Biomimetics Based Design of Damage Tolerant Airframe Panels

The specific innovation proposed is to design an advanced composite airframe panel for damage tolerance by incorporating biologic solutions to a similar problem found in nature, using a biomimetic approach. We will identify principal material (fiber) directions and density profiles about naturally occurring holes in bones through a microscopic and radiographic techniques. These holes are known to be damage tolerant, as they clinically do not represent a fracture or fatigue failure initiation site. In addition to its novel microstructure, bone is also a 2 fiber composite material, consisting of stiff bone mineral crystals embedded in a scaffold of compliant collagen fibers. We will demonstrate the expected low stress concentrations about the hole through mechanical testing and moir¿ interferometry. We will then incorporate these principal material directions and density and use a 2 fiber system in a computational model of a representative airframe panel. This model will be used to demonstrate the advantages of biomimetic design. We believe biomimetic design principles can be used to reduce aircraft weight, as bones are weight optimized due to the energy expenditure required to carry such a relatively heavy tissue. Furthermore, by increasing damage tolerance, life cycle costs of airframes can be reduced significantly.