INFLATABLE COMPOSITE STRUCTURAL COMPONENT AND METHOD
An inflatable structural component having a longitudinal first braided material layer and a longitudinal second braided material layer each forming a panel having a width-wise dimension transverse to a length-wise direction of the component bounded by first and second longitudinal edges along the length-wise direction of the component, the first and second braided material layers enveloping at least a portion of an inflatable longitudinal bladder, the first and second braided material layers arranged such that the first longitudinal edges of the first and second braided material layers are approximately aligned and connected together along a first side of the bladder and the second longitudinal edges of the first and second braided material layers are approximately aligned and connected together along a second side of the bladder.
This application claims the benefit of U.S. provisional patent application 61/834,298, filed Jun. 12, 2013 and which is hereby incorporated herein by reference.
BACKGROUND AND SUMMARY OF THE DISCLOSUREThe present subject matter relates generally to a sub-component or component of an inflatable composite member in a structure.
Prior rapidly deployable structures with inflatable composite structural components have been used to erect temporary, semi-permanent or permanent structures in situ with a minimum of tools and support equipment. Representative structures of this type are generally stored and transported to an erection site in a compact form and deployed by unrolling, unfolding or other processes and inflating portions of the structure that take on a deployed shape and configuration on application of a rigidizing media such as compressed air. Exemplary applications of these structures have been deployed to support special events, commercial activities, military operations, and disaster relief operations.
Disclosed is an inflatable composite structural component comprising a first layer of braided material, at least one intermediate bladder and a second layer of braided material. The first and second layers of braided material include multiple adjacent regions of triaxial or biaxial tow architectures. In particular embodiments, for example, the layers may comprise a first triaxial region adjacent a second biaxial region adjacent a third triaxial region. The outer triaxial regions of the first and second layer of braided fabric are held together with adhesive, stitching, or other means. In certain prior curved air beams, curvature was applied to the braid at the time of braiding “locking” the shape into the structure at the time of braiding with varying length tows around the braid, which had disadvantages in wrinkling of the braid when the deflated structure was laid flat for rolling or folding for transport.
The first layer of braided fabric is manufactured with a first predetermined bias angle and the second layer of braided fabric is manufactured with a second predetermined bias angle. For structural components deployed as generally straight structural components the first and second predetermined bias angles are generally equal and equal to a bias hose angle as discussed below. For structural components deployed as curvilinear structural components the layer of braided fabric situated inside the radius of curvature will have a predetermined bias angle less than the braid hose angle and the layer of braided fabric situated outside the radius of curvature will have a predetermined bias angle greater than the braid hose angle.
Referring now to
An inflatable composite structural component is shown in
Shown in the cross section in
In particular embodiments, edger strips 17 are provided affixed to the first braided material layer 11 and the second braided material layer 12 adjacent the joining edges of the structural panels 15 between the first and second braided material layers, each edger strip 17 wrapping partially around the sides 18, 19 of the bladder 13. The edger strips may be used to reinforce the connections between the first and second braided material layers 11, 12 by carrying a portion of the hoop stress in the enclosure around the bladder when the bladder is inflated and applying pressure against the enclosure. In the partially exploded view of
The bladder 13 is typically an elongated balloon-like container providing a gas barrier configured for inflating and deflating in the structural component. More generally, the bladder is a container configured for filling and retaining rigidizing media in the structural component, and for certain rigidizing media, the bladder may be configured to be emptied of its contents for deflating or breaking-down the structure. The bladder may be made from a material such as natural or synthetic rubber, thermoplastic elastomers, thermoset polymers, or other material as desired for the application.
A braided material typically includes three or more strands of material, commonly called tows, such that each tow is intertwined with other tows in a repeating pattern. Two-dimensional braided materials are those wherein the repeating pattern is largely characterized by two or more principal directions in a plane, typically a longitudinal or axial direction of the braided fabric, and one or more oblique directions, commonly called bias directions, bias directions being a predetermined angle to the longitudinal direction. Three-dimensional braided materials are those wherein additional principal directions, typically being perpendicular to the longitudinal and oblique directions, are used to define the structure and the patterns thereof. For simplicity of description these additional directions are generically referred to as radial directions, whether the structure is generally tubular in form, laid out as a flattened tubular form or in a fabric, or generally planar, form.
