Patent Publication Number: US-2023139946-A1

Title: Composite structures and methods of forming composite structures

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Pat. Application Serial No. 17/690,179, filed Mar. 9, 2022, which claims the benefit of U.S. Provisional Pat. Application Serial No. 63/158,703, filed Mar. 9, 2021, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure provides composite structures and methods of forming composite structures. 
     BACKGROUND 
     Composite materials have a variety of advantages as compared to alternate materials, such as steel, aluminum, or wood. For example, composite materials can be used to form structures having intricate shapes, allowing strength and aesthetics to be optimized. In addition, the potential strength to weight ratio of structures formed using carbon fiber composites is very high. Products formed from carbon fiber composites, commonly referred to as simply “carbon fiber”, are also popular with consumers. 
     Widespread adoption of composite materials has been limited by the relatively high cost of forming composite or carbon fiber structures. These costs are a result of various factors, such as the cost of the materials themselves, and the labor-intensive processes used to form such structures. For example, composite structures are typically formed by laying multiple sheets of composite material in a mold. Each sheet includes fibers that are oriented along one or several directions or plies, and that generally extend from one edge of the sheet to another. More particularly, different layers of material, having the associated ply or plies oriented in a specific direction, are placed in a mold and set into a final form using a two-part epoxy. In addition to being time-consuming and labor-intensive, such techniques are prone to defects when used to form complex, hollow structures time efficiently. Such methods are also unable to take full advantage of the strength to weight ratio of the material. For example, conventional composite structures that are otherwise capable of withstanding designed loads require additional reinforcement in order to provide consumer friendly end products that are resistant to impacts and that have acceptable product lifetimes. In addition, composite structures have typically used thermoset materials that are relatively brittle and difficult to recycle. 
     As an alternative to composite structures that are formed by layering multiple sheets of material in a mold, structures can be formed relatively quickly and cheaply using injection molding. However, the structures formed using such processes are typically quite weak. In addition, it is impossible to form certain three-dimensional shapes using injection molding. 
     SUMMARY 
     Embodiments of the present disclosure provide composite structures and methods of forming composite structures. In accordance with at least some embodiments of the present disclosure, the composite structures can include one or more composite panels or preforms that each include one or more sheets of fiber reinforced thermoplastic material. The composite structures can include at least portions that are hollow. Each composite panel in a composite structure can be joined to at least one other composite panel by a welding or fusing process. In accordance with further embodiments of the present disclosure, a composite structure is provided that includes composite inserts, for example in the form of solid composite structures or block members, or in the form of braided sleeves. In accordance with at least some embodiments of the present disclosure, the composite block members can be configured as shaped core or spacing elements that include reinforcing fibers and thermoplastic material, and can be disposed between at least portions of one or more composite panels. The composite block members can also be provided as separate integral composite structures. Braided sleeves in accordance with embodiments of the present disclosure can be configured as a seamless sleeve of braided reinforcing fibers and thermoplastic threads. A braided sleeve or sleeves can be placed in interior sections or portions of composite panels or preforms. An exterior surface of the braided sleeve can be in contact with interior surfaces of the composite panels. In addition, a braided sleeve can bridge seams or joints between two or more composite panels. A composite structure as disclosed herein can include various combinations of composite panels, composite block members, and braided sleeves. 
     In accordance with embodiments of the present disclosure, each composite panel comprises one or more composite sheets of material that include a plurality of fibers embedded in a thermoplastic material. In accordance with at least some embodiments of the present invention, at least one of the sheets of material in a composite panel includes fibers that are randomly oriented. Moreover, the randomly oriented fibers may be relatively short, such that most of the fibers do not extend from one edge of the sheet to another. Alternatively or in addition, at least one of the sheets of material in a composite panel includes unidirectional fibers, with at least most of the fibers extending between different edges of the sheet of material. The composite panel can additionally include one or layers of core or spacer material between otherwise adjacent sheets of material. The core or spacer material can be provided as shaped composite blocks. Each of the composite blocks can be in the form of shaped fiber reinforced thermoplastic material. In accordance with at least some embodiments of the present invention, the composite panel includes at least one slit or aperture that is within a perimeter of the composite panel. In accordance with still further embodiments of the present disclosure, the slit or aperture extends through all of the sheets making up the composite panel. 
     A composite structure as disclosed herein can incorporate multiple composite components. The composite components can include one or more composite panels, composite blocks, braded sleeves, or combinations of composite panels, braided sleeves, and composite blocks. In accordance with at least some embodiments of the present disclosure, a composite structure includes a three-dimensional composite structure component that includes at least one composite panel that is joined to a second composite structure component that includes at least one composite panel. The second composite structure component can also be formed in three dimensions. Together, first and second composite structure components can define interior volumes. Composite blocks and/or braided sleeves can occupy a portion or an entirety of an interior volume. In addition, each of the composite structure components, and the resulting composite structure, can have an aperture formed within an outer perimeter thereof. In accordance with still other embodiments of the present disclosure, the composite structure components can have an open aperture or cut out portion. 
     Composite structures can also feature at least one hollow section. In accordance with further embodiments of the present disclosure, a volume defined by a hollow section in one or more composite structure components can be occupied by one or more composite blocks and/or one or more braided sleeves. For example, a composite block can be shaped to match contours of interior surfaces of a volume defined by one or more composite panels that is at least partially occupied by the composite block, and an exterior surface of a braided sleeve can be partially or entirely in contact with interior surfaces of a volume defined by one or more composite panels. In a structure that includes composite panels, composite blocks, and braided sleeves as discussed herein, a braided sleeve can extend between a pair of the composite blocks, with all or portions of the composite blocks and the braided sleeve within an interior volume defined by the composite panels. The individual components of a composite structure that includes at least two of a composite panel, a composite block, or a braided sleeve can be one joined to one another by welding or fusing the components to one another. 
     Methods of forming composite panels can include layering multiple composite sheets of thermoplastic impregnated fiber materials, and fusing the multiple sheets using heat and pressure. The different sheets can be selected to provide fibers of a desired tensile strength, length, and orientation or orientations relative to the perimeter of the respective sheet. In addition, the sheets can be oriented with respect to one another to provide strength in desired directions. 
     Methods of forming composite blocks can include layering multiple composite sheets of fiber reinforced thermoplastic material, injection molding fiber reinforced thermoplastic material, or compression molding fiber reinforced thermoplastic material. In accordance with at least some embodiments of the present disclosure, the fiber reinforced thermoplastic material is sourced as waste stock created through the shaping or forming of composite structures. Where the composite block is formed by a layering process, pieces of thermoplastic reinforced sheets can be sized and stacked to at least approximate a desired three-dimensional shape. The stack can then be heated to fuse the layers to one another, forming an integral block of composite material. Where the composite block is formed by injection or compression molding, the waste stock can be processed by a chipping or mulching operation, to reduce the length of included fibers. For injection molding, the waste stock is selected or processed so that the length of the included fibers is relative short (e.g. less than 6 mm), and is then heated and injected into a mold. For compression molding, the waste stock is heated and formed in a mold. Moreover, in a compression molding process, the waste stock can be processed so that the included fibers are randomly oriented in the finished composite block. After any of the aforementioned processes, the composite block can be shaped by trimming, sanding, or the like, to obtain a final shape. 
     A braided sleeve in accordance with embodiments of the present disclosure can include a mixture of a plurality of carbon fiber or other reinforcing fibers and a plurality of fibers formed from or including a thermoplastic material that are woven into a seamless, tubular sleeve. Methods of forming composite structures in accordance with embodiments of the present disclosure that include a braided sleeve include placing an exterior of a braided sleeve against a surface of a composite panel or block. In accordance with at least some embodiments of the present disclosure, some or all side exterior surfaces of a braided sleeve are in contact with an interior surface of one or more composite panels. The ends of the fibers forming the braided sleeve can also be placed in contact with a composite block or with a surface of a composite panel. 
