Results of an Aeroelastic Tailoring Study for a Composite Tiltrotor Wing

Popelka, David; David, Lindsay; Parham, Tom; Berry, Victor; Baker, Donald J.

doi:10.4050/jahs.42.126

Cited by 25 publications

(19 citation statements)

References 3 publications

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“…The feasibility of a stiffness reduction with no impact on aeroelastic stability is thus very appealing. A thickness reduction of the wing of the WRATS model, without significantly degrading whirl-flutter stability, was attempted in the 1990s using passive aeroelastic tailoring [26][27][28]. The experimental verification was appreciably successful.…”

Section: Stability Analysismentioning

confidence: 97%

Multibody simulation of a generalized predictive controller for tiltrotor active aeroelastic control

Mattaboni

Masarati

Mantegazza

2011

Proceedings of the Institution of Mechanical Engineers, Part G:

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A generalized predictive control has been developed for the control of the aeroelasticity and structural dynamics of a tiltrotor. Adaptivity is the key feature of the proposed technique. It gives the controller the capability to autonomously follow the variations of the system. A comprehensive simulation system has been adopted to design and test the adaptive regulator under realistic conditions. The aeroservoelastic tiltrotor has been modelled using a multibody approach, considering the structural dynamics, the aerodynamics, the blade pitch control system kinematics, and actuator and sensor dynamics. Numerical simulations illustrate the capability of the adaptive controller to reduce wing vibrations and loads while significantly extending the flutter-free flight envelope. This controller shows satisfactory performances within the whole flight envelope as it is able to properly work in different rotor trim conditions and varying structural properties in the presence of external disturbances and measurement noise.

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Section: Stability Analysismentioning

confidence: 97%

Multibody simulation of a generalized predictive controller for tiltrotor active aeroelastic control

Mattaboni

Masarati

Mantegazza

2011

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…c mx n1 cos n2 θ tw sin n3 θ tw dx (9) where c is not a function of x and the integers n1, n2, and n3 vary between 0 and 2. These integrals are left unevaluated until a twist function is specified with the other rotor parameters.…”

Section: Prediction Of Air and Ground Resonance Stability Of Soft-inpmentioning

confidence: 99%

Prediction of Air and Ground Resonance Stability of Soft-Inplane Tiltrotors Using a Semispan Analytical Model

Howard¹,

Smith²

2008

j am helicopter soc

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A soft-inplane tiltrotor can be subject to the aeromechanical instabilities of ground and air resonance in addition to whirl flutter. An investigation of these tiltrotor aeromechanical instabilities was undertaken along with an assessment of some methods for improving the stability of a soft-inplane tiltrotor. A new semispan analytical model was developed consisting of a rigid blade rotor coupled to a rigid pylon and an elastic wing with bending-torsion couplings. The results from this model were validated using a 1972 wind tunnel test of the Boeing model 222 tiltrotor. Hover, transition, and cruise configurations were investigated. While the analysis did not predict a ground resonance instability or an air resonance instability in hover, air resonance instabilities are predicted for transition and cruise configurations as well as whirl flutter instabilities at high speeds. Aeroelastic couplings in the rotor blades and wing are shown to affect the air resonance stability in cruise and transition and to be useful in augmenting the inherent stability of the aircraft. Wing vertical bending coupled to wing torsion and rotor low-frequency lag coupled to blade torsion were helpful in avoiding air resonance. Positive blade pitch-lag coupling was quite detrimental to whirl flutter stability. Wing vertical bending-torsion coupling was unable to stabilize all the air resonance regions completely.

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“…In another example of growing industrial interest in composite tailoring, Bell Helicopters published a design study demonstrating the feasibility of an elastically tailored wing for a high speed civil tiltrotor aircraft (Ref. 27). Recent wind tunnel test results showed a large increase in whirl flutter stability boundaries for the tailored wing design.…”

Section: Background and Introductionmentioning

confidence: 97%

Refined structural modeling and structural dynamics of elastically tailored composite rotor blades

Centolanza

Smith

Kumar

1996

37th Structure, Structural Dynamics and Materials Conference

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A refined analytical model based on Vlasov theory is developed to (1) predict the cross-sectional stiffness constants for thin-walled multicell composite rotor blades, (2) determine the location of the shear center for thin-walled multicell composite rotor blade cross-sections, and (3) investigate the effects of using spanwise nonuniform layups to produce a desired twist distribution. The model uses an expanded Vlasov theory that includes transverse shear deformation of the cross-section, a warping function that captures the variation of shear stiffness along the contour of the cross-section, and the effect of 2D ply elasticity. Analytical results are validated with both experimental data and detailed FEM results. The effects of ignoring 2D in-plane ply elasticity, in-plane warping, and local bending moments and curvatures were investigated using the new structural model. The influence of the skin and web thickness on the shear center location and torsion rigidity was also studied. Neglecting the local shell bending moments and twists has a significant effect on torsional rigidity for relatively thicker-walled cross-sections. (Author) Abstract A refined analytical model based on Vlasov theory is developed to (1) predict the cross-sectional stiffness constants for thin walled multi-cell composite rotor blades, (2) determine the location of the shear center for thin walled multicell composite rotor blade crosssections, and (3) investigate the effects of using spanwise non-uniform lay-ups to produce a desired twist distribution. The model uses an expanded Vlasov theory that includes transverse shear deformation of the cross-section, a warping function that captures the variation of shear stiffness along the contour of the cross-section, and the effect of two-dimensional ply elasticity. Analytical results are validated with both experimental data and detailed finite element results.The effects of ignoring two dimensional inplane ply elasticity, inplane warping, and local bending moments and curvatures were investigated using the new structural model. The influence of the skin and web thickness on the shear center location and torsion rigidity was also studied. The results show that the ignoring the two-dimensional inplane ply elasticity has a significant effect on the cross-sectional stiffness. Neglecting the local shell bending moments and twists has a significant effect on torsional rigidity for relatively thicker walled cross-sections. It was found that in-plane warping is not important for thin walled closed cell cross-sections. The shear center position is ' insensitive to the airfoil skin thickness but is sensitive to the web thickness. Torsional rigidity is influenced by the airfoil skin thickness but not influenced by the web thickness for relatively thick skin airfoils. The cross-sectional model was also integrated with a structural dynamic analysis of composite rotor blades. By using spanwise uniform and non-uniform ply-layups, a preliminary investigation on the behnvior of the composite blades was conducte...

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Results of an Aeroelastic Tailoring Study for a Composite Tiltrotor Wing

Cited by 25 publications

References 3 publications

Multibody simulation of a generalized predictive controller for tiltrotor active aeroelastic control

Multibody simulation of a generalized predictive controller for tiltrotor active aeroelastic control

Prediction of Air and Ground Resonance Stability of Soft-Inplane Tiltrotors Using a Semispan Analytical Model

Refined structural modeling and structural dynamics of elastically tailored composite rotor blades

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