Two-dimensional braided materials may be manufactured as generally cylindrical materials, commonly called sleeves, with the axial direction corresponding to the longitudinal axis of the cylinder and the bias directions oblique to and measured from the longitudinal axis. Braided materials manufactured in cylindrical form may then be laid flat to form a two-dimensional fabric having two layers joined along the longitudinal edges. The longitudinal edges may be cut to form two separate and distinct layers, commonly called a double-slit two layer fabric. Alternatively, one edge may be cut and the cylindrical fabric unfolded to form a singly-slit single layer fabric. Instead of a cylindrical form, two-dimensional braided materials may also be manufactured in a single layer flat form, commonly called a tape.
In this disclosure reference to braided fabric is generally directed to two-dimensional fabric forms but one skilled in the art recognizes that three-dimensional braided materials may be used in particular embodiments of the present invention as desired to satisfy requirements of particular applications.
The terms “strand”, “tow”, “yarn”, “yarn bundle”, “fiber” and “fiber bundle” are generally meant to describe what is laid into or intertwined in each of the principal directions of a braided fabric. In this disclosure the term “tow” will generally be used to describe what is laid into or intertwined in each of the principal directions of a braided fabric. A tow is an amalgamation of all material that runs together in a principal direction. A tow can comprise monofilaments, multiple filaments or comprise staple, or spun, material. Tow material can have a variety of cross-sectional shapes, including but not limited to, generally circular, ellipsoidal, triangular and flat tape shapes. Tow material may be subject to intermediate or pre-processing prior to braiding operations. Examples of intermediate or pre-processing may include, but are not limited to, twisting, braiding small numbers of filaments into braided tow materials, pre-impregnation with resins and specialty coating to facilitate braiding and/or subsequent processing. A tow can comprise any combination of these materials and material forms. A tow may comprise one or more than one filament or staple materials. As non-limiting examples, a tow may include carbon materials, basalt, glass materials, thermoplastic polymeric materials, thermoset polymeric materials, a combination of carbon and polymeric materials or a combination of polymeric and glass materials, or some combination thereof. Tows that lay in one of the bias directions of the fabric are commonly called bias tows, identified in
Biaxial braid typically includes only bias tows. Triaxial braid typically includes both bias and axial tows. Hybrid braided fabrics are contiguous materials having regions of biaxial braid and regions of triaxial braid, the regions typically in a desired arrangement.
In particular embodiments, the first braided material layer 11 and second braided material layer 12 are made of a hybrid braided fabric of contiguous material having a plurality of adjacent regions of triaxial and biaxial tow architectures.
The triaxial region 21 and triaxial region 23 of the braided material layer of
The first layer of braided material is manufactured with a first predetermined bias angle and the second layer of braided material is manufactured with a second predetermined bias angle. For structural components deployed as straight structural components the first and second predetermined bias angles are generally equal and equal to the bias hose angle, as defined below. For structural components deployed as curvilinear structural components the layer of braided material situated inside the radius of curvature will generally have a predetermined bias angle less than the braid hose angle and the layer of braided material situated outside the radius of curvature will have a predetermined bias angle greater than the braid hose angle. Referring now to
Triaxial regions 21, 23 include axial tows 25 tending to inhibit the motion of the bias tows 24 thereby maintaining an approximately constant diameter and length under application of external forces.
To provide straight structural elements when the structural components are deployed, the first bias angle 31 is predetermined to be approximately the same as the first braid hose angle 32 when the deployed structural component is under its design load.