     Methods of forming composite structures in accordance with embodiments of the present disclosure include placing a composite panel in a female mold and applying pressure to the composite panel with a male mold, to form a three-dimensional composite structure component. The composite panel can have a slit or aperture formed therein prior to placing the panel in the molds. A first three-dimensional composite structure component can be joined to a second three-dimensional composite structure component to form a completed composite structure. In accordance with further embodiments, the composite structure can include more than two composite structure components. In accordance with further embodiments of the present disclosure, composite inserts such as composite blocks and braided sleeves as disclosed herein are incorporated into composite structures that also include one or more composite panels. More particularly, composite blocks can be positioned such that they contact a surface of a composite panel. A braided sleeve can be pressed against interior surfaces of a volume defined by composite panel or panels by a bladder or mandrel that is positioned within an interior of the braided sleeve, such that the exterior surface of the braided sleeve is in contact with and conforms to the adjacent surface of the composite panels. Moreover, an entire exterior surface of a braided sleeve can thus be placed in contact with a surface of the volume defined by the composite panels. The entire composite structure can be heated to fuse the components to one another, creating an integral structure. Moreover, multiple components of a composite structure, including composite panels, composite blocks, and/or braided sleeves, can be fused to one another in a single operation. 
     Moreover, at least some of the composite structure components can be flat, rather than formed in three dimensions. The composite structure can include an aperture within or through an outside perimeter of the structure that extends through multiple composite structure components. Alternatively or in addition, the composite structure can include one or more hollow portions formed between opposing sections of composite structure components. In accordance with further embodiments of the present disclosure, a composite block can be shaped to occupy a volume between opposing sections of composite structure components. 
     Methods of joining composite structure components include welding or fusing composite structure components, including composite panels and composite blocks, to one another. Welding components can include applying heat to the area of the joint, to raise the temperature of the components to a point that is greater than the glass transition temperature and up to, at, or greater than the melt temperature of the thermoplastic material. In accordance with at least some embodiments of the present disclosure, a joint between adjacent composite structure components is formed by abutting edges of the adjacent components. In addition, a welding strip, which can be a strip of the same thermoplastic material present in the composite structure components, with or without fibers, can be placed along the joint while heat is applied to the joint. In accordance with still further embodiments of the present disclosure, the welding strip can be located within a hollow area of the composite structure, and can be pressed against the composite structure components that are being joined by an inflated bladder, a mandrel, or the like, while heat is being applied to form the joint. In accordance with some embodiments of the present disclosure, a braided sleeve can be located so as to extend along a joint between composite structure components, and can take the place of or can be provided in addition to a welding strip. In accordance with still other embodiments of the present disclosure, a joint between adjacent composite structures is formed by overlapping edges of the adjacent components. Moreover, a joggle or step can be formed in one or both components to enable a smooth exterior (or interior) surface. 
     Additional features and advantages of embodiments of the present disclosure will become more readily apparent from the following description, particularly when considered together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts an example of an assembly incorporating multiple interconnected composite structures in accordance with embodiments of the present disclosure in a side elevation view; 
         FIG.  2    depicts an example of a composite structure incorporating multiple composite components in accordance with embodiments of the present disclosure in a side elevation view; 
         FIG.  3 A  depicts a cross-section of a variant of a composite structure of taken along line 3-3′ of  FIG.  2   ; 
         FIG.  3 B  depicts a cross-section of another variant of a composite structure along line 3-3′ of  FIG.  2   ; 
         FIGS.  4 A- 4 B  depict composite structure components in accordance with embodiments of the present disclosure; 
         FIG.  5    depicts a composite panel in accordance with embodiments of the present disclosure in a side elevation view; 
         FIG.  6    depicts an example layup of a composite panel in accordance with embodiments of the present disclosure; 
         FIG.  7    depicts a sheet of fiber reinforced thermoplastic material in accordance with an embodiment of the present disclosure; 
         FIG.  8    depicts a sheet of fiber reinforced thermoplastic material in accordance with another embodiment of the present disclosure; 
         FIG.  9    depicts a sheet of fiber reinforced thermoplastic material in accordance with another embodiment of the present disclosure; 
         FIG.  10    depicts an example of a sub-assembly incorporating multiple interconnected composite structures in accordance with embodiments of the present disclosure; 
         FIG.  11    depicts an example of a composite structure incorporating multiple composite components in accordance with embodiments of the present disclosure; 
         FIG.  12    is an exploded perspective view of the composite structure incorporating multiple composite components of  FIG.  11   ; 
         FIG.  13    depicts another example of a composite structure incorporating multiple composite components in accordance with embodiments of the present disclosure; 
         FIG.  14    depicts the composite structure of  FIG.  13    in a plan view; 
         FIG.  15    is an exploded perspective view of the exemplary composite structure incorporating multiple composite components of  FIGS.  13  and  14   ; 
         FIGS.  16 A- 16 D  depict components of a variant of the composite structure of  FIGS.  13  and  14   ; 
         FIGS.  17 A- 17 I  depict cross sections of different configurations of the example composite structure of  FIGS.  16 A- 16 C ; 
         FIGS.  18 A- 18 C  depict components of another variant of the composite structure of  FIGS.  13  and  14   ; 
         FIGS.  19 A- 19 H  depict cross sections of different configurations of the example composite structure of  FIGS.  18 A- 18 C ; 
         FIGS.  20 A- 20 D  depict portions of example variants of the composite structure of  FIGS.  13  and  14   ; 
         FIG.  21    depicts a composite panel in accordance with embodiments of the present disclosure; 
         FIGS.  22 - 24    depict sheets of fiber reinforced thermoplastic material in accordance with embodiments of the present disclosure in top plan views; 
         FIG.  25    depicts a portion of a composite structure in accordance with embodiments of the present disclosure in a top plan view; 
         FIG.  26    depicts a seamless braided sleeve in accordance with embodiments of the present disclosure; 
         FIG.  27    is a flowchart illustrating aspects of a method of forming a composite structure in accordance with embodiments of the present disclosure; 
         FIG.  28    depicts a shaping, molding, and fusing step in accordance with embodiments of the present disclosure; and 
         FIG.  29    is a flowchart illustrating aspects of a method of forming a composite structure in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    depicts an example of an assembly  100  incorporating multiple interconnected composite structures in accordance with embodiments of the present disclosure. In general, the assembly  100  includes a main frame  104  and a swingarm assembly  204 . The swingarm assembly  204  includes a pair of seat stays  208  and a chain stay assembly  212 . In addition, in the illustrated example, the assembly  100  includes a link element or member  216  between the chain stays  208  and the mainframe  104 . The various components of the assembly  100  can be connected to one another by pivot point assemblies  220 , to allow the components to move relative to one another in a controlled fashion. Accordingly, in this example, the assembly  100  includes at least portions of a bicycle frame. However, it should be appreciated that embodiments of the present disclosure are not limited to bicycle frames or other bicycle components. 
       FIG.  2    depicts an exemplary composite structure  104 , in this example the main frame of a bicycle, incorporating multiple composite components in accordance with embodiments of the present disclosure. The composite structure  104  includes a closed aperture  112  generally formed between adjacent portions or surfaces  122  of the structure  104 , here generally corresponding to a downtube portion  122   a , a top tube portion  122   b , and a seat tube portion  122   c  of the frame. In accordance with embodiments of the present disclosure, and as discussed in greater detail elsewhere herein, some or all of the various portions  122   a - c  can be in the form of hollow composite structures that include a plurality of composite components. In addition, holes or apertures  224  can be formed in the composite structure  104 , for example at locations corresponding to pivot points  220 , or other structural features, such as mounting points or through holes for connecting other components or accessories. 
       FIGS.  3 A and  3 B  depict variants of the composite structure  104  in a cross-section taken along line 3-3′ in  FIG.  2   . In this example, the composite structure is a main portion of a bicycle frame. However, it should be appreciated that other products comprising unitary or multipart structures can be formed using embodiments of the present disclosure. In particular, composite structures  104  as disclosed herein can be used to form all or portions of various products, including products having complex shapes, a high-strength to weight ratio, and excellent impact resistance. Moreover, as described herein, composite structures  104  can be formed with reduced costs, including reduced labor and production costs, and with reduced manufacturing time, as compared to conventional composite structures  104 . 
