Abstract:
A mold tool for forming a reinforced matrix composite part for a gas turbine engine, comprising a body. The body comprises a body surface capable of receiving a first portion of a composite preform. A first endplate and second endplate are attached to the body and include a substantially planar surface disposed perpendicular to the body surface. A first and second set of plates are attached to the first and second endplate adjacent to the body surface and have a geometries that includes a first and second cavity bounded by the first and second plate and first and second endplate. The first and second cavities have a volume sufficient to receive a second portion of a composite preform. The second cavity is in fluid communication with the first cavity, which is in fluid communication with a vacuum source.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The Application is related to Application No. 11/021,804, filed contemporaneously with the Application on Dec. 22, 2004 entitled “A METHOD FOR FABRICATING REINFORCED COMPOSITE MATERIALS” assigned to the assignee of the present invention and which is incorporated herein by reference in its entirety, and to Application No. 11/021,805, filed contemporaneously with the Application on Dec. 22, 2004 entitled “A REINFORCED MATRIX COMPOSITE CONTAINMENT DUCT” assigned to the assignee of the present invention and which is incorporated herein by reference in its entirety. 
   FIELD OF THE INVENTION 
   This invention relates to an apparatus for making composite materials. In particular, the present invention involves apparatus for making reinforced matrix composite materials. 
   BACKGROUND OF THE INVENTION 
   Aircraft engine design continually requires components of aircraft engines to have lighter weight materials to increase the aircraft&#39;s fuel efficiency and thrust capabilities. In the past, aircraft components have been made with steel. However, steel is relatively heavy and has been replaced with lighter weight high strength materials, such as aluminum or titanium. A further development in producing lightweight parts has resulted in the advent of non-metallic materials, such as composites comprising graphite fibers embedded within a polyimide resin. Composite materials are materials that include embedded fibers inside of a matrix material. The fibers provide reinforcement for the matrix material. The fiber structure prior to being embedded in the matrix is generally referred to as a preform. Graphite fibers embedded within a polyimide resin have drawbacks, including difficulty molding the material into parts, high porosity, microcracking, delamination, and expensive equipment and processes. 
   A composite fan duct for use in a gas turbine engine is required to have high strength flanges and composite material that is substantially devoid of wrinkles and waves. 
   Graphite epoxy composite fan ducts have been manufactured using a cross-over tool, disclosed in U.S. Pat. No. 5,145,621 to Pratt (the &#39;621 Patent), which is herein incorporated by reference in its entirety. In the &#39;621 Patent woven graphite fiber preform is mounted on a large spool to form the graphite epoxy composite fan duct. The fibers are situated to provide a flange at either end of the spool. The shape of the spool substantially defines the final shape of the finished composite. The cross-over tool pulls the fibers of the graphite on a spool to provide tension. The tool pulls the fiber through the use of a complex spider tool that encircles the flange portion of the fibers and provides pressure when in combination with three independent vacuum envelopes. The drawbacks of the cross-over tool and method disclosed in the &#39;621 Patent includes a complicated process, and an expensive tool that is difficult to use. 
   Graphite epoxy composite fan cases have also been manufactured using a mold system utilizing a elastomeric material to assist in providing a force on plies of reinforcing material during manufacture, disclosed in U.S. Pat. No. 5,597,435 to Desautels et al. (the &#39;435 Patent), which is herein incorporated by reference in its entirety. To produce a composite matrix, uncured fiber-reinforced prepreg-type plies (i.e., plies) are mounted onto a mold. Prepreg plies are plies that are impregnated with uncured matrix material before being mounted on the mold. A forcing member and restraining member are placed onto the plies to hold the plies in place. The forcing member is placed between the restraining member and the plies on the mold. The mold, plies, restraining member and forcing member are placed into a furnace and heated. As the assembly is heated, the forcing member uniformly expands and a uniform pressure is applied to the plies. The result is that the plies are compacted as the temperature is raised. The &#39;435 Patent process has the drawback that it only debulks the material and does not pull taut the fabric to provide fiber orientation that provides the finished composite with high strength and uniformity. 
   Current methods for impregnating matrix material into reinforcing fiber preforms involves placing a matrix material film layer or layers on or within layers of the reinforcing fiber preforms to cover all or the majority of the preform. The entire preform is coated so that during a heated resin infusion phase, the matrix material melts and flows through the thickness of the preform to impregnate it. The impregnation is done using single layer or multiple layers of resin film. The resin film is applied onto the entire surface of the reinforcing fiber preform. Alternatively, the matrix material may be interleaved between layers of the preform to cover all the layers of reinforcing fiber preform. Full coverage of the resin layers on the preform entrap air, volatile material from the matrix material or other gases that may form voids (i.e. void space), which can form undesirable porosity in the body of the cured part. The porosity is particularly undesirable in more complex parts at or near part features. Features include portions of composite material that extend from planar sections of the part. Examples of features include stiffener sections or inserts in gas turbine engine parts. Porosity resulting from void space in the cured reinforced matrix composite may reduce the parts&#39; mechanical properties and may create unacceptable surface features such as pitting. The complete coverage of the reinforcing fiber preform has the additional drawback that the method is difficult to practice and requires a significant amount of time to apply, because the resin must be applied over the entire surface area of the preform. 
   The present invention solves the problems of the prior art by providing a method and tool that forms the fiber reinforced matrix composite without the disadvantages of the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention is a mold tool for forming a reinforced matrix composite part for a gas turbine engine, comprising a body. The body comprises a first end, a second end and a body surface capable of receiving a first portion of a composite preform. A first endplate is releasably secured to the first end of the body and has a substantially planar surface disposed perpendicularly to the body surface. A second endplate is attached to the second end of the body and has a substantially planar surface perpendicular to the body surface. A first set of plates is attached to a first surface of the first endplate. The first set of plates comprises at least one first plate disposed adjacent to the body surface. A second set of plates is attached to a first surface of the second endplate. The second set of plates comprises at least one second plate adjacent to the body surface. The first plate and second plate are releasably secured and comprise a substantially planar first plate surface and a substantially planar second plate surface. The first plate and first endplate have a geometry that includes a first cavity bounded by the first plate and first endplate. The second plate and second endplate have a geometry that includes a second cavity bounded by the first plate and first endplate. The first and second cavities have a volume sufficient to receive a second portion of a composite preform. The second cavity is fluidly connected to the first cavity. The first cavity is in fluid communication with a vacuum source. 
