Patent Description:
Satellites require Radio Frequency ("RF") energy concentrating antennas to provide high gain. These antennas comprise precision parabolic or similar shaped antenna reflectors that are carried into space using launch vehicles. During travel, each precision antenna is stowed in a constrained volume within a launch vehicle. Thus, the precision antenna is designed to be transitioned from a relatively compact stowed position to a fully extended position at the time of its deployment. This transition typically relies on deployable mechanical structures. The deployable mechanical structures are often formed of tubes joined together. Each tube is surrounded by a Multi-Layer Thermal Insulation ("MLI") for protection against a relatively large thermal gradient. Changes in temperature of a surrounding environment causes the tubes to change lengths and/or diameter sizes. The MLI helps prevent or minimize the amount of change in the tube lengths and/or diameters. However, the MLI undesirably adds cost, complexity and weight to the deployable mechanical truss structures.

Prior art can be found in <CIT> which generally relates to a CTE-matched hybrid tube laminate doubler.

<CIT> comprises a deployable truss comprising a plurality of column members connected at their ends to form said deployable truss, the plurality of members forming a rigid structure in a deployed state that has a stowage volume less than its deployed volume in a collapsed state.

According to a first aspect, we describe an assembled structure, comprising: a tube structure comprising a plurality of lamina layers comprising at least one first lamina layer formed of a first material having a first coefficient of thermal expansion, and at least one second lamina layer formed of a second material different from the first material and having a second coefficient of thermal expansion different than the first coefficient of thermal expansion; and at least one metallic fitting adhesively bonded to the tube structure; wherein the tube structure has at least one property that is different in an axial direction than a hoop direction; and wherein an axial coefficient of thermal expansion of the tube structure is tailored to provide a net zero coefficient of thermal expansion for the assembled structure.

In some scenarios, more than fifty percent of the lamina layers have fibers that extend in an axial direction. Less than fifty percent of the lamina layers have fibers that extend in a direction angled relative to a central elongate axis of the composite tube. Additionally or alternatively, a hoop coefficient of thermal expansion of the hybrid laminate composite tube structure is tailored to match the coefficient of thermal expansion of the fitting in the hoop direction so as to reduce thermal stress in the hybrid laminate composite tube structure.

In those or other scenarios, the fiber angles of the layers are not symmetric at the midplane of the composite tube wall. Additionally or alternatively, the hybrid laminate composite tube structure has a zero axial coefficient of thermal expansion or a near zero axial coefficient of thermal expansion. The coefficient of thermal expansion of the first material may be a positive coefficient of thermal expansion, and the coefficient of thermal expansion of the second material may be a negative coefficient of thermal expansion.

In those or other scenarios, one or more lamina layers comprise fibers of a first type (e.g., Carbon Fiber Reinforced Polymer ("CFRP"), fiberglass, boron fibers, titanium foil, etc.) and one or more lamina layers comprises fibers of a second type (e.g., CFRP, fiberglass, boron fibers, titanium foil, etc.) different than the first type. Both the volume ratio of the material of the first type to the material of the second type and the angle orientations of the fibers in the lamina layers are tailored to provide the hybrid composite tube structure with a zero axial coefficient of thermal expansion or a near zero axial coefficient of thermal expansion.

In those or other scenarios, each of the first and second lamina layers comprises fibers that extend in a direction that is angled <NUM>° relative to a central elongate axis of the composite tube structure. A third lamina layer may also be provided. The third lamina layer is formed of a material having (<NUM>) the first or second coefficient of thermal expansion and (<NUM>) fibers that extend in a direction that is angled relative to the central elongate axis of the monolithic composite tube structure.

In those or other scenarios, the hybrid laminate composite tube structure is used to form an antenna truss structure.

According to a second aspect, we describe an antenna, comprising: a reflector; and a structure for supporting the reflector, the structure comprising a plurality of composite tube structures adhesively bonded to metallic fittings, each said composite tube structure formed of a plurality of lamina layers comprising at least one first lamina layer formed of a first material having a first coefficient of thermal expansion, and at least one second lamina layer formed of a second material different from the first material and having a second coefficient of thermal expansion different than the first coefficient of thermal expansion; wherein the composite tube structure has at least one property that is different in an axial direction and a hoop direction; and wherein an axial coefficient of thermal expansion of each said composite tube structure is tailored to provide a net zero coefficient of thermal expansion for the structure.

