Patent Description:
Conventionally, various types of aircraft utilize actuators for various operations, such as, for example, deploying landing gear systems. Many such conventional actuator components are made from metallic materials, which are heavy and add weight to an aircraft. Substitution of metals by fiber-reinforced polymer-matrix composites (PMC) is one way to reduce weight of landing gears or aircraft actuators. While PMCs may have various weight-saving benefits, conventional PMCs are not well suited for load transfer, such as axial or torsional loads from composite elements to metallic parts (and vice versa). That is, while composite elements, such as those fabricated in the form of tubes, are capable of handling significant axial loads under both tension and compression, conventional methods of attaching composite materials to other materials, such as metallic materials, can reduce the structural performance of the joint, especially when said joints are subjected to torsional loads.

Composite tubes are known from <CIT> and <CIT>.

The present disclosure provides a joint assembly as defined by claim <NUM>.

In various embodiments, the tapered section includes a diverging section and a converging section. In various embodiments, the tapered section may include at least one groove. In various embodiments, at least one groove may extend across the diverging section and the converging section. In various embodiments, a circumferential width of the at least one groove increases linearly along an axial span of the at least one groove. In various embodiments, a circumferential width of the at least one groove is substantially uniform along an axial span of the at least one groove. In various embodiments, opposing sidewalls that define the at least one groove are each concave along an axial span of the at least one groove. In various embodiments, opposing sidewalls that define the at least one groove are each convex along an axial span of the at least one groove. In various embodiments, opposing sidewalls that define the at least one groove are non-monotonic along an axial span of the at least one groove.

In various embodiments, a radial depth of the at least one groove increases linearly along an axial span of the at least one groove. In various embodiments, a radial depth of the at least one groove is substantially uniform along an axial span of the at least one groove. In various embodiments, a bottom wall of the at least one groove is concave along an axial span of the at least one groove. In various embodiments, a bottom wall of the at least one groove is convex along an axial span of the at least one groove. In various embodiments, a bottom wall of the at least one groove is non-monotonic along an axial span of the at least one groove. In various embodiments, the at least one groove includes a spiral shape that extends along and partially around a surface of the tapered section.

Also disclosed herein, according to various embodiments, is a method of forming a joint assembly as defined by claim <NUM>.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein without departing from the scope of the invention as defined by the claims. Throughout the present disclosure, like reference numbers denote like elements.

The present disclosure describes composite tubes and composite joint assemblies. In various embodiments, the present disclosure relates to connecting composite tubes to other components via a composite joint assembly (e.g., "joints"). Such joints may be used in aircraft systems, such as, for example, landing gear systems. However, the systems and methods of the present disclosure may be suitable for use in non-aircraft systems as well.

As used herein, the term "axial" refers to a position or direction along a longitudinal centerline axis of a composite tube. Also, the term "radial" refers to a position or direction away from the longitudinal centerline axis of the composite tube. For example, a first component that is "radially inward" of a second component means that the first component is positioned closer to the longitudinal centerline axis of the composite tube than the second component.

As mentioned above, substitution of metals by fiber-reinforced polymer-matrix composites (PMC) is one way to reduce weight of landing gears or aircraft actuators. Among significant challenges is implementation of strong joints for load transfer from composite tube elements to metallic parts. In various embodiments, the composite tubes are fabricated to handle axial and/or torsional loads.

Stress concentrations may be generated in areas of the joint in response to axial and/or torsional loading of the composite tube. These stress concentrations indicate the most loaded locations in the composite element and, therefore, may be main factors affecting limits of their structural performance, i.e., their strength. Accordingly, the present disclosure, according to various embodiments, relates to improving joint strength of composite joint assemblies.

With reference to <FIG>, a composite tube <NUM> is illustrated having a body <NUM> and an end portion <NUM>. The end portion <NUM>, according to various embodiments, includes a tapered section <NUM> and an end rim <NUM>. The end rim <NUM> is bound by a radially outward edge <NUM> and a radially inward edge <NUM>. In various embodiments, at least one of the radially outward edge <NUM> and the radially inward edge <NUM> has a non-circular cross-section. The end rim <NUM> may be circumferentially continuous and thus may be a non-circular annulus. As used herein, the term "non-circular annulus" means a ring-like shape that has an inner border that is non-circular and/or an outer border that is non-circular. For example, the radially outward edge <NUM> and/or the radially inward edge <NUM> of the end rim <NUM> may have an undulating, wave-like ring shape.

