• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.173-176
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• 2002

This paper describes the design procedure of composite parts for hingeless hub system of helicopter. These composite parts are composed of flexure and sleeve. The design of this composite flexure is an important technique in hingeless hub system since the rotor system stability and dynamic characteristics depends on this flexure characteristics. The objective of this research is to replace the existing metal hub parts with composite to improve the performance and stability. First, the coupon test of candidate composite material for hub parts was conducted. The hub parts was designed based on test results and the manufacturing possibility by using Fiber Placement System(FPS) was checked. Also the dynamic analysis and stress analysis of composite hub parts was conducted. Through this research, we will find out the possibility of replacing existing metal hub parts with composite.

• Journal of Aerospace System Engineering
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• v.6 no.1
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• pp.1-6
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• 2012

During helicopter rotor system development process, whirl tower test is conducted basically. For conducting whirl tower test during bearingless hub development process, design new blade or using existing blade with repair or remodeling. Because simple shape and efficient aerodynamic characteristic, BO-105 blade is used for hub system development widely. Originally BO-105 Blade is used for hingeless hub, so flap stiffness and lag stiffness on blade root area is relatively low. So appling BO-105 blade to bearingless hub whirl tower test, root area have to be reinforce. In this paper, suggest reinforcement method of BO-105 blade root area.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.119-122
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• 2003

This report describes the procedure of detailed design and structural test for the composite flexure which is a part of the hingeless hub system. First, stacking sequence design for composite flexure was done, and structural analysis by using NASTRAN was made to verify structural stability and safety. Using FPS installed at KIMM, composite flexure was laid up and cured using a autoclave. Before rotor ground test, the basic structural tests such as a bench test, tensile strength test and shear strength test, for flexure, were accomplished. Through replacing existing metal hub part with new fabricated composite flexure, improvement of aeroelastic stability and weight reduction were achieved. This result will be applied to composite rotor system design fur helicopter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.98-105
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• 2005

This paper presents the result of the aeroelastic stability test of the small-scaled hingeless hub system with composite paddle blades in hover and forward flight conditions. Excitation tests of hingeless hub system installed in GSRTS(General Small-scale Rotor Test System) at KARI(Korea Aerospace Research Institute) were carried out to get lead-lag damping ratio of blades with flexures as hub flexure. MBA(Moving Block Analysis) technique was used for the estimation of lead-lag damping ratio. First, blades with metal flexures, then with composite flexures of the same dynamic properties of rotor system as metal one were tested. Tests were done on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively. Composite flexures were found to have better damping characteristics over metal ones in the non-rotating vibration test, and it was confirmed that the use of composite flexures would give observable improvement in aeroelastic stability compared to metal ones in all test conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.29-36
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• 2004

In this work, the effect of composite couplings on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor blade is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear, torsional warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade response and hub loads are calculated using a finite element formulation in space and time. The aerodynamic forces acting on the blade are calculated by quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap $({\delta}3)$ or $pitch-lag({\alpha}1)$ coupling. It is found that the elastic couplings have a substantial effect on the behavior of $N_b/rev$ hub loads. Nearly 10 to 40% of hub loads is reduced by appropriately tailoring the fiber orientation angles in the laminae of the composite blade.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.105-111
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• 2013

Whirl tower test is conducted basically during helicopter rotor system development process. And for whirl tower test of rotor hub system, new design blade or existing blade which is remodeled for new rotor hub system is used. Because of simple shape and efficient aerodynamic characteristic, BO-105 helicopter blade is used for helicopter rotor hub development project widely. Originally BO-105 blade is used for hingeless hub system and blade root is used to flexure. So flap stiffness and lag stiffness at blade root area is relatively low compare with airfoil area. So, in order to apply the BO-105 blade to bearingless hub, blade root area have to be reinforced. And in this process, blade root area's section property is changed. In this paper, we suggest reinforcement method of BO-105 blade root area and study dynamic characteristic of bearingless rotor system with reinforcement BO-105 blade.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.575-580
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• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. 1'he hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_{3}$) coupling. It is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b/}$rev hub loads. About 40% hub loads is reduced by tailoring or redistributing the structural properties of the blade.f the blade.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.734-740
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• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered In the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton’s principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_3$) coupling. It Is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b}$ /rev hub loads. About 40％ hub loads is reduced by tailoring or redistributing the structural properties of the blade.e.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.5
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• pp.390-397
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• 2014

BO-105 helicopter applies hingeless rotor hub system and blade root uses a flexure of hingeless rotor hub system. So bending stiffness reinforcement for flexure was conducted for preparation of whirl tower test using BO-105 blade. Bending moment of flexure area was calculated with FE modeling of section shape for stiffness reinforcement of flexure and thickness of composite material for reinforcement was chosen. Flexure bending stiffness reinforcement was conducted and bending stiffness measurement test was performed before and after bending stiffness reinforcement. And the test data are compared with analysis results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.310-315
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• 2003

This paper described that rotating test and fatigue test of a small-scale hingeless hub system with composite rectangular blades. Generally Rotating stability and fatigue test technique is one of Key-technology on test and evaluation for helicopter rotor system Rotating test of hingeless rotor system was achieved by means of rotor vibration characteristic and aeroelastic stability test GSRTS, equipped with hydraulic actuator and 6-component rotating balance was used to test hingeless rotor system especially for an observation of blade motion including flawing, lagging and feathering. Rotating test was done in hover and forward flight condition. Small-scaled blade fatigue test condition was determined by blade load analysis with the reference table of composite materials(S-N curve). Fatigue test bench was developed for the estimation of blade fatigue life, and tested its characteristic.