     The example composite structure  104  is formed using multiple composite structures or component parts  108   a  and  108   b  (see  FIGS.  3 A and  3 B ), and includes an aperture  112  within the component parts  108  (see  FIG.  2   ) formed within an outside perimeter of the composite structure  104 . The composite structure components  108  are formed in three dimensions, and when joined create a hollow space or interior volume  120  between adjacent interior portions or surfaces  124   a  and  124   b  of the components  108 . In addition, the composite structure components  108  are joined to one another along corresponding inside edge portions  128   a  and  128   b  and outside edge portions  132   a  and  132   b . In accordance with at least some embodiments of the present disclosure, the respective inside edge portions  128   a  and  128   b  and outside edge portions  132   a  and  132   b  are welded or fused to one another, forming a welded joint  136 . In accordance with at least some embodiments of the present disclosure, and as illustrated in  FIG.  3 A , a welding strip  140  can be provided adjacent to some or all of the joints  136 . 
     In accordance with further embodiments of the present disclosure, and as illustrated in  FIG.  3 B , a composite insert in the form of a braided tube or sleeve  138  can be disposed within the interior volume  120 , between the interior surfaces  124   a  and  124   b  of the components  108 . In such embodiments, the braided sleeve  138  can be provided in place of a welding strip. In addition, the braided sleeve  138  in such embodiments can function as an additional structural member or layer, and thus adjacent or surrounding structural components can be provided in a reduced thickness than if the braided sleeve  138  were not present. In accordance with embodiments of the present disclosure, a braided sleeve  138  can include a seamless structure having a plurality of reinforcing fibers and a plurality of thermoplastic threads woven together to form a flexible, tubular structure. Moreover, in at least some embodiments, the braided sleeve  138  is flexible, and has a diameter that can be varied by some amount from a nominal diameter, at least prior to welding or fusing the braided sleeve to an interior surface  124  of a composite structure component or components  108 . Accordingly, a braided sleeve  138  can be placed in contact with most or all of the surfaces of an interior volume  120 , even where the dimensions of the interior volume vary or are irregular. In accordance with still other embodiments, a composite structure  104  can include both a welding strip  140  and a braided sleeve  140 . For instance, a welding strip  140  can be provided that overlays the seams between adjacent edge portions  128   a - b , another welding strip  130  can be provided that overlays the seams between adjacent edge portions  132   a  and  132   b , and a braided sleeve  138  can be provided such that an outer surface of the braided sleeve contacts surfaces of the welding strips  140  that are not in contact with the interior surfaces  124   a  and  124   b  of the components  108  and further contacts surfaces  124   a  and  124   b  that are not covered by welding strips  140  or other components. As another example, a welding strip  140  can extend along a portion of a length of a joint between the components  108 , and a braided sleeve  138  can extend along another portion of the length of the joint between the components  108 . Although the components  108   a  and  108   b  are shown j oined along a butt j oint, alternative or additional joint types, such as but not limited to overlap or j oggle type j oints can be used, alone or in combination with welding strips  140 , one or more braided sleeves  138 , or both welding strips  140  and braided sleeves  138 . 
     Each composite structure component  108  may, for example, comprise one half of the completed composite structure  104 . In addition, the first composite structure component  108   a  and the second composite structure component  108   b  may mirror one another. However, such a configuration is not a requirement. In addition, a composite structure  104  can include any number of composite structure components  108 . Moreover, a single composite structure component  108  can be joined to multiple other composite structure components  108 . 
     With reference now to  FIGS.  4 A- 4 B , example composite structure components  108  are shown in a plan view looking at the interior surfaces  124   a  and  124   b  of the respective components  108   a  and  108   b . More particularly,  FIG.  4 A  illustrates the inside surface  124   a , the inside edge portions  128   a , and the outside edge portions  132   a  of the first composite structure component  108   a , while  FIG.  4 B  illustrates the inside surface  124   b , the inside edge portions  128   b , and the outside edge portions  132   b  of the second composite structure component  108   b . 
     The inside edge portions  128  and/or the outside edge portions  132  can be continuous, or can include discontinuities. Moreover, the inside edge portions  128  and/or the outside edge portions  132 , can be provided in multiple sections. The example composite structure components  108  depicted in  FIGS.  4 A and  4 B  include continuous inside edge portions  128  that define a closed aperture  112  in the frame or composite structure  104 . The example composite structure components  108  additionally feature outside edge portions  132  that include discontinuities. In particular, a first discontinuity is present in an area corresponding to a seat post aperture  304 , and second and third discontinuities are present in areas corresponding to the top  308  and bottom  312  of a head tube portion of the composite structure  104 . As a result of this configuration, the outside edge portions  132  of the example composite structure components  108  are provided in multiple sections: a first section  316   a  and  316   b  between the top  308  and bottom  312  of the head tube portion, a second section  320   a  and  320   b  between the bottom  312  of the head tube portion and the seat post aperture  304 , and a third section  324   a  and  324   b  between the seat post aperture  304  and the top  308  of the head tube portion. 
     In addition, one or more auxiliary apertures can be formed between the inside edge portion  128  and the outside edge portion  132  of one or both of the composite structure components  108 . For example, a first auxiliary aperture  328   a  may be formed in the first composite structure component  108   a  and a corresponding first auxiliary aperture  328   b  may be formed in the second composite structure component  108   b  to accommodate a bottom bracket assembly. As another example, a second auxiliary aperture  332  may be formed in the first composite structure component  108   a  only, to provide a mounting point for a component or accessory. 
     In accordance with embodiments of the present disclosure, each composite structure component  108  is formed from a composite panel  404 . An example composite panel  404 , before the forming process has been performed, is depicted in plan and cross-section views in  FIGS.  5  and  6    respectively. As shown, the composite panel  404  may comprise a planar panel prior to molding to form a composite structure component  108 . Moreover, as illustrated in  FIG.  6   , the composite panel  404  generally includes a plurality of composite sheets  504  that have been fused or welded to form the composite panel  404 . Each composite sheet  504  can include a thermoplastic material  508  and a plurality of reinforcing fibers  512  embedded therein. The composite sheets  504  are fused to one another through the application of heat and pressure.  FIG.  5    depicts a composite panel  404  after trimming of the completed composite panel  404  or the individual sheets  504 , to define inside edges  516  and outside edges  520 . The inside edges  516  define an aperture  524  in the composite panel  404 . Some or all of the inside edges  516  may be coincident with the inside edge or edges  128  of the formed composite structure component  108 . In addition, some or all of the outside edges  520  may be coincident with the outside edge or edges  132  of the composite structure component  108 . Alternatively, the edges  516  and  520  can approximate the respective edges  128  and  132  of the composite structure component  108 . For instance, the edges  128  and  132  of the composite structure component  108  can be formed by trimming after the composite panel  404  has been molded into the three-dimensional shape of the composite structure component  108 . 
     Different composite sheets  504  within a composite panel  404  can have different fiber  512  orientations and configurations, as illustrated in  FIGS.  7 - 9   . For example, one or more composite sheets  504  within a composite panel  404  can feature relatively long fibers  512  that can extend between adjacent edges of the sheet  504 . Such a configuration is illustrated in  FIGS.  7  and  8   , with fibers  512  that extend between different outside edges  520 , or between an outside edge  520  and an inside edge  516 . The composite sheets  504   a  and  504   b  with relatively long fibers  512  can have those fibers configured unidirectionally, such that the fibers  512  extend in the same general direction. In accordance with further embodiments, the fibers  512  can be parallel or substantially parallel to one another. As used herein, fibers  512  are substantially parallel if they extend along a common direction +/-10°. Moreover, two or more sheets  504  having relatively long fibers  512  can be aligned such that the fibers  512  of one composite sheet  504  are at a nonzero angle with respect to the fibers  512  of another one of the composite sheets  504 . Alternatively or in addition, one or more of the composite sheets  504  can have relatively short, randomly oriented fibers  512 . More particularly, the fibers  512  can be randomly oriented in at least a plane encompassing the edges of the composite sheet  504  when that sheet  504  is in a flat configuration.  FIG.  9    depicts a composite sheet  504   c  having randomly oriented fibers  512  embedded within a thermoplastic material  508 . As shown, the fibers  512  in this example are relatively short, and generally do not extend between opposite edges  516  and  520  of the composite sheet  504 . In accordance with still other embodiments, the fibers  512  within a composite sheet  504  can be woven, with subsets of fibers and selected angles with respect to other subsets of fibers within the composite sheet  504 . 
