Abstract:
Methods and structures for a composite truss structure are provided. The structure includes a web formed of a plurality of sheets of composite material, each sheet including a first face and an opposing second face and each face including a length and a width. Each of the plurality of sheets are coupled to at least one other of the plurality of sheets face to face such that the length and width of each face substantially match the length and width of a face of an adjacent sheet. The plurality of sheets are formed to include an upper chord member, a lower chord member, and a plurality of web members extending therebetween. The structure also includes at least a first flange plate coupled to the web proximate an outer periphery of the web.

Description:
BACKGROUND 
       [0001]    Embodiments of the disclosure relate generally to methods and structures for forming lightweight truss members and more particularly, to methods and structures for forming composite wing ribs and truss members. 
         [0002]    Conventional aircraft wing construction generally comprises one or more spars that extend laterally relative to the longitudinal axis of the fuselage to support a plurality of longitudinally extending laterally spaced ribs that define the shape of the air foil. Vertical web portions of the ribs include structural elements configured to carry compressive and tensile loads to maintain the airfoil shape. A truss design for aircraft wing ribs is an efficient method of transferring and distributing loads throughout the wing structure. Additionally truss structures are used for bridges, floors and other supporting structures. At least some known truss structures are heavy due to the use of metal components and structural elements of the truss structure. A lightweight material may be used to make strong lightweight truss structures however, current composite ribs are complicated to manufacture and generally heavy in order to provide sufficient load transfer between the truss structural elements. The assembly of aircraft wings utilizing composite ribs in the wing have also proven to be difficult. 
         [0003]    What are needed are methods and structures for providing lightweight support structures that facilitate fabrication of the truss structures and connecting components and reduce assembly time. 
       SUMMARY 
       [0004]    In one embodiment, a structure for a for a composite truss includes a web formed of a plurality of sheets of composite material, each sheet including a first face and an opposing second face and each face including a length and a width. Each of the plurality of sheets are coupled to at least one other of the plurality of sheets face to face such that the length and width of each face substantially match the length and width of a face of an adjacent sheet. The plurality of sheets are formed to include an upper chord member, a lower chord member, and a plurality of web members extending therebetween. The structure also includes at least a first flange plate coupled to the web proximate an outer periphery of the web. 
         [0005]    In yet another embodiment, a method of forming a composite structural member includes coupling a plurality of sheets of composite material face to face to form a web, shaping the web to form an upper cord and a lower chord, and forming a plurality of openings in the web to form a plurality of structural web members extending between the upper cord and lower chord. The method also includes coupling at least one flange plate to an outer peripheral edge of at least one of the upper cord and the lower chord. 
         [0006]    In another embodiment, a method of forming an aircraft wing including a composite wing rib includes forming a wing rib wherein forming the wing rib includes forming a web from a plurality of composite sheets coupled together in a face to face orientation, forming a plurality of interconnected structural elements in the web including an upper chord member, a lower chord member, and a plurality of web members each defined by a plurality of openings formed in the web, and coupling a flange plate to a side of the wing rib proximate an outer peripheral edge of the wing rib, the flange plate including a laterally extending flange member. The method further includes assembling at least one wing rib to at least one of a forward spar and an aft spar and assembling a trailing edge skin to the spar and wing rib assembly using the laterally extending flange member. The method also includes assembling an upper and a lower center skin to the rib, spar and trailing edge skin assembly such that the center skin overlaps the trailing edge skin and attaching the leading edge skin to the wing assembly such that the leading edge skin overlaps the center skin and trailing edge skin assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a cut-away isometric view of an aircraft wing structure in accordance with an embodiment of the disclosure; 
           [0008]      FIG. 2  is a side cross-sectional view of a truss rib assembly in accordance with an exemplary embodiment of the disclosure; 
           [0009]      FIG. 3  is a section view of the truss rib assembly shown in  FIG. 2  taken along section lines A-A; 
           [0010]      FIG. 4  is a section view of the truss rib assembly shown in  FIG. 2  taken along section lines B-B; 
           [0011]      FIG. 5  is a section view of the truss rib assembly shown in  FIG. 2  taken along section lines C-C. 
           [0012]      FIG. 6  is a section view of the truss rib assembly shown in  FIG. 2  taken along section lines D-D. 
