Abstract:
Apparatus and methods for fabrication of composite components are disclosed. In one embodiment, an apparatus for fabricating a component from a composite material includes a containment member having an internal volume adapted to receive the composite material, and a lid member. An expandable member is disposed within the internal volume adjacent to the composite material, the expandable member being inflatable within the internal volume and adapted to apply an elevated pressure against the composite material that urges the composite material against at least one of the containment member and the lid member. The containment member, the lid member, and the expandable member are further adapted to withstand at least one of the elevated pressure and an elevated temperature suitable for curing the composite material.

Description:
GOVERNMENT LICENSE RIGHTS  
       [0001]     This invention was made with Government support under contract number MDA972-98-9-0004 awarded by the Defense Advanced Research Projects Agency. The Government has certain rights in this invention. 
     
    
     CROSS REFERENCE TO RELATED APPLICATIONS  
       [0002]     This patent application is related to co-pending, commonly-owned U.S. Patent Application No. (t.b.d.) entitled “Conducting Fiber De-icing Systems and Methods” filed concurrently herewith on Oct. 12, 2005 under Attorney Docket No. BING-1-1166, which application is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0003]     The present disclosure relates to composite component fabrication, and more specifically, to apparatus and methods for fabrication of composite components using a sealable container assembly.  
       BACKGROUND OF THE INVENTION  
       [0004]     High strength, light weight composite components are being utilized in a wide variety of articles of manufacture. This is particularly true in the field of aircraft manufacturing. Typical materials used in the manufacture of composite components include glass or graphite fibers that are embedded in resins, such as phenolic, epoxy, and bismaleimide resins. The fiber and resin materials may be formed into a desired shape using a variety of different manufacturing systems and processes, and may then be cured (e.g. under elevated pressure and temperature conditions) to produce the desired component.  
         [0005]     Prior art systems for fabricating composite components typically use an autoclave for providing the elevated pressure and temperature conditions necessary for curing of the resinous materials used to form the components. For example,  FIG. 1  is an end cross-sectional view of a system  100  for manufacturing composite components in accordance with the prior art. The system  100  includes an autoclave  110 , and a forming tool  120  removably positioned within the autoclave  110 . Typically, an uncured composite material  122  is positioned on the forming tool  120 , and a vacuum bag  124  is positioned over the composite material  122 . One or more seals  126  are positioned between the vacuum bag  124  and the forming tool  120  and a space  128  surrounding the composite material  122  between the vacuum bag  124  and the forming tool  120  is evacuated. After evacuation, an elevated pressure P E  and an elevated temperature T E  are created within the autoclave  110  for a desired period of time. The elevated temperature T E  serves to cause the resin within the uncured composite material  122  to flow, and the elevated pressure P E  compacts the composite material  122  to reduce the porosity of the resulting composite component, and to cause the composite material  122  to closely conform to the shape of the forming tool  120 . The continued application of the elevated temperature T E  then serves to cure and solidify the composite material  122 . After it is cured the elevated pressure P E  and the elevated temperature T E  conditions are removed, and the resulting composite component is removed from the autoclave  110 .  
         [0006]     Although desirable results have been achieved using such prior art systems, there is room for improvement. For example, as the size of composite components increases, the cost of suitable autoclaves for fabricating such components also increases. Autoclaves large enough to create suitable elevated pressure and temperature conditions for the fabrication of large composite components, such as components suitable for the manufacture of modern aircraft, typically cost between approximately $20 M to $40 M or more. Therefore, apparatus and methods for fabricating relatively large composite components that at least partially mitigate the costs associated with such fabrication systems would have utility.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention is directed to apparatus and methods for fabrication of composite components using a sealable container assembly. Embodiments of the present invention may advantageously reduce the tooling costs associated manufacturing composite components, and may improve the efficiency of the composite component manufacturing process, in comparison with prior art manufacturing systems and processes.  