     In the example layup of sheets  504  within a composite panel  404  illustrated in  FIG.  6   , a first composite sheet  504   a  comprising a first layer has relatively long fibers  512  oriented in a first direction, a second composite sheet  504   b  comprising a second layer has relatively long fibers  512  oriented in a second direction, which in this example is orthogonal to the first direction, and a third composite sheet  504   c  comprising a third layer has relatively short fibers  512  in random orientations within the thermoplastic material  508 . In an exemplary embodiment, the first composite sheet  504   a  may form an inside surface  124  of a finished composite structure component  108 , while the third composite sheet  504   c  may form an exterior surface of the finished composite structure component  108 . In addition, embodiments of the present disclosure can include spacer or filler sheets or layers between sheets  504  containing thermoplastic material  508  and fibers  512 . A spacer or filler layer can include various materials, such as but not limited to glass or foam embedded in or impregnated with a thermoplastic material  508 . 
     In accordance with at least some embodiments of the present disclosure, the composite panel  404  is formed as a planar or substantially planar panel from textile-like composite sheets  504 . The individual sheets may or may not be flexible at room temperature. Each of the composite sheets  504  may be in the form of a substantially continuous sheet, for example in the shape of a rectangle, that is trimmed to form edges  516  and  520 , and one or more apertures  524 , before they are initially stacked with one another to form the layup of the composite panel  404 . Alternatively, some or all of the composite sheets  504  may be trimmed after being fused to one or more other composite sheets  504 . Whether formed in individual or sub-sets of composite sheets  504 , or in a completed composite panel  404 , the edges  516  and  520  generally follow a pattern that approximates the shape of the composite structure component  108  that will be formed from the composite panel  404 . In addition, all or portions of the edges  516  and  520  can include fringes or slots, and one or more apertures  524  can be formed within the outer perimeter of the composite panel  404 , to assist in obtaining a desired three-dimensional composite structure component  108  from the composite panel  404 . 
       FIG.  10    depicts a sub-assembly  204 , in this example a swingarm assembly, incorporating multiple interconnected components that include multiple composite structures in accordance with embodiments of the present disclosure. The composite structures of the swingarm assembly  204  in this example include a pair of seat stays  208  and a chain stay structure or assembly  212 . The seat stays  208  and chain stay assembly  212  are connected to one another by a pair of pivot point assemblies  220 . In accordance with other embodiments of the present disclosure, the entire swingarm assembly  204  can be formed as an integral structure, rather than as multiple structures interconnected by pivots. 
       FIG.  11    depicts a single seat stay  208 , and is another example of a composite structure incorporating multiple composite components in accordance with embodiments of the present disclosure.  FIG.  12    is an exploded perspective view of the exemplary composite structure incorporating multiple composite components of  FIG.  11   . As shown in the exploded view, each seat stay  208  can include a first component part  228   a , in this example an outside seat stay portion, and a second component part  228   b , in this example an inner seat stay portion. Each component part  228  can itself be a three-dimensional composite structure formed from multiple layers of fiber reinforced thermoplastic material, as described in greater detail elsewhere herein. Various holes or apertures  224  can be formed in the component parts  228 , for example to accommodate fasteners, components, or pivot points. In addition, the seat stay  208  can include one or more composite inserts, such as carbon or composite block members  232  and/or braided sleeves  138 . As discussed elsewhere herein, composite block members  232  can include solid or substantially solid blocks of thermoplastic or fiber reinforced thermoplastic material formed in a shape that conforms to all or a portion of an interior volume formed between two or more component parts. A braided sleeve  138  can extend along some or all of an interior portion of the seat stay  208 , within a volume defined by the component parts  228  for most of a longitudinal extent or length of the seat stay  208 . Accordingly, the braided sleeve  138  can function as an additional structural member or layer. As discussed in greater detail elsewhere herein, in this and other embodiments of the present disclosure, an exterior surface of the braided sleeve  138  can conform and can be fused to the interior surface or surfaces of other composite structure components, such as the component parts  228 . In addition, a braided sleeve  138  can supplement or can replace a welding strip in an area of a joint or j oints between the component parts  228 . Moreover, a first end of the braided sleeve  138  can be adjacent or in contact with a block member  232   a  at or towards a first end of the seat stay  208 , and a second end of the braided sleeve can be adjacent or in contact with a block member  232   b  at or towards a second end of the seat stay  208 . In accordance with still further embodiments, the seat stay  208  can include one or more inserts or attachment elements  236 , including but not limited to composite, carbon, metallic, ceramic, or plastic attachment elements, for receiving fasteners, forming bearing surfaces, or for forming other elements. 
       FIGS.  13  and  14    are views depicting a chain stay assembly  212 , and illustrate another exemplary composite structure incorporating multiple composite components in accordance with embodiments of the present disclosure.  FIG.  15    is an exploded perspective view of the chain stay assembly  212  of  FIGS.  13  and  14   . As shown in this example, the chain stay assembly  212  can include a first component part or composite structure component  240   a , in this example in upper chain stay assembly portion, and a second component part or composite structure component  240   b , in this example a lower chain stay assembly portion. Each component part  240  can itself be a composite structure, as described in greater detail elsewhere herein. Moreover, the chain stay assembly  212  can include one or more carbon or composite block members  232 , one or more braided sleeves  138 , and/or one or more attachment elements  236 . For instance, a first braided sleeve  138   a  can be provided within a first (e.g. a drive side) strut or stay portion of the chain stay assembly  212 . A second braided sleeve  138   b  can be provided within a second (e.g. a non-drive side) stay portion of the chain stay assembly  212 . Accordingly, the first and second braided sleeves  138   a  and  138   b  can function as additional structural elements or layers. As shown in  FIG.  15   , in addition or as an alternative to integration with one or more component parts  240 , a further braided sleeve  138   c  can be integrated with one or more composite block members  232 . For instance, in the illustrated example, a braided sleeve  138   c  extends along one side of the assembly  212  to provide a passageway or housing that enables a control cable or line to be internally routed through the chain stay assembly  212  between an aperture or stop formed in a first one of the block members  232   a  and an aperture or stop formed in a second one of the block members  232   b . In addition, various fixtures or attachment elements  236  included in the chain stay assembly  212  can be at least partially mounted in or received by holes or apertures that are at least partially formed in the block members  232 , whose solid structures are particularly suitable for providing for the secure mounting of such elements in the larger assembly. 
       FIGS.  16 A- 16 C  depict views of composite structure components, and in particular of portions of a chain stay assembly  212 , in accordance with embodiments of the present disclosure. In  FIG.  16 A , a lower chain stay assembly portion  240   b  is depicted in a top plan view. As shown, the edge portion  246   b  is divided into a number of segments, labeled  256   a - h  in the figure, by discontinuities  260 . Each discontinuity can correspond to a hole or aperture  224  in the chain stay assembly  212 .  FIG.  16 B  depicts composite block members  232  and a braided sleeve  138  that can be incorporated into the chain stay assembly  212 . In this example, three composite block members  232  are shown: a first composite block member  232   a  that occupies areas of a front pivot point in both left and right chain stay portions and a connecting or bridge portion between the left side and right side chain stay portions; a second composite block member  232   b  that occupies an area at a rear end of the right side chain stay portion, for example in an area in which attachment elements or integral surfaces for receiving a portion of a rear wheel axel or fastener, for receiving a derailleur, for establishing a pivot point, and/or for receiving or otherwise providing mounting or locating points for other components is located; and a third composite block member  232   c  that occupies an area at a rear end of the left side chain stay portion, for example in an area in which attachment elements for receiving another portion of the rear wheel axel or fastener, for receiving brake caliper mounting hardware, for establishing a pivot point, or for otherwise providing mounting or locating points for other components is located. In addition, a braided sleeve  138   c  that can be included to form a guide or housing for a control cable or line is illustrated.  FIG.  16 C  illustrates those composite block members  232  positioned against the interior surface of the lower chain stay assembly portion  240   b , and the braided sleeve  138   c . Although not shown, additional composite block members  232  and/or braided sleeves  138  can be provided. For example, an additional composite block  232  can be proved in a brake caliper mounting area, and an additional braided sleeve  138  can be provided to receive or form a hydraulic brake line that will connect to the brake caliper. 