In some scenarios, more than fifty percent of the lamina layers have fibers that extend in the axial direction, and/or less than fifty percent of the lamina layers have fibers angled relative to a central elongate axis of the composite tube. Alternatively, or additionally, a hoop coefficient of thermal expansion of the composite tube structure is tailored to match the coefficient of thermal expansion of the fitting in the hoop direction so as to reduce thermal stress in the hybrid laminate composite tube structure.

In those of other scenarios, the fiber angles of the layers are not symmetric at the midplane of the composite tube wall. Additionally or alternatively, the composite tube structure has a zero axial coefficient of thermal expansion or a near zero axial coefficient of thermal expansion. The coefficient of thermal expansion of the first material may be a positive coefficient of thermal expansion, and the coefficient of thermal expansion of the second material may be a negative coefficient of thermal expansion.

In those or other scenarios, one or more lamina layers comprise fibers of a first type (e.g., CFRP, fiberglass, boron fibers, titanium foil, etc.) and one or more lamina layers comprises fibers of a second type (e.g., CFRP, fiberglass, boron fibers, titanium foil, etc.) different than the first type. Both the volume ratio of the material of the first type to the material of the second type and the angle orientations of the fibers in the lamina layers are tailored to provide the composite tube structure with a zero axial coefficient of thermal expansion or a near zero axial coefficient of thermal expansion.

In those or other scenarios, each of the first lamina layer and second lamina layer comprises fibers that extend in a direction that is angled <NUM>° relative to a central elongate axis of the composite tube structure. At least one third lamina layer may also be provided. The third lamina layer is formed of a material having (<NUM>) the first or second coefficient of thermal expansion and (<NUM>) fibers that extend in a direction that is angled relative to the central elongate axis of the composite tube structure.

The embodiments of <FIG> and <FIG> are not according to the present invention and are present for illustration purposes only.

This disclosure is facilitated by reference to the following drawing figures, in which like numerals represent like items throughout the figures.

It will be readily understood that the solution described herein and illustrated in the appended figures could involve a wide variety of different configurations. Thus, the following more detailed description, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of certain implementations in various different scenarios. While the various aspects are presented in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized should be or are in any single embodiment of the invention.

As noted above, satellites require RF energy concentrating antennas to provide high gain. These antennas comprise precision parabolic or similar shaped antenna reflectors that are carried into space using launch vehicles. During travel, each precision antenna is stowed in a constrained volume within a launch vehicle. Thus, the precision antenna is designed to be transitioned from a relatively compact stowed position to a fully extended position at the time of its deployment. This transition typically relies on deployable mechanical truss structures. The deployable mechanical truss structures are often formed of tubes movably joined together. Changes in temperature of a surrounding environment causes the tubes to change lengths and/or diameter sizes, which negatively affects antenna performance since the tension applied to the reflector surface increased or decreased with the changes in tube size. Thus, each tube is surrounded by one or more layers of MLI for protection against a relatively large thermal gradient. Although the MLI helps prevent or minimize the amount of change in the tube lengths and/or diameters, it undesirably adds cost, complexity and weight to the deployable mechanical truss structures.

The word "monolithic" is used herein when referring to curing multiple distinct lamina layers together into a conglomerate structure. A phrase "monolithic hybrid laminate composite tube" is used herein to refer to a cure of lamina layers. The phrase "hybrid laminate composite tube" and/or "hybrid laminate composite tube structure" is(are) used herein to refer to a laminate design, materials and/or orientations. The phrase "composite tube" and/or "composite tube structure" is(are) used herein to refer to a tube as a whole. The term "laminate" refers to all the layers together as a single monolithic structure. The term "lamina" refers to an individual layer of the laminate either before or after cure.

Therefore, the present solution provides a hybrid laminate composite tube structure that can be used to form a variety of larger structures. For example, the hybrid laminate composite tube structure is used to form a deployable mechanical truss structure for space-based applications which do not require outer layers of MLI. The hybrid laminate composite tube structure is formed of a material that has a zero axial CTE or a near zero axial CTE. As such, the hybrid laminate composite tube structure experiences no change or a relatively small amount of change with regard to its elongate length when subjected to extreme temperature changes in a space environment. The present solution is not limited to the particulars of this example.