To provide curved structural elements when the structural components are deployed, the first bias angle 31 is predetermined to be either less than or greater than first braid hose angle 32 when the deployed structural component is under its design load. The relationship between first bias angle 31 and first braid hose angle 32 is predetermined based on the relative position of braided material layer in the as-deployed structure. When the first braided material layer 11 in the as-deployed structure has a radius of curvature generally less than the radius of curvature of the neutral axis of the structural component, the first bias angle 31 will be a predetermined angle less than the braid hose angle 32. Under application of pressure exerted by the bladder in the as-deployed state, biaxial regions of the braided material layer will tend to decrease in length. When the first braided material layer 11 in the as-deployed structure has a radius of curvature generally greater than the radius of curvature of the neutral axis of the structural component, the first bias angle 31 will be a predetermined angle greater than the braid hose angle 32. Under application of pressure exerted by the bladder in the as-deployed state, biaxial regions of the braided layer will tend to increase in length. More particularly, as an example, the braid hose angle is determined to be about 55 degrees. In that example, the layer positioned with a radius of curvature greater than the radius of curvature of the neutral axis of the structural component had a bias angle of 65 degrees, and the layer positioned with a radius of curvature less than the radius of the neutral axis had a bias angle of 45 degrees. Braids of various cross-sectional shapes may have a braid hose angle that is greater or less than 55 degrees, such as between about 52 and 57 degrees. For various applications, the difference between the higher-radius bias angle and the braid hose angle may be the same as the difference between the lower-radius bias angle and the braid hose angle, such as 10 degrees in the particular exemplary embodiment. However, in other embodiments, the difference between the higher-radius bias angle and the braid hose angle may be different than the difference between the lower-radius bias angle and the braid hose angle. In one embodiment having a sleeve with a generally circular cross-section, the braid hose angle is 54.7 degrees. In this example, the layer positioned with a radius of curvature greater than the radius of the neutral axis has a bias angle of 65 degrees, and the layer positioned with a radius of curvature less than the radius of the neutral axis has a bias angle of 40 degrees.
Similarly, as shown in schematic form in
In
The embodiment of
By varying the relationship of bias angle to braid hose angle in the first braided material layer 11 relative to that in second braided layer 12 the embodiments of
For structures utilizing a separate support frame, structural components of the present invention can be deployed utilizing low pressure rigidizing media, e.g. about 0.5 to 2 psi. For higher pressure applications, it may be desired to reinforce the bladder with a braided sleeve. In particular embodiments, the bladder may comprise a braided sleeve surrounding the bladder or embedded into the bladder. In one example, the braid-reinforced bladder comprises a biaxial braided sleeve embedded in an elastomeric matrix. In an alternative embodiment, a braided sleeve is impregnated with an elastomeric solution that is cured to form the bladder. By utilizing a braid-reinforced bladder, the pressure of the rigidizing media can be increased substantially thereby enabling structures to be constructed without separate support frames. In particular embodiments, the braid-reinforced bladder enables pressure in the component between about 2 and 10 psi.
A further advantage of the present invention is that the radius of curvature of a specific structural component can be varied in situ by varying the pressure of the rigidizing media to control the amount of scissoring within the biaxial regions of the braided material layers thereby controlling the relative differences in changes in length of the bias regions.
A method of constructing an inflatable structure, for example as depicted in
The construction method may be semi-automated or fully automated utilizing using conventional composite tape layup methods.
In yet another alternative embodiment of the present invention, a plurality of bladders run adjacent to one another through the structural component along the full length of the component. Another alternate embodiment includes a plurality of bladders running adjacent to one another through the structural component along less than the full length, or alternatively, a plurality of bladders that run end to end through the structural component. A third alternative embodiment includes combinations of the two configurations of bladders. In each embodiment, varying pressures of rigidizing media may be applied to affect the shape and structural rigidity of the structure.
An alternate embodiment of the present invention comprises the first braided material layer and the second braided material layer each incorporating an additional triaxial region in the center of the biaxial region. The triaxial region in the first braided material layer is affixed to the triaxial region of second braided material layer such that two interior spaces are formed thereby creating a figure-eight as-deployed transverse cross-sectional shape of the structural component.
Further alternate embodiments include, but are not limited to, first and second braided material layers embedded in elastomeric matrices to provide a protective or decorative function, multiple layers of braided material in place of each first and second layer of braided material and structural components that deploy into partial toroidal shapes for columnar structures.
