Patent Description:
Conventional structural components, for example aircraft landing gear components, are typically made of metallic materials. These metallic components can be relatively heavy and costly. Substitution of metals with composites is one way to reduce the weight and cost of structural components. Among other challenges is implementation of strong joints for load transfer from composite elements to metallic parts. The composite elements are typically fabricated in the form of tubes and are capable of handling significant axial and bending loads under both tension and compression. <CIT> describes an apparatus comprising an end fitting in accordance with the preamble of claim <NUM>.

<CIT> describes an attachment fitting for composite material structures. <CIT> describes a power transmission device and a method for manufacturing such a device in accordance with the preamble of claim <NUM>.

A tube arrangement is disclosed, comprising a composite tube defining a centerline axis, wherein the composite tube comprises a proximal surface and a distal surface, and an end fitting comprising a first end disposed within the composite tube and a second end extending from the composite tube. An outer surface of the end fitting defines a flared portion defining a terminus of the first end, a lobe portion disposed axially from the flared portion, and a terminating portion disposed axially from the lobe portion. The proximal surface conforms to a geometry of the outer surface of the end fitting. The lobe portion and the flared portion mechanically lock the end fitting to the composite tube to mitigate movement of the end fitting relative to the composite tube.

In various embodiments, the lobe portion defines an annular ridge disposed around the end fitting.

In various embodiments, the annular ridge defines a first convex fitting surface.

In various embodiments, an annular groove is formed into the proximal surface of the composite tube, the annular groove receives the lobe portion.

In various embodiments, the annular groove defines a concave tube surface.

In various embodiments, an annular protrusion is formed into the proximal surface of the composite tube, the annular protrusion is in contact with the lobe portion and the flared portion.

In various embodiments, the annular protrusion defines a convex tube surface.

In various embodiments, the flared portion defines a second convex fitting surface.

In various embodiments, the terminating portion defines a concave fitting surface.

In various embodiments, the concave fitting surface is rounded.

In various embodiments, the composite tube terminates at the terminating portion.

In various embodiments, a combined axial length of the flared portion, the lobe portion, and the terminating portion is between one and three times the maximum diameter of the flared portion.

In various embodiments, the end fitting is monolithic.

A tube arrangement is disclosed and defined in claim <NUM>, comprising a composite tube defining a centerline axis, wherein the composite tube comprises a proximal surface and a distal surface, and an end fitting comprising a first end disposed within the composite tube and a second end extending from the composite tube. An outer surface of the end fitting defines a flared portion defining a terminus of the first end, a lobe portion disposed axially from the flared portion, and a terminating portion disposed axially from the lobe portion, the terminating portion defines a second flared portion, the second flared portion defining a concave fitting surface, wherein the concave fitting surface is rounded, the composite tube terminates at the terminating portion, and the composite tube comprises a rounded, flared proximal surface terminating at the terminating portion. The lobe portion defines an annular ridge diposed around the end fitting, the annular ridge being oriented orthogonal with respect to a ceneterline axis of the end fitting.

In various embodiments, an axial length of the flared portion is between <NUM> and <NUM> times the maximum diameter of the flared portion.

In various embodiments, an axial length of the lobe portion is between <NUM> and <NUM> times the maximum diameter of the lobe portion.

In various embodiments, an axial length of the terminating portion is between <NUM> and <NUM> times the minimum diameter of the terminating portion.

In various embodiments, an axial length between a terminus of the end fitting and a terminus of the terminating portion is between one and three times the maximum diameter of the flared portion.

A method for manufacturing a tube arrangement is disclosed and defined in claim <NUM>, comprising disposing a composite material about an end fitting to form a composite tube defining a centerline axis, wherein the composite tube comprises a proximal surface and a distal surface, and the end fitting comprises a first end disposed within the composite tube and a second end extending from the composite tube, wherein an outer surface of the end fitting defines a flared portion defining a terminus of the first end, a lobe portion disposed axially from the flared portion, and a terminating portion disposed axially from the lobe portion, the proximal surface conforms to a geometry of the outer surface of the end fitting, and the lobe portion and the flared portion mechanically lock the end fitting to the composite tube to mitigate movement of the end fitting relative to the composite tube. The lobe portion defines an annular ridge disposed around the end fitting, the annular ridge being oriented orthogonal with respect to a centerline axis of the end fitting.

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 inventions, 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 invention and the teachings herein. Thus, the detailed description herein is presented for purposes of illustration only and not for limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.

