Abstract:
Three simple tools are used to both preform and mold a composite layup into a J-beam. A first composite charge is preformed into a C-channel using a first tool, and a second composite charge is formed into a Z-channel using both the first tool and a second tool. The C-channel and Z-channel are laid up between the first and second tools, following which a perform composite cap and third tool are added to complete the layup and the tool assembly. The layup may be molded using vacuum bagging techniques and subsequently cured while held in the tool assembly.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure broadly relates to the fabrication of composite structures, and deals more particularly with a method and tools for fabricating composite beams, especially those having a nonsymmetrical cross section geometry, such as a “J” beam. 
       BACKGROUND 
       [0002]    Beams formed from composite materials such as carbon fiber are used in a variety of vehicular applications to carry and distribute loads. For example, in aircraft applications, composite beams having a J-shaped cross section (“J-beam”) may be used to support a floor within the fuselage, such as a floor in a cargo area or a passenger cabin. These beams may also find use in other applications, such as for example, without limitation, fuselages, wings, stabilizers and control surface skin supports, to name a few. Composite beams used in these applications must possess dimensional stability over a wide range of environmental conditions, while meeting other performance specifications, including load carrying ability and rigidity. 
         [0003]    Composite J-beams may be fabricated by assembling a C-channel and a Z-channel and then installing a cap on the beam. Multiple steps and complex tooling may be required to form the features of the C-channel and Z-channel, while additional tools may be required to assemble, mold and cure the layup. This tooling may require tight tolerances in some areas, such as certain radii in order to assure that features of the beam are fully formed and meet specifications. 
         [0004]    Accordingly, there is a need for a method and tools that permit cost-effective fabrication of J-beams using a minimum number of tools to shape or preform components of the layup, and subsequently mold the layup, while meeting design specifications. Embodiments of the disclosure are intended to satisfy this need. 
       SUMMARY 
       [0005]    The disclosed embodiments provide a method and tools for fabricating composite beams, particularly J-beams, in which the cross section of the beam is generally J-shape. A set of matched tools for fabricating the beams includes a minimum number of simple components that are used to both preform composite charges into desired shapes such as C-channels and Z-channels, and to mold and cure the assembled layup. As a result of the simplicity of the tooling, J-beams may be economically manufactured that exhibit good dimensional stability and performance characteristics. 
         [0006]    According to one disclosed embodiment, a method is provided for fabricating a composite beam having a J-shape cross section, comprising the steps of: producing a C-channel by forming a first composite charge over a first tool; moving a second composite charge into contact with the C-channel to form a layup; producing a first flange on one end of the beam by forming a first portion of the second composite charge over one end of the C-channel; producing a second flange on the other end of the beam by forming a second portion of the second composite charge over the second tool; and, curing the layup. The layup may be cured in the tools by orienting the web of the beam at an angle between 25 and 45 degrees relative to horizontal in order to improve compaction at a radius on the beam. 
         [0007]    According to another disclosed embodiment, a method is provided for fabricating a composite beam having a J-shaped cross section, comprising the steps of: forming a C-channel using a first composite charge; forming a Z-channel using a second composite charge; assembling the C-channel and the Z-channel in a set of tooling to form a J-beam layup having a cap and a bottom flange connected by a web; and, placing the J-beam layup in a set of tooling with the plane of the web inclined from horizontal at an angle between approximately 25 and 45 degrees. 
         [0008]    According to still another method embodiment, a composite J-beam may be fabricated by the steps comprising: preforming a first composite charge and a portion of a second composite charge using a first tool; placing the first and second preformed charges between the first and second tools; preforming another portion of the second composite charge using the second tool; molding the preformed first and second composite charges using the first and second tools; and, curing the molded charges while the charges are held between the first and second tools. 