In addition to use of the structural component of the present invention in structures, the invention has expected utility in variable rigidization of airfoil structures to affect changes in lift corresponding to the conditions of wind or to deploy temporary modifications to airfoil structures to affect lift or flight characteristics. Further, such utility may be used to vary drag on high-speed trains or on vehicles to affect performance under varying environmental conditions.
While the above subject matter has been illustrated and described in detail in the drawings and foregoing discussion, the same is to be considered as illustrative and not restrictive in character, it being understood that exemplary embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected by the appended claims and equivalents thereof.
Claims
1. An inflatable structural component comprising
- a longitudinal first braided material layer and a longitudinal second braided material layer each forming a panel having a width-wise dimension transverse to a length-wise direction of the component bounded by first and second longitudinal edges along the length-wise direction of the component, the first and second braided material layers enveloping at least a portion of an inflatable longitudinal bladder,
- the first and second braided material layers arranged such that the first longitudinal edges of the first and second braided material layers are approximately aligned and connected together along a first side of the bladder and the second longitudinal edges of the first and second braided material layers are approximately aligned and connected together along a second side of the bladder.
2. The structural component as claimed in claim 1, further comprising
- a first reinforcing strip affixed to the first braided material layer and the second braided material layer along the first side of the bladder and a second reinforcing strip affixed to the first braided material layer and the second braided material layer along the second side of the bladder.
3. The structural component as claimed in claim 1, further comprising a first structural panel having a first joining edge affixed to the aligned first longitudinal edges.
4. The structural component as claimed in claim 1, further comprising
- a second structural panel having a second joining edge affixed to the aligned second longitudinal edges.
5. The structural component as claimed in claim 1, further comprising
- a sleeve affixed to the first braided material layer and the second braided material layer along the first side of the bladder.
6. The structural component as claimed in claim 5, where the sleeve is integral to the first braided material layer, the second braided material layer, or both.
7. The structural component as claimed in claim 1, where the first braided material layer comprises a biaxial braid having a predetermined bias angle as a function of a braid hose angle.
8. The structural component as claimed in claim 1, where the bladder comprises a braided sleeve embedded in an elastomeric matrix.
9. An inflatable structural component comprising
- a longitudinal first braided material layer and a longitudinal second braided material layer each forming a panel having a width-wise dimension transverse to a length-wise direction of the component bounded by first and second longitudinal edges along the length-wise direction of the component, the first and second braided material layers enveloping at least a portion of an inflatable longitudinal bladder,
- the first and second braided material layers arranged such that the first longitudinal edges of the first and second braided material layers are approximately aligned along a first side of the bladder and the second longitudinal edges of the first and second braided material layers are approximately aligned along a second side of the bladder, and
- a first structural panel having a first joining edge affixed to the aligned first longitudinal edges.
10. The structural component as claimed in claim 9, further comprising
- an edger strip affixed to the first joining edge of the first structural panel between the first and second braided material layers wrapping partially around the first side of the bladder.
11. The structural component as claimed in claim 10, where the edger strip is folded enclosing an outer edge of the first side of the bladder in a pre-deployed configuration.
12. The structural component as claimed in claim 9, further comprising
- a second structural panel having a second joining edge affixed to the aligned second longitudinal edges.
13. The structural component as claimed in claim 12, further comprising
- an edger strip affixed to the second joining edge of the second structural panel between the first and second braided material layers wrapping partially around the second side of the bladder.
14. The structural component as claimed in claim 13, where the edger strip is folded enclosing an outer edge of the second side of the bladder in a pre-deployed configuration.
15. The structural component as claimed in claim 9, where the first braided material layer comprises a biaxial braid having a predetermined bias angle as a function of a braid hose angle.
16. The structural component as claimed in claim 1, where the bladder comprises a braided sleeve embedded in an elastomeric matrix.
Type: Application
Filed: Jun 10, 2014
Publication Date: Dec 18, 2014
Inventors: Andrew A. Head (Cincinnati, OH), Michael S. Braley (Cincinnati, OH), Victor M. Ivers (Amelia, OH)
Application Number: 14/300,335
International Classification: E04B 1/343 (20060101);