In various embodiments, the body <NUM> of the composite tube <NUM> defines a hollow chamber extending along the longitudinal centerline axis <NUM>. The body <NUM> of the composite tube <NUM> may by cylindrical and thus may have a circular cross-sectional shape. Accordingly, the shape of the end portion <NUM> (e.g., the non-circular end rim <NUM>) may be different than the cross-sectional shape of the body <NUM>, which may improve the torsional load transfer capabilities of the composite tube <NUM> when implemented in a joint assembly, as described in greater detail below. Also contributing to the load transfer capabilities of the composite tube <NUM> is the tapering shape of the end portion <NUM>, tapering along longitudinal centerline axis <NUM>. That is, the interface between the tapering shape of the end portion <NUM> and the support wedge(s), as described below, tend to enable the transfer of axial loads, such as axial tension. For example, the end portion <NUM> may be compressed between two metallic parts, such as a radially inward piece and a radially outward piece. The metallic parts may be coupled to each other via mutual bolting or other fastening structures, and may compress the end portion <NUM> of the composite tube there-between to provide reliable load transfer for axial forces, such as axial tension and compression.

In various embodiments, the tapered end portion may converge or diverge. That is, the end portion <NUM>, with continued reference to <FIG>, may converge radially inward in a direction from the body <NUM> toward the end rim <NUM>, the end portion <NUM>, with momentary reference to <FIG>, may diverge radially outward in a direction from the body <NUM> toward the end rim <NUM>, or the end portion <NUM>, with momentary reference to <FIG>, may have a diverging section 420A and converging section 420B. Additional details pertaining to these configurations are included below with reference to the pertinent figures.

In various embodiments, and with reference to <FIG>, the tapered section <NUM> may have a quasi-conical shape. Stated differently, the tapered section <NUM> may have a converging, frustoconical-like shape but the "walls" of the shape may be radially undulating, thus forming fold-like contours into the walls of the tapered section <NUM>. In various embodiments, the tapered section <NUM> of the end portion <NUM> has a plurality of folds that form circumferentially distributed grooves <NUM> extending along the tapered section <NUM>. The grooves <NUM> may be non-periodic in the circumferential direction. That is, the grooves <NUM> may be non-uniformly distributed around the circumference of the tapered section <NUM>. In various embodiments, the folds/grooves <NUM> may extend along the entire length of the tapered section <NUM>, the grooves <NUM> may be shorter than the tapered section <NUM>, or the grooves <NUM> may be longer than the tapered section <NUM>. In various embodiments, the tapered section <NUM> has a non-circular cross-section, which may be similar to the shape of the end rim <NUM>. Said differently, at least one of a radially inward surface <NUM> and a radially outward surface <NUM> of the end portion <NUM> (e.g., the tapered section <NUM> of the end portion <NUM>) may have contours, grooves, channels, etc., that impart a non-circular cross-sectional shape to the end portion <NUM> of the composite tube <NUM>. In various embodiments, the folds/grooves <NUM> are smooth curves that may be free of sharp or abrupt directional changes.

As described in greater detail below with reference to <FIG>, the folds/grooves <NUM> may be formed by crimping and/or clamping an uncured composite tube. Also as described in greater detail below with reference to <FIG>, the composite tube <NUM> may be a polymer-matrix composite (e.g., a fiber-reinforced polymer). In various embodiments, the composite tube <NUM> is made from carbon fiber composite materials, glass fiber composite materials, organic fiber reinforced composite materials, or ceramic matrix composite materials, or combinations thereof. The weight, strength, and stiffness of composite tubes may be dictated by fiber type, fiber stiffness, fiber strength, fiber direction/placement, resin system used, and other parameters of the composite lay-up.

An end view of the end portion <NUM> of the composite tube <NUM>, according to various embodiments, is provided in <FIG>. The end rim <NUM> of the end portion <NUM> may have an undulating shape and thus the radius, relative to the longitudinal centerline axis <NUM>, of the opening defined by the end rim <NUM> may vary. For example, inner radial dimension R1 may be greater than inner radial dimension R2. Said differently, the radial distance between the longitudinal centerline axis <NUM> and the radially inward edge <NUM> of the end rim <NUM> may vary. In various embodiments, the radial distance between the longitudinal centerline axis <NUM> and the radially outward edge <NUM> of the end rim <NUM> may vary. In various embodiments, the wave-like end rim <NUM> includes waves that have uniform shapes and curvatures. In various embodiments, however, the wave-like end rim <NUM> includes wave sections that are not uniform with each other and thus have different shapes and curvatures. In various embodiments, the number of waves may be different than what is shown in the figures. In various embodiments, the number of waves is at least one. In various embodiments, the number of waves is <NUM> or more. For example, in various embodiments, the number of waves is between <NUM> and <NUM>.