   The method and tool of the present invention forms a lightweight reinforced matrix composite material suitable for use as composite containment ducts, such as fan casings, wherein the composite materials have high strength and uniformity. 
   The method of the present invention is particularly suitable for fabrication of turbine airfoil components for gas turbine engines. In particular, the method of the present invention is suitable for the fabrication of composite containment ducts, such as fan casings. An advantage of the present invention is that the present invention allows the fabrication of composite containment ducts capable of containing fan blades that break loose from the gas turbine engine during operation. 
   The method and tool of the present invention is particularly suitable for fabrication of large composite parts, including cylindrical parts having a diameter of greater than about 5 feet, including parts having a diameter of about 10 feet. An advantage of the present invention is that the tool and method are capable of fabricating large parts, such as large composite fan casings, while maintaining the containment properties, the lighter weight, the high strength and the substantial uniformity throughout the part. 
   The method and tool of the present invention provides a method for manufacturing fiber reinforced matrix composites having the shape of the finished product, requiring little or no trimming prior to installation. An advantage of the present invention is that the tool and method produce parts that require little or no additional steps prior to installation and use. The reduction or elimination of addition steps decrease cost and time for fabrication. 
   The method and tool of the present invention provides a method for manufacturing fiber reinforced matrix composites that has a high uniformity of composition and less defects, such as porosity and wrinkling. Uniform composition and less defects allows for less scrapped and/or repaired parts. Less scrapped and/or repaired parts allows for fabrication of composite parts, including large composite parts, with less cost. 
   The method and tool of the present invention provides a method for manufacturing fiber reinforced matrix composites using simple, inexpensive equipment. Additionally, part removal from the tool requires little or no additional disassembly of the tool. An advantage of the present invention is that the equipment and labor costs required to fabricate fiber reinforced composite containment ducts are decreased because the equipment is less expensive and does not require extensive assembly or disassembly during fabrication of the part. 
   The method and tool of the present invention provides a method for manufacturing fiber reinforced matrix composites wherein the process only requires a single vacuum envelope. An advantage of the present invention is that the tool and method is that a single vacuum envelope can provide the necessary containment and forces required to fabricate fiber reinforced composite containment ducts without the use of multiple vacuum envelopes. The use of the single envelope provides a more substantially uniform application of vacuum and requires less assembly and disassembly than multiple envelopes. 
   Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a tool according to the present invention. 
       FIG. 2  is a side view of a tool according to the present invention 
       FIGS. 3 and 4  are cross sectional views alternate embodiments of a first portion of a tool according to the present invention. 
       FIG. 5  is a cross sectional view of a second portion of a tool according to the present invention. 
       FIGS. 6 to 9  illustrate stages of the composite forming method using a tool according to the present invention. 
       FIG. 10  is a schematic view of a matrix material distribution system according to the present invention. 
       FIG. 11  is a perspective view of a composite containment duct according to the present invention 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a composite duct-forming tool  100  according to the present invention. The tool  100  includes a substantially cylindrical body  105 . A first endplate  101  and a second endplate  103  are positioned adjacent to the opposed planar ends of the body  105 . The body  105  and first and second endplates  101  and  103  are fabricated from a material having a greater thermal coefficient of expansion than the workpiece held by the tool  100 . Material for the body  105  and first and second endplates  101  and  103  include, but are not limited to, metals or alloys. Suitable materials for the body  105  include aluminum and steel. The first endplate  101  is fastened to the body  105  with stress relief fasteners  111 . The second endplate  103  adjacent to the body  105  is attached to the body  105 . The body  105  has a substantially cylindrical geometry. The substantially cylindrical body  105  preferably tapers from a smaller diameter adjacent to the first endplate  101  to a larger diameter at the second endplate  103 . Although  FIG. 1  illustrates a cylindrical body  105 , the body is not limited to a cylindrical shape. Alternate geometry for the body include, but are not limited to, rectangular, oval, and triangular geometries. In an alternate embodiment, the body  105  has substantially cylindrical geometry with a smaller diameter at the midpoint between the first and second endplates  101  and  103  and a larger diameter at each of the ends of the body  105 . The body  105  may be fabricated in multiple detachable pieces to facilitate removal of finished reinforced matrix composite parts. 
     FIG. 1  shows a first set of flange shoes  119  positioned adjacent to the first endplate  101  circumferentially around the body  105  on the surface of the first endplate  101  nearest to the second endplate  103 . A second set of flange shoes  107  are positioned adjacent to the second endplate  103  circumferentially around the body  105  on the surface of the second endplate  103  nearest to the first endplate  101 . The flange shoes  107  of each of the first and second set of flange shoes  119  and  121  contact each other at a flange shoe junction  108 . Flange shoes  107  are plates fabricated from a material having a greater thermal coefficient of expansion than the workpiece held by the tool. Material for the flange shoes  107  include, but are not limited to, metals or alloys. Suitable materials for the flange shoes  107  include aluminum and steel. The flange shoes  107  are fastened to the first and second endplates  101  and  103  by stress relief fasteners  111 . In addition to fastening the first and second endplates  101  and  103 , the stress relief fasteners  111  also fasten the first endplate  101  to the body  105 . As shown in  FIG. 1 , the stress relief fasteners  111  fastening the flange shoes  107  extend through the first and second endplates  101  and  103  and through the flange shoes  107 . The stress relief fasteners  111  fastening the first endplate  101  to the body  105  extend through the first endplate  101  and into the body  105 . The stress relief fasteners  111 , according to the present invention, are any fasteners capable of positioning the first endplate  101  and the flange shoes  107  of the first and second flange shoe sets  119  and  121  during the loading of the workpiece, but yield to pressure due to thermal expansion or other forces. Stress relief comes when the fasteners holding the flange shoes  107  yield under appropriate radial stress and the fasteners holding the end flange plate yields to relieve the axial stress. Suitable materials for stress relief fasteners  111  include, but are not limited to, nylon. One or more reservoirs  109  are located on the surface of the first endplate  101 . The reservoirs  109  fluidly communicate with a vacuum source via vacuum lines  115 . The reservoirs  109  are shown as separate components, but they may be manufactured integral to the first endplate  101 . 