         [0008]     In one embodiment, an apparatus for fabricating a component from a composite material includes a containment member having an internal volume adapted to receive the composite material, and a lid member. An expandable member is disposed within the internal volume adjacent to the composite material, the expandable member being inflatable within the internal volume and adapted to apply an elevated pressure against the composite material that urges the composite material against at least one of the containment member and the lid member. The containment member, the lid member, and the expandable member are further adapted to withstand at least one of the elevated pressure and an elevated temperature suitable for curing the composite material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0010]      FIG. 1  is an end cross-sectional view of a system for manufacturing composite components in accordance with the prior art;  
         [0011]      FIG. 2  is an isometric view of a system for manufacturing composite components in accordance with an embodiment of the invention;  
         [0012]      FIG. 3  is a first cross-sectional view of the system for manufacturing composite components of  FIG. 2  taken along line  3 - 3 ;  
         [0013]      FIG. 4  is a flow chart of a method of fabricating composite components in accordance with yet another embodiment of the invention;  
         [0014]      FIG. 5  is a representative curing cycle for curing a composite component within the system of  FIG. 2  in accordance with another embodiment of the invention;  
         [0015]      FIG. 6  is a series of cross-sectional views of a composite component formed using a system for manufacturing composite components in accordance with another embodiment of the invention;  
         [0016]      FIG. 7  is a cross-sectional view of a system for manufacturing composite components in accordance with yet another embodiment of the invention;  
         [0017]      FIG. 8  is a side cross-sectional view of a composite component formed using the system of  FIG. 7  in accordance with a further embodiment of the invention; and  
         [0018]      FIG. 9  is a side elevational view of an aircraft having one or more composite components formed in accordance with alternate embodiments of the invention.  
     
    
     DETAILED DESCRIPTION  
       [0019]     The present invention relates to apparatus and methods for fabrication of composite components using a sealable container assembly. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 2-9  to provide a thorough understanding of such embodiments. The present invention, however, may have additional embodiments, or may be practiced without one or more of the details described below.  
         [0020]      FIG. 2  is an isometric view of a system  200  for manufacturing composite components in accordance with an embodiment of the invention.  FIG. 3  is a cross-sectional view of the system  200  of  FIG. 2  taken along line  3 - 3 . In this embodiment, the system  200  includes a containment member  202  having an opening  204  leading to an internal volume  205 , and flanges  206  extending outwardly from opposing sides proximate the opening  204 . A lid member  208  is positioned on the containment member  202 , and includes an insertion portion  210  ( FIG. 3 ) that fittingly engages within the opening  204  of the containment member  202 . One or more seals  212  are disposed around the opening  204  between the containment member  202  and the lid member  208 , and a plurality of clamps  214  secure the lid member  208  to the flanges  206  of the containment member  202 .  
         [0021]     As shown in  FIG. 3 , an expandable member (or bladder)  217  is positioned within the internal volume  205  of the containment member  202 . The expandable member  217  may be formed of silicone, or any other suitable material. A composite material  216  is formed at least partially around the expandable member  217 , and is positioned between the expandable member  217  and the containment and lid members  202 ,  208 . In some embodiments, the composite material  216  may be formed using successive layers of a fiber-containing resinous material. For example, in alternate embodiments, the fibers within the composite material  216  may include glass, graphite, or polymeric fibers, and the resinous material may include phenolic, epoxy, or bismaleimide resins. Of course, in other embodiments, any suitable materials may be used.  
         [0022]     As further shown in  FIG. 2 , a first port  218  is disposed through the containment member  202  and is in fluid communication with the internal volume  205  of the containment member  202 . A second port  220  is also disposed through the containment member  202  and is in fluid communication with the expandable member  214 . A vacuum source  222  may be coupled to the first port  218 , and a pressure source  224  may be coupled to the second port  220 . In alternate embodiments, one or both of the first and second ports  218 ,  220  may be disposed through the lid member  208 , depending on the particular configuration of the composite component  216 .  
         [0023]      FIG. 4  is a flow chart of a method  400  of fabricating composite components in accordance with yet another embodiment of the invention. As shown in  FIG. 4 , the method  400  includes forming the uncured composite material at least partially around the expandable member  217  within the containment member  202  at a block  402 . For example, in one particular embodiment, an approximately “U-shaped” portion  401  of uncured composite material is formed on the inner surfaces of the containment member  202 , the expandable member  217  is positioned within the “U-shaped” portion, and a second, relatively flat portion  403  of uncured composite material is then formed over the expandable member  217 . At a block  404 , the lid member  208  is positioned onto the containment member  202  with the insertion portion  210  fittingly engaged into the opening  204  of the containment member  202 . The lid member  208  is secured to the containment member  202  at a block  406 . For example, in one embodiment, the clamps  214  are used to clamp the lid member  208  to the flanges  206  of the containment member  202 .  
