The Projects

On-going Projects        Completed Projects        Contact Information

On-going Projects

• Pre-stressing of Bonded Repairs
• Objectives: Quantify the effect(s) of prestressing the substrate in a bonded repair.
• Sponsor: The Air Force Research Lab (AFRL) Air Vehicles Directorate (VASE)
• Status: On-going
• Hybrid and Muli-Layer Patches for Bonded Repair
• Objectives: Determine the effectiveness and feasibility of multi-layer Glare and hybrid (Boron/Ep + Glare) bonded repairs
• Sponsor: The U. S. Air Force Aeronautical System Center Aging Aircraft Office (ASC/SMA)
• Status: On-going
• Bonded Repairs to Thick Structures
• Objectives: Compare effectiveness of Fiber-Reinforced, High-Modulus patches to Glare patches on repairs to stiffened/thick structures.
• Sponsor: The Air Force Research Lab (AFRL) Air Vehicles Directorate (VASE)
• Status: On-going
• The Composite Repairs to Metallic Structures (CRMS) Manual
• Objectives: Develop the Design & Analysis (D&A) portion of a composite repairs manual with the eventual goal of incorporation in to a Mil-Handbook.
• Sponsor: In-house effort.  Portion sponsored by the Air Force Research Lab (AFRL) Materials Directorate (ML)
• Status: On-going
• Effects on Crack Growth Rate in Multi- vs. Single-Layer Cold Expanded Material
  • Objective: Determine if crack growth rate is different for multi-layered cold worked holes than for single-layer cold worked holes, as single-layered cold working is the only data available.  The current available data is insufficient, as cold expansion is performed in multiple layers on the A-10.    
  • Oversight: In-house effort (AFOSR)
  • Estimated Completion: December 2004
• Fatigue Performance of Corroded Upper Wing Skin Material to Determine Threshold Thickness Loss
  • Objective: Chemically corroding a machined divot in AA7075 will provide a structural threat at or beyond a specific thickness loss. CAStLE shall determine this threshold value to recommend maintenance (grind-out or bonded repair) for the E-8C. 
  • Oversight: AVHM
  • Estimated Completion: December 2004

C-130 Center Wing Box Flight Data Acquisition

• Objectives:
• Measure accurate flight loads, strain, acceleration, etc. for a variety of mission parameters on an operational USCG HC-130
• Validate various existing models for relating aero loads to strain
• Provide environmental data to AVHM corrosion kinetics team
• Sponsor:  ASC/AAA
• Status:  On-going

C-130 Tear Down and Failure Analysis

• Objectives:

  • Harvest critical structural components from retired C-130 airframe
  • Use NDI to determine focus sites for failure analysis investigations
  • Determine the root cause of failure for those sites
• Sponsor:  ASC/AAA
• Status:  On-going

C-5 Structural Failure Analysis

• Objectives:  Determine the root cause of failure for sites selected by the sponsor
  Sponsor:  Warner-Robins/C-5 Program Office
  Status:  On-going
TG-10B Landing Gear Loads Flight Data Acquisition
• Objectives: 

  • Measure accurate operational loads for TG-10B landing gear
  • Correlate measured strains and accelerations to operational event
  • Provide data to ASC/YTG (Glider Program Office).
• Sponsor:  ASC/AAA
• Status:  On-going
• Legacy Material Evaluation (AA 7079)
  • Objectives: 

    • Assess the validity of published AA 7079 material properties from harvested C-5 skin
  • Sponsor:  AFOSR
  • Status:  Ongoing

    Stress Corrosion Cracking (SCC) Rate Determination for Thin Sheet

    • Objectives: 
      • Determine SCC rate in thin sheet.
    • Sponsor:  AFOSR
    • Status:  Ongoing

• Effects of Humidity on Crack Growth in Aluminum Alloys
• Objectives: Understand the influence of humidity on fatigue crack growth in an aluminum alloy.
• Principal Investigator: Mr. Derk R. Daverschot
• Sponsor: In-house effort.
• Status: Complete
• Stress and Strain Distribution in Stiffened Wing Panel (Cadet Project)
• Objective: Determine stress and strain fields in a thick, stiffened wing plank using finite element, strain gage, and photoelastic methods.
• Status: Complete
• Using Capacitance of Fiber-Metal Laminate Patch to Detect Damage (Cadet Project)
• Objective: Determine whether the capacitance in a fiber metal laminate patch can be used to measure damage progression under the patch.
• Status: Complete
• Fatigue Performance of E-8C Upper Wing Skin Material
  • Objective: Determine if exfoliation corrosion has detrimental effects on fatigue life of AA7178 when exposed to spectrum loads.
  • Oversight: AVHM
  • Status: This portion is complete, however parallel efforts are still under way. 
• Transition Fit Fastener Finite Element Analysis
  • Objectives: 

    • Detailed modeling of a transition fit fastener installed in E-8/B-707 upper wing skin
    • Provide stress field results to AVHM corrosion kinetics team
  • Sponsor:  ASC/AAA
  • Status:  Closed. Results published in USAFA TR 04-04
• Stress Concentration Factor Finite Element Analysis
  • Objectives: 

    • Compare 3-D result with published 2-D stress concentration data
    • Perform convergence studies using MSC/PATRAN output tools
  • Sponsor:  ASC/AAA
  • Status:  Closed. Results published in USAFA TR 04-03

For copies of completed project reports, please email:

castle@usafa.af.mil

USAFA Center for Aircraft Structural Life Extension
HQ USAFA/DFEM
2354 Fairchild Dr, Suite 6H2
USAF Academy CO 80840-6240
Phone: (719) 333-3618
Fax: (719) 333-2944
DSN Prefix: 333
Last Updated 23 October 2006
castle@usafa.af.mil