           [0013]      FIG. 7  is a section view of the truss rib assembly shown in  FIG. 2  taken along section lines E-E. 
           [0014]      FIG. 8  is a side cross-sectional view of a truss rib assembly in accordance with another exemplary embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The following detailed description illustrates the disclosure by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the disclosure, describes several embodiments, adaptations, variations, alternatives, and uses of the disclosure, including what is presently believed to be the best mode of carrying out the disclosure. 
         [0016]      FIG. 1  is a cut-away isometric view of an aircraft wing structure  100  in accordance with an embodiment of the disclosure. In the exemplary embodiment, aircraft wing structure  100  includes a plurality of truss rib assemblies  102  extending in a forward direction  104  and an aft direction  106  between a leading edge  108  and a trailing edge  110  of aircraft wing structure  100 . Aircraft wing structure  100  also includes a forward wing spar  112  and an aft wing spar  114  extending from a fuselage of the aircraft (not shown). A lower wing covering section or skin  116  is joined to lower portions of truss rib assemblies  102  between leading edge  108  and trailing edge  110 . Similarly, an upper wing covering section or skin  118  is bonded to upper portions of truss ribs  102  between leading edge  108  and trailing edge  110 . 
         [0017]      FIG. 2  is a side cross-sectional view of a truss rib assembly  102  in accordance with an exemplary embodiment of the disclosure. Although described as a rib for an aircraft airfoil such as a wing, it should be understood that the structures and methods of fabricating such structures may be used for other composite truss structures, for example, but not limited to joists, roof trusses, and bridge deck support members. In such embodiments, truss rib assemblies  102  are configured to receive one or more decking members for supporting the decking member thereon. 
         [0018]    In the exemplary embodiment, truss rib assembly  102  comprises a composite truss structure. Truss rib assembly  102  includes an upper chord member  202 , a lower chord member,  204 , and a plurality of web members  206  extending therebetween. Each of upper chord member  202 , lower chord member,  204 , and web members  206  are formed of at least a first portion  202  and a second portion  204  mounted side by side. Each portion is formed of a fiber reinforced sheet material such as but not limited to plain weave (PW) or 5-hardness (5H) material. Fiber reinforced materials such as fiber glass, graphite, aromatic polyamide, such as but not limited to Aramid fiber epoxies or thermoplastics may also be used. Each portion is bonded or consolidated together. After the portions are bonded or consolidated together all of the truss structural elements form a box structure for each structural element. A cap  206  of the rib is open and becomes closed when the wing skin is bonded to the rib. A foam core may be utilized in the hollow spaces of the rib or truss. 
         [0019]    In the exemplary embodiment, truss rib assembly  102  includes a lateral flange that is coupled to an outer periphery of truss rib assembly  102  that extends laterally away from truss rib assembly  102 . Lateral flange  208  may have a right hand portion and a left hand portion that each extend away from each other. In other embodiments, only a right hand or left hand flange is used. In the exemplary embodiment, flange  208  extends about the entire periphery of truss rib assembly  102 . In an alternative embodiment, truss rib assembly  102  only extends about a portion of the periphery of truss rib assembly  102 . A forward spar flange  210  and an aft spar flange  212  are formed similarly to lateral flange  208 , but circumscribe an inner periphery of each spar opening,  214  and  216  respectively. Flanges  208 ,  210 ,  212  illustrated at the spar and cap locations are configured to bond the rib and or rib sections to the individual skins to form skin assemblies and then bond the subassemblies into a completed wing. Each web opening  218  is circumscribed by a respective right hand and/or left hand flange  220  that extends inwardly into web opening  218 . 
         [0020]    Although truss rib assembly  102  is illustrated as being fabricated as a unitary truss rib assembly  102 , it should be understood that truss rib assembly  102  may be fabricated from more that one separate piece to facilitate different wing assembly methods. The use of such composite truss ribs are not limited to aircraft wings, but also to floor or roof trusses on buildings, and bridge trusses that are manufactured in different locations and are erected on site. 
