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Aeroelastic Vulnerability Assessment

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: Develop a validated computational tool for evaluating aeroelastic effects of threat-damaged flight surfaces in support of aerospace platform vulnerability assessments and Title 10 Live Fire Test & Evaluation (LFT&E). 

DESCRIPTION: Live Fire Test & Evaluation (LFT&E) programs traditionally evaluate an aircraft’s vulnerability posture against a wide variety of ballistic threats for specific flight conditions using a combination of modeling tools and static or quasi-static testing techniques. Conclusions drawn from these evaluations, particularly those resulting in a “survivable” engagement, are often used for the full spectrum of flight conditions and damage extents. However, the scope of this approach encompasses only a subset of vulnerabilities, while other vulnerabilities linked to dynamic instabilities of the damaged structure could significantly impact the conclusions drawn within the overall assessment. Therefore, the scope of vulnerability assessments needs to be broadened, beginning with a CFD based tool that identifies circumstances where aeroelastic effects become a significant factor in the aircraft’s ability to sustain flight after a threat impact. Computational aeroelastic modeling techniques have been formerly applied to studying combat damaged air vehicles, ranging from efficient, coupled fluid and finite element models, to more intensive, high-fidelity models [1, 2, 3, 4]. Despite these efforts and the advancements in the treatment of structural bodies in aeroelastic modeling [5], an efficient and robust tool has yet to be developed for the survivability analyst. Such a tool is critical to understanding the true vulnerability posture of aircraft when these analyses are performed in the aircraft design and/or LFT&E stages of acquisition programs. This topic solicits a time-accurate, fast-running algorithm for describing the aeroelastic response of damaged structures and for defining critical damage/flight conditions, constituting a loss of load-carrying capability of the structure jeopardizing a 30-minute sustained flight capability post-impact. A typical analysis should include altitudes within ranges of current and future ground- or air-based threats (i.e. small arms and missiles) and speeds ranging anywhere within the aircraft’s flight profile (i.e., speeds associated with fighters/transport/unmanned vehicles as well as rotor blades). This analysis tool needs to quantify the aeroelastic response to ballistic and/or thermal damage mechanisms relative to the limits of the structure’s normal fight envelope. The analysis tool should be user friendly by non-experts such that the aeroelastic/aerothermoelastic analysis could be executed for a wide variety of platform applications. The analysis tool needs to be fully validated. The analysis tool should be applicable to any geometry (fighter wing, transport aircraft, rotor blade) and threat condition (ranging from small arms to missiles). The analysis tool must be amenable for integration with current vulnerability assessment tools in use at an Air Force Vulnerability Analysis Facility. 

PHASE I: Develop and demonstrate a time-accurate, fast-running algorithm that describes the aeroelastic response of damaged structures, and the critical damage/flight conditions constituting a loss of sustained flight capability and an approach for validating the computational tool. 

PHASE II: Develop and validate a computational tool for evaluating aeroelastic effects of threat-damaged flight surfaces for aerospace platform vulnerability assessments and defining critical damage/flight conditions constituting a loss of load-carrying capability of the structure. 

PHASE III: Military Application: Phase III would result in the efficient, validated tool being distributed to aircraft vulnerability analysts (OEMs and government) enabling them to identify critical flight and threat engagement scenarios causing aeroelastic vulnerabilities, and the extent of that vulnerability such that further investigation or design revision could be executed. Commercial Application: The analysis methodologies are independent of what produces a hole through the dynamic structure. These methodologies can transition to companies that design/build aircraft, helicopters, large scale UAVs, wind turbine blades, propellers, turbine engines, and space launched vehicles. 

REFERENCES: 

1: Farhat, C. "Methodologies for Predicting and Testing the Effects of Combat Damage on Flight Envelopes." AFRL-SR-AR-TR-06-000 Dec 200

2:  Moshier, Hinrichsen, and Coules. "Dynamic Loading Methodologies." AFRL-ASIST-14-0 Dec 200

3:  R.L. Hinrichsen, M.A. Moshier. "Using Coupled Fluid/Structure Interaction Code to Predict Fighter Aircraft Wing Response to AAA Damage." 2nd MIT Conference on Computational Fluid and Solid Mechanics, 17-20 June 2003, Elsevier Ltd.

4:  M. A. Moshier, R. L. Hinrichsen, G.J. Czarnecki, Dynamic Loading Methodologies, AIAA Journal, Vol. 41, Number 11, PP 2291-2294, Nov. 200

KEYWORDS: Aeroelasticity, Aerothermoelasticity, Aircraft Survivability, Aircraft Vulnerability, Combat Damage Assessment, Damaged Structures 

CONTACT(S): 

Adam Goss (OLAC) 

(937) 255-4246 

adam.goss@us.af.mil 

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