Patent Publication Number: US-2018045221-A1

Title: Strut for an aircraft engine

Description:
FEDERALLY SPONSORED RESEARCH 
     This invention was made with government support under contract number FA8650-09-D-2922 of the U.S. Air Force. The government may have certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     The present subject matter relates generally to a strut for an aircraft engine. 
     BACKGROUND OF THE INVENTION 
     A gas turbine engine includes a fan section and a core engine. The core engine includes serial axial flow relationship, a high pressure compressor to compress an airflow entering the core engine, a combustor in which a mixture of fuel and the compressed air is burned to generate a propulsive gas flow, and a high pressure turbine which is rotated by the propulsive gas flow and which is connected by a shaft to drive the high pressure compressor. A typical bypass turbofan engine adds a low pressure turbine aft of the high pressure turbine which drives a fan of the fan section located forward of the high pressure compressor. A splitter aft of the fan divides fan flow exiting the fan into core engine flow and bypass flow around the core engine. 
     The fan section includes one or more stages of fan rotor blades and a strut assembly. The strut assembly includes circumferentially spaced struts mounted to a hub at radially inner ends and to an assembly outer case at radially outer ends. The outer case defines a circular shape, such that a circular flowpath surface is defined for a flowpath through the fan section. 
     The struts of the strut assembly must be capable of withstanding relatively large forces generated during operation of the gas turbine engine. These forces may include static forces from a weight of the various components of the gas turbine engine, as well as dynamic forces generated during, e.g., in certain maneuvers of an aircraft including the gas turbine engine. During operation of the gas turbine engine, these forces can urge the struts to buckle. The struts are typically formed in a thick and relatively robust manner in order to withstand the static and dynamic forces. However, such may lead to relatively heavy struts for the strut assembly. 
     Accordingly, a strut better able to withstand the static and dynamic forces would be useful. Moreover, a strut better able to withstand the static and dynamic forces, while reducing an overall weight of the strut, would be particularly beneficial. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one exemplary embodiment of the present disclosure, a strut is provided for a gas turbine engine defining a circumferential direction. The strut defines a span and includes a body defining a first side and an opposite second side. The first side is spaced from the second side along the circumferential direction. The body includes an inner section, a middle section, and an outer section arranged in series order along the span of the strut. The inner section, middle section, and outer section each define a thickness between the first and second sides. The thickness of the middle section is greater than the thicknesses of the inner section and the outer section. 
     In another exemplary embodiment of the present disclosure, a strut assembly is provided for a gas turbine engine defining a circumferential direction. The strut assembly includes an inner hub and an outer structural case. The strut assembly additionally includes a strut extending between the inner hub and the outer structural case. The strut defines a span and a midline extending along the span through a thickest portion of the strut. The strut further defines a first side and an opposite second side, the first side spaced from the second side along the circumferential direction. The strut includes an inner section, a middle section, and an outer section arranged in series order along the span of the strut. The inner section, middle section, and outer section each define a thickness between the first and second sides extending through the midline. The thickness of the middle section is greater than the thicknesses of the inner section and the middle section. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a schematic cross-sectional view of an exemplary gas turbine engine according to various embodiments of the present subject matter. 
         FIG. 2  is a close-up, schematic, cross-sectional view of a forward strut assembly, also referred to as a front frame assembly, of the exemplary gas turbine engine of  FIG. 1 . 
         FIG. 3  is an isolated, axial view of the exemplary forward strut assembly of  FIG. 2 . 
         FIG. 4  is a close-up view of a strut attached to an outer structural case of the exemplary forward strut assembly of  FIG. 2  in accordance with an exemplary aspect of the present disclosure. 
         FIG. 5  is a side view of a strut of the exemplary forward strut assembly of  FIG. 2  in accordance with an exemplary aspect of the present disclosure. 
         FIG. 6  is a spanwise, cross-sectional view of the exemplary strut of  FIG. 5 , taken along Line  6 - 6  of  FIG. 5 . 
         FIG. 7  is a spanwise, cross-sectional view of the exemplary strut of  FIG. 5 , taken along Line  7 - 7  of  FIG. 5 . 