         [0009]    According to another embodiment, tooling is provided for fabricating a composite J-beam, comprising: a matched tooling assembly for preforming and molding a composite layup having a J-shaped cross section. The matched tooling assembly includes a first tool over which a first portion of the layup may be preformed into a C-channel, a second tool over which a second portion of the layup may be formed into a Z-channel, and, a third tool for compressing a third portion of the layup defining a cap on the J-beam. 
         [0010]    According to another disclosed embodiment, tooling apparatus is provided for fabricating a composite J-beam having a bottom flange, a pair of top flanges connected to the bottom flange by a web, and a cap covering the top flanges. The tooling apparatus comprises: a first tool having three adjacent surfaces for preforming and molding portions of the bottom of the flange, the web and one of the flanges; a second tool having three adjacent tool surfaces for molding portions of the bottom flange, the web and the other top flange, and, a third tool having a tool surface for molding the cap. One of the three tool surfaces for molding a portion of the web may be inclined at an angle between approximately 25 and 45 degrees relative to horizontal. 
         [0011]    Other features, benefits and advantages of the disclosed embodiments will become apparent from the following description of embodiments, when viewed in accordance with the attached drawings and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATIONS 
         [0012]      FIG. 1  is a flow diagram illustrating one method embodiment for fabricating a composite J-beam. 
           [0013]      FIG. 2  is an end view illustrating a composite J-beam fabricated in accordance with the disclosed embodiments. 
           [0014]      FIG. 3  is an exploded end view illustrating preformed components of a layup used to fabricate the J-beam shown in  FIG. 2 . 
           [0015]      FIG. 4  is a cross sectional view of one tool used to fabricate the composite J-beam. 
           [0016]      FIG. 5  is a cross sectional illustration of a layup in the assembled tooling used to vacuum bag mold and cure the layup. 
           [0017]      FIG. 6  is an isometric view of the tooling assembly shown in  FIG. 5 . 
           [0018]      FIGS. 7   a - 7   h  are cross sectional views illustrating a method for fabricating a composite J-beam. 
           [0019]      FIG. 8  is a flow diagram illustrating the steps of another method embodiment. 
           [0020]      FIG. 9  is a flow diagram of an aircraft production and service methodology. 
           [0021]      FIG. 10  is a block diagram of an aircraft. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Referring first to  FIGS. 1-6 , embodiments of the disclosure relate to a method and tooling used to fabricate a composite J-beam  30  ( FIG. 2 ) which may be used for example, and without limitation, to support a cargo floor (not shown) in a vehicle such as an aircraft (not shown). The J-beam  30  may also be used other applications, such as for example, without limitation, fuselages, wings, stabilizers and control surface skin supports, to name a few. As best seen in  FIG. 2 , the J-beam  30  broadly comprises a top, double flange  32 , connected to a single bottom flange  34  by a central web  36 . The bottom flange  34  is connected to the web  36  by a radius  35 . The J-beam  30  may be of any length, depending on the application, and may have a cross section that varies in dimension along its length. For example, the J-beam  30  may vary in thickness or have a variable gage along its length. 
         [0023]    As shown in  FIG. 3 , the J-beam  30  may be formed from four preformed, composite charges  30   a  that are assembled into a layup  30   b  that is vacuum bag molded and cured in a tool assembly  55  ( FIGS. 5 and 6 ). The composite charges  30   a  may each comprise a prepreg formed from any of various combinations of reinforcing fibers held in a resin, including for example, and without limitation, a carbon fiber epoxy. The layup  30   b  comprises a U-channel  38 , a Z-channel  40 , a cap  42  and a filler  44  sometimes also referred to as a “noodle”. The U-channel  38  includes a web portion  38   a  connecting top and bottom flange portions  38   b ,  38   c . Similarly, the Z-channel  40  includes a web portion  40   a  connecting top and bottom flange portions  40   b ,  40   c . When laid up and placed in the tool assembly  55 , flange portions  38   b ,  40   b  extend in opposite directions and are essentially coplanar, while flange portions  38   c ,  40   c  overlap so as to form the bottom flange  34  of the J-beam  40 . The web portions  38   a ,  40   a  are stacked side-by-side to form the web  36  of the J-beam  30 . The filler  44  may be placed in any gap (not shown) that may exist between the top flange portions  38   b ,  40   b . The cap  42  is placed over the upper flange portions  38   b ,  40   b , and together, form the top flange  32  of the J-beam  30 . 