     FIG. 2  illustrates one embodiment of the tool  100  oriented with the first and second endplates  101  and  103  oriented horizontally on the drawing. The orientation shown in  FIG. 2  illustrates the embodiment of the invention wherein the tool  100  is loaded into an autoclave with the first endplate  101  oriented substantially horizontally above the second endplate  103  and with the center axis of the body  105  being oriented substantially in the vertical direction. Although this embodiment refers to an autoclave, any chamber having the ability to heat and provide pressure to the tool is suitable for use with the present invention.  FIG. 2  shows the flange shoes  107  arranged circumferentially around the body  105 . A first set of flange shoes  119  are fastened to the first endplate  101  on the surface nearest to the second endplate  103 . A second set of flange shoes  121  are fastened to the second endplate  103  on the surface nearest to the first endplate  101 . 
   A channel  201  is machined in flange shoe junction  108  between individual flange shoes  107  along the surface adjacent to the second endplate  103  to form a fluid connection from the inner surface  205  adjacent to the body  105  to the outer periphery of the flange shoe junctions  108 . At the outer periphery of the flange shoe junction  108 , a siphon tube  113  is attached and placed in fluid connection with the channel  201  adjacent to the second endplate  103 . The siphon tube  113  is in fluid connection with a reservoir  109  adjacent to the first endplate  101 . Each reservoir  109  is a hollow chamber that is capable of containing matrix material under vacuum. Each reservoir  109  is in fluid connection with a cavity  203  defined by the flange shoes  107 , the lower surface of the first endplate  101  and the inner surface  205  of body  105 . The cavity  203  is of sufficient volume to permit insertion of a portion of a workpiece (shown as fiber fabric  301  in  FIGS. 3-5 ). The workpiece is preferably a portion of a reinforcing fiber fabric. The reservoirs  109  are also in fluid connection with a vacuum source  117  through vacuum lines  115 . The vacuum source  117  provides vacuum to the reservoirs  109  to draw vacuum on the material in reservoirs  109 . 
     FIG. 3  shows a cross sectional view representing view  3 - 3  in  FIG. 2 . The cross section shown in  FIG. 3  provides an enlarged view of a portion of the first endplate  101  wherein the first endplate  101  oriented vertically in the drawing. The first endplate  101  and body  105  are loaded with a fiber fabric preform  301 . The fiber fabric preform  301  includes a flange portion  305  that extends from the body  105  along the first endplate  101 . Flange shoes  107  are fastened to the first endplate  101  with a stress relief fastener  111 . Likewise, the first endplate  101  is fastened to the body  105  with a stress relief fastener  111 . 
     FIG. 3  shows the fiber fabric preform  301  positioned along the body  105  and angled at an angle of about 90° to form a flange shape in the cavity  203  defined by the flange shoes  107 , the first endplate  101  and the inner surface  205  of the body  105 . Cavity  203  defined by flange shoes  107 , first endplate  101  and body  105  is in fluid communication with the reservoirs  109  through a matrix material distribution channel  303 . The reservoirs  109  are in fluid communication with at least one vacuum line  115  and at least one siphon tube  113 . 
     FIG. 4  shows a cross sectional view representing view  3 - 3  in  FIG. 2 . The sectional view shows a portion of the composite duct-forming tool  100  having the same arrangement of body  105 , flange shoes  107 , fiber fabric preform  301 , and first endplate  101  as  FIG. 3 . However, the embodiment illustrated in  FIG. 4  has the siphon tube  113  inserted into a siphon tube recess  401  in the flange shoes  107 . The siphon tube  113  is in fluid communication with a matrix material distribution channel  403 . The matrix material distribution channel  403  extends from the siphon tube  113  to the cavity  203  defined by the flange shoes  107 , the first endplate  101  and the inner surface  205  of the body  105 . Cavity  203  defined by flange shoes  107 , first endplate  101  and inner surface  205  of body  105  is in fluid communication with reservoirs  109  through reservoir channel  405 . The reservoirs  109  are in fluid communication with a vacuum source  117  via vacuum line  115 . 
     FIG. 5  shows a cross sectional view representing view  5 - 5  in  FIG. 2 . The cross section shown in  FIG. 5  provides an enlarged view of a portion of the second endplate  103  oriented vertically in the drawing, loaded with a workpiece of fiber fabric preform  301 .  FIG. 5  also shows flange shoes  107  fastened to the second endplate  103  with a stress relief fastener  111 . The second endplate  103  is fastened to the body  105  by a second endplate fastener  505 . The second endplate fastener  505  is a fastener that does not yield under pressure, like the stress relief fastener  111 . The second endplate fastener  505  may be any fastener that does not yield under the stresses generated by the tool  100 . In an alternate embodiment, the second endplate  103  and the body  105  may be permanently attached or a machined single piece. In this embodiment, the second endplate  103  is integral to the body  105  and may be machined or cast as a single piece having the body  105  extend from the second endplate  103 . Alternatively, the body  105  and the second endplate  103  may be welded together. 
   The embodiment illustrated in  FIG. 5  has the siphon tube  113  inserted into a siphon tube recess  501  in flange shoes  107 . The siphon tube  113  is in fluid communication with a matrix material discharge channel  503 . The matrix material distribution channel  503  extends from the siphon tube to cavity  203  defined by flange shoes  107 , second endplate  103  and inner surface  205  of body  105 . 
     FIGS. 6-9  illustrate the composite duct-forming tool  100  according to the present invention loaded with the workpiece  301  and matrix material  601  to be formed into a composite.  FIGS. 6-9  illustrate various stages in the matrix material infiltration and curing process.  FIG. 6  illustrates the tool  100  before loading into the autoclave (not shown).  FIG. 7 and 8  illustrate the tool  100  during heating.  FIG. 9  illustrates the tool  100  under autoclave pressure.  FIGS. 6-9  show a cross section taken radially from the center axis of the cylinder portion of the body  105  of the tool  100  shown in  FIGS. 1 and 2 .  FIGS. 6-9  illustrate the tool  100  having a body  105 , a first endplate  101 , a second endplate  103 , and flange shoes  107 , arranged as shown in  FIGS. 1 and 2 . For illustration purposes,  FIGS. 6-9  do not show the stress relief fasteners  111  and  505 , the siphon tubes  113 , the reservoirs  109 , the vacuum lines  115 , the matrix material discharge channels  503  or the matrix material distribution and vacuum channels  303 ,  403  and  405 . It is noted that each of the above element are present in the tool  100  loaded into the autoclave, as well as a vacuum membrane or bag  605  surrounding the tool  100 . 