         FIG. 8  is a spanwise, cross-sectional view of the exemplary strut of  FIG. 5 , taken along Line  8 - 8  of  FIG. 5 . 
         FIG. 9  is a graph charting a thickness of the exemplary strut of  FIG. 5  along a midline of the exemplary strut of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. 
       FIG. 1  is a schematic representation of an aircraft gas turbine engine  10  in accordance with one embodiment of the present disclosure. The gas turbine engine  10  defines an axial direction A, a radial direction R, and a circumferential direction C (i.e., a direction extending about the axial direction A, see  FIG. 3 ). The gas turbine engine  10  includes an engine centerline  12  extending along the axial direction A depicted in phantom for reference and has, in serial flow relationship, a fan section  14 , a high pressure compressor  16 , a combustion section  18 , a high pressure turbine  20 , and a low pressure turbine  22 . The high pressure compressor  16 , the combustion section  18  and high pressure turbine  20  are often referred to as a core engine  24 . 
     The fan section  14  is illustrated as a multi-stage fan section having first, second, and third stage fan blades  26 A,  26 B, and  26 C, respectively, disposed within an annular fan duct  28 . The fan section  14  additionally includes a strut assembly supporting at least in part the fan section  14 . Specifically, for the embodiment depicted, the fan section  14  includes a forward strut assembly  30  located forward of the first stage fan blades  26 A. Additionally, disposed adjacent to each of the first, second, and third stage fan blades  26 A,  26 B, and  26 C, the fan section  14  includes stages of guide vanes. Specifically, the exemplary fan section  14  depicted includes first stage guide vanes  32 A located aft of the first stage fan blades  26 A, second stage guide vanes  32 B located aft of the second stage fan blades  26 B, and third stage guide vanes  32 C located aft of the third stage fan blades  26 C. The first, second, and third stage guide vanes  32 A,  32 B,  32 C are each disposed around the engine centerline  12 , along the circumferential direction C. In certain embodiments, the third stage guide vanes  32 C may further be configured as struts. 
     Fan air  34  exits the fan section  14  and an annular splitter  36  splits the fan air  34  into a bypass air portion  38  bypassed around the core engine  24  through a bypass duct  40  and into a core engine air portion  42  passed through a diffusion duct  44  into the core engine  24 . At an aft end of the fan section  14  is a fan frame  46  including a circumferentially disposed plurality of structural struts  48 . The struts  48  extend radially across a fan bypass inlet  50  of the bypass duct  40  and a core engine inlet  52  of diffusion duct  44 . The splitter  36  is sectioned and attached to the struts  48  and splitter  36  extends axially between the fan bypass inlet  50  and the core engine inlet  52 . 
     Within the core engine  24 , a high pressure rotor shaft  54  connects, in driving relationship, the high pressure turbine  20  to the high pressure compressor  16  and a low pressure rotor shaft  56  drivingly connects the low pressure turbine  22  to the fan section  14 . Fuel is burned in the combustion section  18  producing a hot gas flow  58  which is directed through the high pressure and low pressure turbines  20  and  22 , respectively, to power the engine  10 . The hot gas flow  58  is discharged into an exhaust section  60  of the engine  10  where it is mixed with the bypass air portion  38  from the bypass duct  40  and exhausted through a variable nozzle  62  at the aft end of the engine  10 . An afterburner  64  may be used for thrust augmentation. The exemplary engine  10  illustrated in  FIG. 1  is typical of a military gas turbine aircraft engine  10 , such as the General Electric F-110. 
     It should be appreciated, however, that the exemplary gas turbine engine  10  depicted in  FIG. 1  is provided by way of example only, and in other embodiments of the present disclosure, the gas turbine engine  10  may have any other suitable form or configuration. For example, in other exemplary embodiments, the gas turbine engine  10  may additionally include a low pressure compressor forward of the HP compressor  16  and aft of the fan section  14 . Further, in still other embodiments, the gas turbine engine may instead be configured as any other suitable turbofan engine, a turboshaft engine, a turboprop engine, etc. 