         [0024]    The tool assembly  55  broadly includes a first tool  56 , a second tool  58  and a third tool in the form of a flat caul plate  60 . The first tool  56  is generally rectangular in cross section and includes three adjacent, flat tool surfaces  56   a ,  56   b  and  56   c . Tool surfaces  56   a  and  56   b  are connected by a radius corner  63 , while tool surfaces  56   b  and  56   c  are connected by a radius corner  67 . When assembled as part of the tool assembly  55 , the first tool  56  is disposed within the U-channel  38  portion of the layup  30   b  and thus provides tool surfaces  56   a ,  56   b ,  56   c  against which three corresponding surfaces of the layup  30   b  are compressed during the molding process. 
         [0025]    The second tool  58  includes tool surfaces  58   a ,  58   b ,  58   c  which form a Z-pattern matching the shape of the Z-channel  40  ( FIG. 3 ). Tool surfaces  58   a  and  58   b  are connected by a radius corner  62 , while tool surfaces  58   b  and  58   c  are connected by a radius corner  67 . Tool surface  58   c  may terminate in a lip  64 , if desired, which acts as a support for the caul plate  60 . Tool  58  may include a flat base  58   d  which supports the tool assembly  55  on any suitable surface (not shown). Tooling surfaces  58   a ,  58   b  are connected through a radius corner  62  where it is important to assure that sufficient compaction of the layup  30   b  is achieved and that bridging of the layup  30   b  during curing is avoided. In order to increase compaction of the layup  30   b  in the area of the radius corner  62  during curing, the tool surfaces  58   a ,  58   b ,  58   c  may be oriented such that the radius corner  62  is positioned below the bottom flange  34  and the web  36 , relative to horizontal. This orientation is achieved by inclining the tool surface  58   b  at an angle φ relative to horizontal that may be between approximately  25  and 45 degrees. As a result of this angle of inclination, compaction forces are distributed during the vacuum bag molding process so that possible bridging of the prepreg at the radius corner  62  is prevented, which in turn may avoid resin starvation at the radius corner  62 . Also, as a result of the inclination angle, gravity may aid the resin to flow into the area of the radius corner  62 . The inclination angle also results in gravity applying forces to the charges that tends to self-index the layup  30   b  in the tool set  55  during the assembly process, so that the radius area  35  of the layup  30   b  is drawn down into the radius corner  62  of the second tool  58 . 
         [0026]    The caul plate  60  is essentially rectangular in cross section and may include a flat lower tool surface  60   a  that bears against and compresses the flat preform charge  42  which bears against the upper flanges  38   b ,  40   b  ( FIG. 3 ). The radius corners  65 ,  67  produce corresponding radii  38   d ,  40   d  between the cap  32  and web  36  (see  FIGS. 2 and 3 ). 
         [0027]      FIG. 1  shows the steps of one method for forming the J-beam  30  using the tool set  55  shown in  FIG. 5 . Referring particularly now to  FIGS. 1 and 7   a - 7   h , at step  46 , the C-channel  38  is shaped by preforming a first flat, uncured prepreg composite charge  38  over the first tool  56 . Next, at step  48 , a second flat, uncured prepreg composite charge is placed over the C-channel  38 . As shown at step  50 , the lower beam flange  34  of the layup  30   b  is produced by forming the second flat charge over one end  38   c  of the C-channel  38 . At  52 , one of the upper beam flanges  40   b  is produced by forming the second composite charge over tool surface  58   c  of the second tool  58 . Finally, the layup  30   b  is molded using the tool assembly  55  and vacuum bagging techniques, following which the layup  30   b  is cured at step  55 . Forming of the charges  30   a  may be performed using conventional hot forming techniques, carried out, for example and without limitation, under a vacuum bag by applying heat to the charges  30   a  using an oven, heat lamps or heat blankets (not shown). 
