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Wave Isolation

Description:

OBJECTIVE: Develop a method to isolate signal transfer between the fluid and structure in a hydrodynamic ram (HRAM) impact event. 

DESCRIPTION: Aircraft fuel tanks are intrinsically vulnerable to ballistic threats due to their large capacity and location. These ballistic threats have the possibility of leading to catastrophic structural failure by creating an internal damage mode classified as HRAM; this categorizes the event of pressure shocks that have potential to inflict long-lasting overpressures. Recent methods have been explored to understand the effects of HRAM on fuel tank structures; however, these methods were unable to isolate the fluid wave from structural wave during testing. The presence of the structural wave affected test results, producing inconsistent testing conditions and inadequate data collection. This effort will identify a robust method for isolating wave propagation to the fluid, and/or establishing a significant propagation delay in the surrounding structure. The solution must be robust enough to withstand numerous HRAM impact events. Improvements are necessary to collect more accurate HRAM data feeding modeling and simulation of structural skin/joint/spar failures. 

PHASE I: Analyze the interaction between fluid and metallic structure, specifically skin, joints, and spars, subjected to high pressure impulses from fluids. Develop a robust methodology to isolate, or delay, the wave propagation from the RAMGUN metallic structure to the fluid and, subsequently, the “target” that influences test results. Solutions should be robust enough to withstand numerous HRAM impact events; pressure produced would not exceed 34MPa (5kpsi). 

PHASE II: Implement Phase I methodology to the RAMGUN and surrogate aircraft fuel tanks. The solutions need to demonstrate the ability to produce consistent results as well as reduce the impact of the structural wave propagation on the testing material. Proposed solutions should not interfere or dampen the water column wave propagation and the results that it produces on the test specimen. 

PHASE III: Military Applications: Advancement will provide means to measure existing aircraft fuel tank structural strength against HRAM threats. Furthermore, the methodology improves confident levels in assessing military aircraft vulnerabilities with upgraded research integrated into platform survivability modeling and simulation. Solutions/findings would also potentially have applicability to Navy vessel structural integrity studies. Commercial Applications: Solutions will allow commercial airliners opportunity to conduct studies on aircraft skin, joint, and spar strength to dynamic HRAM pressures and impulses versus static testing. 

REFERENCES: 

1: Czarnecki, Greg. "Assessment of Fuel System Failure Effects – Skin-Spar Joint Resistance to Hydrodynamic Ram." (2016).

2:  Czarnecki, G.J., "Evaluation of Skin-spar Joint Resistance to Hydrodynamic Ram"

3:  Report Numbers: DTIC ADA464155, AFRL-WS-WP-TR-2007-9002, Report Date 2006-03-01

4:  3. Kane, David, "Composites Affordability Initiative-Phase 2 Pervasive Technology Task 5.1-Methods and Performance Requirements", Report Numbers: DTIC ADB297905

5:  AFRL-ML-WP-TR-2004-4052

6:  Report Date 2002-03-01

KEYWORDS: Hydrodynamic Ram, Fuel Tank Survivability 

CONTACT(S): 

Adam Goss 

(937) 255-4246 

adam.goss@us.af.mil 

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