     FIG. 6  shows the tool  100  before loading into the autoclave. The tool  100  is first loaded with a fiber fabric preform  301 . On the fiber fabric preform  301 , a layer of matrix material  601  is coated on the surface. The matrix material  601  is preferably bulk resin weighed out into discrete portions. Bulk resin is uncured resin that has not been processed into a final form (e.g., sheets or plies) and is capable of being separated into discrete portions. At room temperature, the bulk resin is preferably a pliable solid. The bulk resin is separated into substantially rectangular portions, which are placed on the surface of the fiber fabric preform  301 . It is noted that any shape portion that provides resin to the surface of the fiber fabric preform  301  is suitable for use with the invention. After placing the portions onto the surface of the fiber fabric preform  301 , the rectangular portions are conformed to the surface shape. The rectangular portions are preferably pliable at room temperature. The rectangular sections of bulk resin may optionally be pre-heated to increase the pliability of the resin to assist in conforming the rectangular portions to the surface shape. A suitable resin may include, but is not limited to, epoxy or polyamide resin. The matrix material  601  is coated onto the surface of the fiber fabric preform  301  so that a greater amount of matrix material  601  (i.e., a greater amount of matrix material per unit of surface area) is coated onto the center  607  of the fiber fabric preform  301  (i.e., the midpoint between the first and second endplates  101  and  103 ) and a lesser amount (i.e., a lesser amount of matrix material per unit of surface area) is coated on the edges  609  of the fiber fabric preform  301  (i.e., the area adjacent the first and second endplates  101  and  103 ). Although this embodiment refers to bulk resin, any matrix material capable of forming a reinforced matrix composite may be used with the present invention. 
   After the tool  100  is loaded with the matrix material  601 , an elastomer caul  603  is placed onto the matrix material  601  coated fiber fabric preform  301 . The caul  603  is formed from a material that is a barrier to the passage of matrix material  601 . Suitable material for the caul  603 , includes, but is not limited to, silicone. Any material which will not bond with the matrix material and which can withstand the heat and pressure and is flexible may be used as the material for the caul  603 . The caul  603  is positioned so that the matrix material  601  may only travel along the fiber fabric preform  301 , into the area adjacent to the first and second endplates  101  and  103  where the matrix material  601  may enter the matrix material discharge channels  503  or the matrix material distribution and vacuum channels  303 ,  403  and  405 , the siphon tubes  113  or the reservoirs  109 , as illustrated in  FIGS. 1-5 . Once the tool  100  is loaded, the loaded tool  100  is placed inside a vacuum bag  605 . Tool  100  of the present invention provides a method for manufacturing fiber reinforced matrix composites wherein the process only requires a single vacuum bag  605 . 
     FIG. 7  illustrates the tool  100  and the movement of matrix material  601  when exposed to heat, during heating and holdings steps of a curing cycle. The matrix material  601  upon heating becomes liquid or fluid and begins to infiltrate the fiber fabric preform  301  to create a partially impregnated fiber fabric preform  701 . As the matrix material  601  becomes liquid or fluid, the material flows from the center  607  of the fiber fabric preform  301  (i.e., the midpoint between the first and second endplates  101  and  103 ) in the direction of arrows  703 . As the matrix material  601 , now a liquid resin, moves from the center  607  of the fiber fabric preform  301  to the outer edges  609 , air, volatile gases devolve from the matrix material  601 , and other materials, such as impurities or gases trapped in the fiber fabric preform  301 , that potentially could cause void space are pushed by the flow of bulk matrix material  601  toward the outer edges  609  of the fabric adjacent to the first and second endplates  101  and  103 . Excess matrix material  601 , air, volatile gases from the bulk matrix material  601  and other materials that potentially could cause void space flow into the siphon tube  113  and are drawn into either the reservoirs  109  or into cavity  203  defined by flange shoes  107 , second endplate  101  and inner surface  205  of the body  105  through the matrix material distribution channel  403 , as illustrated in  FIGS. 1-5 . 
     FIG. 8  illustrates the tool  100  and partially impregnated fiber fabric preform  701  when exposed to heat, during the heat up and hold steps of the curing cycle. The first endplate  101 , second endplate  103 , the body  105 , and the flange shoes  107  are fabricated from a material that has a greater thermal coefficient of expansion than the partially impregnated fiber fabric preform  701 . As a result, during heat-up, as shown in  FIG. 8 , each of the first endplate  101 , second endplate  103 , the body  105 , and the flange shoes  107  expand in all directions as shown by arrows  801 . The partially impregnated fiber fabric preform  701  expands very little in comparison to the body  105 . The difference in the amount of thermal expansion of the tool  100  against the partially impregnated fiber fabric preform  701  results in a tensional force shown by arrows  803  that acts to pull the partially impregnated fiber fabric preform  701  taut. Fiber fabric preforms  701  that are pulled taut before matrix material curing provide uniform materials with high strength substantially free of waves and wrinkles. 
     FIG. 9  illustrates the tool  100  when exposed to pressure, during the heat up and hold steps of the curing cycle. Flange shoes  107  are fabricated with a large surface area  903  in the plane parallel to the first and second endplates  101  and  103 . As the pressure in the autoclave is increased during the curing cycle, the force of the pressure of the autoclave atmosphere shown by arrows  901  on the vacuum bag  605  and flange shoes  107  surface is multiplied by the surface area  903  of flange shoes  107 . Flange shoes  107  surface is greater in surface area  903  than the fiber fabric preform  701  forming the flange-like shape so as to add substantial position holding force from autoclave pressure. The pressure holds the fiber fabric preform  701  in place while the body  105  expands and pulls the fiber fabric preform  301  taut. 
     FIG. 10  illustrates a matrix material distribution system  1000  according to the present invention for fabricating a fiber-reinforced matrix composite (not shown). A fiber fabric preform  1005  is loaded with matrix material  1001 , wherein a greater amount of matrix material  1001  is positioned in the center  1019  of the fiber fabric preform  1005  than at the edges  1021 . 
