design for bonded aircraft structures, as well as the design's capability to meet all current performance requirements. The team fatigue-tested the pi-bonded structures twice, with the bonded joint remaining intact both times. With the designs, process controls, and quality assurance techniques in place to support future aircraft designs using bonded pi joints, advanced weapon system designs can now leverage this extensively tested technology for increased performance, reduced cost, and decreased cycle time.