WO2012049500A1 - Matériaux, dispositifs et structures comprenant un matériau, et procédé de formation d'un matériau - Google Patents

Matériaux, dispositifs et structures comprenant un matériau, et procédé de formation d'un matériau Download PDF

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Publication number
WO2012049500A1
WO2012049500A1 PCT/GB2011/051969 GB2011051969W WO2012049500A1 WO 2012049500 A1 WO2012049500 A1 WO 2012049500A1 GB 2011051969 W GB2011051969 W GB 2011051969W WO 2012049500 A1 WO2012049500 A1 WO 2012049500A1
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WO
WIPO (PCT)
Prior art keywords
multistable
length
along
bending stiffness
variations
Prior art date
Application number
PCT/GB2011/051969
Other languages
English (en)
Inventor
Steven Daynes
Paul Weaver
Original Assignee
The University Of Bristol
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The University Of Bristol filed Critical The University Of Bristol
Publication of WO2012049500A1 publication Critical patent/WO2012049500A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C30/00—Supersonic type aircraft
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B13/00—Conduits for emptying or ballasting; Self-bailing equipment; Scuppers
    • B63B13/02—Ports for passing water through vessels' sides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/02—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/04—Air intakes for gas-turbine plants or jet-propulsion plants
    • F02C7/042—Air intakes for gas-turbine plants or jet-propulsion plants having variable geometry
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
    • F02M35/10—Air intakes; Induction systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/02—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes
    • B64D2033/0253—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes specially adapted for particular type of aircraft
    • B64D2033/026—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes specially adapted for particular type of aircraft for supersonic or hypersonic aircraft
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D2241/00—NACA type air intakes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Definitions

  • a material, devices and structures including a material, and a method of forming a material
  • Embodiments of the present invention relate to a material, devices and structures including a material, and a method of forming a material
  • Fluid intakes are used in many different applications and in many different forms.
  • a ram air intake is, for example, used to provide air at a comparatively high pressure to an engine.
  • Such engines may be provided in a vehicle - e.g. an aircraft, a watercraft, or a land vehicle. Intakes may also be used to deliver fluids other than air - e.g. water.
  • An intake may be required intermittently.
  • an element may be provided to close the intake when it is not in use - to reduce drag for example.
  • Such an element may comprise a door which covers an entrance of the intake when it is not needed.
  • the element may be actuated by an actuator which, together with the element, forms an intake closure system.
  • the mass of the intake closure system must be kept to a minimum - this is a particularly significant issue for aircraft.
  • the element comprises a plate which is moved into a position which closes the entrance to the intake by a mechanical actuator and which is held in the closed position by the actuator.
  • one aspect of the invention provides a method of manufacturing a multistable member, the method comprising: forming a member with one or more variations in bending stiffness along a length of the member such that the member will have two or more substantially stable forms when the member is subjected to one or more boundary conditions; and deforming the member to subject the member to the one or more boundary conditions to form a multistable member which is configured for actuation between a first and a second substantially stable form, wherein the two or more substantially stable forms are determined by the one or more variations in the bending stiffness along the length of the multistable member and the one or more boundary conditions to which the member is subjected.
  • forming the member comprises forming the member with a thickness which varies along the length of the member.
  • the variation in thickness along the length of the member comprises one or more trenches along the length of the member.
  • the or each trench has substantially curved walls or substantially straight walls.
  • deforming the member comprises deforming the member into a deformed state by reducing the distance from one part of the member to another part of the member.
  • forming the member comprises forming an elongate member.
  • the length of the member is a length which is parallel with a longitudinal axis of the elongate member.
  • the length of the member is a length which is perpendicular to a longitudinal axis of the elongate member.
  • forming the member comprises forming a member with a width which varies along a length thereof. In an embodiment, forming the member comprises forming the member from a composite material.
  • At least one of the one or more variations in bending stiffness is a variation in the second moment of area of the member or a variation in the Young's modulus of the member.
