Abstract:
A continuous fiber brake rotor preform and apparatuses and methods for manufacturing the preform are disclosed herein. The preform comprises a plurality of continuous fiber streams or filaments forming a substantially helical structure having layers or flights compressed together in the preform&#39;s longitudinal direction. Each continuous fiber stream or filament may comprise the same or different types of fiber, extends substantially between longitudinally disposed preform ends, and resides laterally adjacent to another continuous fiber stream or filament within each layer or flight of the helical structure. The radial distance between each continuous fiber stream or filament and the preform&#39;s longitudinal axis varies with angular location about the longitudinal axis. The preform further comprises web or z-direction fiber interspersed within the helical structure with certain of the web or z-direction fibers and continuous fiber streams or filaments extending at least partially in the longitudinal direction between the preform&#39;s layers or flights.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates, generally, to the field of brake rotor preforms and to apparatuses and methods for manufacturing brake rotor preforms and similarly fabricated articles. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many high-performance brake rotors used in aircraft, automobiles, and other vehicles are manufactured from fibrous brake rotor preforms (also sometimes referred to herein as “preforms”). The preforms are typically formed using two methods. According to the first method, the preforms are made from layers of annular-shaped segments of woven and/or non-woven cloth having fibers extending in chordal, radial, or both directions, or having some other ordered structure. According to the second method, layers of woven or nonwoven cloth are combined to create an ordered structure with the in-plane fibers. In both methods, the layers are then needled together in the vertical direction with a needling machine in an attempt to form a unitary structure from the layers. After needling, the structure formed in the second method is cut into toroidal-shaped preforms, resulting in twenty percent (20%) to thirty percent (30%) of the cloth being wasted. Typically, the preforms of both methods are then carbonized by heating to a temperature of greater than 1,200 degrees Celsius in a non-reactive atmosphere. Subsequently, a carbon matrix is added to the preforms using a carbon vapor deposition (CVD) or resin infiltration process to make a carbon-carbon composite friction material. After optional heat treating in a furnace, the preforms are then machined to produce brake rotors. 
         [0003]    Unfortunately, manufacturing woven and non-woven material from fiber is relatively expensive and, hence, preforms made from woven and non-woven material can be expensive. Also, woven fabric material tends to block the diffusion of gases, thereby making the uniform addition of the carbon matrix to the preforms more difficult and causing the preforms to have carbon matrices that are not uniform throughout the preforms. As a consequence, woven fabric material has an additional disadvantage in the manufacture of the preforms. In addition, an inventory of woven and non-woven segments or cloth must be maintained, with the woven and non-woven materials being separately handled and loaded into the needling machine. Such inventorying and handling are time-consuming and increase production costs. Therefore, there is a need in the industry for preforms made from less expensive material and for apparatuses and methods for manufacturing such preforms that do not require the inventorying and handling of woven and non-woven materials, that permit the uniform addition of a carbon matrix to the preforms, and that resolve these and other problems, difficulties, and shortcomings associated with the manufacture of carbonized brake rotor preforms. 
       SUMMARY OF THE INVENTION 
       [0004]    Broadly described, the present invention comprises a continuous fiber brake rotor preform and apparatuses and methods for manufacturing the preform. According to an example embodiment, the continuous fiber brake rotor preform comprises a plurality of continuous fiber streams or filaments forming a substantially helical structure having layers or flights that are compressed together in the longitudinal direction of the structure. Each continuous fiber stream or filament may comprise the same type of fiber as that of other continuous fiber streams or filaments, or may comprise one or more types of fibers that are different from those of other continuous fiber streams or filaments. Each continuous fiber stream or filament extends substantially from a first end of the helical structure to a second end disposed longitudinally opposite the first end. Generally, each continuous fiber stream or filament resides laterally adjacent to another continuous fiber stream or filament within each layer or flight of the helical structure and adjacent to one or more other continuous fiber streams or filaments of longitudinally adjacent layers or flights. The continuous fiber streams or filaments are arranged such that the radial distance between each continuous fiber stream or filament and the structure&#39;s longitudinal axis varies with angular location about the longitudinal axis within a layer or flight of the helical structure. The radial distance also varies for each continuous fiber stream or filament at each angular location about the structure&#39;s longitudinal axis from layer-to-layer or flight-to-flight such that the same continuous fiber stream or filament does not substantially overlay itself from layer-to-layer or flight-to-flight. 
