Abstract:
A method of manufacturing a carbon composite duct assembly includes providing a first carbon composite fabric layer having a first section. The first section is formed into a first portion and a second portion. The first portion is separately moveable relative to the second portion. The first portion overlaps the second portion to define a first corner of the first carbon composite fabric layer. The first carbon composite fabric layer is formed into at least a portion of a duct extending along an axis.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 11/761,489, filed Jun. 12, 2007. 
    
    
     This invention was made with government support under Contract No. n00019-02-c-3003, awarded by the Department of the Navy. 
    
    
     BACKGROUND 
     This disclosure relates to a method of manufacturing a carbon composite duct assembly, such as for a turbine engine. 
     A turbine engine may have a bypass duct assembly. The bypass duct assembly provides a source of thrust for the engine and generally surrounds the engine core. The assembly comprises several ducts: an intermediate case duct, a split flange duct and a forward augmenter duct. The intermediate case duct is upstream of the split flange duct, which is followed downstream by the forward augmenter duct. 
     To provide access to the engine core, the split flange duct is made of two halves split generally along the length of the duct. Each half interfaces with the other half through a flange, an axial flange, extending along the length of the duct. In addition, the split flange duct interfaces with the intermediate case duct and the forward augmenter duct through circumferential flanges that surround the opening of the split flange duct on each side. For each half of the split flange duct, the axial flange and the circumferential flange intersect, forming a corner. 
     Bypass ducts have typically been made of metal. Recently, carbon fiber has become an alternative source of material for the parts of the turbine engine. One problem presented by the use of carbon fiber has been to attempt to create the corner formed by the circumferential flange and the axial flange. For metal ducts, the corner is either welded, forged or machined. With respect to carbon fiber, however, these techniques are not available for forming a corner. 
     SUMMARY 
     An exemplary method of manufacturing a carbon composite duct assembly includes providing a first carbon composite fabric layer having a first section. The first section is formed into a first portion and a second portion. The first portion is separately moveable relative to the second portion. The first portion overlaps the second portion to define a first corner of the first carbon composite fabric layer. The first carbon composite fabric layer is formed into at least a portion of a duct extending along an axis. 
     The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a cross-sectional view of a turbine engine. 
         FIG. 2  illustrates a view of a bypass duct assembly for the turbine engine of  FIG. 1 . 
         FIG. 3  illustrates a plan view of a portion of the bypass duct assembly of  FIG. 2 , showing a circumferential flange and an axial flange intersecting to form a corner. 
         FIG. 4  illustrates a technique for manufacturing the corner of  FIG. 3 , showing a section of the carbon composite fabric layer. 
         FIG. 5  illustrates the forming of separate portions of the section of  FIG. 4 . 
         FIG. 6  illustrates the overlapping of each portion of  FIG. 5 . 
         FIG. 7  illustrates the overlapped portions forming a corner. 
         FIG. 8  illustrates a second carbon composite fabric layer. 
         FIG. 9  illustrates a corner created in the second carbon composite fabric layer having a different overlap than the overlap of  FIG. 7 . 
         FIG. 10  illustrates the layering of the first carbon composite fabric layer onto the second carbon composite fabric layer. 
         FIG. 11  illustrates the layered first carbon composite fabric layer and a second carbon composite fabric layer. 
         FIG. 12  illustrates a male mold for forming the first carbon composite fabric layer and a second carbon composite fabric layer into one half of the carbon composite duct assembly. 
         FIG. 13  illustrates a female mold for the formation of the other half of a carbon composite duct assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example of a turbine engine  10 , here a turbo fan engine. As other types of turbine engines, such as a turbo jet engine, will likewise benefit from the inventive technique, the term turbine engine is not limited to the disclosed embodiment. As shown, turbine engine  10  has fan  12  through which ambient air is propelled. A multi-stage compressor  14  pressurizes the air and is in communication with the combustor  16  that mixes the compressed air with fuel. The combustor  16  ignites the fuel-air mixture. Expanded gas then passes through the turbine section  18  as shown. Within turbine engine  10  is bypass duct assembly  20 . Bypass duct assembly  20  serves to provide additional thrust. 
     With reference to  FIG. 2 , a portion of bypass duct assembly  20  has three ducts: intermediate case duct  28 , carbon composite duct assembly  24 , here a split flange duct, and forward augmenter duct  32 . Carbon composite duct assembly  24  extends along axis A. Carbon composite duct assembly  24  has duct body  36  having opening  40  on each end permitting airflow along axis A through duct body  36 . Duct body  36  is made of two parts to permit access to the core of turbine engine  10 . Duct body  36  has first duct body portion  64  and second duct body portion  68  as shown. 