         [0028]    Another embodiment of the method of fabricating the J-beam  30  is shown in  FIG. 8  which will now be described with reference also to  FIGS. 7   a - 7   h . Beginning at step  74  ( FIG. 7   a ) a flat, uncured prepreg composite charge  66  is placed on the flat tool surface  56   b  of the first tool  56 . Next, at step  76 , the ends of the flat charge  66  are formed or bent down over the sides of tool surfaces  56   a ,  56   c  to form the flange portions  38   b ,  38   c . These first two steps  74 ,  76  provide a process  78  for forming the C-channel  38 . The next series of steps  88  will result in the formation of the Z-channel  40 . Beginning at step  80 , a second flat, uncured prepreg composite charge  68  which may comprise a suitable prepreg, is placed over the web portion  38   a  of the U-channel  38 . One end  68   a  of the second composite charge  68  overhangs the channel portion  38   b , while the opposite edge  68   b  is supported by a flat tool  70  which is slightly spaced from the first tool  56  to form a gap  72  for receiving the flange  38   c . Next, at step  82 , shown in  FIG. 7   d , the outer edge  68   a  of the second charge  68  is formed or bent downwardly over the flange portion  38   b  while the C-channel  38  remains supported by the first tool  56 . 
         [0029]    At step  84 , the fully formed U-channel  38  and the partially formed Z-channel  36  are placed in the tool assembly  55 , as shown in  FIG. 7   e , with the web portion  36  of the layup  30   b  held at the angle φ (see  FIG. 4 ) which, as previously described may be between approximately 25 and 45 degrees. At step  86  ( FIG. 7   f ) the outer edge  68   b  is bent or formed downwardly onto the tool surface  56   c  thereby producing the upper flange  40   b  of the Z-channel  40 . 
         [0030]    Next, at step  90 , as shown in  FIG. 7   g , the filler  44  and cap  42  are installed, following which, as shown at step  92  ( FIG. 7   h ) the caul plate  60  is placed over the cap  42 . Then, at step  94 , compaction pressure is applied to the tool assembly using, for example and without limitation, conventional vacuum bagging techniques. The compacted layup  30   b  is then cured, as shown at  92 , in the tool assembly  55  using, for example and without limitation, an autoclave (not shown). 
         [0031]    Embodiments of the disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace and automotive applications. Thus, referring now to  FIGS. 9 and 10 , embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method  96  as shown in  FIG. 9  and an aircraft  98  as shown in  FIG. 10 . Aircraft applications of the disclosed embodiments may include, for example, without limitation, composite stiffened members such as fuselage skins, wing skins, control surfaces, hatches, floor panels, door panels, access panels and empennages, to name a few. During pre-production, exemplary method  96  may include specification and design  98  of the aircraft  116  and material procurement  100 . During production, component and subassembly manufacturing  102  and system integration  104  of the aircraft  98  takes place. Thereafter, the aircraft  98  may go through certification and delivery  106  in order to be placed in service  108 . While in service by a customer, the aircraft  98  is scheduled for routine maintenance and service  110  (which may also include modification, reconfiguration, refurbishment, and so on). 
         [0032]    Each of the processes of method  96  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of venders, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
         [0033]    As shown in  FIG. 10 , the aircraft  98  produced by exemplary method  96  may include an airframe  112  with a plurality of systems  114  and an interior  116 . Examples of high-level systems  114  include one or more of a propulsion system  118 , an electrical system  122 , a hydraulic system  120 , and an environmental system  124 . Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the automotive industry. 
         [0034]    Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method  96 . For example, components or subassemblies corresponding to production process  102  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  116  is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages  102  and  104 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  96 . Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft  96  is in service, for example and without limitation, to maintenance and service  110 . 
         [0035]    Although the embodiments of this disclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.