The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform
Farhan Gandhi - One of the best experts on this subject based on the ideXlab platform.
-
zero poisson s ratio cellular honeycombs for flex skins undergoing one dimensional morphing
Journal of Intelligent Material Systems and Structures, 2010Co-Authors: K R Olympio, Farhan GandhiAbstract:Cellular honeycomb cores with overlying flexible face sheets have been proposed for use as flex skins for morphing aircraft. The cellular cores, which provide underlying support to the face sheets for carrying aerodynamic loads, must have low in-plane stiffness and high in-plane strain capability. For one-dimensional morphing applications such as span-, chord-, or Camber-Change, restraining the Poisson’s contraction (or bulging) that a conventional cellular honeycomb core would otherwise experience in the non-morphing direction results in a substantial increase in the effective modulus in the morphing direction. To overcome this problem, this article develops zero Poisson’s ratio hybrid and accordion cellular honeycombs. Cellular Material Theory is extended, and analytical solutions for the mechanical properties and global strains of the hybrid and accordion cellular honeycombs are developed. The analytical results show excellent agreement with ANSYS finite element results. Comparing the properties shows ...
-
flexible matrix composite skins for one dimensional wing morphing
Journal of Intelligent Material Systems and Structures, 2010Co-Authors: Gabriel Murray, Farhan Gandhi, Charles E BakisAbstract:Morphing aircraft wings require flexible skins that can undergo large strains, have low in-plane stiffness and very high out-of-plane flexu ral bending stiffness. The large strain capability is especially important for gross morphi ng applications such as span Change where the skins may be required to undergo axial st rains of the order of 50% or greater. Low in-plane stiffness allows morphing to be accomplished at a reasonable energy cost while high bending stiffness ensures that skin sections b etween supports do not suffer from significant out-of-plane deformation under aerodynamic pressure loads. For some morphing applications (for example, wing span-, chord-, or Camber-Change), the required deformation is mostly one-dimensional. In such a c ase, a Flexible Matrix Composite (FMC) skin is proposed as a possible solution. A FMC comprises of stiff fibers (for example fiberglass) embedded in a soft high-strain capable matrix material (for example, silicone). The idea is to align the matrix-dominated direction along the morphing direction. This allows the skin to undergo large strain at low ener gy cost. However, the high-stiffness in the fiber-dominated direction, along with applied tensi on along the fiber-dominated direction is critical in providing the membrane skin with a larg e out-of-plane stiffness and consequently, the ability to withstand aerodynamic pressure loads. An analysis for a FMC skin panel under in-plane axial loads and out-of-plane pressur e loads is developed, and this is validated against experiment. The analysis is then used to c onduct design studies. A comparison of the FMC skin to a skin comprising of just the matri x material illustrates the importance of the fiber's stiffness in resisting out-of-plane def ormation under pressure loading. The influence of the matrix and fiber properties and ap plied tension on the out-of-plane deformations and morphing capability is examined in detail.
-
zero v cellular honeycomb flexible skins for one dimensional wing morphing
48th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2007Co-Authors: K R Olympio, Farhan GandhiAbstract:Morphing aircraft wings require flexible skins that can undergo large strains, have low in-plane stiffness and very high out-of-plane flexural bending stiffness. The large strain capability is especially important for gross morphing applications such as span Change where the skins may be required to undergo axial strains of the order of 50% or greater. Low in-plane stiffness allows morphing to be accomplished at a reasonable energy cost while high bending stiffness ensures that skin sections between supports do not suffer from significant out-of-plane deformation under aerodynamic pressure loads. One solution proposed is to use sandwiched skins with flexible face-sheets and cellular cores. The cellular cores can be designed to be high-strain capable, have low axial stiffness and high bending stiffness. For some morphing applications (for example, wing span Change or chord or Camber Change), the required deformation is mostly one-dimensional. In such a case, cellular cores with zero Poisson’s ratios, which do not display contraction (or bulge) perpendicular to the morphing direction are desired. Restraining the Poisson’s contraction (or bulge) of a “conventional” cellular honeycomb results in the effective axial stiffness in the morphing direction increasing by over an order of magnitude. This paper proposes “hybrid” and “accordion” cellular honeycombs, where regular cells (with positive cell angle) and auxetic cells (with negative cell angle) are combined so as to provide large strain capability in one direction (the morphing direction) together with zero Poisson’s ratio. Cellular material theory is extended to allow for the analysis of such hybrid and accordion cellular honeycombs, and the results are validated using the Finite Element code ANSYS. Thereafter, the properties and behavior of the hybrid and accordion zero Poisson’s ratio cellular honeycombs are thoroughly examined vis-a-vis conventional cellular honeycombs which have single cell-type.