         [0005]    The continuous fiber brake rotor preform further comprises web or z-direction fiber interspersed and mixed within the helical structure. Certain of the web or z-direction fibers and certain of the continuous fiber streams or filaments extend at least partially in the longitudinal direction between layers or flights of the helical structure. According to an example embodiment, the continuous fiber streams or filaments comprise tow fiber and the web fiber comprises loose or cut staple fiber. 
         [0006]    The apparatuses for manufacturing the continuous fiber brake rotor preform comprise, in accordance with an example embodiment, an apparatus configured with a spreader to receive a continuous fiber input stream and to divide, or spread, the continuous fiber input stream into multiple continuous fiber output streams or filaments. The apparatus is also configured with a rotating and elevationally-positionable bowl having an annular-shaped cavity for receiving and layering the continuous fiber output streams or filaments to produce a helical structure having layers or flights and in which a large portion of the continuous fiber output streams or filaments extend from a first end of the helical structure to a longitudinally opposed second end of the helical structure. The spreader is adapted to move in a radial direction relative to the bowl&#39;s central longitudinal axis during rotation of the bowl such that the radial distance of each continuous fiber output stream or filament relative to the longitudinal axis generally varies at each angular location about the longitudinal axis and varies from layer-to-layer or flight-to-flight. 
         [0007]    According to an example embodiment, the apparatus further comprises a delivery head for delivering web fiber to the bowl. The delivery head is configured to translate in a radial direction relative to the bowl&#39;s longitudinal axis in order to spread the web fiber across the continuous fiber output streams or filaments already present within the bowl. A radially-extending roller located between the spreader and delivery head is operative to act in concert with vertical positioning of the bowl and compresses the continuous fiber output streams or filaments and web fiber of the preform as the continuous fiber brake rotor preform is built up within the bowl. In addition, the apparatus comprises a needling head adapted for movement in a direction substantially perpendicular to the first and second longitudinal ends of the preform being formed and for needling the preform to pull fibers of the continuous fiber output streams and web fiber generally in the longitudinal direction and between layers or flights of the preform. A linear vertical displacement transducer and associated circuitry are adapted to control the elevation of the bowl (and, hence, of the preform) relative to the spreader, roller, delivery head, and needling head. 
         [0008]    The methods for manufacturing the continuous fiber brake rotor preform comprise, according to an example embodiment, forming a helical structure of continuous fiber generally extending between longitudinally disposed ends thereof and having a plurality of layers or flights therebetween. The methods include, without limitation, steps of receiving a continuous fiber input stream, splitting the continuous fiber input stream into multiple continuous fiber output streams, and arranging the continuous fiber output streams in such layers or flights. The step of arranging includes varying the radial distance of each continuous fiber output stream relative to the central longitudinal axis of the preform within each layer or flight and between longitudinally adjacent layers or flights at angular locations about the longitudinal axis. The methods further include steps of adding web fiber between the layers or flights of the preform and needling the continuous fiber output streams and web fiber to better link the layers or flights together with fibers of the continuous fiber output streams and web fiber pulled between the layers or flights substantially in the direction of the preform&#39;s longitudinal axis. 
         [0009]    Advantageously, the continuous fiber brake rotor preform has more uniform and improved mechanical and structural properties than other preforms due, at least in part, to the continuous fiber output streams or filaments extending substantially between the preform&#39;s longitudinal first and second ends. The more uniform and improved mechanical and structural properties are also due, at least in part, to the varying radial distances of each continuous fiber output stream or filament relative to the preform&#39;s longitudinal axis within layers or flights and between longitudinally adjacent layers or flights. Also advantageously, the use of continuous fiber or filaments eliminates the need to inventory and handle of woven and non-woven annular segments and eliminates difficulties in carbonization attributable to woven materials. 
         [0010]    Other uses, advantages and benefits of the present invention may become apparent upon reading and understanding the present specification when taken in conjunction with the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  displays a schematic, side view of certain components of a needling machine, in accordance with an example embodiment of the present invention, for manufacturing a continuous fiber brake rotor preform. 
           [0012]      FIG. 2  displays a schematic, top plan view of the components of the needling machine of  FIG. 1 . 
           [0013]      FIG. 3  displays a schematic, cross-sectional view of a portion of a continuous fiber brake rotor preform manufactured in accordance with the example embodiment of the present invention, taken along line  3 - 3  of  FIG. 2 . 