   In order to form the fiber reinforced matrix composite (not shown) according to the present invention, the fiber fabric preform  1005  coated with the matrix material  1001  is mounted vertically and the system  1000  is exposed to vacuum through vacuum line  1007  and sufficient heat to make the matrix material  1001  viscous. The movement of the matrix material  1001  within the fiber fabric preform  1005  is illustrated as arrows  1015  and  1016  in  FIG. 10 . Initially, the viscous matrix material  1001  travels in two directions shown by arrows  1015  and  1016 . A larger portion of the matrix material  1001  (shown as arrow  1015 ) travels in the direction of gravity (arrow  1009 ) and a smaller portion (shown as arrow  1016 ) is drawn in a direction toward the vacuum line  1007 . The vacuum line  1007  is fluidly connected to vacuum source  1023 . 
   The matrix material  1001  traveling in the direction of gravity (shown by arrow  1009 ) gathers in a collection well  1011 . The collection well  1011  fluidly communicates with a distribution well  1013  through a siphon tube  1003 . The distribution well  1013  is a chamber adjacent to the vacuum line  1007  and the upper edge of the fiber fabric preform  1005 . Matrix material  1001  is drawn from the collection well  1011  to the distribution well  1013  by suction from the vacuum line  1007 , as shown by arrows  1017 . The system is self-regulating and continues until the matrix material  1001  throughout the fiber fabric preform  1005  material is substantially uniformly distributed throughout the fiber fabric preform  1005 . The system is self-regulating in that siphon tube  1003  continues to draw matrix material  1001  from the collection well  1011  to the distribution well  1013  as long as the pressure differential across the matrix material  1001  impregnated fiber fabric preform  1005  is greater than the pressure differential across the siphon tube  1003 . Once the pressure across the siphon tube  1003  is equal to the pressure across the impregnated fiber fabric preform  1005 , the matrix material  1001  is no longer drawn from the collection well  1011  to the distribution well  1013 . The resultant matrix impregnated fiber fabric preform  1005  contains substantially uniform distribution of matrix material  1001 . The impregnated fiber fabric preform  1005  is further heated to complete the curing cycle and to produce a fiber reinforced matrix composite. 
     FIG. 11  illustrates a composite containment duct  1100  according to the present invention. Composite containment duct  1100  is the product made by tool  100  (see FIGS.  1 - 2 ). Composite containment duct  1100  is a single piece having a duct body  1103  and integral high strength flanges  1101 . Additionally, holes  1105  are machined into the flange  1101  to allow fasteners to attach the composite containment duct  1100  to other bodies. Flanges  1101  provide a surface to which composite containment duct  1100  may be attached to another body. Another body may include a second composite containment duct  1100 . The attachment of two containment ducts has the advantage of additional length and the ability to create ducts that have converging and diverging duct areas. In this embodiment, a composite containment duct  1100  has a tapered duct body  1103 , wherein the diameter of the duct at one flange is larger than the diameter of the duct at the other flange. In some containment duct applications, a containment duct having both a converging portion and a diverging portion is desirable. To form a containment duct  1100  that converges in one portion and diverges in another portion, a tapered containment duct  1100  is attached by the flanges at the end of the containment duct having the smaller duct diameter to a second substantially identical tapered containment duct  1100 . Attachment of the flanges at the smaller duct diameter permits a duct that diverges from one end of the combined containment duct to the center and diverges from the center of the combined containment duct to a second end of the combined containment duct. The flanges may also be fastened to a portion of a gas turbine engine (not shown). In one embodiment, the flanges may be fastened to the gas turbine engine so that the fan blades (not shown) of the gas turbine engine are positioned in the interior portion  1107  of the duct body  1103  substantially along the outer periphery of the path of the fan blade tips to provide containment of the fan blades. 
   One embodiment of the present invention includes providing a tool  100  having a surface having the shape of the desired composite. In one embodiment of the invention, the body  105  is substantially the shape of a cylindrical containment duct. In this embodiment, the cylindrical duct preferably tapers inward toward the center axis of the body  105 . The shape of the finished reinforced matrix composite is not limited to substantially cylindrical shapes. Any shape having flanged outer edges may be fabricated by the method of the present invention. Suitable shapes, in addition to the substantially cylindrical ducts, include, but are not limited to, ducts having complex cross-sectional geometry (e.g., rectangular ducts, triangular ducts or oval ducts), flat panels, and other complex shapes having wall-structures. Additionally, wall-structures having features may be formed using the tool  100  and method of the present invention. The tool  100  of the present invention, likewise, has body  105  of substantially the same shape as the finished composite. 
   The tool  100  is fabricated from a material having a coefficient of thermal expansion greater than the coefficient of thermal expansion of the fiber fabric preform  301 . One criteria for selection of the tool material is the amount of tension desired in the fiber fabric preform  301 . The greater the tension desired, the greater the coefficient of thermal expansion should be for the tool material. The less tension desired, the less the coefficient of thermal expansion should be for the tool material. Preferably, the tool  100  is fabricated from a metallic material. Fibers that make up the fiber fabric preform  301  have a relatively low coefficient of thermal expansion when compared to metallic materials. Therefore, when the tool  100  is exposed to heat, the tool material expands at a rate much faster than the rate of expansion for the fiber fabric preform  301 . The tension created by the expansion of the tool  100  in relation to the expansion of the fiber fabric preform  301  acts to pull the fiber fabric preform  301  taut and substantially aligns the fibers to produce a high strength, uniform composite substantially devoid of waves and wrinkles. The greater the thermal expansion of the tool  100  in relation to the fibers, the greater the tension created. Suitable materials for fabrication of the tool  100  include, but are not limited to, aluminum and steel. 
   The reinforcing material for the composite matrix is preferably woven fiber fabric. The fiber fabric is a preform capable of forming a reinforced matrix composite. A variety of fibers is suitable for use in composite matrix materials. The fibers may be woven or plied upon each other to form a composite preform. In one embodiment of the invention, the fiber fabric preform  301  is a triaxial woven fabric of strand bundles. The triaxial woven fabric has one strand bundle running axially, with another stand bundle oriented at about +60° from the bundle in the axial direction and a third strand bundle oriented at −60° from the bundle in the axial direction. Suitable fibers for forming the fiber fabric preform  301  include, but are not limited to, carbon, graphite, glass and polyamide fibers. The fiber fabric preform  301  is preferably dry. By dry, it is meant that there is no matrix material impregnated into the fiber fabric prior to loading the fiber fabric preform  301  onto the tool  100 . 