     Referring now to  FIGS. 2 and 3 , views are provided of the fan section  14 , or more particularly, of the forward strut assembly  30  of the fan section  14  of the exemplary engine  10  of  FIG. 1 . Specifically,  FIG. 2  provides a close-up, side, cross-sectional view of the forward strut assembly  30  of the exemplary fan section  14  depicted in  FIG. 1  installed in the engine  10 , and  FIG. 3  provides an isolated, axial view of the forward strut assembly  30  of the exemplary fan section  14  depicted in  FIG. 1 . 
     As is depicted most clearly in  FIG. 2 , the forward strut assembly  30  supports rotation of the plurality of stages of fan blades  26 A,  26 B,  26 C of the exemplary fan section  14 . More particularly, the forward strut assembly  30  includes a plurality of struts  66  extending generally along the radial direction R between an outer structural case  72  and an inner hub  74 . For the embodiment depicted, each strut  66  generally includes a body  76  extending between an inner end  78  and an outer end  80 , an inner mounting flange  82  formed integrally with the body  76  at the inner end  78  of the body  76 , and an outer mounting flange  84  formed integrally with the body  76  at the outer end  80  of the body  76 . The inner mounting flange  82  is configured for attachment to the inner hub  74  and the outer mounting flange  84  is configured for attachment to the outer structural case  72 . Additionally, the outer structural case  72  of the forward strut assembly  30  is, in turn, configured for attachment to a frame or nacelle (not depicted) of the engine  10 . Notably, the exemplary engine  10  depicted also includes a forward seal member  86  for forming a seal with the frame or nacelle of the engine  10 . 
     Referring still to  FIG. 2  in particular, the inner hub  74  of the forward strut assembly  30  is attached to a bearing housing  88 . For the embodiment depicted, the inner hub  74  is bolted to the bearing housing  88  through a plurality of bolts  90 . The bearing housing  88  encloses a forward fan bearing  92  for supporting a rotor assembly  94  of the fan section  14 . As discussed above, the rotor assembly  94  of the fan section  14  may be attached to, or may be an extension of, the LP shaft  56  of the engine  10 . In certain embodiments, the forward fan bearing  92  may be configured as a ball bearing, a roller bearing, or any other suitable bearing. 
     Moreover, each of the plurality of struts  66  of the forward strut assembly  30  are configured with a guide vane  96 . Each of the guide vanes  96  are positioned directly aft of a respective strut  66  and operable with a variable guide vane system  98 . The variable guide vane system  98  is configured to rotate each of the plurality of guide vanes  96  about a guide vane axis  100 , such that the plurality of guide vanes  96  may direct an airflow entering into the fan section  14  over the forward strut assembly  30  in a desired manner. 
     Referring now particularly to  FIG. 3 , and as will be discussed in greater detail below, the exemplary forward strut assembly  30  depicted includes a plurality of struts  66  formed in a manner to have an increased resistance to buckling. Accordingly, the exemplary forward strut assembly  30  may require fewer struts  66  to support an anticipated amount of force. For example, the exemplary forward strut assembly  30  includes between thirteen (13) and twenty-one (21) struts  66  spaced along the circumferential direction C. Specifically for the embodiment depicted, the forward strut assembly  30  includes thirteen (13) struts  66 . However, in other embodiments, the forward strut assembly  30  may instead include any other suitable number of struts  66 . In certain embodiments, the plurality of struts  66  may be spaced substantially evenly along the circumferential direction C, or in other embodiments the plurality of struts  66  may be asymmetrically spaced along the circumferential direction C. 
     Further, the inner hub  74  defines an inner hub radius  102  and the outer structural case  72  similarly defines an outer structural case radius  104 . The inner hub radius  102  and outer structural case radius  104  are each defined along the radial direction R from the axial centerline  12  to a respective mounting surface. More particularly, the inner hub radius  102  is defined along the radial direction R from the axial centerline  12  to a mounting surface  106  of the inner hub  74 . Notably, for the embodiment depicted, the mounting surface  106  of the inner hub  74  defines an angle relative to the axial centerline  12  (see  FIG. 2 ). Accordingly, the hub radius  102  is more specifically defined for the embodiment depicted along the radial direction R from the axial centerline  12  to an aft end of the mounting surface  106  of the inner hub  74 . Similarly, the outer structural case radius  104  is defined along the radial direction R from the axial centerline  12  to a mounting surface  108  of the outer structural case  72 . 