           [0014]      FIG. 4  displays a schematic, top plan view of tow fiber of a first layer of a continuous fiber brake rotor preform manufactured in accordance with the example embodiment of the present invention. 
           [0015]      FIG. 5  displays a schematic, top plan view of tow fiber of a second layer of a continuous fiber brake rotor preform manufactured in accordance with the example embodiment of the present invention that is vertically adjacent to the first layer of  FIG. 4 . 
           [0016]      FIG. 6  displays a schematic, top plan view of the tow fibers of the first and second vertically adjacent layers of a continuous fiber brake rotor preform manufactured in accordance with the example embodiment of the present invention, illustrating the radial offset of the tow fibers of vertically adjacent layers. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0017]    Referring now to the drawings in which like numerals represent like elements or steps throughout the several views,  FIGS. 1 and 2  respectively display schematic, side and top plan views of certain components of an apparatus  100 , in accordance with an example embodiment of the present invention, for manufacturing a continuous fiber brake rotor preform  102  (also sometimes referred to herein as a “preform  102 ”) substantially comprising tow fiber  104 . The apparatus  100  (also sometimes referred to herein as a “needling machine  100 ”) includes a bowl  106  having a vertical inner wall  108  and vertical outer wall  110  that form a body of revolution about a central vertical axis  112 . The bowl  106  defines an annular-shaped cavity  114  (see  FIG. 2 ) extending between the inner and outer walls  108 ,  110  for the receipt of tow fibers  104  and, according to the example embodiment, staple fibers  116 . The inner and outer walls  108 ,  110  are located at radii relative to the central vertical axis  112  that are appropriate for the dimensions of the particular preform  102  then being made so as to receive the tow fibers  104  of preform material therebetween and aid in forming the preform  102  as a continuous helix-like structure primarily of tow fibers  104 . The bowl  106  also has a false bottom formed by a bottom plate  118  that is annularly-shaped and sized to translate vertically between the bowl&#39;s inner and outer walls  108 ,  110 . A drive mechanism (not visible) is configured to raise and lower the bottom plate  118  during operation of the needling machine  100 . The drive mechanism is also adapted to rotate the bowl  106  and bottom plate  118  about central vertical axis  112  at an appropriate rotational speed. 
         [0018]    The needling machine  100  also comprises a foam base  120  that has an annular-shape and that is sized to extend substantially between the bowl&#39;s inner and outer walls  108 ,  110 . The foam base  120  sits atop the bottom plate  118  and is raised and/or lowered in unison with the bottom plate  118 . The foam base  120  has an upper surface  122  and an opposed lower surface  124 , and defines a thickness, T, therebetween. The upper surface  122  supports the preform  102  and the lower surface  124  rests on and adjacent to the bottom plate  118 . According to the example embodiment, the foam base  120  is manufactured from a foam material having a low density and/or a fast rebound rate such that when barbed needles  176  (described below) of the needling machine  100  penetrate and downwardly deflect portions of the upper surface  122  of the foam base  120  during needling of the preform  102 , the deflection is minimized and any deflected portions of the foam base  120  rapidly return to their original non-deflected position and state. Such foam material may comprise a cross-linked polyethylene or similar semi-rigid material having a density in the range of 2.5 to 8.0 pounds per cubic foot, with densities between 3.0 and 3.5 pounds per cubic foot being most desirable. Also according to the example embodiment, the foam base  120  may have a thickness, T, measuring generally between 0.75 inch and 3.0 inches, with a thickness, T, of 1.0 inch being most common. 
         [0019]    Additionally, the needling machine  100  comprises a spreader  130  for receiving a continuous input stream  132  of tow fiber  104  from a tow fiber source (not visible, but perhaps comprising a roll or drum about which tow fiber  104  has been previously wound) and spreading the input stream  132  into multiple output streams  134  of tow fiber  104 , with each output stream  134  comprising one or more filaments of tow fiber  104 . The spreader  130  directs the output streams  134  of tow fiber  104  into the bowl  106  substantially parallel to one another and at respective distances from the bowl&#39;s central vertical axis  112 . Since the bowl&#39;s central vertical axis  112  is collinear with the central vertical axis  136  of the preform  102 , the tow fibers  104  of the preform  102  are also substantially parallel to one another and located at respective distances from the preform&#39;s central vertical axis  136  as the output streams  134  of tow fibers  104  exit the spreader  130 . 