  • Another aspect of the present invention provides a device comprising: a multistable member deformed to subject the multistable member to one or more boundary conditions, there being one or more variations in bending stiffness along a length the multistable member such that the multistable member can be moved between a first and a second substantially stable form by the application of an actuating force to the multistable member, the first and second substantially stable forms being determined by the one ore more variations in the bending stiffness along the length of the multistable member and the one or more boundary conditions of the multistable member.
  • the multistable member has a thickness which varies along the length of the member. In an embodiment, the variation in thickness along a length of the multistable member comprises one or more trenches along the length of the member. In an embodiment, the or each trench has substantially curved walls or substantially straight walls. In an embodiment, the or each trench is a trench across the entire length of the multistable member.
  • one or more of the boundary conditions are such that a distance from one end of the member to another end of the member is reduced in the deformed state of the multistable member.
  • the multistable member comprises an elongate member.
  • the length of the multistable member is a length which is parallel with a longitudinal axis of the elongate member.
  • the length of the multistable member is a length which is perpendicular to a longitudinal axis of the elongate member. In an embodiment, a width of the multistable member varies along a length thereof.
  • the multistable member is formed from a composite material.
  • At least one of the variations in bending stiffness is a variation in the second moment of area of the member or a variation in the Young's modulus of the member.
  • a fluid intake including a device as above.
  • the fluid intake further comprises an actuator configured to apply the actuating force on the multistable member.
  • a vehicle including a fluid intake as above.
  • the vehicle is an aircraft, a watercraft, or a land vehicle.
  • a multistable member having one or more variations in bending stiffness along a length the multistable member such that, when the multistable member is deformed to subject the multistable member to one or more boundary conditions, the multistable member can be moved between a first and a second substantially stable form by the application of an actuating force to the multistable member, the first and second substantially stable forms being determined by the one or more variations in the bending stiffness along the length of the multistable member and the one or more boundary conditions of the multistable member.
  • Figure 1 shows a perspective view of an example embodiment with transparent sections for clarity
  • Figures 2 and 3 show a side view of an example embodiment in two different configurations;
  • Figure 4 shows an end view of an example embodiment;
  • Figure 5 and 6 show the operation of an actuator system
  • Figure 7 shows a plan view of an example multistable member of an embodiment
  • Figure 8 shows a side view of an example multistable member of an embodiment
  • Figure 9 shows a deformed and non-deformed multistable member of an embodiment
  • Figure 10 shows schematic views of example embodiments
  • Figure 1 1 shows a zoomed view of part of a multistable member of an embodiment
  • Figure 12 shows a graph of example thickness variation in a multistable member of an embodiment.
  • an embodiment of the present invention comprises a fluid intake system 1 which may be a ram air intake.
  • the fluid intake system 1 may be provided in a surface 2 of a vehicle.
  • the vehicle 3 is, in various embodiments, an aircraft 3a, a watercraft 3b, or a land vehicle 3c.
  • the fluid intake system 1 comprises an entrance aperture 4 defined by a wall of which the surface 2 is a part.
  • a scoop body 5 is arranged adjacent the entrance aperture 4 and is configured to direct fluid which passes through the entrance aperture 4.
  • the fluid is directed to an engine cooling system 6 (see figure 10) but may be directed to any component of the vehicle 3 requiring the delivery of fluid.
  • the entrance aperture 4 and scoop body 5 are configured to match or substantially match the configuration of the submerged-duct entrance developed by the National Advisory Committee for Aeronautics (details of which can be found in NACA ACR No. 5I20; "An Experimental Investigation of NACA Submerged-Duct Entrances").
  • the entrance aperture 4 is generally triangular in shape with divergent curved side edges 7 which diverge from each other in the expected direction of fluid flow 8.
  • a narrowest part 9 of the entrance aperture 4 is, therefore, located upstream in an embodiment and a widest part 10 of the entrance aperture 4 is located downstream in an embodiment (upstream and downstream being with respect to the expected direction of fluid flow 8).
  • the widest part of the entrance aperture 4 may include a substantially straight edge connecting the two divergent curved side edges 7 of the entrance aperture 4.
  • the narrowest part 9 of the entrance aperture 4 may also include a substantially straight edge 12 connected to the two divergent curved edges 7 of the entrance aperture 4.