     Given that the struts  66  of the exemplary forward strut assembly  30  are capable of withstanding an increased amount of force, fewer struts may be required, meaning that a size of the inner hub  74  may be reduced (as less surface area on the mounting surface  106  is required to mount the struts  66 ). Accordingly, a ratio of the inner hub radius  102  to the outer structural case radius  104  may also be reduced. For example, for the embodiment depicted, a ratio of the inner hub radius  102  to the outer structural case radius  104  is less than about 1:4. It should be appreciated, that terms of approximation, such as “about” or “approximately,” refer to being within a 10% margin of error. 
     For the embodiment depicted, the inner hub  74  of the forward strut assembly  30  defines a substantially circular shape, and accordingly, the mounting surface  106  is also substantially circular. The outer structural case  72  includes a plurality of mounting pads  110  and a plurality of case ligaments  112 . Each of the plurality of case ligaments  112  extends between adjacent mounting pads  110 , connecting the adjacent mounting pads  110 . For the embodiment depicted, each of the plurality of mounting pads  110  and case ligaments  112  extend in a substantially straight direction, such that the outer structural case  72  generally defines a polygonal shape. Accordingly, the mounting surface  108  is also substantially straight. It should be appreciated, however, that in other exemplary embodiments, the outer structural case  72  may instead be configured to define a substantially circular shape. 
     As used herein, the term “substantially straight” with reference to the plurality of case ligaments  112  refers to the particular case ligament  112  defining a radius of curvature greater than at least two times a radial length of one or more of the plurality of struts  66  of the forward strut assembly  30 . Further, the term “substantially straight” may also refer to a case ligament  112  defining a straight reference line extending in a straight direction between the adjacent mounting pads  110  (between which the case ligament  112  extends) completely enclosed within the case ligament  112 . 
     As briefly discussed above, each of the plurality of struts  66  includes an inner mounting flange  82  attaching the respective strut  66  to the inner hub  74  and an outer mounting flange  84  attaching the respective strut  66  to the outer structural case  72 . More particularly, the outer mounting flange  84  of each respective strut  66  attaches the strut  66  to a respective mounting pad  110  of the outer structural case  72 . 
     Referring now briefly also to  FIG. 4 , a close-up view is provided of an outer mounting flange  84  of a strut  66  of the plurality of struts  66  attached to a mounting pad  110  of the outer structural case  72 . For the embodiment depicted, the outer mounting flange  84  of the plurality of struts  66  is configured as a T-shaped flange. As noted, the outer mounting flange  84 , configured for the embodiment depicted as a T-shaped flange, is formed integrally with the body  76  of the strut  66  at the outer end  80  of the strut  66 . The T-shaped mounting flange includes oppositely extending projections  114  for mounting the strut  66 . Specifically, the strut assembly  30  includes mounting brackets/plates  116  positioned opposite the respective mounting pads  110  of the T-shaped flanges and mounting plates  118  positioned on an inner surface of the oppositely extending projections  114 . For the embodiment depicted, bolts  120  extend from the mounting brackets  116 , through the respective mounting pad  110 , through the oppositely extending projections  114 , and to the mounting plates  118 . It should be appreciated, that for the embodiment depicted, the outwardly extending projections  114  each define a thickness T P . The thickness T P  is defined generally along the radial direction R. Additionally, for the exemplary strut assembly  30  described herein, each of the plurality of struts  66  includes an outer mounting flange  84  configured as a T-shaped flange attaching the strut  66  to a respective mounting pad  110  and a similar manner. 
     Referring again to  FIG. 3 , for the embodiment depicted the plurality of mounting pads  110  and case ligaments  112  are formed integrally of a composite material. For example, in certain embodiments, each of the plurality of mounting pads  110  and case ligaments  112  may be formed of a carbon fiber reinforced composite material, or any other suitable composite material. 