         [0020]    According to the example embodiment and as indicated by arrow  138 , the spreader  130  translates back and forth in cooperative timing with rotation of the bowl  106  in order to vary the respective distance of each output stream  134  of tow fiber  104  from the bowl&#39;s central vertical axis  112  as the bowl  106  rotates. By varying the respective distance of each output stream  134  in this manner, the respective tow fibers  104  of the preform  102  are located at different distances from the preform&#39;s vertical central axis  136  at different angular positions about the preform&#39;s central vertical axis  136 . Also according to the example embodiment, the spreader  130  translates back and forth as indicated by arrow  138  such that the tow fibers  104  corresponding to a particular output stream  134  of each vertically adjacent layer  142  (or “flight  142 ”) of the preform&#39;s helix-like structure are generally offset at different radial distances from the preform&#39;s central vertical axis  136 , or “out of phase”, at each angular location about the preform&#39;s central vertical axis  136 . 
         [0021]    The needling machine  100  also comprises a delivery head  150  that, as indicated by arrow  152 , translates back and forth between the bowl&#39;s inner and outer walls  108 ,  110  along a radius  154  of the bowl  106 . The delivery head  150  receives loose staple fiber  116  via a conduit  156  extending between the delivery head  150  and a staple fiber source  158 . According to the example embodiment, the staple fiber source  158  may comprise a device for chopping staple fiber  116  into a desirable size and for blowing the staple fiber  116  through conduit  156  to the delivery head  150 . As the bowl  106  rotates, the staple fiber  116  falls from the delivery head  150  onto the preform  102  being manufactured at random locations and as distributed by the translation of the delivery head  150 . The chopped, loose staple fiber  116  acts as web, or z-direction, fiber of the preform  102 . 
         [0022]    Additionally, the needling machine  100  comprises a roller  160  mounted between the bowl&#39;s inner and outer walls  108 ,  110  along a radius  162  extending from the bowl&#39;s central vertical axis  112 . According to the example embodiment, the roller  160  is located arcuately between the spreader  130  and delivery head  150 . During operation of the needling machine  100 , the roller  160  rotates about a shaft (not visible) and in contact with the upper surface of the preform  102  being manufactured. The roller  160 , according to the example embodiment, has a conical cross-sectional shape when cut by a horizontal plane and has a smaller diameter nearest the bowl&#39;s inner wall  108  and a larger diameter nearest the bowl&#39;s outer wall  110 . The roller  160  exerts a generally downward force on the preform  102  tending to press, or compress, the tow fiber  104  of the vertically adjacent layers  142  of the preform  102  together in the vertical direction. Operation of the roller  160  also tends to push the staple fiber  116  generally downward into the vertically adjacent layers  142  of the preform so as to aid in linking the vertically adjacent layers  142  together in the preform&#39;s vertical direction. 
         [0023]    In addition, the needling machine  100  comprises a needling head  170  and a needling board  172  mounted to and vertically beneath the needling head  170 . The needling head  170  is driven by a drive mechanism (not visible) that causes the needling head  170  and, hence, the needling board  172  to travel rapidly and repeatedly in vertically up and down directions as indicated by double-headed arrow  174 . The needling board  172  has a plurality of barbed needles  176  securely mounted therein such that when the needling board  172  translates up and down, the barbed needles  176  move up and down through a fixed distance. During operation of the needling machine  100  and needling of the tow fiber  104  and staple fiber  116  to form the preform  102 , the barbed needles  176  pull fibers of the preform&#39;s uppermost vertically adjacent layers  142  downward into vertically adjacent layers  142  located beneath the uppermost layers  142  or into the foam base  120 . By pulling fibers of the uppermost vertically adjacent layers  142  into vertically adjacent layers  142  beneath the uppermost vertically adjacent layers  142 , the uppermost and lower vertically adjacent layers  142  become interconnected and form a substantially unitary preform structure. 
