Low Weight, Damage Tolerant Advanced Composite Airframe

Advanced composite materials are increasingly used in wing and fuselage structures. These materials permit a lower part count, weight, and potentially manufacturing and operational costs. These benefits are limited by inherently low damage tolerance and the industry reticence to eliminate excessive riveting. Skin/stiffener constructions are typical of composite airframes. The skin/stiffener joint jas a highly leveraged effect upon airframe const, weight, and performance. Fasteners, localized padups, and other options to improve stiffener attachment performance are currently available. Unfortunately, all of these approaches increase weight and cost. Foster-Miller's z-fiber technology dramatically improves resistance to delamination (Mode 1 fracture toughness, GIC is improved 40X). Z-fibers have also reduced impact damage area and improved stiffener attachment strength. Z-fiber technology is compatible with all contemporary composites materials and manufacturing processes. We propose that z-fiber technology can dramatically improve skin/stiffener performance. Foster-Miller proposes to optiimize the z-fiber skin/stiffener attachment using analysis and test. Lockheed will support our Phase I efforts with data and will review our analyses and conclusions. Our baseline will include Lodkheed's advances in stiffener design. We will define representative structures suitable for a Phase II effort.