As used herein, "distal" refers to the direction radially outward, or generally, away from the centerline axis of a tube. As used herein, "proximal" refers to a direction radially inward, or generally, towards the centerline axis of a tube.

As used herein, the term "concave surface" refers to a surface having an outline or periphery that curves inward like the interior of a circle or spheroid. As used herein, the term "convex surface" refers to a surface having an outline or periphery that curves outward like the exterior of a circle or spheroid.

The present disclosure describes composite tube arrangements having a composite tube and at least one end fitting. The end fitting may be made from a metallic material. A composite may comprise a polymer matrix composite. The composite may comprise a polymer matrix composite reinforced by fibers such as a carbon, glass, organic fibers, or combinations thereof. Such composite tube 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.

A hybrid metallic/composite tube joint of the present disclosure may include an end of a composite tube and an end fitting. A composite tube joint may experience bending loads. Composite tube joints having a flared terminus, a lobe portion, and a terminating portion, of the present disclosure, may mitigate slipping of the composite tube with respect to the end fitting, and may reduce stress and flexural shear in the composite tube when under bending loads.

In various embodiments, a composite tube joint of the present disclosure may be useful for various components including, but not limited to, linkages, connecting rods, actuator rods, struts, structural supports, etc..

With reference to <FIG>, a schematic view of a tube arrangement comprising a hybrid metallic/composite tube joint <NUM> and a hybrid metallic/composite tube joint <NUM> are illustrated, in accordance with various embodiments. Hybrid metallic/composite tube joint <NUM> and hybrid metallic/composite tube joint <NUM> may be disposed at either end of a composite tube <NUM>. Although illustrated as having a hybrid metallic/composite tube joint <NUM> at a first end and a hybrid metallic/composite tube joint <NUM> at a second end, it is contemplated herein that composite tube <NUM> may comprise only one hybrid metallic/composite tube joint <NUM> at an end thereof. With additional reference to <FIG>, hybrid metallic/composite tube joint <NUM> may experience an axial load, represented by arrows <NUM>. The axial load may be a tensile load or a compressive load. Hybrid metallic/composite tube joint <NUM> may experience a bending moment, represented by arrows <NUM>. Hybrid metallic/composite tube joint <NUM> may experience a flexural shear load, represented by arrows <NUM>.

With combined reference to <FIG>, a tube arrangement <NUM> (also referred to herein as a hybrid metallic/composite tube arrangement) is illustrated, in accordance with various embodiments. Tube arrangement <NUM> generally comprises a composite tube <NUM> and at least one end fitting, such as end fitting <NUM> and/or end fitting <NUM>. Composite tube <NUM> may define a centerline axis <NUM>. Composite tube <NUM> and end fitting <NUM> may be coaxially disposed about centerline axis <NUM>. Composite tube <NUM> and end fitting <NUM> may be coaxially disposed about centerline axis <NUM>. Composite tube <NUM> may comprise a proximal surface <NUM> and a distal surface <NUM>. A cross-section geometry (e.g., taken perpendicular to centerline axis <NUM>) of composite tube <NUM> may be circular or may be non-circular (e.g., elliptical). Centerline axis <NUM> may be linear or may be non-linear.

In various embodiments, end fitting <NUM> and/or end fitting <NUM> are configured to couple composite tube <NUM> to an adjacent component. End fitting <NUM> and/or end fitting <NUM> may comprise any suitable attachment feature, including a lug, a clevis, a rod, or the like. In various embodiments, end fitting <NUM> and/or end fitting <NUM> are made from a metallic material. In various embodiments, end fitting <NUM> is formed as a single, monolithic piece. In various embodiments, end fitting <NUM> is formed as a single, monolithic piece. End fitting <NUM> and/or end fitting <NUM> may be configured to transfer loads (e.g., axial loads, bending loads, and/or flexural shear loads) between composite tube <NUM> and end fitting <NUM> and/or end fitting <NUM>, respectively.

In various embodiments, end fitting <NUM> comprises a first end <NUM> disposed within composite tube <NUM> and a second end <NUM> extending from composite tube <NUM>. With combined reference to <FIG> and <FIG>, an outer surface <NUM> of end fitting <NUM> may define a flared portion (also referred to herein as a first flared portion) <NUM>. Flared portion <NUM> may define a terminus <NUM> of first end <NUM>. In various embodiments, flared portion <NUM> defines a convex surface <NUM> (also referred to herein as a second convex fitting surface). In this regard, flared portion <NUM> may be rounded or curved.