     Additionally, each of the plurality of case ligaments  112  defines an inner surface  122  along the radial direction R (i.e., a radially inner surface), which as will be discussed below extends axially and circumferentially as well. Given that for the embodiment depicted each of the plurality of case ligaments  112  extend in a substantially straight direction between adjacent mounting pads  110 , the radially inner surfaces  106  of the case ligaments  112  together define a non-circular shape (i.e., a polygonal shape) as viewed along the axial direction A. In order to allow for the outer structural case  72  to define a flowpath surface  124  (i.e., an inner radial surface of the outer structural case  72  as a whole, defining a flowpath through the fan section  14 ) that more closely resembles a circle for aerodynamic purposes, the forward strut assembly  30  further includes a plurality of wedge members  126  positioned along the inner surfaces  106  of the case ligaments  112 , adjacent to the mounting pads  110 . For certain exemplary embodiments, each of the plurality of wedge members  126  may extend a variety of lengths (such as between thirty percent and fifty percent of a length of the case ligament  112 , i.e., a distance between adjacent mounting pads  110 , adjacent to which it is positioned). Notably, the lengths of the wedge members  126  may vary as a function of a spacing of the struts  66 , which may be spaced between 24° or 30° apart, and may have two or more different spacing angles between struts  66 . 
     Referring now to  FIG. 5 , an isolated, side view of a single strut  66  of the exemplary forward strut assembly  30  described above with reference to  FIGS. 2 through 4  is provided. The strut  66  defines a span S extending along a length of the strut  66 , as shown. Additionally, as previously discussed, the strut  66  includes a body  76  defining an inner end  78  and an outer end  80 , an outer mounting flange  84  formed integrally with the body  76  at the outer end  80  of the body  76 , and an inner mounting flange  82  formed integrally with the body  76  at the inner end  78  of the body  76 . As is also depicted, the body  76  of the strut  66  defines a forward end  128  and an aft end  130 . The exemplary strut  66  depicted is operable with a guide vane  96  at the aft end  130  (see  FIG. 2 ). 
     Moreover, the body  76  of the strut  66  includes an inner section  132 , a middle section  134 , and an outer section  136  arranged in series order along the span S of the strut  66 . For the embodiment depicted, the inner section  132  includes approximately an inner thirty percent (30%) of the span S of the strut  66 , the middle section  134  includes approximately a middle forty percent (40%) of the span S of the strut  66 , and the outer section  136  includes approximately an outer thirty percent (30%) of the span S of the strut  66 . 
     Reference will now also be made to  FIGS. 6 through 8 .  FIG. 6  provides a spanwise, cross-sectional view of the body  76  of the strut  66  along Line  6 - 6  in  FIG. 5 ;  FIG. 7  provides a spanwise, cross-sectional view of the body  76  of the strut  66  along Line  7 - 7  in  FIG. 5 ; and  FIG. 8  provides a spanwise, cross-sectional view of the body  76  of the strut  66  along Line  8 - 8  in  FIG. 5 . More particularly,  FIG. 6  provides a spanwise, cross-sectional view of the outer section  136  of the body  76  of the strut  66 ,  FIG. 7  provides a spanwise, cross-sectional view of the middle section  134  of the body  76  of the strut  66 , and  FIG. 8  provides a spanwise, cross-sectional view of the inner section  132  of the body  76  of the strut  66 . 
     As is depicted in  FIGS. 6 through 8 , the body  76  of the strut  66  further defines a first side  138  and an opposite second side  140 , the first side  138  spaced from the second side  140  along the circumferential direction C (see  FIG. 3 ) of the gas turbine engine  10 . Additionally, the outer section  136  defines an outer thickness T O  between the first and second sides  138 ,  140 , the middle section  134  defines a middle thickness T M  between the first and second sides  138 ,  140 , and the inner section  132  defines an inner thickness T I  between the first and second sides  138 ,  140 . The middle thickness T M  of the middle section  134  is greater than the outer and inner thicknesses T O , T I  of the outer and inner sections  136 ,  132  to increase a load capacity of the strut  66 . Accordingly, the strut  66  depicted in  FIGS. 5 through 8  includes a greater mid-span thickness. 