  • the narrowest part 9 of the entrance aperture includes a curved rather than a straight 12 edge. It will be appreciated that the aforementioned edges are defined by the wall of which the surface 2 is a part.
  • the scoop body 5 includes a base wall 13 and a pair of opposing side walls 14.
  • the base wall 13 extends from the general area of the narrowest part 9 of the entrance aperture 4 towards (and potentially beyond) the widest part 10 of the entrance aperture 4.
  • the pair of opposing side walls 14 oppose each other across a width of the base wall 13 and are connected to the base wall 13 and to an inner surface 15 of a wall of the vehicle 3 - the inner surface 15 may be a surface of a wall which opposes the surface 2 across a width of the wall.
  • the base wall 13 and opposing side walls 14 may be convergent in the expected direction of fluid flow 8.
  • the base 13 and side 14 walls converge into a single substantially circular wall 16.
  • the substantially circular wall 16 is configured for attachment to a fluid conduction pipe (not shown).
  • the scoop body 5 extends in the expected direction of fluid flow 8 beyond the widest part 10 of the entrance aperture 4.
  • the fluid intake system 1 further comprises a multistable member 17.
  • the multistable member 17 is located generally within a volume defined by the air scoop body 5 (although one or more parts of the multistable member 17 - for example one or more ends thereof - may be located outside this volume).
  • the multistable member 17 is configured such that it may, at any one time, take one of at least two different forms.
  • the multistable member 17 may take a first form (see figure 2) in which it substantially closes the entrance aperture 4 of the fluid intake system 1 and a second form (see figure 3) in which fluid is substantially free to flow through the entrance aperture 4 into at least part of the volume defined by the scoop body 5.
  • the multistable member 17 may be actuated between the first and second forms in a number of different manners.
  • an actuator system 18 (see figures 5 and 6) is provided to cause the multistable member
  • an actuator system 18 is provided to cause the multistable member 17 to move from the second form to the first form.
  • an actuator system 18 is provided to cause the multistable member 17 to move from the second form to the first form.
  • an actuator system 18 is provided to cause the multistable member 17 to move from the second form to the first form.
  • the actuator system 18 is provided to cause movement of the multistable member 17 to and from the first and second forms.
  • the actuator system 18 includes one or more mechanical actuators - for example one or more pushrods coupled to a driving arrangement - which are configured to apply a force to the multistable member 17 to cause movement of the multistable member 17.
  • the multistable member 17 is configured for actuation by fluid pressure.
  • the relative pressure on one side of the multistable member 17 compared to the other side of the multistable member 17 may cause actuation of the multistable member from the first to the second form or vice versa.
  • an inflatable bladder is provided as part of the actuator system 18.
  • the inflatable bladder is provided between the base wall 13 of the scoop body 5 and the multistable member 17. Inflation of the inflatable bladder will apply a force on the multistable member 17 which, when sufficient, will cause actuation of the multistable member 17.
  • Fluid may be provided to the inflatable bladder through an aperture 26 in the scoop body 5. Fluid may be removed from the inflatable bladder through an aperture which may be the same as the aperture 26 through which fluid may be provided.
  • the multistable member 17 is tethered towards either end thereof to another part of the fluid intake system 1 . In an embodiment, the multistable member 17 is tethered towards a first end 19 thereof to the scoop body 5 or surface 2 towards the narrowest part 9 of the entrance aperture 4.
  • the multistable member 17 is tethered towards a second end 20 thereof to the scoop body 5 towards the widest part 10 of the entrance aperture 4. In an embodiment, the multistable member 17 is tethered at a location which is beyond the widest part 10 of the entrance aperture 4 in the expected direction 8 of fluid flow.
  • the multistable member 17 is described in more detail below.
  • the multistable member 17 is substantially flat when not tethered and the distance between two parts (e.g. two ends) of the multistable member 17 is a first predetermined distance.
  • the multistable member 17 has a single stable geometry or form.
  • the multistable member 17 is flexed and deformed when tethered such that the distance between the two parts of multistable member 17 when tethered is less than the first predetermined distance - and may be a second predetermined distance (see B of figure 9).
  • the deformation of the multistable member 17 causes the multistable member 17 to adopt a multistable configuration such that at least the first and second forms are stable forms.
