Patent Publication Number: US-2017350048-A1

Title: Short fiber composite material

Description:
BACKGROUND 
     The subject matter disclosed herein relates to fiber reinforced composite materials, and more particularly to composite materials having discontinuous fiber reinforcement. 
     Continuous fibers, such as continuous carbon fibers or continuous glass fibers, are traditionally used as reinforcement for polymer matrix composite (PMC) material. Continuous fiber tows, or rovings, are used to make either prepreg tapes (including the fiber and a matrix material such as epoxy resin) or woven into a fabric. Prepreg tapes with continuous fibers are generally not flexible enough to form components with complex shapes. Further, the mechanical performance of the uni-directional continuous fiber prepreg materials are superior to woven fabric reinforced composites due to the fiber undulation necessary to construct the woven fabric. 
     As an alternative to the continuous fiber construction, materials with relatively short fiber lengths are being produced. One method of such production begins with continuous fibers, which are then stretched until the continuous fibers break into shorter fibers. Such a process is costly, since it uses continuous fibers as its basis. Further, the stretch-break process is difficult to control. Other short fiber production technologies exist, but those processes result in randomly-oriented short fibers, in which the directional or anisotropic advantages of composite materials are lost. 
     SUMMARY 
     In one embodiment, a method of forming a fiber reinforced composite material includes cutting a plurality of reinforcing fibers to a selected length, directing the plurality of reinforcing fibers through a fiber alignment mechanism, orienting the plurality of reinforcing fibers in a selected direction via the fiber alignment mechanism, and adhering the aligned plurality of reinforcing fibers to a substrate material to form the fiber reinforced composite material. 
     Additionally or alternatively, in this or other embodiments the fiber alignment mechanism is one of air, an ultrasonic field or an alignment blade. 
     Additionally or alternatively, in this or other embodiments directing the plurality of reinforcing fibers through the filter alignment mechanism includes directing the plurality of reinforcing fibers through an electrical field to orient the plurality of reinforcing fibers in the selected direction. 
     Additionally or alternatively, in this or other embodiments adhering the aligned plurality of reinforcing fibers to the substrate material includes adhering the aligned plurality of reinforcing fibers to a matrix material. 
     Additionally or alternatively, in this or other embodiments the aligned plurality of reinforcing fibers and the substrate material are directed through a consolidation roller to adhere the aligned plurality of reinforcing fibers to the substrate material. 
     Additionally or alternatively, in this or other embodiments the fiber reinforced composite material is collected at an output roller. 
     Additionally or alternatively, in this or other embodiments the plurality of fibers is a plurality of carbon fibers or glass fibers. 
     In another embodiment, a system for manufacturing a fiber reinforced composite material includes a feed mechanism to direct a substrate material along a selected path, a cutting mechanism to cut a plurality of reinforcing fibers to a selected length, and a fiber alignment mechanism to orient the plurality of reinforcing fibers in a selected direction before adhering the plurality of reinforcing fibers to the substrate material. 
     Additionally or alternatively, in this or other embodiments the fiber alignment mechanism is one of an airflow, or an ultrasonic emitter. 
     Additionally or alternatively, in this or other embodiments the fiber alignment mechanism includes a conductive element configured to emit an electrical field, the electrical field configured to orient the plurality of reinforcing fibers in a selected direction when the plurality of reinforcing fibers pass through the electrical field. 
     Additionally or alternatively, in this or other embodiments the fiber alignment mechanism includes an alignment blade to mechanically orient the plurality of reinforcing fibers in a selected direction. 
     Additionally or alternatively, in this or other embodiments a consolidation roller adheres the plurality of reinforcing fibers to the substrate material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic illustration of an embodiment of a fiber reinforced composite material; 
         FIG. 2  is an illustration of a manufacturing process for a fiber reinforced composite material; 
         FIG. 3  is an illustration of another embodiment of a manufacturing process for a fiber reinforced composite material; and 
         FIG. 4  is an illustration of yet another embodiment of a manufacturing process for a fiber reinforced composite material. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure includes continuous relatively low-cost manufacturing processes for fabricating short-fiber tapes or prepreg materials in which the short fibers are aligned in a selected direction. The processes integrate cutting to length, alignment, and impregnation of the aligned fibers into a matrix material sequentially. 
     Referring now to  FIG. 1 , shown is a schematic illustration of an embodiment of a fiber reinforced composite material  12 . The composite material  12  includes a matrix film  14 , which in some embodiments includes an adhesive material, such as an epoxy adhesive material. The composite material includes a plurality of reinforcing fibers  18 , such as carbon fibers or glass fibers, arrayed in the matrix film  14 . The reinforcing fibers  18  are discontinuous and are aligned and oriented to extend in a selected direction. One skilled in the art will readily appreciate that other fibers may be utilized in the composite material  12 . 