         [0024]    Further, the needling machine  100  includes a vertical linear displacement transducer  180  (also sometimes referred to herein as “VLDT  180 ”) that is fixedly secured to other structure of the needling machine  100  above the bowl&#39;s annular-shaped cavity  114  at a position along a radius  182  extending from the bowl&#39;s central vertical axis  112  and between the bowl&#39;s inner and outer walls  108 ,  110  (see  FIG. 2 ). The vertical linear displacement transducer  180  is operative to continually measure the vertical distance between the top surface of the then uppermost layer  142  of the preform  102  and the vertical linear displacement transducer  180 . Upon determining this vertical distance, the VLDT  180  produces an output signal that causes the bowl&#39;s drive mechanism to lower the bowl&#39;s bottom plate  118  sufficiently to maintain the top surface of the uppermost layer  142  of the preform  102  consistently at substantially the same vertical elevation. 
         [0025]    During operation of the needling machine  100 , the bowl  106  rotates clockwise about central vertical axis  112  as indicated by arrow  190  to form a preform  102  substantially from continuous tow fiber  104  rather than from pre-cut annular segments of woven and non-woven fiber. As the bowl  106  rotates, the needling machine  100  receives a continuous input stream  132  of tow fiber  104  from a tow fiber source that is fed into the spreader  130  where the input stream  132  is separated into multiple adjacent, continuous output streams  134  of tow fiber  104 . The spreader  130  translates generally between the bowl&#39;s inner and outer walls  108 ,  110  while the bowl  106  rotates so that the output streams  134  of tow fiber  104  are laid initially atop the foam base  120  and, after one complete rotation of the bowl  106 , atop the prior vertically adjacent layer  142  of the preform  102 . 
         [0026]    As each vertically adjacent layer  142  of tow fiber  104  is laid down, the bowl&#39;s bottom plate  118  is lowered to maintain the upper surface of the preform  102  at a substantially constant vertical elevation. The spreader&#39;s translation and rotation of the bowl  106  causes the output streams  134  of tow fiber  104  to be laid down at varying distances relative to the preform&#39;s central vertical axis  136  at different angular locations about the preform&#39;s central vertical axis  136 . The spreader&#39;s translation and rotation of the bowl  106  also cause the tow fiber  104  corresponding to a particular output stream  134  to be laid down so that, in each vertically adjacent layer  142 , or flight  142 , of the preform  102 , the tow fiber  104  is generally offset at different distances from the preform&#39;s central vertical axis  136  and is “out of phase”, at each angular location about the preform&#39;s central vertical axis  136 . By virtue of such tow fiber  104  being out of phase, the preform  102  has more consistent and uniform physical and mechanical properties throughout. 
         [0027]    Once the tow fiber  104  is initially laid down, tow fiber  104  rotates in unison with the bowl  106  under roller  160 . The tow fiber  104  is pushed in a generally downward vertical direction by the roller  160 . The downward pressure of the roller  160  tends to compact the vertically adjacent layers  142 , or flights  142 , of the preform  102  and cause any previously added loose staple fiber  116  (as described below) to be pushed downward between layers  142  or flights  142  of the preform  102  and/or into a particular orientation such that the loose staple fiber  116  does not become re-oriented during subsequent operations on the preform  102 . 
         [0028]    Then, after further rotation of the bowl  106  under the delivery head  150 , loose staple fiber  116  is delivered from the delivery head  150  onto the preform  102  being manufactured. The delivery head  150  translates substantially between the inner and outer walls  108 ,  110  of the bowl  106  while delivering loose staple fiber  116  to the preform  102  being manufactured. Such translation tends to more uniformly spread the staple fiber  116  in the radial direction of the preform  102 . Some of the loose staple fiber  116  remains on the upper surface of the preform  102 , while some of the loose staple fiber  116  falls downward into other layers  142  of the preform  102 . 
         [0029]    As the bowl  106  continues to rotate, the most recently laid down tow fiber  104  and staple fiber  116  pass under the needling board  172  where the tow fiber  104  and staple fiber  116  are engaged by the board&#39;s barbed needles  176  when the needling board  172  moves in a downward vertical direction relative to the preform  102 . The engaged tow and staple fibers  104 ,  116  are pulled in a downward vertical direction toward the foam base  120  and into vertically adjacent layers  142 , if any, beneath the most recently laid down tow and staple fibers  104 ,  116 . Downward pulling of the engaged tow and staple fibers  104 ,  116  into such vertically adjacent layers  142 , or flights  142 , tends to vertically interconnect the vertically adjacent layers  142  of the preform  102  into a unitary structure and also tends to prevent the vertically adjacent layers  142 , or flights  142 , of the preform  102  from separating or delaminating. 