   The matrix material  601  for use in the reinforced matrix composite of the present invention is a curable material that forms a high strength matrix composite when reinforced with reinforcing fibers. Suitable matrix materials  601  for use in the reinforced composite material of the present invention include, but are not limited to, epoxy and polyimide. 
   The process of the present invention includes loading the tool  100  with the material for forming the reinforced matrix composite. The tool  100  is first loaded with the material for reinforcement of the matrix in the finished composite material. The reinforcing material is preferably a fiber fabric preform  301 . The fabric of fibers is preferably a fabric having a woven structure. Preferably the woven structure has three independent bundles of fibers woven so as to have orientations of 60° angles to each other. The fibers are preferably graphite fibers. The fabric may include, but is not limited to triaxial graphite fiber. A preferred fiber fabric preform  301  includes the triaxial graphite fiber with a 24 k (i.e., 24,000 strand) bundle tow in the axial direction and two 12 k (i.e., 12,000 strand) bundles in the +60° direction from the tow in the axial direction and two 12 k bundles in the −60° direction from the tow in the axial direction. 
   In one embodiment of the invention, the tool  100  preferably has a preselected geometry of a spool. The spool shape includes a substantially cylindrical body  105  affixed to two endplates  101  and  103 . At least one of the two endplates  101  and  103  is fastened to the body and is detachable. In this embodiment of the present invention, the tool  100  is oriented with the endplates  101  and  103  positioned having their planar surfaces oriented vertically in order to load the tool  100  with the reinforcing fiber material. The graphite fiber fabric preform  301  is positioned around the body  105  of the spool. A flange portion  305  of the preform is positioned along the length of each of endplates  101  and  103 . The flange portion  305  of the fabric extending along the first and second endplates  101  and  103  forms a flange-like shape. 
   Once the fiber fabric preform  301  is loaded onto the tool, a plurality of plates (i.e., flange shoes  107 ) are arranged abutting one another along the periphery of the tool  100  along the endplates  101  and  103 . A first set of plates is adjacent to the first endplate  101 . A second set of plates is adjacent to the second endplate  103 . The plates are preferably metallic and have at least one surface having a surface area  903  greater than the surface area of the length of material extending along the length of the endplates  101  and  103 . The plates are positioned to provide support for the fabric material extending along the endplates  101  and  103  and forming the flange portion  305  and are fastened to the endplates with stress release fasteners  111 . Each stress release fastener  111  is a fastener that positions the shoe at room temperature prior to the curing cycle and releases the flange shoes  107  from the first and second endplates  101  and  103  during the heat up portion of a curing cycle. As the tool expands axially, the stress release fasteners are designed to yield rather than prevent movement of the tool. So, the fastener maintains the flange shoes  107  in position, against the flange, but yields to allow the tool to expand axially. 
   In one embodiment of the invention, one or more of the plates are provided with channels  201 ,  303 ,  403 ,  405 ,  503  to facilitate circulation of excess resin. The channels  201 ,  303 ,  403 ,  405 ,  503  permit passage of matrix material  601  from the area of the tool carrying the matrix coated fibers to outside the area of the tool carrying the matrix coated fibers. The channels  201 ,  303 ,  403 ,  405 ,  503  allow excess matrix material  601  to pass into or out of the area of the tool  100  holding the fiber fabric preform  301 . When the tool  100  is positioned to have the first and second endplates  101  and  103  aligned horizontally with respect to the autoclave during loading, the second endplate  103  at the bottom includes one or more openings that are fluidly communicate to the area of the tool providing the vacuum, preferably at or near the top first endplate  101  of the tool. The tool  100  includes reservoirs  109  positioned on the top of the first endplate  101  when the first and second endplates  101  and  103  are aligned horizontally. In this embodiment, the vacuum fluidly communicate with reservoirs  109 , as well as fluid communication with openings in the flange shoes  107 . The fluid communications act as a siphon allowing excess matrix material  601  that pools because of gravity to travel to the area of the tool having suction, thereby providing matrix material  601  to areas of the fiber having less matrix material  601 , including the areas at or near the first endplate  101 . The siphon tubes  113  allow a uniform distribution of the matrix material  601  across the fiber fabric preform  301 . 
   The tool  100  is then covered with matrix material  601 , preferably in bulk form. The matrix material  601  is loaded onto the fiber fabric preform  301  by coating matrix material  601  directly onto the surface of the fiber fabric preform  301 . The placement of the matrix material  601  onto the reinforcing fiber fabric preform  301  includes placing a preselected amount of matrix material  601  onto the surface of the fiber fabric preform  301 . The preselected amount of matrix material  601  is an amount sufficient to impregnate the preform. The matrix material  601  is stacked or laid up on the surface in discrete portions. Once the matrix material  601  is placed onto the surface of the fiber fabric preform a barrier caul  603  is placed over the matrix material  601  to hold it in place until the tool is loaded into the autoclave. During the heating phase, the stacked or laid up matrix material layers (i.e. lay up) will melt and infiltrate into the fiber fabric preform  301 . Force applied to the matrix material  601  from the autoclave pressure on the caul  603  will assist the matrix material  601  in penetrating the fiber fabric preform  301  and in spreading outward across the fiber fabric preform  301 . The molten matrix material mass forms a wavefront as it flows across the fiber fabric preform  301  that forces the gaseous pockets out of the preform before the resin begins to set up and cure. In particular, the wavefront pushes out air, volatile material from the bulk matrix material  601 , such as solvent vapor, and other gases that are capable of forming voids, such as impurity gas pockets remaining in the matrix material or in the fiber fabric preform  301 . The placement of the matrix material  601  also permits the impregnation of preforms having complex shapes. Complex shapes include preforms having more complex geometric features than a flanged cylinder. Features may be present in preforms having more than one pathway for matrix material flow prior to curing. For example, reinforced matrix composite parts may include planar wall portions having attached stiffener or insert features. 