     In accordance with embodiments of the present disclosure, a composite block  232  can be formed using various means, including placing layers of thermoplastic  508  fiber  512  reinforced sheets  504  on top of one another to form a rough block having a shape approximating the final shape of the three dimensional composite block  232 , and applying heat and pressure to the rough block, for example by placing it in a heated mold, to form the final composite block  232  structure. In such embodiments, the orientation of the reinforcing fibers  512  within the individual sheets  504  used to form the composite block  232  can be selected such that their orientation is nonparallel to a joint or j oints, including but not limited to butt j oints  244  and overlapping joints  254 , in an area of a structure  212  incorporating the composite block  232 . Accordingly, the orientation of the fibers  512  in a composite block  232  can be selected to span a joint line between composite panels or components. In accordance with further embodiments of the present disclosure, the fibers  512  in composite sheets  504  forming the interior surfaces of joined composite panels can be parallel to one another and also parallel to fibers  512  in a composite block occupying a volume between the composite panels, at least along and near the joint line. An example of such a configuration is depicted in  FIG.  17 I , showing a side cross-section view of an interior of an assembly along line G-G′ in  FIG.  16 D , and in particular depicting the orientation of the fibers  512  in the composite block  232  and in the interior sheets forming the interior surfaces  248   a  and  248   b  of the composite panels included in the assembly  212 . Although components included in a chain stay assembly  212  are used to illustrate this aspect of embodiments of the present disclosure, it should be appreciated that other components and structures can be constructed as discussed herein. 
       FIGS.  17 A-H  depict cross sections of an example composite structure in accordance with embodiments of the present disclosure. Although the example is of a chain stay assembly  212  as generally illustrated in  FIGS.  13 - 16   , it should be appreciated that the various configurations can be applied to other composite structures. As shown in  FIG.  17 A , at least at the cross-section taken along line A-A′ of  FIG.  14   , the upper chain stay assembly portion  240   a  is joined to the lower chain stay assembly portion  240   b  by a butt joint  244 . Accordingly, an edge portion  246   a  of the upper chain stay assembly portion  240   a  and an edge portion  246   b  of the lower chain stay assembly portion  240   b  abut and are fused or otherwise joined to one another. In addition, an interior surface  248   a  of the upper chain stay assembly portion  240   a  and an interior surface  248   b  of the lower chain stay assembly portion  240   b  define an interior volume  252  therebetween. Moreover, in this example, at least at line A-A′ the interior volume  252  is occupied by a composite block member  232   a . As described in greater detail elsewhere herein, the composite block member  232  can be fused or otherwise joined to the chain stay assembly portions  240 , forming an integral composite structure. At least in areas of the butt joint  244  adjacent the composite block member  232   a , a welding strip can be replaced by the composite block  232   a . In other embodiments, a welding strip  140  can be provided between the area of the butt joint  244  and the composite block member  232   a  (as shown in  FIG.  17 B , which is an example of a cross-section taken along section line B-B′ of  FIG.  14   ). In accordance with at least some embodiments of the present disclosure, the composite structure can additionally include one or more braided tubes  138 . For instance, as shown in the figure, a braided tube  138   c  can be provided as a guide or passageway to house an electronic control and/or power cable, a mechanical control cable, a hydraulic line, hydraulic fluid, or the like. In addition, multiple braided sleeves  138  can be included, for example to operate or control multiple different mechanisms or devices. If included, at least portions of a braided sleeves  138  in the form of a guide or passageway can be disposed between an exterior surface of the composite block  132   a  and an interior surface  248   a  or  248   b  of the composite panels, and/or can be disposed within a receiving channel formed partially or entirely within the composite block  132   a . Moreover, the braided tube  138  can be fused to the composite block  132  and/or to an interior surface  248   a  or  248   b . 
     As shown in  FIGS.  17 C and  17 D , which are views of an example of the chain stay assembly  212  in a cross-section taken along line B-B′ of  FIG.  14   , the upper chain stay assembly portion  240   a  can be joined to the lower chain stay assembly portion  240   b  by a plain overlapping joint  254  ( FIG.  17 C ), or by a recessed overlapping joint  254  incorporating a joggle  258  in one of the portions  240  (here the lower chain stay assembly portion  240   b ), which creates a shoulder portion  262 , against which an end portion  246   a  of the upper chain stay assembly portion  240   a   abuts ( FIG.  17 D ). Moreover, although illustrated at section line B-B′, these and other joint configurations can be used at other locations. Accordingly, different joint types can be established between components of a composite structure at different locations of interconnection between those components. In this example, a portion of the interior surface  248   a  of the upper chain stay assembly portion  240   a  is joined to an exterior surface  256   b  of the lower chain stay assembly portion  240   b . In addition, interior surfaces  248  of the upper chain stay assembly portion  240   a  and the lower chain stay assembly portion  240   b  define an interior volume  252  that is occupied by a composite block member  232 , such that exterior surfaces of the composite block  132  in that area are entirely in contact with and fused to the interior surfaces  248   a  and  248   b  of the composite panels (except in an area of the braided sleeve  138   c ). As can be appreciated by one of skill in the art after consideration of the present disclosure, the overlapping joint  254  can be alternately configured. For instance, the exterior surface of the upper chain stay assembly portion  240   a  can be joined to an interior surface of the lower chain stay assembly portion  240   b . As another example, a recessed lap joint can include an area of reduced thickness in one or both of the composite panels in the area of overlap. 
     With reference now to  FIGS.  17 E-H , different example joints that can be established between component portions are illustrated at a cross-section taken along line C-C′ of  FIG.  14   , which in this example is an area in which a composite block is not included. Accordingly, interior surfaces  248  of the upper chain stay assembly portion  240   a  and the lower chain stay assembly portion  240   b  define an interior volume  252  that is open or unfilled. More particularly, the joints can include a plain overlapping joint  254  ( FIG.  17 E ), a recessed overlapping joint  254  ( FIG.  17 F ), a butt joint  244  ( FIG.  17 G ), and a butt joint  244  with a welding strip  140  ( FIG.  17 H ). Alternatively or in addition, the upper chain stay assembly portion  240   a  can joined to the lower chain stay assembly portion  240   b  by or along a joint that includes various alignment features, such as locating pins or ridges in one of the portions that are received by corresponding holes or troughs in the other one of the portions.  FIGS.  18 A- 18 C  depict views composite structure components, and in particular of portions of a chain stay assembly  212  in accordance with other embodiments of the present disclosure. In  FIG.  18 A , a lower chain stay assembly portion  240   b  is depicted in a top plan view, 
       FIG.  18 B  depicts composite block members  232  and braided sleeves  138  that can be incorporated into the chain stay assembly  212 .  FIG.  18 C  depicts the various composite block members  232   and braided sleeves  138  positioned within or relative to the lower chain stay assembly portion  240   b . In this example, three composite block members  232  are shown: a first composite block member  232   a  that occupies areas of a front pivot point in both left and right chain stay portions and a connecting or bridge portion between the left side and right side chain stay portions; a second composite block member  232   b  that occupies an area at a rear end of the right side chain stay portion, for example in an area in which attachment elements or integral surfaces for receiving a portion of a rear wheel axel or fastener, for receiving a derailleur, for establishing a pivot point, and for receiving or otherwise providing mounting or locating points for other components is located; and a third composite block member  232   c  that occupies an area at a rear end of the left side chain stay portion, for example in an area in which attachment elements for receiving another portion of the rear wheel axel or fastener, for receiving brake caliper mounting hardware, for establishing a pivot point, or for otherwise providing mounting or locating points for other components is located. Braided sleeves  138   a  and  138   b  are included that extend along at least a portion of the longitudinal extents of the right and left sides of the chain stay assembly  212 . In accordance with embodiments of the present disclosure, an end of a braided sleeve  138  can abut or can be spaced apart from a composite block  232 . In accordance with further embodiments of the present disclosure, at least portions of the braided sleeves  138  can be formed over other components. For example, a first end of the braided sleeves  138   a  and  138   b  can extend over portions of the composite block member  232   a  within a first overlap area  272  and a second end of the braided sleeves  138   a  and  138   b  can extend over respective portions of the composite blocks  232   b  and  232   c  within a second overlap area  276  (see  FIG.  18 C ). In addition, a braided sleeve  138   c  that can be included to form a guide or housing for a control cable or line is illustrated. Although shown as being provided as structural reinforcing members in both the left and right chain stay portions of the assembly  212 , it should be appreciated that asymmetrical arrangements are possible. For instance, a braided sleeve  138  can be provided as a reinforcing member only in the drive side chain stay of the assembly  212 . 