In various embodiments, and with reference to <FIG>, because of the non-circular shape of the end portion <NUM> of the composite tube <NUM>, the angled orientation of the tapered section <NUM> may vary around the circumference of the end portion <NUM>. <FIG> is a side view of the composite tube <NUM> of <FIG> from viewpoint "B-B" in <FIG> while <FIG> is a side view of the composite tube <NUM> of <FIG> from viewpoint "C-C" in <FIG>. As used herein, "α" is the angle between the longitudinal centerline axis <NUM> of the body <NUM> of the composite tube <NUM> and the tapered section <NUM> that forms the end portion <NUM>. Thus, "α" refers to the bend angle of either external or internal surfaces of the tapered section <NUM> of the end portion <NUM> relative to the body <NUM>. In various embodiments, α<NUM> in <FIG>, which corresponds with R1, is less than α<NUM> in <FIG>, which corresponds with R2. In various embodiments, bend angle α may be between <NUM> degrees and <NUM> degrees. In various embodiments, the bend angle α may be selected according to the specifics of a given application/configuration (e.g., depending on an expected/anticipated load transfer).

In various embodiments, and with reference to <FIG>, a joint assembly <NUM> is provided. The joint assembly <NUM> includes the composite tube <NUM> coupled to one or more support wedges <NUM>, <NUM>. Said differently, at least one support wedge <NUM>, <NUM> may at least partially engage at least one of the radially inward surface <NUM> and the radially outward surface <NUM> of the end portion <NUM> of the composite tube <NUM> (though in <FIG> the wedge(s) <NUM>, <NUM> are shown removed from the respective surfaces <NUM>, <NUM> of the end portion <NUM>, in practice the wedge(s) <NUM>, <NUM> are contacting the respective surfaces <NUM>, <NUM> of the end portion <NUM>). In various embodiments, engagement between the support wedge(s) and the end portion <NUM> is direct contact. The direct contact may be enhanced by pre-stress where the end portion and the support wedge(s) are mutually compressed during assembly of the joint and/or during service. In various embodiments, the wedged/tapered interface between the support wedge(s)s and the end portion prevents pull-apart in response to axial tension. The support wedge(s) <NUM>, <NUM> may have contours that complement the non-circular shape of the end portion <NUM> of the composite tube <NUM>, as described in greater detail below with reference to <FIG>.

In various embodiments, the support wedge(s) <NUM>, <NUM> are made from a metallic material. The support wedge(s) <NUM>, <NUM> may be made from other materials, such as fiber-reinforced PMC, and/or ceramic materials, among others. The support wedge(s) <NUM>, <NUM> may be held against (e.g., engaged with) the end portion <NUM> by applying mechanical force, for example by threaded retraction of first support wedge <NUM> with respect to second support wedge <NUM>, or vice versa, or other similar attachment means. In various embodiments, the process of curing the composite tube <NUM> bonds the support wedge <NUM>, <NUM> to the composite tube <NUM>. In various embodiments, adhesives, resins, or bonding agents may be utilized to bond the support wedge(s) <NUM>, <NUM> to the composite tube <NUM>.

In various embodiments, and with continued reference to <FIG>, the joint assembly <NUM> may include a first support wedge <NUM> and a second support wedge <NUM>. The first support wedge <NUM> may be an internal support wedge <NUM> and thus may be inserted within the opening defined by the end rim <NUM> formed by converging tapered section <NUM> of the end portion <NUM> of the composite tube <NUM> to engage a radially inward surface <NUM> of the end portion <NUM>. The second support wedge <NUM> may be an annular external support wedge <NUM> that is disposed about and substantially circumscribes the end portion <NUM> to engage a radially outward surface <NUM> of the end potion <NUM>.