Outer surface <NUM> of end fitting <NUM> may define a lobe portion <NUM>. Lobe portion <NUM> may be disposed axially from flared portion <NUM>. Lobe portion <NUM> may be axially adjacent flared portion <NUM>. In various embodiments, lobe portion <NUM> defines a convex surface <NUM> (also referred to herein as a first convex fitting surface). In this regard, lobe portion <NUM> may be rounded or curved. In various embodiments, lobe portion <NUM> defines an annular ridge <NUM> disposed perimetrically around the end fitting <NUM>. The annular ridge <NUM> may define the convex surface <NUM>.

Outer surface <NUM> of end fitting <NUM> may define a terminating portion <NUM>. Terminating portion <NUM> may be disposed axially from lobe portion <NUM>. Terminating portion <NUM> may be axially adjacent lobe portion <NUM>. Lobe portion <NUM> may be disposed axially between terminating portion <NUM> and flared portion <NUM>. Composite tube <NUM> may terminate at terminating portion <NUM>. In various embodiments, terminating portion <NUM> defines a cylindrical surface <NUM>. In this regard, terminating portion <NUM> may comprise a constant diameter, in accordance with various embodiments. In various embodiments, terminating portion <NUM> may be tapered.

Composite tube <NUM> may be formed around end fitting <NUM> in a known manner during manufacture of tube arrangement <NUM> using, for example, a filament winding process, and/or a resin film infusion process, among others. In this regard, composite tube <NUM> may comprise a fiber-reinforced polymer. The proximal surface <NUM> of composite tube <NUM> may conform to the geometry of outer surface <NUM> of end fitting <NUM>. In this regard, an annular groove <NUM> may be formed into the proximal surface <NUM> of the composite tube <NUM>. The annular groove <NUM> may define a concave surface <NUM> (also referred to herein as a concave tube surface). The annular groove <NUM> may receive the lobe portion <NUM>. Furthermore, an annular protrusion <NUM> may be formed into the proximal surface <NUM> of the composite tube <NUM>. The annular protrusion <NUM> may define a convex surface <NUM> (also referred to herein as a convex tube surface). The annular protrusion <NUM> may be in contact with the lobe portion <NUM> and the flared portion <NUM>. Stated differently, the annular protrusion <NUM> may be partially formed by the lobe portion <NUM> and partially formed by the flared portion <NUM>. Furthermore, the maximum diameter D1 of terminating portion <NUM> may be less than the maximum diameter D2 of lobe portion <NUM>. Furthermore, the minimum inside diameter D4 of annular protrusion <NUM> may be less than the maximum outside diameter D3 of flared portion <NUM>. In this manner, the lobe portion <NUM> and the flared portion <NUM>, together with composite tube <NUM>, mechanically lock the end fitting <NUM> to the composite tube <NUM> to mitigate movement of the end fitting <NUM> relative to the composite tube <NUM>.

In various embodiments, the axial length L1 of flared portion <NUM> may be equal to between <NUM> and <NUM> times the maximum diameter D3 of flared portion <NUM>. In various embodiments, the axial length L2 of lobe portion <NUM> may be equal to between <NUM> and <NUM> times the maximum diameter D2 of lobe portion <NUM>. In various embodiments, the axial length L3 of terminating portion <NUM> may be equal to between <NUM> and <NUM> times the maximum diameter D1 of terminating portion <NUM>.

In various embodiments, end fitting <NUM> may be similar to end fitting <NUM>, except that the terminating surface of end fitting <NUM> comprises a flared portion defining a rounded, concave surface. In this manner, end fitting <NUM> may effectively transfer bending loads between end fitting <NUM> and composite tube <NUM>, reducing the amount of stress at the terminus of composite tube <NUM>. In this regard, end fitting <NUM> may be configured for applications where the bending moment is less dominant. Conversely, end fitting <NUM> may be configured for applications where the bending moment is more dominant.