       FIGS.  19 A-H  depict cross sections of the example composite structure in accordance with embodiments of the present disclosure. Although the example is of a chain stay assembly  212  as generally illustrated in  FIGS.  13 - 15  and  18   , it should be appreciated that the various configurations can be applied to other composite structures. As shown in  FIG.  19 A , and similar to the embodiment of  FIG.  17 A , at least at the cross-section taken along line A-A′ of  FIG.  14   , the upper chain stay assembly portion  240   a  is joined to the lower chain stay assembly portion  240   b  by a butt joint  244 . Accordingly, an edge portion  246   a  of the upper chain stay assembly portion  240   a  and an edge portion  246   b  of the lower chain stay assembly portion  240   b  abut and are fused or otherwise joined to one another. In addition, an interior surface  248   a  of the upper chain stay assembly portion  240   a  and an interior surface  248   b  of the lower chain stay assembly portion  240   b  define an interior volume  252  therebetween. Moreover, in this example, at least at line A-A′, the interior volume is occupied by a composite block member  232   a . The composite block member  232  can be fused or otherwise joined to adjacent portions of the chain stay assembly  240 , forming an integral composite structure. 
     In accordance with at least some embodiments of the present disclosure, at least a portion of a braided sleeve  138   a  can be interposed between a composite block  232  and interior surfaces of composite structure components. For example, as shown in  FIGS.  19 B- 19 D , which are views of an example of the chain stay assembly  212  in a cross-section taken along line B-B′ of  FIG.  14   , a braided sleeve can surround a composite block  232  or a portion of the composite block  232 . At least at that section, the completed assembly  212  is a fused structure that includes the chain stay assembly portions  240 , the braided sleeve  138 , and the composite block  232 . As examples, a junction between the upper  240   a  and lower  240   b  chain stay assembly portions can include a butt joint  244  with a weld strip  140  between the joint  244  and the braided sleeve  138  ( FIG.  19 B ), a plain overlapping joint  254  ( FIG.  19 C ), or a recessed overlapping joint  254  ( FIG.  19 D ). Accordingly, different joint types can be established between components of a composite structure at different locations of interconnection between those components. As can be appreciated by one of skill in the art after consideration of the present disclosure, other configurations of a joint between composite structure components in an assembly incorporating a braided sleeve  238  and a composite block  232  can be alternately configured. 
     With reference now to  FIGS.  19 E- 19 H , different example joints that can be established between component portions in which a braided sleeve  138  is incorporated into the assembly are illustrated at a cross-section taken along line C-C′ of  FIG.  14   , which in this example is an area in which a composite block is not included. Accordingly, interior surfaces  248  of the upper chain stay assembly portion  240   a  and the lower chain stay assembly portion  240   b  define an interior volume  252  that is in contact with an exterior surface of a braided sleeve  138 , and with an open or unfilled volume defined by an interior surface of the braided sleeve  138 . More particularly, the braided sleeve  138  can be disposed such that the exterior surface of the braided sleeve conforms to the interior surfaces  248   a  and  248   b  of the portions  240  of the assembly, and the joints between those portions  240  can include plain overlapping joints  254  ( FIG.  19 E ), a recessed overlapping joint  254  ( FIG.  19 F ), a butt joint  244  ( FIG.  19 G ), and a butt j oint  244  with a welding strip  140  ( FIG.  19 H ). A braided sleeve  138  with an open interior volume can also be used with other types of joints between assembly portions  240 , including but not limited to joints that also include various alignment features, such as locating pins or ridges in one of the portions that are received by corresponding holes or troughs in the other one of the portions. 
       FIGS.  20 A- 20 C  depict portions of variations of a composite assembly, such as but not limited to a chain stay assembly  212 , in accordance with embodiments of the present disclosure in a cross section view along section line D-D′ of  FIG.  14   . As shown, a braided sleeve  138  can be disposed within an interior volume  252  formed between the interior surfaces  248   a  and  248   b  of component parts or portions  240   a  and  240   b  respectively. More particularly, an exterior surface of the braided sleeve  138  can be in contact with and can be fused to at least portions of the interior surfaces  248   a  and  248   b . As depicted in  FIGS.  20 A and  20 B , a thickness of the component parts  240  can be reduced in areas where the braided sleeve is in contact with those component parts  240 . In addition, a braided sleeve  138  can not only conform to different interior volume shapes in a transverse cross-section, for example as depicted in  FIGS.  19 B- 19 H , but it can alternatively or additionally conform to different interior volume shapes in a longitudinal cross section direction, for example as depicted in  FIGS.  20 B and  20 C . Moreover, as shown in  FIGS.  20 A- 20 C , a braided sleeve need not abut or receive a composite block  232 .  FIG.  20 D  depicts a portion of a composite structure, such as but not limited to a chain stay assembly  212 , in a side elevation view. In this example, an aperture or window is formed in one or both of the portions  240 , such that a portion of the exterior of the braided sleeve  138  forms a portion of the exterior surface of the assembly  212 . However, other portions of the exterior of the braided sleeve  138  are in contact with interior surfaces of the portions  240 . For example, at the ends of the braided sleeve  138 , the entire outer circumference of the braided sleeve can be in contact with, and can be fused to, interior surfaces  248  of the portions  240 . Moreover, along at least one continuous line extending between the ends of the braided sleeve  138 , the braided sleeve is in contact with the interior surface  248  of at least one of the portions  240 . 
     In accordance with embodiments of the present disclosure, and as illustrated in  FIG.  21   , a composite structure component, such as but not limited to a component or part of a chain stay assembly  212 , can be formed from a composite panel  404 , in this case in a size that encompasses an overall area of the component. The composite panel  404  includes a number of layers or sheets of fiber reinforced thermoplastic material  504  (for example as illustrated in  FIG.  6   ). In this way, a seat stay  204  or chain stay assembly  212  or other assembly can be constructed in a manner similar to a composite structure  104 .  FIG.  22    depicts an example of a first sheet  504   a  of a fiber reinforced thermoplastic material, with the fibers  512 , such as but limited to carbon fibers, embedded in, impregnated with, or otherwise interposed with a thermoplastic material  508 , that extend between opposite edges of the sheet  504   a , and that are oriented along a first direction.  FIG.  23    depicts an example of a second sheet  504   b  of a fiber reinforced thermoplastic material, with fibers  512  that extend between opposite edges of the sheet  504   b , and that are oriented along a second direction.  FIG.  24    depicts an example of a third sheet  504   c  of a fiber reinforced thermoplastic material, with relatively short, randomly oriented fibers  512 . As illustrated in the figures, the individual sheets  504   a - c  can be cut or trimmed into a shape that approximates a shape of the composite structure component after forming, prior to being joined to one another to form a composite panel  404 . Alternatively or in addition, the composite panel  404  incorporating the sheets  504  can be cut or trimmed after the sheets  504  have been joined to one another. As shown, fibers in at least two the first  504   a  and second  504   b  sheets can be cut or interrupted as part of forming the finished composite panel. For example, in forming a first open aperture  1208  in a first sheet  504   a , a first reinforcing fiber  512   a  can be segmented into a first segment  512   a   1  and a second segment  512   a   2 . 