In various embodiments, and with reference to <FIG>, various configurations of a joint assembly are provided. Joint assembly 105A, with reference to <FIG>, includes an end rim 124A that has both a non-circular radially outward edge 126A and a non-circular radially inward edge 128A, according to various embodiments. In various embodiments, the internal support wedge 132A may be contoured to complement the radially inward surface <NUM> (<FIG>) of the end portion <NUM> of the composite tube <NUM> and the annular external support wedge 134Amaybe contoured to complement the radially outward surface <NUM> (<FIG>) of the end portion <NUM> of the composite tube <NUM>.

Joint assembly 105B, with reference to <FIG>, includes an end rim 124B that has a non-circular radially outward edge 126B and a circular radially inward edge 128B, according to various embodiments. In various embodiments, the internal support wedge 132B may have a circular cross-section that complements a frustoconical, radially inward surface of the end portion <NUM> of the composite tube <NUM> and the annular external support wedge 134B may have a non-circular cross-section and thus may be contoured to complement the radially outward surface of the end portion <NUM> of the composite tube <NUM>. In various embodiments, having only one of the surfaces of the end portion <NUM> be non-circular decreases manufacturing costs (e.g., less complex machining/manufacturing) and provides a similar torsional load transfer benefit. Joint assembly 105C, with reference to <FIG>, includes an end rim 124C that has a circular radially outward edge 126C and a non-circular radially inward edge 128C, according to various embodiments. In various embodiments, the internal support wedge 132C may have a non-circular cross-section that complements a radially inward surface of the end portion <NUM> of the composite tube <NUM> and the annular external support wedge 134C may have a circular cross-section and thus may have a frustoconical shape to complement the circular radially outward surface of the end portion <NUM> of the composite tube <NUM>. In various embodiments, having only one of the surfaces of the end portion <NUM> be non-circular decreases manufacturing costs (e.g., less complex machining/manufacturing) and provides a similar torsional load transfer benefit.

In various embodiments, and with reference to <FIG>, a method <NUM> for manufacturing a joint assembly is provided. The method <NUM> includes forming a non-circular end portion of a composite tube at step <NUM> and engaging a support wedge to the end portion of the composite tube at step <NUM>, according to various embodiments. The method <NUM> further includes curing or solidifying the composite tube at step <NUM>. In various embodiments, step <NUM> includes rendering at least one of a radially outward edge and a radially inward edge of an end rim of the end portion non-circular.

In various embodiments, the composite tube may be formed of a thermoset or a thermoplastic material. In various embodiments, initially forming the composite tube may be performed using various manufacturing methods. For example, the method <NUM> may include laying up a fiber matrix material (e.g., fiber matt, fibers, prepreg, etc.) around/over a removable mandrel. The fiber matrix material may be applied over the mandrel using winding or wrapping techniques, such as a filament-winding technique or an automatic filament placement technique, among others. In various embodiments, the method <NUM> may include additively manufacturing steps. The method <NUM> may include impregnating the fiber matrix material with an uncured polymer thermoset resin, a molten thermoplastic polymer, or a thermoplastic polymer in solution. This resin impregnation step may be repeated with additional layers of fiber or fiber-matt matrix material. With thermoplastic materials, the method <NUM> may include heating the polymer matrix composite to consolidate, shape, and anneal the thermoplastic composite tube. Examples of thermoset polymer resins used in the various embodiments include, but not limited to, epoxy, polyimide, bis-maleimide, polyurethane, and blends or combinations thereof. Examples of thermoplastic polymers used in the various embodiments include, but are not limited to, polyetheretherketone, polyetherimide, polysulfone, polyphenylsulfone, polyphenylene sulfide, and blends or combinations thereof. Examples of fibers used in the various embodiments include, but not limited to, carbon fibers, aramid fibers, glass fibers, and combinations thereof.

In various embodiments, forming the non-circular end portion at step <NUM> and engaging the support wedge at step <NUM> may be performed substantially simultaneously. For example, an internal support wedge may be inserted into one (or both) open ends of the composite tube. The internal support wedge may have an external surface that has a desired non-circular cross-section (e.g., that includes grooves or channels). An external clamping force may be applied (e.g., a radial force, an axial force, or both) using clamp components, such as clamp shell molds, to form the end portion of the composite tube to the desired, non-circular shape. In various embodiments, instead of using separate external clamping components, the method may include using the annular external wedge support to provide the clamping pressure/force. In response to the end portion of the composite tube being molded or formed to the desired, non-circular shape, the composite tube may be cured with the internal wedge support secured within the converging tapered section of the composite tube. In various embodiments, the term "curing" may refer to curing thermoset materials or solidifying thermoplastic materials.