Outer surface <NUM> of end fitting <NUM> may define a terminating portion <NUM>. Terminating portion <NUM> may be disposed axially from lobe portion <NUM>. Terminating portion <NUM> may be axially adjacent lobe portion <NUM>. Lobe portion <NUM> may be disposed axially between terminating portion <NUM> and flared portion <NUM>. Composite tube <NUM> may terminate at terminating portion <NUM>. In various embodiments, terminating portion <NUM> is flared outward (i.e., away from centerline axis <NUM>). In this regard, terminating portion <NUM> may be referred to herein as a flared portion or a second flared portion. In various embodiments, terminating portion <NUM> defines a concave surface <NUM> (also referred to herein as a concave fitting surface). In this regard, terminating portion <NUM> may be rounded or curved, in accordance with various embodiments. In this manner, the terminus of composite tube <NUM> which terminates at terminating portion <NUM> may comprise a rounded, flared proximal surface <NUM> conforming to the geometry of terminating portion <NUM>.

Composite tube <NUM> may be formed around end fitting <NUM> in a known manner during manufacture of tube arrangement <NUM> using, for example, a filament winding process, and/or a resin film infusion process, among others. The proximal surface <NUM> of composite tube <NUM> may conform to the geometry of outer surface <NUM> of end fitting <NUM>. In this regard, an annular groove <NUM> may be formed into the proximal surface <NUM> of the composite tube <NUM>. The annular groove <NUM> may define a concave surface <NUM> (also referred to herein as a concave tube surface). The annular groove <NUM> may receive the lobe portion <NUM>. Furthermore, an annular protrusion <NUM> may be formed into the proximal surface <NUM> of the composite tube <NUM>. The annular protrusion <NUM> may define a convex surface <NUM> (also referred to herein as a convex tube surface). The annular protrusion <NUM> may be in contact with the lobe portion <NUM> and the flared portion <NUM>. Stated differently, the annular protrusion <NUM> may be partially formed by the lobe portion <NUM> and partially formed by the flared portion <NUM>. Furthermore, the minimum diameter D5 of terminating portion <NUM> may be less than the maximum diameter D6 of lobe portion <NUM>. Furthermore, the minimum inside diameter D8 of annular protrusion <NUM> may be less than the maximum outside diameter D7 of flared portion <NUM>. In this manner, the lobe portion <NUM> and the flared portion <NUM>, together with composite tube <NUM>, mechanically lock the end fitting <NUM> to the composite tube <NUM> to mitigate movement of the end fitting <NUM> relative to the composite tube <NUM>.

In various embodiments, the axial length L4 of flared portion <NUM> may be equal to between <NUM> and <NUM> times the maximum diameter D7 of flared portion <NUM>. In various embodiments, the axial length L5 of lobe portion <NUM> may be equal to between <NUM> and <NUM> times the maximum diameter D6 of lobe portion <NUM>. In various embodiments, the axial length L6 of terminating portion <NUM> may be equal to between <NUM> and <NUM> times the minimum diameter D5 of terminating portion <NUM>. In various embodiments, the total combined axial length L7 of flared portion <NUM>, lobe portion <NUM>, and terminating portion <NUM> may be between <NUM> and <NUM> times the maximum diameter D7 of flared portion <NUM> (<NUM> ≤ L7/D7 ≤ <NUM>). Stated differently, the axial length L7 between terminus <NUM> (see <FIG>) and the end <NUM> of terminating portion <NUM> may be between <NUM> and <NUM> times the maximum diameter D7 of flared portion <NUM>. In various embodiments, the total combined axial length L7 of flared portion <NUM>, lobe portion <NUM>, and terminating portion <NUM> may be between <NUM> and <NUM> times the maximum diameter D7 of flared portion <NUM> (<NUM> ≤ L7/D7 ≤ <NUM>).

Claim 1:
A tube arrangement, comprising:
a composite tube (<NUM>) defining a centerline axis, wherein the composite tube (<NUM>) comprises a proximal surface and a distal surface; and
an end fitting (<NUM>) comprising a first end disposed within the composite tube and a second end extending from the composite tube;
wherein an outer surface of the end fitting (<NUM>) defines a flared portion (<NUM>) defining a terminus of the first end, a lobe portion (<NUM>) disposed axially from the flared portion (<NUM>), and a terminating portion (<NUM>) disposed axially from the lobe portion, the terminating portion defines a second flared portion, the second flared portion defining a concave fitting surface, wherein the concave fitting surface is rounded, the composite tube terminates at the terminating portion, and wherein the lobe portion defines an annular ridge disposed around the end fitting, the annular ridge being oriented orthogonal with respect to a centerline axis of the end fitting and the distal surface of the composite tube conforms to the geometry of the outer surface of the end fitting, and characterised in that the composite tube comprises a rounded, flared proximal surface terminating at the terminating portion.