       FIG.  25    is a detail of a portion of a composite structure at which a discontinuity  260  between edge segments  246  is present. As can be seen in this figure, different fibers  512  can extend between different portions of the structure. For example, a first fiber  512   a  can extend between a first discontinuity  260   a  and edge segment  256   h , a second fiber  512   b  can extend between the first discontinuity  260   a  and a second discontinuity  260   b , a third fiber  512   c  can extend between edge segment  256   a  and the second discontinuity  260   b , and a fourth fiber  512   d  can extend between edge segment  256   a  and edge segment  256   g . 
     A braided sleeve  138  in accordance with embodiments of the present disclosure is depicted in  FIG.  26   . In general, the braided sleeve  138  is a seamless, tubular structure formed from a braid of reinforcing fibers  512 , such as but not limited to carbon fibers, and thermoplastic or thermoplastic impregnated threads or fibers  2604 . The braided sleeve  138  can be configured in various nominal exterior diameters, and can be formed to have any length. At least prior to incorporation into a composite structure, the braided sleeve  138  is a flexible woven or braided fabric, such that exterior surfaces of the braded sleeve  138  can be placed against surfaces that are not strictly cylindrical. Accordingly, the braided sleeve  138  can be manipulated such that it can be placed in contact with interior surfaces of component parts  240  that define curved, asymmetric, or irregular volumes, within at least some range of volume sizes and configurations. In accordance with further embodiments of the present disclosure, the braided sleeve  138  can have a nominal diameter that can be increased by increasing a spacing between adjacent reinforcing fibers  512  and thermoplastic threads or fibers  2604 , and that can be decreased by decreasing a spacing between adjacent reinforcing fibers  512  and thermoplastic threads or fibers  2604 . 
     With reference now to  FIG.  27   , aspects of a process or method for producing a composite structure  104  in accordance with embodiments of the present disclosure are depicted. Initially, at step  2704 , a single composite panel  404  is formed. Forming the composite panel  404  can include selecting or forming from a larger piece of material a composite sheet that contains one or more sheets  504  of appropriate size, that incorporate a thermoplastic material  508 , and that have reinforcing fibers  512  in selected orientations. In addition, forming the composite panel  404  can include creating a layup or stack of composite sheets  504 , with different composite sheets  504  having a selected fiber  512  density and orientation relative to the other sheets  504 . The stack can include one or more spacer layers containing a filler material, but not fibers, and the same thermoplastic material as the thermoplastic material  508  of the other sheets  504 . The composite sheets  504 , and any spacer layers, within the stack can then be fused using heat and pressure, to form the composite panel  404 . More particularly, forming the composite panel  404  can include heating the thermoplastic material  508  in the composite sheets  504  to equal to or greater than the melting point of the thermoplastic material in order to fuse the composite sheets  504  to one another. The pressure applied during the composite panel  404  forming process can be greater than 100 psi. In further embodiments, the pressure applied during the composite panel  404  forming process can be greater than 400 psi. In still other embodiments, the pressure applied during the composite panel  404  forming process can be greater than 1000 psi. The composite panel  404  may have a generally flat or planar configuration, 
     At step  2708 , the composite panel  404  is shaped. Shaping the composite panel  404  can include cutting or trimming exterior boundaries of the composite panel to approximate a shape of the component part to be formed, entirely or in part, by the composite panel  404 . In addition, shaping the composite panel  404  can include forming a closed aperture  524  within a perimeter of the panel  404 , and/or forming an open aperture  1208  that crosses a perimeter of the composite panel  404 . In accordance with further embodiments of the present disclosure, forming a composite panel  404  can also include giving the panel  404  a selected contour or three-dimensional shape, for example to approximate a final shape of the composite structure component  108  or  240  formed from the composite panel  404 , and/or the final mold. 
     The composite panel  404  can then be preformed (step  2712 ). Preforming the composite panel  404  can include disposing the panel  404  on or adjacent a preform mold while applying heat to make the panel more pliable. For example, a heated fluid or a matched mold can be applied to a side of the composite panel  404  opposite the side adjacent the preform mold, causing the composite panel  404  to conform to or approximate the shape of the mold. Alternatively or in addition, the preform mold itself can be heated. In general, the heating of the composite panel  404  is controlled so as to maintain the temperature of the thermoplastic material  508  within the fused composite sheets  504  of the composite panel  404  to a temperature that is at or above the glass transition temperature and at or below the melting temperature of the thermoplastic material  508 . The preform molding step forms a preformed composite panel or portion  240 . In accordance with at least some embodiments of the present disclosure, the step of preforming, to create a preformed composite panel need not be performed, and the composite panel  404  can be placed in a final mold as a planar or substantially planar element. 
     At step  2716 , the preformed composite panel  240 , or if no preforming is performed, the composite panel  404 , is placed in one side of a final mold  2804  (see  FIG.  28   ). Next a determination is made as to whether a composite block  232  will be incorporated into the composite structure (step  2720 ). If a composite block  232  is to be included, it is sized and otherwise configured, and is placed against an interior surface of the composite panel  404  (step  2724 ). After placing any composite blocks  232 , or if no composite blocks  232  are to be included, the process can next include a determination as to whether a braided sleeve  138  will be included in the composite structure (step  2728 ). If a braided sleeve  138  is to be included, it is sized and placed against a surface of the composite panel  404  (step  2732 ). Where one or more composite blocks  232  are included in the composite structure, placing the braided sleeve can include abutting an end of the braided sleeve  138  against a surface of a composite block  232 , and/or placing a portion of the braided sleeve  138  over a portion of a composite block  232 . Moreover, placing a braided sleeve  138  can include placing a braided sleeve  138  having a nominal diameter that is equal or about equal (e.g. within +/- 10%) to an average diameter of an interior volume between panels  240 , and having a length that extends for at least most of a length of a component portion formed by the panels  240 . In accordance with at least some embodiments of the present disclosure, the braided sleeve  138  is positioned so that it forms an interior layer of composite materials in the composite structure. That interior layer can be located in or adjacent areas of the panels  240  having an otherwise reduced thickness. 
     Next, a forming element  2808  (see  FIG.  28   ) is placed in an interior volume between the panels  240  (step  2736 ). In accordance with embodiments of the present disclosure, a forming element  2808  is a bladder, inflatable bladder, or a mandrel that is used to maintain a desired interior volume characteristic of the composite structure. In general, a forming element  2808  or a portion of a forming element is placed in areas that in the finished component will be an open volume between opposing interior surfaces of adjacent components  108  or  240 . Where a braided sleeve  138  is included in the composite structure, a forming element  2808  or a portion of a forming element can be disposed within an interior of the braided sleeve  138  so as to shape or conform the braided sleeve  138  to an interior surface of the adjacent component  108  or  240 , as depicted in  FIG.  28   . In connection with a braided sleeve  138  provided as a cable guide or the like, an insert or mandrel can be placed therein to maintain a desired interior channel or passageway. 
     At step  2740 , a companion composite panel  404 , for example shaped into a portion  240  of the component using the process described above, is placed in another side  2812  ( FIG.  28   ) of the final mold  2804 . The mold halves are then brought together, and heat and pressure are applied to fuse the composite panels  404  to one another, and to any included composite blocks  232  and braided sleeves  138  (step  2744 ). The formed composite structure  104 , in the three-dimensional shape imparted by the final mold  1108 , is then cooled and removed from the final mold  1108  (step  2748 ). Any bladders, mandrels, or other internal forming elements  2808  can then be removed from the completed structure. Alternatively, any forming elements provided as sacrificial components can be left in the structure. The composite structure is then complete, and is ready for final finishing, such as sanding and painting. 