         [0030]    After passing under the needling board  172 , the most recently laid down tow and staple fibers  104 ,  116  and top surface of the preform  102  rotate under the VLDT  180 . The VLDT  180  determines the elevation of the top surface and outputs a signal to the bowl&#39;s drive mechanism to lower the bowl&#39;s bottom plate  118  sufficiently to maintain the top surface of the preform  102  consistently at the same vertical elevation during manufacture of the entire preform  102 . Through further rotation of the bowl  106 , the most recently laid down tow and staple fibers  104 ,  116  rotate under the spreader  130  where new tow fiber  104  is laid down on the preform  102 . Operation of the needling machine  100  continues according to the method described above until the entire preform  102  is manufactured. After removal of the preform  102  from the bowl  106 , the preform  102  may be die cut to true up the inner and outer radial dimensions of the preform  102  in accordance with the specifications for the preform  102 . 
         [0031]    By virtue of the preform  102  being manufactured from a continuous stream of tow fiber  104 , the preform  102  has a substantially helical structure having vertically adjacent layers  142  or flights  142  similar to the threads of a screw.  FIG. 3  displays a cross-sectional view of a portion of a continuous fiber brake preform  102  manufactured using the needling machine  100  and methods described herein. In  FIG. 3 , the vertically adjacent layers  142 , or flights  142 , of the helical structure of the preform  102  are visible. Also, as indicated by the cross-hatching, the tow fiber  104  of vertically adjacent layers  142  or flights  142  is offset at varying distances relative to the preform&#39;s central vertical axis  136  to provide greater strength and more consistent physical and mechanical properties throughout. Such offset is more clearly understood by viewing  FIGS. 4-6 . 
         [0032]      FIG. 4  displays a schematic, top plan view of the tow fiber  104  of a first layer  142 A of a sector of the preform  102  showing the tow fiber  104  offset at various distances relative to the preform&#39;s central vertical axis  136  as the tow fiber  104  extends about the central vertical axis  136 .  FIG. 5  displays a schematic, top plan view of the tow fiber  104  of a second layer  142 B of the same sector of the preform  102  showing the tow fiber  104  offset at various distances relative to the preform&#39;s central vertical axis  136  as the tow fiber  104  extends about the central vertical axis  136 . The effect of the offsetting from layer-to-layer (or flight-to-flight) is seen in  FIG. 6  where the top plan view of the tow fiber  104  of the first layer  142 A of a sector of the preform  102  from  FIG. 4  is superimposed on the top plan view of the tow fiber  104  of the second layer  142 B of the same sector of the preform  102  from  FIG. 5 . As seen in  FIG. 6 , the tow fiber  104  of each vertically adjacent layer  142 A,  142 B is variously radially offset relative to the preform&#39;s central vertical axis  136  with the tow fiber  104  of each adjacent layer  142 A,  142 B being also variously offset relative to the tow fiber  104  of the other. Thus, through appropriate translation of the spreader  130  during manufacture of the preform  102 , the tow fibers  104  of vertically adjacent layers  142 A,  142 B are not vertically aligned, thereby improving the physical and mechanical properties of the preform  102 . 
         [0033]    In an alternate embodiment of the present invention, the staple fiber  116  may be conveyed to the delivery head  150  rather than being blown and supplied to the delivery head  150  by conduit  156 . In another alternate embodiment of the present invention, the staple fiber  116  may be replaced by web fiber from a roll of web fiber that is unrolled in the radial direction. In still another alternate embodiment of the present invention, the roller  160  may be positioned at a location between the delivery head  150  and needling board  172  so that the most recently laid down tow fiber  104  is pressed in a generally downward vertical direction after staple fiber  116  is added thereto. In yet another alternate embodiment of the present invention, multiple spreaders  130  may be utilized to refine the offset of each stream of tow fiber  104 . 
         [0034]    It should be understood and appreciated that the apparatuses and methods of manufacturing a preform described herein produce a preform where the fiber angles near the preform&#39;s inside radius are different than the fiber angles near the preform&#39;s outside radius. It should be further understood and appreciated that in yet another alternate embodiment using multiple spreaders fed with separate tows of fiber with different feed rates, the difference between the fiber angles near the preform&#39;s inside radius and the preform&#39;s outside radius is reduced. 
         [0035]    Whereas the present invention has been described in detail above with respect to an example and alternate embodiments thereof, it should be appreciated that variations and modifications might be effected within the spirit and scope of the present invention.