Referring now to <FIG>, there are provided illustrations of a monolithic composite tube structure <NUM>. The monolithic composite tube structure <NUM> comprises an elongate cylindrical hollow body <NUM>. Body <NUM> has an elongate length <NUM> that extends along a central elongate axis <NUM>. The body <NUM> also has a diameter <NUM>. The body <NUM> is formed of a hybrid component structure that contains a plurality of laminated layers <NUM>,.

The laminated layers <NUM>,. , <NUM> include fibers of the same or at least two different types (e.g., at least one layer containing first fibers formed of carbon and at least one second layer containing second fibers formed of boron, tungsten, titanium, and/or fiberglass). The fibers of each laminated layer can point or extend in (a) a direction that is parallel to or angled <NUM>° relative to the central elongate axis <NUM> (e.g., α = <NUM>°) or (b) a direction that is angled relative to the central elongate axis <NUM> (e.g., <NUM>° < +α < +<NUM>° or -<NUM>° < -α < <NUM>°). However, more than fifty percent of the laminated layers may have fibers that extend in an axial direction <NUM> (i.e., α = <NUM>°), and less than fifty percent of the laminated layers may have fibers that extend in a direction angled relative to the central elongate axis <NUM> of the monolithic composite tube structure <NUM> (e.g., <NUM>° < +α < +<NUM>° or -<NUM>° < -α < <NUM>°).

The laminated layers <NUM>,. , <NUM> are arranged concentrically. This ensures that the fiber angles α are symmetric over a diameter <NUM> of the tube <NUM>. Notably, the fiber angles α of the laminated layers <NUM>,. , <NUM> are not symmetric over the midplane through the thickness of the hybrid laminate. This means that the total fiber angle value of layer(s) above a middle layer is different than the total fiber angle value of layer(s) below the middle layer. This feature distinguishes the present solution from conventional flat laminates which have fibers symmetrically positioned about the midplane or through the thickness of the laminate material. <FIG> provides an illustration showing a difference between symmetry across a diameter of a tube versus symmetry through a thickness of the tube.

The hybrid component material of the tube structure <NUM> has at least one property that is different in an axial direction <NUM> (i.e., a direction that extends parallel to a central elongate axis <NUM> of the tube) and a hoop or transverse direction <NUM> (i.e., a direction that extends perpendicular to the central elongate axis <NUM> of the tube). The properties include, but are not limited to, a CTE, a stiffness, and/or a strength. In this regard, the present solution distinguishes from conventional flat panel hybrid laminates since the present solution is not isotropic or quasiisotropic. The term "isotropic" means the same properties in all directions. The term "quasiisotropic" means the same properties in at least two directions. In flat materials, the two directions include an x-axis (or <NUM>°) direction (corresponding to the axial direction <NUM> of a tube) and a y-axis (or <NUM>°) direction (corresponding to the transverse hoop direction <NUM> of a tube).

The hybrid composite laminate is formed of two or more different composite materials combined together to tailor a CTE of the tube so as to arrive at a zero axial CTE or a near zero axial CTE. The axial CTE is the CTE that indicates how much the length <NUM> of the tube <NUM> is going to expand and contract in an axial direction <NUM> when subjected to temperature changes. In space-based antenna applications, the zero axial CTE and/or near zero axial CTE negate(s) the negative system performance that is caused by the relatively large temperature extremes of a surrounding environment.