         [0024]     At a block  408 , a vacuum is applied to the space between the expandable member  217  and the containment and lid members  202 ,  208 . More specifically, the vacuum source  222  is used to pull vacuum through the first port  218 , evacuating the space around the uncured composite material. At a block  410 , an elevated temperature T E  is applied to the system  200 , such as by installing the system  200  into an oven. At a block  412 , an elevated pressure P E  is applied within the expandable member  217 , such as by providing a pressurized gas or fluid from the pressure source  224  through the second port  220 . The elevated temperature and pressure conditions T E , P E  may be applied (blocks  410 ,  412 ) for one or more periods as desired to suitably cure the composite material  216  within the system  100 . Next, at a block  414 , the elevated temperature and pressure conditions T E , P E  are relieved, and the lid member  208  is removed at a block  416 . The cured composite component  216  is then removed from the system  100  at a block  418 .  
         [0025]     Because in some embodiments, the containment member  102  and the lid member  108  may be heated and cooled with the composite component  216  engaged within the internal volume  205 , it may be desirable that containment and lid members  102 ,  108  have coefficient of thermal expansion characteristics that are very similar to that of the composite component  216 . In one particular embodiment, for example, the containment and lid members  102 ,  108  may be formed of a Nickel-containing steel alloy commonly referred to as Invar steel and known for its relatively low thermal expansion coefficient. Alternately, the containment and lid members  102 ,  108  may be formed of aluminum, steel, titanium, or any other suitable materials. With continued reference to  FIG. 4 , in alternate embodiments of methods in accordance with the present invention, the cured composite component may be removed from the containment member (block  418 ) prior to the relieving of the elevated temperature condition (block  414 ) to prevent damage to the cured composite component by the differential thermal expansion/contraction during cooling of the containment and lid members  102 ,  108 .  
         [0026]     It will be appreciated that embodiments of apparatus and methods in accordance with the present invention may provide significant advantages over the prior art. For example, because fabrication systems in accordance with the present invention utilize an expandable member to provide the desired pressure conditions on the composite component, and because the entire system may be installed into an oven that operates at normal ambient pressures to provide the desired temperature conditions, the need for large autoclaves is eliminated. Also, the costs of pumps, vacuums, and heating systems used in embodiments of the invention may be substantially reduced in comparison with those systems used in prior art manufacturing assemblies. Thus, embodiments of the invention may significantly reduce the tooling costs associated manufacturing composite components in comparison with prior art manufacturing systems. In some embodiments, for example, manufacturing systems in accordance with the invention may cost approximately two orders of magnitude less than prior art systems requiring an autoclave.  
         [0027]     Embodiments of the invention may also improve the efficiency of the manufacturing process. For example, because the volumes that are pressurized within the expandable member may be substantially smaller than the volumes of prior art autoclaves, the portions of the manufacturing process that involve subjecting the composite components to an elevated pressure condition may be performed more quickly and efficiently in comparison with the prior art manufacturing processes.  
         [0028]     It will be appreciated that the values and durations of the elevated temperature T E  and the elevated pressure P E  conditions may vary depending on the particular design features of the composite component being formed, including the resinous materials and fiber materials contained in the uncured composite material. For example,  FIG. 5  is a representative curing cycle  500  for curing a composite component within the system of  FIG. 2  in accordance with another embodiment of the invention. In this embodiment, the curing cycle  500  includes a first portion  502  of approximately 1 to 3 hours in duration wherein vacuum is applied to the volume containing the uncured composite material, prior to the elevation of the temperature and pressure within the system  100 . During a second portion  504  of the curing cycle  500 , the vacuum continues to be applied while the temperature of the system  100  is gradually elevated from a non-elevated temperature level to a first temperature level (e.g. approximately 150° F.) and maintained at that level for a first period of time.  
         [0029]     During a third portion  506 , with the vacuum applied and the temperature maintained at the first temperature level, the pressure within the expandable member  217  begins to be increased from a non-elevated pressure level. At some point, typically during the second or third portions  504 ,  506  of the curing cycle  500 , a resinous portion of the uncured composite material undergoes a first phase change  505  from a first solid state to an oil (or liquid or semi-liquid) state. As the pressure continues to be increased within the expandable member  217 , the temperature of the system  100  begins increasing again during a fourth portion  508  of the curing cycle  500 . During a fifth portion  510  of the curing cycle  500 , the pressure reaches a first elevated pressure level (e.g. approximately 100 psi) and is held constant at that level while the temperature continues to increase to a second elevated temperature level (e.g. between approximately 250° F. to 350° F.).  