     Individual composite structures formed from one or multiple composite panels  404 , can be joined together to form larger composite structures during or after a step of final molding. Accordingly, the formation of composite structure components  108  in their final form, and the formation of the composite structure  104  from such components  108 , can be performed simultaneously. For instance, multiple preformed composite panels  404  can be fused to one another during a step of final molding. As another example, composite structures can be joined together after final molding by fusing or bonding the different structures, including unitary or multiple component structures, to one another, forming a larger composite structure. Fusing can include reheating the individual structure in the area of the j oint to a temperature that is at or less than the melting point of the composite, and at or higher than the heat deflection temperature, per ASTM D648, of the composite. As still another example, structures formed from multiple substructures can be bonded to one another using an adhesive. The joint at the seam or interface between the individual composite structures can be a butt joint, a lap joint, or can include different types of joints at different locations. 
     As discussed herein, one or more composite blocks  232  and/or braided sleeves  138  can be joined to a surface or surfaces of one or more composite panels  404  during the forming process. A composite block  232  can extend between opposing interior surfaces of composite panels  404 , and can function to apply pressure to those opposing surfaces during molding or forming of a composite structure. A braided sleeve  138  can be placed in contact with interior surfaces of composite panels, and can provide an additional layer or layers of long reinforcing fibers  512 , as well as additional thermoplastic material. Moreover, during the step of heating and applying pressure, a composite block or blocks  232  and braided sleeves  138  can be fused to a panel or panels  404  and can then function as part of an integral composite structure, including but not limited to a mainframe  104 , a seat stay  208 , or a chain stay assembly  212  of a bicycle. 
     In accordance with embodiments of the present disclosure, a composite block  232  can be formed from trimmings or other waste material resulting from the production of various composite structure components. Accordingly, a composite block  232  can include a thermoplastic material and a plurality of fibers  512  embedded therein. Moreover, a composite block  232  can be formed by layering sheets of fiber reinforced thermoplastic material, compression molding, or injection molding. Where a composite block  232  is formed by layering, layers or panels having relatively long, unidirectionally aligned fibers can be collected or aggregated and selectively oriented within the composite block  232 , and the various layers can be fused to one another. Fusing can include heating the aggregated fiber reinforced thermoplastic material to a temperature that is at or greater than the melting point of the thermoplastic material, and optionally by also applying pressure. Where a composite block  232  is formed by molding, a collection or aggregation of mulched or chipped fiber reinforced thermoplastic material can be used as the base stock. For compression molding, the fibers  512  can be relatively long, including long enough to extend from one side of the composite block  232  to another. The compression molding includes heating the aggregated thermoplastic fiber reinforced material to a temperature that is at or less than the melting point of the thermoplastic material, but higher than the deflection point of the thermoplastic material, and applying pressure using a mold. For injection molding, a finer mulch is desirable, so that the length of the fibers  512  is reduced, facilitating injection of the material into the mold. In addition, the injection molding process includes heating the aggregated thermoplastic fiber reinforced material to a temperature that is at or greater than the melting point of the thermoplastic material. Whether formed by layering or molding, the final three-dimensional shape of the composite block  232  can be finalized through trimming, sanding, or other processes. 
       FIG.  29    is a flowchart illustrating aspects of forming a composite block  232  by a molding process in accordance with embodiments of the present disclosure. Initially, at step  2904 , base stock or material is collected or aggregated. The base stock can include fiber reinforced thermoplastic material that has been trimmed or otherwise removed from sheets or panels or even complete structures. Accordingly, the base stock can include fiber reinforced thermoplastic material separated from composite panels constructed in accordance with embodiments of the present disclosure that might otherwise be discarded as waste. Embodiments of the present disclosure thus provide methods for recycling fiber reinforced thermoplastic material. The base stock is then sized (step  2908 ). Sizing the base stock can include mulching or chipping to reduce included fiber lengths to less than or equal to a desired maximum size. As an example, for a compression molded composite block  232 , the fibers  512  may be relatively long (e.g. greater than 6 mm in length), while for an injection molded composite block  232 , the fibers  512  are relatively short (e.g. less than 6 mm in length). The sized base stock is then aggregated, heated and introduced to a mold (step  2912 ). In a compression molding process, the heated and sized base stock can be formed to a final or near-final composite block  232  shape by clamping the material between two mold halves. In an injection molding process, the sized base stock is heated until the thermoplastic material is liquefied or is sufficiently pliable for introduction to an injection mold. The thus formed composite block  232  is then removed from the mold and cooled (step  2916 ). The composite block  232  can then be finished by trimming away flash or otherwise performing a final shaping (step  2920 ). The shaped composite block  232  can then be joined to other components of a composite structure (step  2924 ). In accordance with embodiments of the present disclosure, joining the composite block  232  to other components can include placing the composite block  232  within an area of a finally or partially shaped composite panel, and joining a second composite panel to the first composite panel such that the composite block is held within a volume defined by interior surfaces of the composite panels, and heating the components to fuse them to one another. Accordingly, joining a composite block  232  to other composite structure components and the j oining of those other composite structure components can be performed simultaneously. The process can then end. 
     As discussed herein, the composite sheets  504  can include one or more sheets having a large number of randomly oriented fibers  512  that are impregnated in a thermoplastic material  508 . More particularly, the fibers  512  are randomly oriented in at least a plane encompassing the edges of the composite sheet  504  while that sheet is held flat. The composite sheet  504  is relatively thin, for example, but without limitation, having a thickness of from about 0.3 mm to about 4 mm. The fibers  512  in such a sheet  504  are relatively short, having, for example, but without limitation, a length of from 4 mm to 25 mm. As another example, the fibers in a sheet  504  having relatively short, randomly oriented fibers, can be from about 2 mm to about 25 mm in length, where about is +/- 10% of the nominal length. Moreover, fibers  512  of different lengths can be incorporated into a single composite sheet  504 . In accordance with the exemplary embodiments of the present disclosure, the composite sheets  504  includes from about 1 gram per cubic centimeter to about 2 grams per cubic centimeter of fibers  512 . By volume, the ratio of fibers  512  to thermoplastic material  508  can be selected such that from 20% to 70% of the volume comprises fibers  512 , and such that the remainder of the volume comprises the thermoplastic material  508 . The fibers  512  of a sheet  504  having a unidirectional, woven, or random orientation can comprise fibers having a selected tensile strength. For example, the fibers  512  can have a high modulus or stiffness and/or high tensile strength (e.g. a modulus greater than 280 Gpa and a tensile strength greater than 2,500 Mpa), and can comprise carbon fibers. As another example, fibers  512  of different tensile strengths can be included in a single composite sheet  504 . In accordance with at least some embodiments of the present disclosure, the fibers  512  may comprise recycled materials. For instance, the fibers  512  may be obtained from cuttings created in forming sheets of traditional, continuous ply carbon fiber materials. The thermoplastic material  508  can comprise any material that can be formed or re-formed by heating. For example, the thermoplastic material  508  may comprise a polyamide or a thermoplastic resin. In accordance with exemplary embodiments of the present disclosure, the composite sheet  504  weighs from about 1.2 g/cc to about 1.8 g/cc. 
     According to at least some embodiments of the present disclosure, composite structures or composite structure components are formed by molding one or more composite panels that each include one or more composite sheets containing a thermoplastic material and fibers impregnated with the thermoplastic material into a desired three-dimensional configuration. In accordance with further embodiments of the present disclosure, multiple composite structure components can be fused or otherwise joined together to form a composite structure. In accordance with still further embodiments, the formation of a composite structure containing multiple composite structure components, including composite panels and composite inserts, that are fused to one another can be performed simultaneously with the molding or final molding of composite panels into the final shapes of the respective composite structure components. Moreover, components formed from metal or other materials may be fused to one or more of the composite structure components at the same time that the composite structure components are fused to one another to form the composite structure. 
     The foregoing discussion has been presented for purposes of illustration and description. Further, the description is not intended to limit the disclosed structures, systems and methods to the forms disclosed herein. Consequently, variations and modifications commensurate with the above teachings, within the skill or knowledge of the relevant art, are within the scope of the present disclosure. The embodiments described hereinabove are further intended to explain the best mode presently known of practicing the disclosed structures, systems and methods, and to enable others skilled in the art to utilize the disclosed structures, systems and methods in such or in other embodiments and with various modifications required by the particular application or use. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.