Uninhabited Air Vehicles Enabling Science for Military Systems (2000) / Chapter Skim
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4 Airframe Materials and Structures
4 Airframe Materials and Structures
Pages 50-58
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From page 50... ...
are as follows: · defining the design environment in which future UAVs will operate, including loads definition, reliability requirements, and aeroelasticity · reducing manufacturing costs for airframe structural components, including advanced composite materials and multifunctional materials (i.e., structural materials that also serve another primary purpose) · improving design processes to support reduced cycle time, rapid prototyping, and low-cost fabrication 50
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From page 51... ...
STRUCTURAL DESIGN Probabilistic Methods The design of aircraft structure considers interactions among many complex processes, including material selection, fabrication, assembly, operations, and maintenance. The primary material parameters that affect a structural design are strength and stiffness, which are traditionally characterized by deterministically derived design property values, or "allowables." Allowables are statistically reduced values based on experimental data and on assumed statistical models or distributions.
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From page 52... ...
First, the uncertainties and difficulties in accurately characterizing the operational environment for UAVs could require an overly conservative statistical safety factor for structural design when using deterministic design criteria. Probabilistic design and analysis would reveal more of the information about a structure to allow for a more realistic assessment of performance and operating life.
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From page 53... ...
The development of basic property relationships and potential failure modes are needed for implementing probabilistic design approaches and reducing the amount of large-scale verification testing required. Simulation Methods Techniques and software codes should be developed for computational simulations of structural responses to operational environments throughout the structure' s lifetime at both the material and structural levels.
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From page 54... ...
In addition to modular structural designs and reduced size and weight discussed in Chapter 2, advances in low-cost materials and processes will provide opportunities for reducing the cost of airframe structural components. The implementation of innovative, low-cost manufacturing processes, along with consideration of manufacturing costs and sustainment throughout the design process, will be key to the development of cost-effective UAV airframes.
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From page 55... ...
long-term technology development. Analysis tools and design methodologies are being developed to automate and improve predictions of the characteristics of composite components so that designs can be less conservative and the excess weight associated with overdesign can be avoided.
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From page 56... ...
A key manufacturing technology used by the MALD program was compression molding of sheet-molding compounds to produce discontinuously reinforced composite components. These materials and processes are similar to those widely used in the automotive industry.
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HEALTH MONITORING AND HEALTH MANAGEMENT Prognostics and health monitoring are being used today to assess air vehicle systems. Systems such as engines, auxiliary power units (APUs)
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From page 58... ...
Neural networks can potentially monitor many locations on an aircraft and reduce the number of sensors required. Piezoelectric-based health monitoring systems have been demonstrated in the laboratory for integrated damage detection of both metallic and composite structures (Lichtenwalner et al., 19971.
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