   In one embodiment of the invention, the matrix material  601  is resin separated into rectangular block sections, positioned onto the surface, and conformed to the surface of the fiber fabric preform. A suitable resin may include, but is not limited to, epoxy and/or polyimide. The matrix material  601  is coated onto the surface of the fiber fabric preform  301  so that a greater amount of matrix material  601  is coated onto the center  607  of the fiber fabric preform  301  (i.e., the midpoint  607  between the first and second endplates  101  and  103 , as illustrated in  FIG. 6 ) and less is coated on the edges  609  of the fiber fabric preform  301  (i.e., the area adjacent the first and second endplates  101  and  103 , as illustrated in  FIG. 6 ). 
     0054  Once the fiber fabric preform  301  is coated with the matrix material  601 , the matrix material coated fiber fabric preform  301  is coated with an elastomeric sheet (i.e., caul  603 ). The caul  603  acts as a barrier to isolate and control the flow of matrix material into the fiber fabric preform  301 . After the caul  603  is positioned, the caul  603  is sealed against the tool  100  to form a barrier and prevent flow of matrix through the caul  603 , but allow flow along the fiber fabric preform  301 . 
     0055  Once the caul  603  has been placed around the fabric-matrix material and sealed, the tool  100 , including caul  603  and matrix material  601  coated fiber fabric preform  301 , is placed inside a vacuum envelope or bag  605 . A vacuum source  117  is connected to the vacuum bag  605  and the tool  100  to provide reduced pressure (i.e., vacuum). The vacuum source  605  preferably draws a vacuum of up to about 28 inches of mercury and more preferably up to about 30 inches of mercury. The vacuum provides a driving force for distribution of the matrix material  601  during the heat up and curing phases of the process. The vacuum is drawn on the tool  100  through the vacuum bag  605 . The loaded tool  100  is then heated. While the tool  100  is being heated, a positive pressure of gas external to the vacuum bag  605  is provided. The positive pressure is preferably provided with an inert gas, such as nitrogen. During the heating and holding cycle the positive pressure is preferably increased to pressures of up to about 200 lb/in 2  or more, and preferably up to about 220 lb/in 2  or more. When loaded into the autoclave, the tool  100  is preferably oriented with the plane of the first and second endplates  101  and  103  aligned horizontally with respect to the autoclave. 
   In order to form the composite, the caul-covered fiber fabric preform  301  loaded with matrix material  601  is heated. The matrix material  601  becomes viscous at higher temperatures and flows into (i.e., impregnates) the fiber fabric preform  301 . Simultaneously, the tool  100  on which the fiber fabric perform  301  is loaded expands due to thermal expansion. Since the fiber fabric preform  301  experiences little or no thermal expansion, the fiber fabric preform  301  is pulled taut, providing at least some tension and alignment of fibers in the fiber fabric preform  301 . The tool  100  and the matrix coated fiber fabric preform  301  is then heated to a temperature to permit the matrix material to fully impregnate the fiber fabric preform  301 . After the fiber fabric preform  301  is substantially impregnated, the tool  100  and fiber fabric preform  301  are heated to a curing temperature, and is held at the curing temperature until the fiber reinforced matrix composite is cured. The method includes at least the following steps: a first heating step, a first holding step, second heating step, a second holding step and a cooling step. The temperature is slowly increased to the first holding temperature. A suitable rate of temperature increase includes but is not limited to range of from about ½° F./min to about 1° F./min. The temperature and time for the first holding step is sufficient to allow the matrix material to infiltrate the reinforcing fibers. A suitable temperature for the first holding step includes, but is not limited to the range of from about 300° F. to about 325° F. Suitable temperatures for the first holding step include, but are not limited to about 310° F. The temperature and time for the second holding step is sufficient to cure the matrix material. A suitable temperature for the second holding step includes, but is not limited to the range from about 350° F. to about 375° F. Suitable temperatures for the second holding step include, but are not limited to about 360° F. Once cured, the reinforced matrix composite is slowly cooled to room temperature. 
   During the heating steps, the heating gases of the autoclave are distributed across the tool  100  to provide uniform heating of the matrix impregnated fiber fabric. Preferably, the body  105  is hollow and/or has an interior surface, opposite the surface on which the fiber fabric preform  301  is positioned. In this embodiment, the interior surface is exposed to the heating atmosphere to heat the fiber fabric preform  301  and matrix material  601  through the body  105 . In a preferred embodiment as shown in  FIG. 1 , the tool body is hollow and substantially cylindrical in shape. The exterior (i.e., the surface on which the fiber fabric preform  301  is positioned) and the interior of the cylinder are exposed to the heating atmosphere through the vacuum bag  605 . The inlet to the hollow portion of the cylinder may include a diffuser to uniformly distribute the heating atmosphere. The heating atmosphere distributes the heat uniformly across the matrix impregnated fiber fabric  701  to uniformly cure of the reinforced composite matrix. 
   During the heating and vacuum cycle, the caul  605  permits the matrix material  601  to travel either in the direction toward the vacuum or in the direction of gravity. More matrix material  601  travels in the direction of gravity than in the direction of the vacuum. The openings in the flange shoes  107  permit excess matrix material to exit the portion of the tool  100  holding the fiber. When the tool  100  is positioned with the first and second endplates  101  and  103  aligned horizontally, the endplate at the bottom (i.e., second endplate  103 ) includes one or more openings  201  that are fluidly connected to the area of the tool  100  providing the vacuum at or near the reservoirs  109 . The area of the tool  100  providing the vacuum is preferably at or near the top endplate (i.e., first endplate  101 ) of the tool  100 . In one embodiment, the tool  100  includes reservoirs  109  positioned on the top of the first endplate  101  when the first and second endplates  101  and  103  are aligned horizontally. In this embodiment, the vacuum source  117  is connected to the reservoirs  109 , as well as the fluid connection to the openings in the flange shoes  107 . The fluid connections act as a siphon allowing excess matrix material that pools because of gravity to travel to the area of the tool  100  having suction and providing matrix material to the area of the fiber having less matrix material  601 . 