  • the multistable member 17 is configured to ensure that the first and second forms are stable forms when the multistable member 17 is deformed in a predetermined manner. In order to achieve this effect, there are one or more variations in the bending stiffness of the multistable member 17 along a length of at least a portion of the multistable member 17.
  • the one or more variations in the bending stiffness may each comprise a variation in Young's modulus and/or a variation in the second moment of area of the multistable member 17.
  • a first variation in the bending stiffness of the multistable member 17 is a variation in Young's Modulus and a second variation in the bending stiffness of the multistable member 17 is a variation in the second moment of area.
  • the variations in bending stiffness may be variations with respect to, for example, the bending stiffness of adjacent parts of the multistable member 17.
  • the one or more variations in bending stiffness comprise one or more respective portions or parts of the multistable member 17 which have a bending stiffness which is different to one or more adjacent portions or parts of the multistable member 17.
  • a change in Young's modulus may be a change in effective Young's modulus - for example, in a multistable member 17 formed from a laminate, the Young's modulus along a length of the multistable member 17 may be dependent on the Young's modulus along the length of each layer in the laminate. References to a variation in the Young's modulus are to be construed accordingly.
  • the variation in bending stiffness may, therefore, equally be described as a variation in the cumulative bending stiffness of the layers in a laminate multistable member 17.
  • the multistable member 17 may have multiple stable forms (two or more) and these stable forms are dependent on the tether conditions (known as the "boundary conditions") and the variation in the bending stiffness along a length of the multistable member 17.
  • the boundary conditions can be altered by altering the tethering position (and, hence the deformation) of the multistable member 17.
  • the bending stiffness may by varied by, for example, altering a thickness of a part of the multistable member 17 along a length thereof (see figure 1 1 ) and/or by varying the effective Young's modulus along a length thereof.
  • the bending stiffness may vary along a length of the multistable member 17 which is substantially parallel with a longitudinal axis of the multistable member 17 or, for example, substantially perpendicular to a longitudinal axis of the multistable member 17 (which may be substantially aligned with a transverse axis of the multistable member 17).
  • the multistable member 17 is formed from a composite material. In an embodiment, the multistable member 17 is formed from laminated layers of woven carbon fibre reinforced plastic (CFRP) material. A thickness variation of the multistable member 17 may, therefore, be achieved by excluding one or more layers of material in order to achieve the required thickness.
  • CFRP carbon fibre reinforced plastic
  • the multistable member 17 (see figures 7 and 8) has a first 21 and a second 22 side surface which oppose each other across a depth or thickness of the multistable member 17.
  • the multistable member 17 has two longitudinal edges 23 which oppose each other across a width of the multistable member 17.
  • the longitudinal edges 23 are not, in an embodiment, parallel but are curved.
  • the maximum width of the multistable member 17 is generally midway along a length of the multistable member 17.
  • the multistable member 17 has two transverse edges 24 which oppose each other across the length of the multistable member 17.
  • the transverse edges 23 may, in an embodiment, be parallel with each other.
  • the required variations in the bending stiffness of the multistable member 17, may be achieved by forming one or more trenches 25 across the width of the multistable member 17.
  • the or each trench 25 has a depth through the multistable member 17 which is predetermined and which is selected in order to achieve a desired stable form for the multistable member 17.
  • the or each trench 25 may, in an embodiment, extend from between the longitudinal edges 23 of the multistable member 17 generally across the entire width of the multistable member 17.
  • the or each trench 25, in an embodiment is generally parallel with one or both of the transverse edges of the multistable member 17 and may be generally perpendicular to a longitudinal axis of the multistable member 17.
  • each trench 25 has a different depth of at least one other trench 25.
  • the required variations in the bending stiffness are achieved by changing the lay-up of the multistable member 17. As will be appreciated, by altering the lay-up it is possible to alter the effective Young's modulus of the multistable member 17 in order to provide the variations in bending stiffness.
  • the one or more trenches 25 cause the multistable member 17 to adopt a predetermined stable form - for example, one of the first and second forms discussed above.
