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Any aircraft development process in modern times employs advanced materials and design concepts to obtain weight and performance benefits. The materials and design concepts have to be tested at coupon level, sub-component level, and component level in order to ensure the design adequacy and confirm airworthiness. This paper presents the results of an investigation, examining the strength and stiffness characteristics of an MLG (Main Landing Gear) spar joint in a trainer aircraft wing. The spar is a sandwich construction spar with plywood as core material. GFRP is used as face sheet material with aluminium plate reinforcement as main load bearing member. The spar is connected to skin and ribs through bonding using Flox and joining layers. A feature-level test specimen was designed and fabricated to simulate the joint. The specimen was tested to evaluate the static strength and to show design compliance. Critical load case of one-wheel landing case was considered for testing. A robust test rig with loading fixtures is designed and developed for supporting and testing the MLG spar joint specimen which is validated by finite element simulations. The structural response of the main landing gear spar joint such as strains was monitored by strain gauges bonded at critical locations on the test feature. Totally 4 rosette gauges were bonded at critical locations for monitoring the strain response of the MLG Spar joint during the test. The tip deflection at the free end of the spar joint was monitored using LVDT. Both vertical and drag directional loads were applied in design limit load case (DLL) and design ultimate load case (DUL). The spar joint successfully sustained the 100% DLL loads of Fx = 2.76 kN and Fz = 6.90 kN and upon further loading, failed at 170% DLL. Major failure was observed in the hole region present in the sandwich rib. The failure has further propagated in the joining layers connecting the rib and spar. Testing of this MLG spar joint test feature has given the confidence to pursue this design in the wing structure.

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Structural Testing of Main Landing Gear Spar Joint of a Composite Trainer Aircraft

  • 会议论文

  • 发表日期：

    2025年

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  • M. Mohan Kumar,
  • C. Surendra,
  • N. Lohith,
  • Kumari Asha,
  • N. Paranthaman

摘要

Any aircraft development process in modern times employs advanced materials and design concepts to obtain weight and performance benefits. The materials and design concepts have to be tested at coupon level, sub-component level, and component level in order to ensure the design adequacy and confirm airworthiness. This paper presents the results of an investigation, examining the strength and stiffness characteristics of an MLG (Main Landing Gear) spar joint in a trainer aircraft wing. The spar is a sandwich construction spar with plywood as core material. GFRP is used as face sheet material with aluminium plate reinforcement as main load bearing member. The spar is connected to skin and ribs through bonding using Flox and joining layers. A feature-level test specimen was designed and fabricated to simulate the joint. The specimen was tested to evaluate the static strength and to show design compliance. Critical load case of one-wheel landing case was considered for testing. A robust test rig with loading fixtures is designed and developed for supporting and testing the MLG spar joint specimen which is validated by finite element simulations. The structural response of the main landing gear spar joint such as strains was monitored by strain gauges bonded at critical locations on the test feature. Totally 4 rosette gauges were bonded at critical locations for monitoring the strain response of the MLG Spar joint during the test. The tip deflection at the free end of the spar joint was monitored using LVDT. Both vertical and drag directional loads were applied in design limit load case (DLL) and design ultimate load case (DUL). The spar joint successfully sustained the 100% DLL loads of Fx = 2.76 kN and Fz = 6.90 kN and upon further loading, failed at 170% DLL. Major failure was observed in the hole region present in the sandwich rib. The failure has further propagated in the joining layers connecting the rib and spar. Testing of this MLG spar joint test feature has given the confidence to pursue this design in the wing structure.