In some scenarios, the two different types of fibers contained in the hybrid composite laminate are selected to include (a) a first type of fibers that have a negative axial CTE whereby the fibers shrink in size when exposed to increased temperatures and (b) a second type of fibers that have a positive axial CTE whereby the fibers expand or elongate when exposed to increased temperatures. When the negative CTE constituent is combined with the positive CTE constituent in the single monolithic laminate, a net CTE is produced. The net CTE comprises a weighted average CTE of the two constituents. Accordingly, the hybrid component material of tube structure <NUM> comprises a ratio of negative axial CTE constituent(s) to positive axial CTE constituent(s) that provides a weighted average CTE that results in a zero axial CTE or a near zero axial CTE. The weighted average CTE is a function of ply CTEs, ply thicknesses, total number of plys, and ply fiber angle. Such a function may be defined by classical lamination theory which is well known in the art. The ratio of the first type of fibers to the second type of fibers is controlled by the total number of constituents, the total number of constituent layers, and/or the layer thicknesses. The hybrid component material of tube structure <NUM> can have any number of constituents greater than or equal to two, any number of constituent layers, and/or any layer thicknesses. These characteristics of the plys are selected in accordance with a given application so as to provide a laminate material with a zero axial CTE or a near zero axial CTE. As noted above, the weighted average CTE also depends on the ply fiber angles, i.e., the fiber directions relative to the central elongate axis <NUM> of the composite tube structure <NUM>. The ply fiber angles can all be zero relative to a central elongate axis <NUM> of the composite tube structure (i.e., have zero ply fiber angles α = <NUM>°), can all be non-zero relative to the central elongate axis <NUM> of the composite tube structure (i.e., have non-zero ply fiber angles α ≠ <NUM>°), or can comprise a combination of zero and non-zero ply fiber angles. As such, the CTE of the present hybrid component material can be controlled by: altering the ratio of the first type of fibers to the second type of fibers; and/or altering the angle(s) of non-axial ply layer(s).

The tube structure also has a hoop CTE which indicates how much the tube's diameter <NUM> is going to expand and contract in a hoop or transverse direction <NUM>. The hoop CTE is a non-zero CTE that is different than the axial CTE. In some scenarios, the hoop CTE of the tube structure <NUM> is tailored to match a CTE of a material that the tube interfaces with when used to form a larger structure (e.g., a deployable antenna truss structure). For example, the hoop CTE of the tube structure <NUM> is matched to a CTE of a metal end fitting used to couple the tube <NUM> to another tube. This CTE matching reduces thermal stress in the tube structure <NUM>. The tube structure <NUM> may also have an axial CTE tailored to provide a net zero CTE for an assembled structure (e.g., a deployable antenna truss structure). The present solution is not limited in this regard.

Referring now to <FIG>, there is provided a flow diagram of an illustrative method <NUM> for making a monolithic tube structure (e.g., monolithic tube structure <NUM> of <FIG>). Method <NUM> begins with <NUM> and continues with <NUM> where at least one first lamina layer is wrapped around a cylindrical tool (e.g., a non-tapered male cylindrical mandrel which may be made of metal). The first lamina layer is formed of a first composite material that has a first CTE. Next in <NUM>, at least one second lamina layer is wrapped around the cylindrical tool. The second lamina layer is formed of a second composite material that is different from the first composite layer and has a second CTE that is different than the first CTE. The first lamina layers and the second lamina layers may alternate.

In <NUM>, heat and pressure are applied to the plurality of individual lamina layers. The heat and pressure can be applied using a vacuum bag and an autoclave. Vacuum bags and/or autoclaves are well known in the art, and therefore will not be described herein. A monolithic composite tube structure is formed through the application of heat and pressure in <NUM>. In this regard, it should be noted that resins of the first and second lamina layers flow when the heat and pressure are applied thereto. Polymers of the resins link together so as to couple the first and second lamina layers to each other. The monolithic tube structure has: at least one property that is different in the axial direction (e.g., axial direction <NUM> of <FIG>) and the hoop direction (e.g., hoop direction <NUM> of <FIG>); an axial CTE tailored to provide a net zero CTE for an assembled structure; and/or a hoop CTE tailored to match the CTE of a fitting in the hoop direction so as to reduce thermal stress in the monolithic tube structure. In some scenarios, more than fifty percent of the first and second lamina layers have fibers extending in the axial direction, and less than fifty percent of the first and second layers have fibers extending in a direction that is angled relative to the central elongate axis (e.g., central elongate axis <NUM> of <FIG>) of the monolithic tube structure. The composite tube structure is removed from the cylindrical tool in <NUM>.

The process of <NUM>-<NUM> can be optionally iteratively repeated to create any given number of monolithic composite tube structures needed to form a larger tube structure (e.g., an antenna truss structure).