  • the application of a force to one side 21 ,22 of the multistable member 17 causes movement of the multistable member 17 to another stable form.
  • the multistable member 17 may be moved between the first and second forms to open and close the entrance aperture 4.
  • the movement of the multistable member 17 from one stable form to another is, in an embodiment, a snap-movement which occurs very quickly once a force applied to the multistable member 17 exceeds a threshold.
  • a width of the multistable member 17 generally adjacent the entrance aperture 4 is greater than a width of the entrance aperture 4.
  • a stable form of the multistable member 17 is such that the multistable member 17 would extend beyond the surface 2 of the vehicle 1 .
  • the abutment of the multistable member 17 with the inner surface 15 comprises a further boundary condition.
  • the multistable member 17 is provided with a raised section which is arranged to extend at least partially through the entrance aperture 4 when the multistable member 17 is in second form. This may help to improve the flow of a fluid over the surface of the vehicle 3.
  • the raised section may have a shape which corresponds with a shape of the entrance aperture 4.
  • a part of the multistable member 17 will abut against a part of the base wall 13 of the scoop body 5.
  • the movement of the multistable member 17 is, in an embodiment, restrained by abutment against the scoop body 5.
  • this abutment comprises another further boundary condition.
  • the width of the multistable member 17 is selected for use in a NACA-type submerged duct in accordance with equation 1 below:
  • l_x is the width of the multistable member 17
  • Xdim is the maximum width of the multistable member 17
  • ydim is the maximum length of the multistable member 17; and y is the distance from midway along a length of the multistable member 17 along the longitudinal axis thereof (for the avoidance of doubt, as used herein x is the distance across the width of the multistable member 17 and z is the distance through a depth of the multistable member).
  • the maximum length of the multistable member 17 is about 316mm and the maximum width of the multistable member 17 is about 100mm.
  • the ends 19,20 of the multistable member 17 are intended to be displaced by about 65 mm with respect to each other in a direction which is both perpendicular to the longitudinal and transverse axes of the multistable member 17.
  • This intended displacement of the ends 19,20 of the multistable member 17 with respect to each other may comprise a distance substantially equal to an internal depth of the scoop body 5 plus an additional distance to take into account a depth of a wall of the vehicle 3 to which the scoop body 5 is attached.
  • the internal depth of the scoop body 5 is about 60mm and the depth of the wall is about 5mm.
  • the ends 19,20 of the multistable member 17 are intended to be displaced by about 16mm with respect to each other in a direction which is parallel with the longitudinal axis of the multistable member 17.
  • the multistable member 17 is tethered - generally as discussed above. Therefore, the maximum length of the multistable member 17 is given by equation 2 below:
  • Equation 2 in which w° is the out-of-plane displacement which is, in turn, given by equation 3 below for a given part of the multistable member 17:
  • Equation 3 in which y is representative of the position of the multistable member 17.
  • a nominal second moment of area of 66.67mm 4 is assumed - which is equivalent to a beam cross-section with a width of 100mm and a thickness of 2mm.
  • the actual variation in the second moment of area along the longitudinal axis of the multistable member 17 is given by equation 4 below:
  • Equation 4 in which l xx is the second moment area along the longitudinal axis of the multistable member 17.
  • the variation in the second moment area from -ydim 2 to ydim 2 can, therefore, be seen to halve at four locations. These locations are hinge points which extend across the width of the multistable member 1 7. In an embodiment, the hinge points are achieved by reduction in the thickness of the multistable member 17.
  • the variation in the thickness of the multistable member 17 is given by equation 5 below:
  • Equation 5 in which H is the thickness of the multistable member 17. This takes into account the variation in the width of the multistable member 17 along the length of the multistable member 17.
  • the thickness determined using equation 5 is discretised into multiples of the thickness of a layer of the woven CFRP material - which may be 0.25mm in an embodiment. The same would potentially apply to other laminate materials which could be used according to other embodiments.
  • the thickness of the multistable member 17 may, in an embodiment, vary as shown in figure 12.