         [0021]      FIG. 3  is a section view of truss rib assembly  102  taken along section lines A-A (shown in  FIG. 2 ). In the exemplary embodiment, truss rib assembly  102  is formed by one or more sheets of composite material cutout to form upper chord member  202 , lower chord member,  204 , and web members  206 . The sheets are bonded together side by side and flanges applied to the periphery of truss rib assembly  102  and openings  218 . The flange at section A-A includes a left hand lateral portion  302  and a right hand lateral portion  304  each extending away from a centerline  306  of the composite sheets. The flange also includes a right hand flange portion  308  that extends into opening  218  and a left hand flange portion  310  that is complementary to flange portion  308 . In the exemplary embodiment, right hand flange portion  308  and left hand flange portion  310  are co-bonded to facilitate coupling the composite sheets together. Left hand lateral portion  302  and a right hand lateral portion  304  are configured to receive skin members in a bonding relationship to facilitate assembling a wing structure. 
         [0022]      FIG. 4  is a section view of truss rib assembly  102  taken along section lines B-B (shown in  FIG. 2 ). In the exemplary embodiment, truss rib assembly  102  taken along section lines B-B includes forward spar flange  210  on both sides of forward spar opening  214  and flanges  220  that extend into openings  218  and that facilitate coupling the composite sheets together. 
         [0023]      FIG. 5  is a section view of truss rib assembly  102  taken along section lines C-C (shown in  FIG. 2 ). In the exemplary embodiment, truss rib assembly  102  taken along section lines C-C includes a left hand flange half  502  and a right hand flange half  504  and flanges  220  that extend into openings  218  and that facilitate coupling the composite sheets together. 
         [0024]      FIG. 6  is a section view of truss rib assembly  102  taken along section lines D-D (shown in  FIG. 2 ). In the exemplary embodiment, truss rib assembly  102  taken along section lines D-D includes a left hand flange half  602  and a right hand flange half  604  and flanges  220  that extend into openings  218  and that facilitate coupling the composite sheets together. 
         [0025]      FIG. 7  is a section view of truss rib assembly  102  taken along section lines E-E (shown in  FIG. 2 ). In the exemplary embodiment, truss rib assembly  102  taken along section lines E-E includes aft spar flange  212  on both sides of aft spar opening  216  and on each of a left hand flange  702  and a right flange  704 . Truss rib assembly  102  also includes lateral flange  208  that extends along upper chord member  202  and lower chord member  204 . Aft spar flange  212  facilitates coupling truss rib assembly  102  to aft spar  114  and lateral flange  208  facilitates coupling covering sections or skin members to truss rib assembly  102  during assembly. 
         [0026]      FIG. 8  is a side cross-sectional view of a truss rib assembly  800  in accordance with another exemplary embodiment of the disclosure. In the exemplary embodiment, truss rib assembly  800  is fabricated in three portions, a forward portion  802 , a center portion  804 , and an aft portion  806 . Each portion is formed of a composite sheet material such as PW or 5H material or a continuous fiber wound in channels oriented in a pattern representing a respective portion of an upper chord  810 , a lower chord  812 , and interconnecting structural members  814  forming the truss web. In some embodiments, it may be advantageous to form one or more of forward portion  802 , a center portion  804 , and an aft portion  806  of sheet material while other portions are formed of placed fib fabricated material. Assembly is accomplished by joining forward portion  802 , a center portion  804 , and an aft portion  806 . In one embodiment, forward portion  802  and center portion  804  are assembled to a forward spar (not shown) prior to being joined to each other and center portion  504  and an aft portion  506  are assembled to a rear spar (not shown) prior to being joined to each other. 
         [0027]    The above-described methods of forming composite structural members and composite truss structures formed thereby are cost-effective and highly reliable. The methods and structures include composite sheet material formed and bonded together in a truss that includes an upper and lower chord as well as a web containing plurality of structural truss elements. The truss includes flange members for facilitating stiffening the truss and attaching skin or decking to the truss members. The composite sheet material is bonded or consolidated together to facilitates providing strength and stability. The lightweight truss simplifies handling with less or smaller support equipment. Accordingly, the methods and structures facilitate reducing weight and fabrication time, and improving strength and stiffness of the structural member in a cost-effective and reliable manner. 
         [0028]    While embodiments of the disclosure have been described in terms of various specific embodiments, those skilled in the art will recognize that the embodiments of the disclosure can be practiced with modification within the spirit and scope of the claims.