In various embodiments, forming the non-circular end portion at step <NUM> also includes tapering the end portion of the composite tube to form a tapered section that converges radially inward in a direction from the body to the end rim. The tapering step may also be performed substantially simultaneously as steps <NUM> and <NUM>.

In various embodiments, and with reference to <FIG>, a method <NUM> for manufacturing a joint assembly is provided. The method <NUM> includes forming an end portion of a composite tube with at least one groove formed thereon at step <NUM>. The method <NUM> may further include engaging a support wedge to the end portion of the composite tube at step <NUM> and curing or solidifying the composite tube at step <NUM>. In various embodiments, step <NUM> includes rendering at least one of a radially outward edge and a radially inward edge of an end rim of the end portion non-circular.

In various embodiments, and with reference to <FIG>, the composite tube <NUM> may be a straight cylinder before being worked, and the straight cylinder may be worked to give the end portion <NUM> the tapered/conical shape. Further, end portion may be crimped or otherwise radially compressed to form the grooves <NUM>. That is, for example, the outer radius R3 of the end portion <NUM> of the composite tube <NUM> before crimping and/or before forming the grooves <NUM> may be larger than the outer radius R4 of the end portion <NUM> of the composite tube <NUM> after crimping and/or after forming the grooves <NUM>. The tapering and the crimping may be performed simultaneously, or via separate steps.

In various embodiments, and with reference to <FIG>, the composite tube <NUM> may initially have a tapered/conical end portion <NUM> before imparting the non-circular shape to the end portion <NUM>. That is, the composite tube <NUM> may be provided (originally manufactured) with a cylindrical body <NUM> having a longitudinal centerline axis <NUM>, and may be originally manufactured to have a tapered section <NUM> (e.g., a conical end portion <NUM>). The crimping/compressing of the end portion <NUM> may result in the formation of the grooves <NUM>. This crimping/compressing of the end portion may, according to various embodiments, decrease the radius of the end rim <NUM>. That is, R3 in <FIG> may be larger than R4 in <FIG>. In various embodiments, R3 may equal R4.

In various embodiments, and with reference to <FIG>, the end portion <NUM> of the composite tube <NUM> may diverge from the body <NUM>. That is, the end portion <NUM> may have tapered section <NUM>, which may include tapering walls that diverge radially outward, relative to the longitudinal centerline axis <NUM> of the composite tube <NUM>. As used herein, the term "tapered" refers to either converging radially inward or diverging radially outward. The composite tube may be originally manufactured as a straight cylinder, such as the one shown in <FIG>, or the composite tube <NUM> may be manufactured to have a diverging/conical shape, as shown in <FIG>. The subsequent crimping/compressing of the end portion <NUM> may result in the formation of the grooves <NUM>. This crimping/compressing of the end portion <NUM> may, according to various embodiments, decrease the radius of the end rim <NUM>. That is, R3 in <FIG> may be larger than R4 in <FIG>. In various embodiments, R3 may equal R4. Additional details pertaining to this diverging configuration are included below with reference to <FIG>, <FIG>.

In various embodiments, and with reference to <FIG>, the end portion <NUM> of the composite tube <NUM> may have both a diverging section 420A and a converging section 420B. That is, the end portion <NUM> may have tapering, diverging walls 422A that diverge radially outward, relative to the longitudinal centerline axis <NUM> of the composite tube <NUM>, with tapering, converging walls 422B that converge radially inward, relative to the longitudinal centerline axis <NUM> of the composite tube <NUM>. The grooves <NUM> formed on the end portion <NUM> of the composite tube <NUM> may extend across at least a portion of both the diverging section 420A and the converging section 420B. As previously noted, the outer radius R3 of the end portion <NUM> of the composite tube <NUM> before forming the grooves <NUM> may be larger than the outer radius R4 of the end portion <NUM> of the composite tube <NUM> after forming the grooves <NUM>. In various embodiments, R3 may be equal to R4. Additional details pertaining to this diverging/converging configuration are included below with reference to <FIG>, <FIG>.