  • the stable forms of the multistable member 17 (otherwise known as the stable geometries) may be determined using equation 6 below:
  • ⁇ is the total potential energy of the multistable member 17
  • Q * is the transformed reduced stiffness tensor (in the indicated directions);
  • ⁇ ⁇ is the total strain in the transverse axis of the multistable member 17;
  • £ y is the total strain in the longitudinal axis of the multistable member 17;
  • Yxy is the total shear strain;
  • L y is the length of the multistable member 17.
  • Equations 6 and 7 can be combined to arrive at equation 8 below:
  • E Young's modulus (in the indicated direction).
  • the stable forms of the multistable member 17 can, therefore, be calculated (approximately) by minimising the total potential energy as given by Equation 8 with respect to the position, y ; of the multistable member 17.
  • Finite element analysis may be used to determine the stable forms of the multistable member 17.
  • Equation 8 provides the strain energy of the multistable member 17.
  • the difference in the strain energy between the first and second forms of the multistable member 17 is equal to the work required for the actuation between the stable forms of the multistable member 17.
  • the distance moved by any given part of the multistable member 17 can be determined using Equation 3. Therefore, the actuation force can be calculated by dividing the value of the work required for the actuation by the value of the distance moved by the part of the multistable member 17 between the stable forms of the multistable member 17.
  • a multistable member 17 can be manufactured from a woven CFRP material using known techniques to form a multistable laminate having a thickness variation as determined by applying the above method.
  • Embodiments of the present invention can be applied to other uses and are not limited to the above described use as part of a fluid intake system 1 .
  • embodiments of the present invention could include other door-like arrangements for other apertures.
  • Embodiments of the present invention have been described with reference to a fluid intake for a vehicle for convenience only; aspects of these described embodiments can be applied to other embodiments. It will be appreciated that embodiments include the multistable material as well as systems, structures, and devices in which that material is used - such as vehicles.
  • embodiments of the present invention have been described above in relation to the formation of the multistable member 17 from woven CFRP material, the use of other materials is envisaged.
  • embodiments of the present invention include multistable members 17 constructed out of metal or plastic materials.
  • embodiments of the present invention may include a multistable member 17 formed from laminated material.
  • the multistable member 17 adopts a stable or substantially stable form which does not require continued support by the actuator system 18 to withstand forces which are below the threshold force required to cause actuation of the multistable member 17.
  • a multistable member 17 may be formed by determining the required stable forms for the multistable member 17 for a given set of boundary conditions, determining the variations in the bending stiffness to achieve the required stable forms, forming the member 17 accordingly, and then deforming and flexing the member 17 to subject the member 17 to the boundary conditions and thereby to form the multistable member 17.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Geometry (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Air-Conditioning For Vehicles (AREA)

Abstract

L'invention concerne un procédé de fabrication d'un élément multistable, lequel consiste à: former un élément possédant une ou plusieurs variations de rigidité à la courbure dans le sens de la longueur de l'élément de sorte qu'il possède deux formes essentiellement stables ou plus lorsqu'il est soumis à une ou plusieurs conditions limites ; et déformer l'élément de manière à le soumettre à ladite ou auxdites conditions limites de manière à former un élément multistable conçu pour passer d'une première à une seconde forme essentiellement stable, les première et seconde formes essentiellement stables étant déterminées par ladite ou lesdites variations de rigidité à la courbure dans le sens de la longueur de l'élément multistable, et par ladite ou lesdites conditions limites auxquelles l'élément multistable est soumis.
PCT/GB2011/051969 2010-10-14 2011-10-12 Matériaux, dispositifs et structures comprenant un matériau, et procédé de formation d'un matériau WO2012049500A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1017371.4 2010-10-14
GB1017371.4A GB2484661A (en) 2010-10-14 2010-10-14 A fluid intake comprising a multistable member and method of manufacturing said multistable member

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WO2012049500A1 true WO2012049500A1 (fr) 2012-04-19

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FR3014845A1 (fr) * 2013-12-16 2015-06-19 Snecma Systeme de prelevement de fluide

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3014845A1 (fr) * 2013-12-16 2015-06-19 Snecma Systeme de prelevement de fluide
US9976480B2 (en) 2013-12-16 2018-05-22 Snecma Fluid intake system

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GB201017371D0 (en) 2010-11-24

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