     Referring now to  FIG. 2 , illustrated is an example of a manufacturing process  10  for fabricating the composite material  12  with discontinuous fibers oriented along a selected direction. The process  10  utilizes the matrix film  14 , and in some embodiments, the matrix film  14  is provided in roll form for feeding into the manufacturing process  10 . Reinforcing fiber material  16 , including reinforcing fibers  18 , is provided for utilization in the manufacturing process  10 . 
     The matrix film  14  is fed continuously from a feed portion, for example, a feed roller  20  to an output portion, for example, an output roller  22 . While the matrix film  14  follows this path from the feed roller  20  to the output roller  22 , the reinforcing fiber material  16  is fed into the manufacturing process  10  over the matrix film  14 . The reinforcing fiber material  16  may be in the form of, for example, a narrow sheet, a tow or roving, or a yarn. The reinforcing fiber material  16  proceeds through a fiber cutter  24  where the reinforcing fiber material  16 , and thus the reinforcing fibers  18  in the reinforcing fiber material  16 , are cut to a selected fiber length. 
     The cut reinforcing fibers  18  are then laid on the passing matrix film  14 . In some embodiments, the fiber cutter  24  is located over the matrix film  14 , so the cut reinforcing fibers  18  are placed on the matrix film  14  via gravity. The matrix film  14  has a selected degree of tackiness or stickiness allowing for movement of the cut reinforcing fibers  18  on the matrix film  14  while maintaining adhesion of the cut reinforcing fibers  18  at the matrix film  14 . The matrix film  14  and cut reinforcing fibers  18  proceed to a fiber orientation mechanism  26 . The fiber orientation mechanism  26  acts on the cut reinforcing fibers  18  to move the cut reinforcing fibers  18  to a selected orientation, for example, orienting the cut reinforcing fibers  18  along a length  28  of the matrix film  14 , or conversely, across a width of the matrix film  14 . In other embodiments, the selected orientation may be not along the length  28  or across the width, but may be at an angle nonparallel to both the width and the length  28 . 
     The fiber orientation mechanism  26  may utilize one or more technologies to move the cut reinforcing fibers  18  to the selected location as the cut reinforcing fibers  18  are placed on the matrix film  14 , or after the cut reinforcing fibers  18  contact the matrix film  14 . Such technologies may include, but are not limited to, a flow of air to orient the cut reinforcing fibers  18 , dielectrophoresis, where the cut reinforcing fibers  18  are subjected to an uneven electrical field to orient the cut reinforcing fibers  18 , or ultrasonic waves may be utilized to align the cut reinforcing fibers  18 . In other embodiments, as shown in  FIG. 3 , a plurality of alignment blades  40 , which may be stationary or moving, are used to align and orient the cut reinforcing fibers  18 . Once the cut reinforcing fibers  18  are aligned in the selected orientation, the matrix film  14  and cut reinforcing fibers  18  are passed through a consolidation mechanism, for example, consolidation rollers  30 , where the cut reinforcing fibers  18  and the matrix film  14  are consolidated to form the composite material  12 , in the form of a composite material tape, which is wound onto the output roller  22 . 
     Another embodiment of the manufacturing process is illustrated in  FIG. 4 . In the embodiment of  FIG. 4 , instead of collecting the cut reinforcing fibers  18  at the matrix material  14 , a paper  32  or other such material with a selected degree of adhesion is utilized to collect the cut reinforcing fibers  18 . Once the reinforcing fibers  18  are cut, or alternatively chopped, at the fiber cutter  24 , the cut reinforcing fibers  18  pass through the fiber orientation mechanism  26  for alignment in the selected direction. In the embodiment shown in  FIG. 4 , the fiber orientation mechanism is an electrical field or voltage potential applied at conductive elements  34 . A voltage is applied across the conductive elements  34 , and the cut reinforcing fibers  18  pass between the conductive elements  34  and are thus subjected to the electrical field, resulting in the alignment of the cut reinforcing fibers  18  in the selected direction. 
     The oriented or aligned cut reinforcing fibers  18  proceed, in some embodiments via gravity, to the paper  32  to which the cut reinforcing fibers  18  are adhered. In some embodiments, the reinforcing fibers  18  and paper  32  then may pass through a tackifier, such as a spray tackifier  36  to further adhere the cut reinforcing fibers  18  to the paper  32 , and may proceed through consolidation rollers  30 . As needed, the paper  32  may proceed past the fiber cutter  24  more than once to collect additional cut reinforcing fibers  18 . The paper  32  and cut reinforcing fibers  18  can then be fully impregnated with matrix material  14  resulting in the composite material  12  with discontinuous reinforcing fibers  18  with an alignment in a selected direction. 
     The composite material  12  with aligned, discontinuous reinforcing fibers  18  may be more readily utilized to fabricate complexly-shaped components because the discontinuity of the reinforcing fibers  18  increases flexibility of the composite material  12 . Further, because of the alignment of the reinforcing fibers  18 , the anisotropic or directional property features of a traditional composite material are maintained. 
     While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate in spirit and/or scope. Additionally, while various embodiments have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.