In various embodiments, and with reference to <FIG>, <FIG>, the tapered section <NUM> may have a quasi-conical shape. Stated differently, the tapered section <NUM> may have a diverging, cone-like shape but the "walls" of the cone-like shape may be circumferentially undulating, thus forming fold-like contours into the walls of the tapered section <NUM>. In various embodiments, the tapered section <NUM> of the end portion <NUM> has a plurality of folds that form circumferentially distributed grooves <NUM> extending along the tapered section <NUM>. In various embodiments, the folds/grooves <NUM> may extend along the entire length of the tapered section <NUM>, the grooves <NUM> may be shorter than the tapered section <NUM>, or the grooves <NUM> may be longer than the tapered section <NUM>. In various embodiments, the tapered section <NUM> has a non-circular cross-section, which may be similar to the shape of the end rim <NUM>. Said differently, at least one of a radially inward surface and a radially outward surface of the end portion <NUM> (e.g., the tapered section <NUM> of the end portion <NUM>) may have contours, grooves, channels, etc., that impart a non-circular cross-sectional shape to the end portion <NUM> of the composite tube <NUM>. In various embodiments, the folds/grooves <NUM> are smooth curves that may be free of sharp or abrupt directional changes.

In various embodiments, the wave-like end rim <NUM> includes waves that have uniform shapes and curvatures in the hoop direction. In various embodiments, however, the wave-like end rim <NUM> includes wave sections that are not uniform with each other and thus have different shapes and curvatures. In various embodiments, the number of waves may be different than what is shown in the figures. In various embodiments, the number of waves is at least one. In various embodiments, the number of waves is <NUM> or more. For example, in various embodiments, the number of waves is between <NUM> and <NUM>. The end rim <NUM> of the end portion <NUM> may have an undulating shape and thus the radius, relative to the longitudinal centerline axis <NUM>, of the opening defined by the end rim <NUM> may vary, similar to the configuration described above with reference to <FIG>. Further, the composite tube <NUM> may be made from the same or similar materials as those described above with reference to the converging composite tube <NUM>. Still further, the bend angle between the longitudinal centerline axis <NUM> of the body <NUM> of the composite tube <NUM> and the tapered section <NUM> may be have a similar magnitude, but in a diverging direction, to the angle "α" described above.

In various embodiments, and with reference to <FIG>, the composite tube <NUM> may be implemented in a joint assembly <NUM>. The joint assembly <NUM> may be similar to the joint assembly <NUM> described above with reference to <FIG>, with the exception that the tapered walls <NUM> diverge instead of converge. The composite tube <NUM> may be coupled to one or more support wedges <NUM>, <NUM>. Said differently, at least one support wedge <NUM>, <NUM> may at least partially engage at least one of the radially inward surface and the radially outward surface of the end portion <NUM> of the composite tube <NUM> (in <FIG>, the wedge(s) <NUM>, <NUM> are shown removed from the respective surfaces of the end portion <NUM> in order to clearly show the respective pieces, in implementation the wedge(s) <NUM>, <NUM> are contacting the respective surfaces of the end portion <NUM>). In various embodiments, engagement between the support wedge(s) and the end portion <NUM> is direct contact. The direct contact may be enhanced by pre-stress where the end portion and the support wedge(s) are mutually compressed during assembly of the joint and/or during service. In various embodiments, the wedged/tapered interface between the support wedge(s)s and the end portion prevents pull-apart in response to axial tension. <FIG> is a cross-sectional view of the joint assembly <NUM> from viewpoint "D-D" identified in <FIG>. The support wedge(s) <NUM>, <NUM> may have contours that complement the non-circular shape of the end portion <NUM> of the composite tube <NUM>. The support wedge(s) <NUM>, <NUM> may be similar and analogous to those described above with reference to <FIG>, <FIG>.

In various embodiments, and with reference to <FIG>, <FIG>, the end portion <NUM> of the composite tube <NUM> may have a bulbous shape that is formed of a diverging section 420A and a converging section 420B, and one or both of these subsections 420A, 420B may have grooves <NUM> formed on the tapering surface <NUM>. That is, the diverging section 420A may extend from the body <NUM> and the converging section 420B may extend from the diverging section 420A and may terminate at an end rim <NUM>. The diverging section 420A of the composite tube <NUM> may be similar and analogous to the diverging configuration described above, and the converging section 420B may be similar and analogous to the converging configuration described above. In various embodiments, folds/grooves <NUM> may be only in section 420A, only in section 420B, or may extend across both sections 420A and 420B. Also, the composite tube <NUM> may be implemented in a joint assembly <NUM>. The joint assembly <NUM> may include one or more support wedges <NUM>, <NUM> that are coupled to the end portion <NUM>. <FIG> is a cross-sectional view of the joint assembly <NUM> from viewpoint "E-E" identified in <FIG> is a cross-sectional view of the joint assembly <NUM> from viewpoint "F-F" identified in <FIG>.