     Further, for the embodiment depicted, the inner, middle, and outer thicknesses T I , T M , T O  are measured proximate the aft end  130  of the body  76  of the strut  66  (i.e., closer to the aft end  130  than the forward end  128 ). More specifically, the body  76  defines a midline  142  extending from the inner end  78  to the outer end  80  and along the span S. The midline  142  extends through a thickest portion of the body  76  of the strut  66 . For the embodiment depicted, the inner, middle, and outer thicknesses T I , T M , T O  of the inner, middle, and outer sections  132 ,  134 ,  136  respectively, are measured through the midline  142 . 
     In certain embodiments, the middle thickness T M  of the middle section  134  may be at least about 10% greater than the inner and outer thicknesses T I , T O  of the inner and outer sections  132 ,  136 . For example, in certain embodiments, the middle thickness T M  of the middle section  134  may be at least about 15% greater than the inner and outer thicknesses T I , T O  of the inner and outer sections  132 ,  136 . However, in other embodiments, the middle thickness T M  may instead be less than 10% greater than the inner and outer thicknesses T I , T O . 
     Referring briefly now also to  FIG. 9 , a chart is provided graphing a thickness of the body  76  of the strut  66  through the midline  142  and along the span S of the strut  66 . As is depicted, the inner thickness T I  of the inner section  132  is a minimum thickness of the inner section  132  measured through the midline  142 , the outer thickness T O  of the outer section  136  is similarly a minimum thickness of the outer section  136  measured through the midline  142 , and the thickness of the middle section  134  is a maximum thickness of the middle section  134  measured through the midline  142 . As is also shown by the chart in  FIG. 9 , for the embodiment depicted a thickness through the midline  142  of the body  76  of the strut  66  increases at the inner end  78  from the inner thickness T I  and at the outer end  80  from the outer thickness T O . Such an increase in thickness may be to provide greater strength and stability at the inner and outer mounting flanges  82 ,  84 , respectively. 
     Referring again to the spanwise, cross-sectional views of  FIGS. 6 through 8 , for the embodiment depicted the body  76  of the strut  66  defines, for the embodiment depicted, a hollow cavity  144  between the first side  138  and second side  140 . The hollow cavity  144  extends within the body  76  substantially from the inner end  78  of the body  76  to the outer end  80  of the body  76 . The hollow cavity  144  is positioned forward of the midline  142 , such that the hollow cavity  144  may reduce a weight of the strut  66 , without significantly reducing a strength of the strut  66 , or more particularly, without significantly reducing a resistance of the strut  66  to buckling forces. It should be appreciated, however, that in other embodiments, the strut  66  may not define the cavity  144 . 
     Notably, as with the outer structural case  72 , the strut  66  may be formed of a composite material. For example, the strut  66  may be formed of a carbon fiber reinforced material. Alternatively, however, in other embodiments, the strut  66  may be formed of any other suitable composite material. As the strut  66  may be formed of a composite material, the plies or layers forming the strut  66  may be split at the inner and outer ends  78 ,  80  of the body  76  to form the inner and outer mounting flanges  82 ,  84 . Accordingly, as noted above with reference to  FIG. 4 , the oppositely extending projections  114  of the outer mounting flange  84  (i.e., configured as a T-shaped mounting flange) define a thickness T P . The thickness T P  of the oppositely extending projections  114  are for the embodiment depicted less than or equal to about half of the outer thickness T O  of the outer section  136  of the body  76 . However, in other exemplary embodiments, the outer mounting flange  84  may be formed in any other suitable manner to include projections  114  having any other suitable thickness T O . 
     Inclusion of a strut assembly having a strut formed in accordance with one or more the present embodiments may allow for a stronger strut more resistant to buckling forces. Specifically, as will be appreciated, inclusion of a greater mid-span thickness increase a resistance of the strut to buckling. At the same time, forming a strut in accordance with one or more of the present embodiments of a composite material may also reduce a weight of the strut and of a corresponding strut assembly. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.