Method <NUM> may continue with optional <NUM>. In <NUM>, a structure is assembled by adhesively bonding the monolithic tube structure to at least one fitting (e.g., a metallic fitting forming a joint between two or more monolithic tube structures). In some scenario, the structure comprises an antenna or an antenna truss structure. The fitting can include, but is not limited to, an end fitting for a tube structure. Adhesives are well known in the art, and therefore will not be described herein. Any known or to be known adhesive can be used herein without limitation. As noted above, an axial CTE of the monolithic tube structure is tailored to provide a net zero CTE for the assembled structure. The tailoring can involve changing ply angles, ply thicknesses, ratios of positive CTE constituents to negative CTE constituents, and/or the type(s) of fiber(s) contained in each layer of the composite material. Additionally, a hoop CTE of the monolithic tube structure is tailored to match the CTE of the fitting in the hoop direction so as to reduce thermal stress in the monolithic tube structure. This type of matching can be achieved by changing ply angles, ply thicknesses, ratios of positive CTE constituents to negative CTE constituents, and/or the type(s) of fiber(s) contained in each layer of the composite material. Subsequently, <NUM> is performed where method <NUM> ends or other processing is performed.

The following EXAMPLES are provided to illustrate certain embodiments of the present solution. The following EXAMPLES are not intended to limit the present solution in any way.

A composite tube structure is formed of a laminate material. The laminate material is created in accordance with the above described process <NUM>. The particulars of the laminate material are illustrated in the following TABLE <NUM>.

As shown in TABLE <NUM>, the laminate material comprises three laminated layers. The first and third layers are formed of a material having a first coefficient of thermal expansion CTE<NUM>. The second or middle layer is formed of a material having a second coefficient of thermal expansion CTE<NUM>. The second coefficient of thermal expansion CTE<NUM> is different from the first coefficient of thermal expansion CTE<NUM>. The three laminated layers are selected to have properties and relative arrangements that provide a tube structure with a zero axial CTE or a near zero axial CTE.

In some scenarios, the first and third layers are formed of a prepreg material containing fibers of a first type, and the second layer is formed of a prepreg material containing fibers of a second type. The second type is different than the first type. For example, in some scenarios, the first type of fibers is a non-metal type of fibers (e.g., carbon fibers), and the second type of fibers is a metal type of fibers (e.g., boron, tungsten or titanium). In other scenarios, the first type of fibers is a metal type of fibers, and the second type of fibers is a non-metal type of fibers. In other scenarios, the first type of fibers is a first non-metal type of fibers, and the second type of fibers is a second non-metal type of fibers. Yet in other scenarios, the first type of fibers is a first metal type of fibers, and the second type of fibers is a second metal type of fibers. The present solution is not limited to the particulars of these scenarios.

The first and third layers have the same or different cure ply thickness. Accordingly in some scenarios, the first and third layers have the same thickness th<NUM>. But in other scenarios, the first layer has a thickness of th<NUM> and the third layer has a thickness of th<NUM>. The second or middle layer has a thickness th<NUM> that is different than the thicknesses of the first and third layers.

Each of the three layers contains a plurality of fibers that extend parallel to each other. The first and second layers are arranged so that the fibers thereof extend parallel relative to the central elongate axis (e.g., central elongate axis <NUM> of <FIG>) of the composite tube. Such an arrangement of the first and second layers provides stiffness down the central elongate axis of the composite tube.

The third layer is arranged so that the fibers thereof extend in a direction that is angled relative to the central elongate axis of the monolithic composite tube structure (e.g., angled by ±<NUM>-<NUM>°). In order to provide the angled relationship between third layer's fiber direction and the central elongate axis direction, the material spirals down the length of the tube in a first direction (e.g., a clockwise direction or counterclockwise direction). Such an arrangement of the third layer provides transverse strength and stiffness of the composite tube structure (i.e., strength and stiffness in the hoop direction <NUM> of <FIG>).

The axial CTE of the composite tube structure formed of the above described laminate material is tailored by: altering the angle of the non-axial ply layer (i.e., the third layer); and/or altering the ratio of the second type of fibers to the first type of fibers.

As shown in TABLE <NUM>, the laminate material comprises nine laminated layers. Layers <NUM>-<NUM> and <NUM>-<NUM> comprise a prepreg tape formed of carbon fibers and a resin, and have a cured ply thickness of <NUM> mils. The midplane layer <NUM> comprises a prepreg tape formed of boron fibers and a resin, and has a cured ply thickness of <NUM> mils. The carbon fibers can include, but are not limited to, M55J carbon fibers available from Toray Composite Materials America, Inc. of Tacoma, Washington. The boron fibers can include, but is not limited to, boron coated tungsten wires from Specialty Materials of Lowell, Massachusetts. The resin of layers <NUM>-<NUM> can include, but is not limited to, an RS-<NUM> resin available from Toray Composite Materials America, Inc. of Tacoma, Washington.