K R Olympio - One of the best experts on this subject based on the ideXlab platform.
-
zero poisson s ratio cellular honeycombs for flex skins undergoing one dimensional morphing
Journal of Intelligent Material Systems and Structures, 2010Co-Authors: K R Olympio, Farhan GandhiAbstract:Cellular honeycomb cores with overlying flexible face sheets have been proposed for use as flex skins for morphing aircraft. The cellular cores, which provide underlying support to the face sheets for carrying aerodynamic loads, must have low in-plane stiffness and high in-plane strain capability. For one-dimensional morphing applications such as span-, chord-, or Camber-Change, restraining the Poisson’s contraction (or bulging) that a conventional cellular honeycomb core would otherwise experience in the non-morphing direction results in a substantial increase in the effective modulus in the morphing direction. To overcome this problem, this article develops zero Poisson’s ratio hybrid and accordion cellular honeycombs. Cellular Material Theory is extended, and analytical solutions for the mechanical properties and global strains of the hybrid and accordion cellular honeycombs are developed. The analytical results show excellent agreement with ANSYS finite element results. Comparing the properties shows ...
-
zero v cellular honeycomb flexible skins for one dimensional wing morphing
48th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2007Co-Authors: K R Olympio, Farhan GandhiAbstract:Morphing aircraft wings require flexible skins that can undergo large strains, have low in-plane stiffness and very high out-of-plane flexural bending stiffness. The large strain capability is especially important for gross morphing applications such as span Change where the skins may be required to undergo axial strains of the order of 50% or greater. Low in-plane stiffness allows morphing to be accomplished at a reasonable energy cost while high bending stiffness ensures that skin sections between supports do not suffer from significant out-of-plane deformation under aerodynamic pressure loads. One solution proposed is to use sandwiched skins with flexible face-sheets and cellular cores. The cellular cores can be designed to be high-strain capable, have low axial stiffness and high bending stiffness. For some morphing applications (for example, wing span Change or chord or Camber Change), the required deformation is mostly one-dimensional. In such a case, cellular cores with zero Poisson’s ratios, which do not display contraction (or bulge) perpendicular to the morphing direction are desired. Restraining the Poisson’s contraction (or bulge) of a “conventional” cellular honeycomb results in the effective axial stiffness in the morphing direction increasing by over an order of magnitude. This paper proposes “hybrid” and “accordion” cellular honeycombs, where regular cells (with positive cell angle) and auxetic cells (with negative cell angle) are combined so as to provide large strain capability in one direction (the morphing direction) together with zero Poisson’s ratio. Cellular material theory is extended to allow for the analysis of such hybrid and accordion cellular honeycombs, and the results are validated using the Finite Element code ANSYS. Thereafter, the properties and behavior of the hybrid and accordion zero Poisson’s ratio cellular honeycombs are thoroughly examined vis-a-vis conventional cellular honeycombs which have single cell-type.
Charles E Bakis - One of the best experts on this subject based on the ideXlab platform.