In various embodiments, <FIG> shows an end portion of a composite tube without any grooves, while <FIG> show grooves <NUM> (shown as 525B, 525C, 525D, 525E, and 525F in the figures) formed in the end portion that have different circumferential width configurations. That is, <FIG> show different circumferential shapes of the grooves <NUM> formed in the end portion of the composite tube. While the depictions in <FIG> show the end portion of the composite tube in a converging configuration (e.g., converging toward longitudinal centerline axis <NUM>), the features and shapes of the grooves discussed herein are also applicable to the diverging configuration and/or the combo configuration that includes both a diverging section and a converging section. In various embodiments, and with reference to <FIG>, a circumferential width of the at least one groove 525B increases linearly along an axial span of the at least one groove 525B. Said differently, opposing sidewalls 535B, also referred to as "external contours," of the groove 525B may be linear. In various embodiments, and with reference to <FIG>, a circumferential width of the groove 525C is substantially uniform, with exception of the very tip with finite curvature, along an axial span of the groove 525C. That is, the opposing external contours 535C that define the groove 525C may be substantially parallel to each other. In various embodiments, and with reference to <FIG>, the opposing external contours 535D that define the groove 525D are each concave along an axial span of the groove 525D. In various embodiments, and with reference to <FIG>, the opposing external contours 535E that define the groove 525E are each convex along an axial span of the groove 525E. In various embodiments, and with reference to <FIG>, the opposing external contours 535F that define the groove 525F are non-monotonic along an axial span of the groove 525F. That is, the opposing external contours 535F may have an undulating shape. In various embodiments, different combinations of the grooves shown in <FIG> can be used together within one implementation. Also, in various embodiments, grooves of different sizes, e.g., with different lengths, different widths, different depths, etc., can be used.

In various embodiments, <FIG> shows an end portion of a composite tube without any grooves, while <FIG> show grooves <NUM> (shown as 625B, 625C, 625D, 625E, and 625F in the figures) with different radial depth configurations. That is, <FIG> show different radial depth profiles of the grooves <NUM>, relative to the radially outward surface <NUM> of the tapered section, formed in the end portion of the composite tube. While the depictions in <FIG> show the end portion of the composite tube in a converging configuration, the features and shapes of the grooves discussed herein are also applicable to the diverging configuration and/or the combo configuration that includes both a diverging section and a converging section. In various embodiments, and with reference to <FIG>, a radial depth of the at least one groove 625B increases linearly along an axial span of the groove 625B. Said differently, the bottom wall 631B of the groove 625B may be linear and may, in the depicted instance, converge at a steeper angle than the radially outward surface 621B of the tapered section/end portion of the composite tube. In various embodiments, and with reference to <FIG>, the radial depth of the groove 625C is substantially uniform along an axial span of the groove 625C. That is, the distance between the bottom wall 631C and the projected radial location of radially outward surface 621C is substantially uniform. In various embodiments, and with reference to <FIG>, the bottom wall 631D of the groove 625D is concave along an axial span of the groove 625D, relative to the radially outward surface 621D. In various embodiments, and with reference to <FIG>, the bottom wall 631E of the groove 625E is convex along an axial span of the groove 625E, relative to the radially outward surface 621E. In various embodiments, and with reference to <FIG>, the bottom wall 631F of the groove 625F is non-monotonic along an axial span of the groove 625F, relative to the radially outward surface 621F. That is, the bottom wall 631F may have an undulating shape. In various embodiments, different combinations of the grooves shown in <FIG> can be used together within one implementation. Also, in various embodiments, distribution of depth of the grooves in the hoop direction can be non-uniform, and/or depths in different grooves can be different.

Claim 1:
A joint assembly comprising:
a composite tube (<NUM>) comprising a body (<NUM>) having a longitudinal centerline axis (<NUM>) and an end portion comprising an end rim (<NUM>) that is circumferentially continuous, wherein at least one of a radially outward edge (<NUM>) and a radially inward edge (<NUM>) of the end rim is non-circular; and characterized by
a support wedge (<NUM>, <NUM>) that at least partially engages at least one of a radially inward surface of the end portion and a radially outward surface of the end portion; wherein the end portion of the composite tube comprises a tapered section (<NUM>) that diverges radially outward in a direction from the body to the end rim.