Notably, the carbon fibers have a negative axial CTE such that they will shrink in size when exposed to increased temperatures. In contrast, the boron fibers have a positive axial CTE so that they will expand or elongate when exposed to increased temperatures. When the negative CTE constituent is combined with the positive CTE constituent in a single monolithic laminate, a net CTE is provided (e.g., a weighted average CTE of the two constituents) that comprises a zero axial CTE or a near zero axial CTE.

Each of the nine layers contains a plurality of fibers that extend parallel to each other. Layers <NUM>, <NUM>, <NUM>-<NUM>, <NUM> and <NUM> are arranged so that the fibers thereof extend parallel relative to the central elongate axis (e.g., central elongate axis <NUM> of <FIG>) of the composite tube structure. Such an arrangement of the layers <NUM>, <NUM>, <NUM>-<NUM>, <NUM> and <NUM> provides stiffness and strength down the central elongate axis of the composite tube structure. The stiffness and strength in the axial direction (e.g., direction <NUM> of <FIG>) can be decreased by removing some of the layers containing fibers that extend parallel relative to the central elongate axis, and can be increased by adding more layers containing fibers that extend parallel relative to the central elongate axis.

Layers <NUM> and <NUM> are arranged so that the fibers thereof extend in a direction that is angled relative to the central elongate axis of the hybrid laminate composite tube structure (e.g., angled by ±<NUM>° or <NUM>°). In order to provide the positive angled relationship between the third layer's fiber direction and the central elongate axis direction, the prepreg tape spirals down the length of the tube in a first direction (e.g., a clockwise direction). In order to provide the negative angled relationship between seventh layer's fiber direction and the central elongate axis direction, the prepreg tape spirals down the length of the tube in a second direction (e.g., a counter clockwise or anticlockwise direction) opposed from the first direction. Such an arrangement of the third and seventh layers provide transverse strength and stiffness of the hybrid laminate composite tube structure (i.e., strength and stiffness in the hoop direction <NUM> of <FIG>).

The axial CTE of the hybrid laminate composite tube structure formed of the above described laminate material is tailored by: altering the angle of the non-axial ply layers (i.e., the third and seventh layers); and/or altering the ratio of the boron to carbon.

Referring now to <FIG>, there are provided illustrations of an illustrative extendable reflector structure <NUM> implementing the present solution. The extendable reflector structure <NUM> has an appearance that is similar to a conventional radial perimeter truss reflector. In general, the deployable reflector structure <NUM> has a circular, parabolic shape when it is in its fully extended position as shown in <FIG>. The deployable reflector structure <NUM> includes the flexible antenna reflector surface <NUM>, the surface shaping (or tension) cord network <NUM>, and a support structure <NUM>. The support structure <NUM> is also referred to herein an antenna truss structure or a perimeter hoop structure.

The reflector surface <NUM> is formed from any material that is suitable as an antenna's reflective surface. Such materials include, but are not limited to, reflective wire knit mesh materials similar to light weight knit fabrics. In its fully extended position shown in <FIG>, the reflector surface <NUM> has a size and shape selected for directing RF energy into a desired pattern. For example, the reflector surface <NUM> has a scalloped cup shape with concave peripheral edge portions <NUM>. The present solution is not limited in this regard.

The reflector surface <NUM> extends around a central longitudinal axis <NUM> of the extendable reflector structure <NUM>. As such, the reflector surface <NUM> may be a curve symmetrically rotated about the central longitudinal axis <NUM>, a paraboloid rotated around an offset and inclined axis, or a surface shaped to focus the RF signal in a non-symmetric pattern.

The reflector surface <NUM> is fastened to the support structure <NUM> via the surface shaping cord network <NUM>. The surface shaping cord network <NUM> supports the reflector surface <NUM> creating a parabolic shape. The reflector surface <NUM> is dominantly shaped by the surface shaping cord network <NUM>.