-
flexible matrix composite skins for one dimensional wing morphing
Journal of Intelligent Material Systems and Structures, 2010Co-Authors: Gabriel Murray, Farhan Gandhi, Charles E BakisAbstract:Morphing aircraft wings require flexible skins that can undergo large strains, have low in-plane stiffness and very high out-of-plane flexu ral bending stiffness. The large strain capability is especially important for gross morphi ng applications such as span Change where the skins may be required to undergo axial st rains of the order of 50% or greater. Low in-plane stiffness allows morphing to be accomplished at a reasonable energy cost while high bending stiffness ensures that skin sections b etween supports do not suffer from significant out-of-plane deformation under aerodynamic pressure loads. For some morphing applications (for example, wing span-, chord-, or Camber-Change), the required deformation is mostly one-dimensional. In such a c ase, a Flexible Matrix Composite (FMC) skin is proposed as a possible solution. A FMC comprises of stiff fibers (for example fiberglass) embedded in a soft high-strain capable matrix material (for example, silicone). The idea is to align the matrix-dominated direction along the morphing direction. This allows the skin to undergo large strain at low ener gy cost. However, the high-stiffness in the fiber-dominated direction, along with applied tensi on along the fiber-dominated direction is critical in providing the membrane skin with a larg e out-of-plane stiffness and consequently, the ability to withstand aerodynamic pressure loads. An analysis for a FMC skin panel under in-plane axial loads and out-of-plane pressur e loads is developed, and this is validated against experiment. The analysis is then used to c onduct design studies. A comparison of the FMC skin to a skin comprising of just the matri x material illustrates the importance of the fiber's stiffness in resisting out-of-plane def ormation under pressure loading. The influence of the matrix and fiber properties and ap plied tension on the out-of-plane deformations and morphing capability is examined in detail.
Gabriel Murray - One of the best experts on this subject based on the ideXlab platform.
-
flexible matrix composite skins for one dimensional wing morphing
Journal of Intelligent Material Systems and Structures, 2010Co-Authors: Gabriel Murray, Farhan Gandhi, Charles E BakisAbstract:Morphing aircraft wings require flexible skins that can undergo large strains, have low in-plane stiffness and very high out-of-plane flexu ral bending stiffness. The large strain capability is especially important for gross morphi ng applications such as span Change where the skins may be required to undergo axial st rains of the order of 50% or greater. Low in-plane stiffness allows morphing to be accomplished at a reasonable energy cost while high bending stiffness ensures that skin sections b etween supports do not suffer from significant out-of-plane deformation under aerodynamic pressure loads. For some morphing applications (for example, wing span-, chord-, or Camber-Change), the required deformation is mostly one-dimensional. In such a c ase, a Flexible Matrix Composite (FMC) skin is proposed as a possible solution. A FMC comprises of stiff fibers (for example fiberglass) embedded in a soft high-strain capable matrix material (for example, silicone). The idea is to align the matrix-dominated direction along the morphing direction. This allows the skin to undergo large strain at low ener gy cost. However, the high-stiffness in the fiber-dominated direction, along with applied tensi on along the fiber-dominated direction is critical in providing the membrane skin with a larg e out-of-plane stiffness and consequently, the ability to withstand aerodynamic pressure loads. An analysis for a FMC skin panel under in-plane axial loads and out-of-plane pressur e loads is developed, and this is validated against experiment. The analysis is then used to c onduct design studies. A comparison of the FMC skin to a skin comprising of just the matri x material illustrates the importance of the fiber's stiffness in resisting out-of-plane def ormation under pressure loading. The influence of the matrix and fiber properties and ap plied tension on the out-of-plane deformations and morphing capability is examined in detail.
Paul M Weaver - One of the best experts on this subject based on the ideXlab platform.
-
composite corrugated structures for morphing wing skin applications
Smart Materials and Structures, 2010Co-Authors: C Thill, Julie A Etches, Ian P Bond, Kevin D Potter, Paul M WeaverAbstract:Composite corrugated structures are known for their anisotropic properties. They exhibit relatively high stiffness parallel (longitudinal) to the corrugation direction and are relatively compliant in the direction perpendicular (transverse) to the corrugation. Thus, they offer a potential solution for morphing skin panels (MSPs) in the trailing edge region of a wing as a morphing control surface. In this paper, an overview of the work carried out by the present authors over the last few years on corrugated structures for morphing skin applications is first given. The second part of the paper presents recent work on the application of corrugated sandwich structures. Panels made from multiple unit cells of corrugated sandwich structures are used as MSPs in the trailing edge region of a scaled morphing aerofoil section. The aerofoil section features an internal actuation mechanism that allows chordwise length and Camber Change of the trailing edge region (aft 35% chord). Wind tunnel testing was carried out to demonstrate the MSP concept but also to explore its limitations. Suggestions for improvements arising from this study were deduced, one of which includes an investigation of a segmented skin. The overall results of this study show that the MSP concept exploiting corrugated sandwich structures offers a potential solution for local morphing wing skins for low speed and small air vehicles.