     Extending lengthwise or along axis A of first duct body portion  64  is first axial flange  44 . Provided around opening  40  is another flange, here first peripheral flange  48 , a circumferential flange extending around the circumference of opening  40 . Second duct body portion  68  has second axial flange  52  extending along axis A as well as second peripheral flange  56 , again a circumferential flange surrounding opening  40 . First duct body portion  64  and second duct body portion  68  interface along first axial flange  44  and second axial flange  52 . In addition, each half, first duct body portion  64  and second duct body portion  68 , also interface in part at first peripheral flange  48  and second peripheral flange  56 . First duct body portion  64  and second duct body portion  68  are connected at flanges as known. In addition, carbon composite duct assembly  24  interfaces and connects to intermediate case duct  28  along first peripheral flange  48  and second peripheral flange  56 . Forward augmenter  32  interfaces and connects to carbon composite duct assembly  24  through first peripheral flange  48  and second peripheral flange  56  on the other side of carbon composite duct assembly  24 . 
     With reference to  FIG. 3  as shown, first axial flange  44  intersects first peripheral flange  48  at first corner  74 . Because carbon composite duct assembly  24  is made of carbon composite fabric, there is a difficulty in creating this corner.  FIGS. 4-13  illustrate how a corner is manufactured. With reference to  FIG. 4 , there is provided first carbon composite fabric layer  60 , a portion of which will form first peripheral flange  48  while the other portion will form first axial flange  44 . First carbon composite fabric layer  60  has first section  70 . Along line K, first section  70  is cut creating first portion  82 , a tab, and second portion  86 , another tab. First portion  82  is now relatively moveable with respect to second portion  86 . First portion  82  may rotate about axis A while second portion  86  may rotate about axis B, an axis perpendicular to axis A. Second portion  86  is rotated about axis B in the direction of arrow X to the position shown in  FIG. 5 . As shown in  FIG. 5 , first portion  82  may be rotated about axis A in the direction of arrow Y to the position shown in  FIG. 6 . Then, first portion  82  may then be turned in the direction of arrow Z into second portion  86  forming first overlap  80  as shown in  FIG. 7 . First portion  82  is adhered to second portion  86  with known adhesives thereby forming first corner  74 . As can be seen, first corner  74  is made from first axial flange  44  and first peripheral flange  48 . In addition, as shown, first carbon composite fabric layer  60  has first plurality of carbon strands  78 , say for example, extending generally along axis A. 
     Following formation of first corner  74 , other additional layers may be created. With reference to  FIG. 8 , there is provided second carbon composite fabric layer  90 . Second carbon composite fabric layer  90  has first axial flange  45  and first peripheral flange  49 . Ultimately, second carbon composite fabric layer  90  will overlap the first carbon composite fabric layer  60  so that first axial flange  44  overlaps with first axial flange  45  and first peripheral flange  48  will overlap with first peripheral flange  49  to form flanges of multiple carbon composite fabric layers. Referring back to  FIG. 8 , second section  94  of second carbon composite fabric layer  90  is cut along line L thereby creating third portion  106  and fourth portion  110 . Similar to the construction of first corner  74 , first axial flange  45  may be turned in the direction of arrow Y while first peripheral flange  49  can be turned in the direction of arrow X so that third portion  106  overlaps fourth portion  110  to form second corner  114  as shown in  FIG. 9 . As further shown in this figure, second carbon composite fabric layer  90  has a second plurality of carbon strands  98 , say for example, generally extending along axis B. 
     As shown in  FIG. 10 , second carbon composite fabric layer  90  is layered over first carbon composite fabric layer  60  such that first plurality of carbon strand  78  of first carbon composite fabric layer  60  are transverse to second plurality of carbon strands  98 . In this way, first plurality of carbon strands  78  lays across second plurality of carbon strands  98  to create a stronger duct body  36 . 
     In addition, first overlap  80  extends along first axis B while second overlap  102  extends along second axis A. By layering second carbon composite fabric layer  90  onto first carbon composite fabric layer  60  in this way, first corner  74  may be layered onto second corner  114  so that first overlap  80  is displaced from second overlap  102  as shown in  FIG. 11 . By alternating overlaps in this way, the corner of duct body  36  is strengthened. Excess material may be machined off or otherwise removed at locations H and I so that duct body  36  conforms to specification. The layering of each carbon composite fabric layer can occur in the manner described above with alternating overlaps and having carbon strands of each layer intersect each other, thereby producing a resilient duct body  36 . 
     To form duct body  36 , the layering of carbon composite fabric layers, such as first carbon composite fabric layer  60  and second carbon composite fabric layer  90 , occurs on male mold  120 , which is shaped in a semi-cylindrical fashion in the desired shape of duct body  36 . To permit first carbon composite fabric layer  60  to lay flat on semi-cylindrical male mold  120 , first carbon composite fabric layer  60  is darted, cut, along first peripheral flange  48  along lines M thereby allowing first carbon composite fabric layer  60  to curl over male mold  120 . Other layers are likewise darted along peripheral flanges. First carbon composite fabric layer  60  is layered onto male mold  120  followed by second carbon composite fabric layer  90  in the direction of arrow G. 
     With reference to  FIG. 13 , there is shown a female mold  130 . Male mold  130  may be used to form second duct body portion  68  in the same manner as first duct body portion  64  as shown in  FIG. 12 . As shown, layers of carbon composite fabric, such as third carbon composite fabric layer  134  and fourth carbon composite fabric layer  138  are disposed into male mold  130 . 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.