         [0030]     During a sixth portion  512  of the curing cycle  500 , the pressure is maintained at the first elevated pressure level and the temperature is maintained at the second elevated temperature for a specified curing period (e.g. approximately 2 to 3 hours). At some point, typically during the sixth portion  512 , the resinous portion of the composite material undergoes a second phase change  511  from the oil (or liquid or semi-liquid) state to a second solid state. Also, at a vacuum termination point  514  during the sixth portion  512  (e.g. approximately half way through the specified curing period) the vacuum is removed. During a seventh portion  516  of the curing cycle  500 , the pressure within the expandable member  217  is maintained at the first elevated pressure level while the temperature of the system  100  is cooled to the non-elevated temperature level. Finally, with the temperature reduced to the non-elevated temperature level, the pressure is reduced to the non-elevated pressure level during an eighth portion  518  of the curing cycle  500 .  
         [0031]     Referring again to  FIG. 3 , it should be appreciated that the cross-sectional shape of the composite component  216  fabricated using embodiments of the present invention is not limited to the particular embodiment shown in  FIG. 3 . Composite components having a variety of different cross-sectional shapes may be formed using embodiments of the present invention. Also, the cross-sectional shape of the composite components may remain constant or may vary along the length of the containment member  202 . For example,  FIG. 6  is a series of cross-sectional views of a composite component  616  formed using a system  600  for manufacturing composite components in accordance with another embodiment of the invention. As shown in  FIG. 6 , the cross-sectional shape of the composite component  616  varies from an approximately circular shape at a first station A, to an approximately square shape at a third station C, and to an approximately rectangular shape at a fifth station E. Of course, in alternate embodiments, composite components having other cross-sectional shapes may be fabricated.  
         [0032]      FIG. 7  is a cross-sectional view of a system  700  for manufacturing composite components in accordance with yet another embodiment of the invention. In this embodiment, the system  700  includes an approximately “U”-shaped containment member  702  having an opening  704  and flanges  706  extending outwardly from opposing sides proximate the opening  704 . A lid member  708  is hingeably coupled to the containment member  702  by a hinge  703 , and includes an insertion portion  710  that fittingly engages within the opening  704  of the containment member  702 . Seals  712  are disposed around the opening  704  between the containment member  702  and the lid member  708 . A locking device  714  secures the lid member  708  in a closed position over the opening  704  of the containment member  702 . In this embodiment, the locking device  714  is coupled to a supply line  715  that provides a hydraulic (or pneumatic) flow to drive the locking device  714 , thereby locking the lid member  708  in the closed position. The locking device  714  may be a separate component from the containment and lid members  702 ,  708 , or alternately, may be integrally-formed with at least one of the containment and lid members  702 ,  708 . In further embodiments, the locking device  714  may be any suitable type of device that secures the lid member  708  in the closed position, including an electrical device, a hydraulic device, a pneumatic device, a magnetic device, a mechanical device, or any other desired type of locking mechanism.  
         [0033]     As shown in  FIG. 7 , an expandable member (or bladder)  717  is positioned within the containment member  702 , and a composite component  716  is formed partially around the expandable member  717 , and is positioned between the expandable member  717  and the containment member  702 . In the manner described above with reference to  FIG. 2 , a vacuum source may be coupled to the space occupied by the composite component  716 , and a pressure source may be coupled to the expandable member  717 . In this embodiment, the composite component  716  includes a first composite layer  719 , a second composite layer  721 , and relatively thicker third composite portions  725  are coupled to the first and second composite layers  719 ,  721 . A vacuum (or first) port  718  is disposed through the lid member  708  and is in fluid communication with the space&#39;surrounding the composite component  716 , while a pressure (or second) port  720  is disposed through the lid member  708  and is in fluid communication with the expandable member  717 .  