The surface shaping cord network <NUM> defines and maintains the shape of the reflector surface <NUM> when in use. In this regard, the surface shaping cord network <NUM> includes a plurality of interconnected cords (or thread like strings) <NUM>. The cords <NUM> are positioned between the reflector surface <NUM> and the support structure <NUM> so as to provide structural stiffness to the reflector surface <NUM> when the perimeter truss antenna is in use.

When the extendable reflector structure <NUM> is in its fully deployed configuration, the surface shaping cord network <NUM> is a stable structure under tension. The tension is achieved by applying pulling forces to the cords by means the support structure <NUM>.

The support structure <NUM> is a foldable structure that can be transitioned from a fully stored or non-extended position shown in <FIG> to a fully extended position shown in <FIG>. A partially extended position of the support structure <NUM> is shown in <FIG>. The support structure <NUM> is formed of a plurality of rigid battens <NUM> that are coupled to each other via joint mechanisms <NUM>, <NUM>. Joint mechanisms <NUM> simply allow battens to bend into and away from adjacent battens as shown in <FIG>. In contrast, joint mechanisms <NUM> allow battens to move away from and towards adjacent battens, as well as allow horizontal battens <NUM> to slide therethrough as also shown in <FIG>.

The rigid battens <NUM> are formed of a plurality of hybrid laminate composite tube structures. The monolithic composite tube structures used here from battens <NUM> are the same as or similar to the monolithic composite tube structure <NUM> of <FIG>. As such, the discussion provided above in relation to the monolithic composite tube structure <NUM> is sufficient for understanding the rigid battens <NUM>. Notably, a hoop CTE of the rigid battens <NUM> is matched to a CTE of a material of the joints <NUM>, <NUM> that the battens interface with when used to form the support structure <NUM>.

Referring now to <FIG>, there is provided an illustrative of illustrative fittings <NUM>, <NUM> coupled to a composite tube structure <NUM>. The fittings <NUM>, <NUM> may be formed of metal. The fittings <NUM>, <NUM> are coupled to the tube <NUM> via an adhesive and/or other coupling means (e.g., screws, nuts, bolts, clamps, snap-fit couplers, etc.). The fitting <NUM> includes, but is not limited to, a fitting having a part number <NUM>-<NUM> (fitting, pivot, guide) and being is available from Proto Labs, Inc. of Minnesota. The fitting <NUM> includes, but is not limited to, a fitting having a part number <NUM>-<NUM> (fitting, latch, tension tube) and being available from Proto Labs, Inc. of Minnesota. The composite tube structure <NUM> is the same as or similar to composite tube structure <NUM>. As such, the above discussion of composite tube structure <NUM> is sufficient for understanding composite tube structure <NUM>.

Referring now to <FIG>, there is provided an illustration of an illustrative mandrel <NUM> that can be used to create a composite tube structure in accordance with the present solution. The mandrel <NUM> includes, but is not limited to, a mandrel having a part number <NUM>-<NUM> (PT Mandrel, <NUM>/<NUM>") and being available from Convertech of New Jersey.

The described features, advantages and characteristics disclosed herein may be combined in any suitable manner. One skilled in the relevant art will recognize, in light of the description herein, that the disclosed systems and/or methods can be practiced without one or more of the specific features. In other instances, additional features and advantages may be recognized in certain scenarios that may not be present in all instances.

Claim 1:
An assembled structure (<NUM>), comprising:
a tube structure (<NUM>) comprising a plurality of lamina layers (<NUM>, <NUM>) comprising
at least one first lamina layer (<NUM>, <NUM>) formed of a first material having a first coefficient of thermal expansion (CTE<NUM>), and
at least one second lamina layer (<NUM>, <NUM>) formed of a second material different from the first material and having a second coefficient of thermal expansion (CTE<NUM>) different than the first coefficient of thermal expansion (CTE<NUM>); and
at least one metallic fitting (<NUM>, <NUM>) adhesively bonded to the tube structure (<NUM>);
wherein the tube structure (<NUM>) has at least one property that is different in an axial direction (<NUM>) than a hoop direction (<NUM>); and
wherein an axial coefficient of thermal expansion of the tube structure (<NUM>) is tailored to provide a net zero coefficient of thermal expansion for the assembled structure (<NUM>).