   As the tool  100  is heated, it thermally expands. The tool  100  is made of a material that expands at a rate in excess of the rate of expansion of the fiber fabric preform  301  and matrix material  601 . Therefore, as the tool  100  expands, the fiber fabric preform  301  expands at a significantly lesser rate and is pulled taut by the expanding tool  100 , creating pre-stressed fiber reinforcement. Once the matrix material  601  has been substantially distributed and cured at the larger tool surface area  903 , the tool  100  is then permitted to cool down to ambient temperatures. The tool  100  material thermally contracts with the falling temperature. However, the fiber consolidated with matrix material, which was pulled taut and cured at the size of the tool  100  surface at the higher temperature, thermally contracts at a significantly lesser rate. As the tool  100  material cools, the fiber consolidated with matrix material  601  exerts a force on at least one of the first and second endplates  101  and  103  because the surface of the cured reinforced matrix material  601  at lower temperatures is larger than the tool surface at lower temperatures. The at least one first and second endplate  101  and  103  is allowed to move and the fasteners holding the at least one of the endplates (i.e., first endplate  101 ) yield, allowing the endplate to be moved as the body of the tool  100  expands. Thus, the yielding of the fasteners  111  does not allow the flange assembly to restrain the body of the tool  100 . Once the cycle is complete and reinforced bulk matrix material  601  having the prestressed reinforcing fibers are cured and cooled, the reinforced bulk matrix material  601  is removed from the tool  100  and trimmed, if necessary. Also, if necessary due to the geometry of the finished part, the body  105  may be disassembled to facilitate removal of the cured, reinforced matrix composite part. The fasteners  111  are disposable and are not reused. 
   The various surfaces of the tool  100  that come in contact with the matrix material  601  may optionally be coated with a release film, such as polytetrafluoroethylene. The release does not stick to the tool components and facilitate easy removal of the finished part. For example, the body  105 , the first and second endplates  101  and  103 , the flange shoes  107 , and/or the caul  605  may be coated with polytetrafluoroethylene. 
   In alternate embodiment of the present invention, a pre-impregnated fiber fabric preform  301  is loaded onto the tool  100  of the present invention. Pre-impregnated fiber fabric preform  301  is fabric that is loaded with uncured matrix material  601  prior to being loaded onto the tool  100  of the present invention. Flange shoes  107  are positioned on the tool  100  and adjacent to the pre-impregnated fiber fabric preform  301 . Flange shoes  107  for use with pre-impregnated fiber fabric preform  301  additionally have rails, guides or a similar mechanism, to guide flange shoes  107  displacement when autoclave pressure is applied. As in the embodiment having the fiber fabric preform  301  that is not pre-impregnated with matrix material  601 , flange shoes  107  are greater in surface area than the fiber fabric preform  301  in the flange portion  305  to add substantial position holding force from autoclave pressure. As the tool  100  expands during cure cycle heat up, it pulls the fibers of the fiber fabric preform  301  taut over the flange shoes  107  radius. The rails, guides, or similar mechanism, are positioned to permit the flange shoes  107  to only allow force on the fabric once the tool  100  has expanded to an extent corresponding to heat sufficient to make the matrix material  601  in the pre-impregnated fiber fabric viscous. Once the matrix material  601  is viscous, the flange shoes  107  are permitted to exert force on the fiber fabric preform  301  and pull the fiber fabric taut. As in the embodiment with the dry fiber fabric, pulling the fiber fabric taut creates a pre-stressed fiber reinforced matrix composite. The tool  100  and finished product cool down and the tool  100  thermally contracts but the finished reinforced matrix composite does not contract as much. Flange shoes  107  and the first endplate  101  are fastened with stress relief fasteners  111 . Relief comes when the stress relief fasteners  111  holding the flange shoes  107  give under appropriate radial stress and the stress relief fasteners  111  holding the first endplate  101  gives to relieve the axial stress. 
   One embodiment of the invention includes a composite containment duct  1100  having less than or equal to 2.5% void space. The composite containment duct  1100  preferably has less than 2.0% void space and most preferably less than 1% void space. 
   The composite containment duct  1100  according to the present invention has improved containment properties. One embodiment of the present invention is a graphite fiber-epoxy matrix composite containment duct  1100 . The graphite-fiber epoxy matrix composite of the present invention has the properties of having high strength, including strong flanges, being lightweight and successfully passing a blade-out test. A blade-out test is a test wherein a gas turbine engine is mounted with a full set of fan blades and a containment duct around the periphery of the blade path. The fan blades are subjected to rotational speeds equivalent to the rotational speeds achieved during aircraft takeoff. One or more blades are ejected from the mounting and are allowed to impact the containment duct. A successful blade-out test holds the blade inside the containment duct. The method of the present invention is particularly suitable for fabrication of turbine airfoil components for gas turbine engines. In particular, the method of the present invention is suitable for the fabrication of containment ducts, such as fan casings, which withstand a blade-out test. 
   The method and tool  100  of the present invention is capable of fabricating large parts. The size of the part is slightly less than the size of the surface of the tool  100 . The tool  100  and method of the present invention are particularly suitable for fabrication of parts having large wall-structures, including cylindrical parts having a diameters of about 5 feet or greater, including cylindrical parts having a diameter of about 10 feet. In one embodiment, the tool of the present invention may create a cylindrical part having a diameter of about ten feet or greater that maintain substantially uniform matrix distribution and the low void content. 
   The flanges  1101  of the containment duct  1100  of the present invention have high strength. One contributing factor for high strength is the fact that the flanges  1101  are formed as an integral part of the containment duct  1100 . Additionally, the fibers within the flange  1101  are pulled taut, providing substantially alignment and increased strength. Additionally, the matrix distribution within the containment duct is substantially uniform across the duct body  1103  and across the flanges  1101 . The substantially uniform distribution within the flanges  1101  contribute the high strength of the flanges  1101 . The flanges  1101 , like the wall-portions have pre-stressed reinforcing fibers and uniform matrix distribution. 
   The method and tool  100  of the present invention provides composites of near-net-shape after impregnation and curing of the fiber fabric preform  301 . The tool  100  provides the fiber fabric preform  301  with the shape of the desired product, while impregnating it with matrix material  601 . Once cured, the matrix material  601  impregnated fiber fabric preform  301  is of near-net-shape, requiring little or no trimming. The method for manufacturing fiber reinforced matrix composites according to the present invention provides composite parts substantially having the shape of the finished product, requiring little or no trimming prior to installation. 
   Removal of the finished part from the tool  100  of the present invention is relatively simple and inexpensive. In addition to the optional release film, the first endplate  101  detaches from the body allowing removal of the part from the body  105 . The tool  100  does not require disassembly beyond the components of the tool  100  that detach during the curing cycle. Therefore, the removal of the finished part requires very little labor and is inexpensive. 
   While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.