         [0034]     In some embodiments, a conductive-fiber layer  723  is formed between the first and second composite layers  719 ,  721 , as shown in  FIG. 7 . More specifically,  FIG. 8  is a side cross-sectional view of an airfoil section  800  that includes the composite component  716  of  FIG. 7  in accordance with another alternate embodiment of the invention. In this embodiment, the airfoil section  800  includes the composite component  716  coupled to a central load-bearing portion  760 , and a trailing edge portion  762  is coupled to the load-bearing portion  760 . In one embodiment, the central load-bearing portion  760  may be a composite spar member formed using apparatus and methods in accordance with the invention, including, for example, the composite component  616  described above and shown in  FIG. 6 .  
         [0035]     The airfoil section  800  further includes a deicing system  750 , as disclosed more fully in co-pending, commonly-owned U.S. patent application Ser. No. ______ filed concurrently herewith under Attorney Docket No. BING-1-1166, which application is incorporated herein by reference. In this embodiment, the deicing system  750  includes a first conductive lead  752  coupled between the conductive-fiber layer  723  of the composite component  716 , and a second conductive lead  754  coupled to a power source (not shown). As described more fully in the above-referenced U.S. patent application Ser. No. ______ (filed concurrently herewith under Attorney Docket No. BING-1-1166), the deicing system  750  may be operated to remove a layer of ice  764  that may form on a leading edge portion of the composite component  716 . In one embodiment, the airfoil section  800  is a cross-sectional view of a rotor blade of a rotary aircraft. Alternately, the airfoil section  800  may be a portion of a wing, a control surface, or any other aerodynamically-shaped structure, including a portion of an aircraft or any other suitably-shaped structure.  
         [0036]     It will be appreciated that a wide variety of components and products may be manufactured using embodiments of the present invention, and that the invention is not limited to the specific embodiments described above and shown in the accompanying figures. For example,  FIG. 9  is a side elevational view of an aircraft  900  having one or more composite components  902  formed in accordance with another embodiment of the invention. The aircraft  900  includes a fuselage  905  including wing assemblies  906 , a tail assembly  908 , and a landing assembly  910 . The aircraft  900  further includes one or more propulsion units  904 , a control system  912  (not visible), and a host of other systems and subsystems that enable proper operation of the aircraft  900 . It will be appreciated that apparatus and methods in accordance with the present invention may be utilized in the fabrication of any number of composite components  902  of the aircraft  900 , including, for example, the various components and sub-components of the tail assembly  908 , the wing assemblies  906 , the fuselage  905 , and any other suitable portion of the aircraft  900 . In general, except for the composite components  902  formed in accordance with the present invention, the various components and subsystems of the aircraft  900  may be of known construction and, for the sake of brevity, will not be described in detail herein.  
         [0037]     Although the aircraft  900  shown in  FIG. 9  is generally representative of a commercial passenger aircraft, including, for example, the 737, 747, 757, 767, 777, and 7E7 models commercially-available from The Boeing Company of Chicago, Ill. the inventive apparatus and methods disclosed herein may also be employed in the assembly of virtually any other types of aircraft. More specifically, the teachings of the present invention may be applied to the manufacture and assembly of other passenger aircraft, fighter aircraft, cargo aircraft, rotary aircraft, and any other types of manned or unmanned aircraft, including those described, for example, in The Illustrated Encyclopedia of Military Aircraft by Enzo Angelucci, published by Book Sales Publishers, September 2001, and in Jane&#39;s All the World&#39;s Aircraft published by Jane&#39;s Information Group of Coulsdon, Surrey, United Kingdom, which texts are incorporated herein by reference.  
         [0038]     It may also be appreciated that alternate embodiments of apparatus and methods in accordance with the present invention may be utilized in the manufacture of a wide variety composite components for, for example, boats, automobiles, canoes, surfboards, recreational vehicles, or any other suitable vehicle or assembly. Embodiments of apparatus and methods in accordance with the present invention may be employed in the fabrication of a multitude of composite components, particularly components have a non-planar or arcuate outer surface. In some particular embodiments, for example, composite components fabricated in accordance with the teachings of the present disclosure may have a “C-channel” cross-sectional shape, which is a particularly common geometric shape for a variety of composite components, including but not limited to those used on aircraft (e.g. ribs or other structural members in empennage, wing, and flooring members of the aircraft).  
         [0039]     As described above, embodiments of apparatus and methods in accordance with the present invention may substantially reduce the costs associated with manufacturing structures that include composite components. Because the tooling costs may be reduced, and the manufacturing process efficiencies may be improved, the costs associated with manufacturing structures that include composite components may be substantially improved in comparison with prior art systems and methods.  
         [0040]     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.