Abstract:
An assembly comprising a first composite fiber reinforced part that is joined to a second part by a clinch joint. The first part includes a first layer of resin that is reinforced with fibers and a second layer of resin that is devoid of fibers and applied to one side of the first layer of fiber reinforced resin. The second part contacts the first layer of the first part. The first part and second part are joined by a clinch joint including a pressed out portion that is pressed into a clinching portion. The second layer of resin contains the fibers in the first part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/155,694, filed Jan. 15, 2014, currently pending, the disclosure of which is hereby incorporated in its entirety by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    A composite panel and method of making the composite panel that is adapted to be joined to another panel with a clinch joint. 
       BACKGROUND 
       [0003]    Composite panels are used to manufacture structural and body panels for vehicles and in other products. Composite panels are made of polymeric resins that are reinforced with carbon fibers, glass fibers, natural fibers, or the like. Composite panels are strong, light weight and may be used in a wide variety of product applications. 
         [0004]    Composite panels may be assembled to other panels made of aluminum, steel or composites. Common fasteners, rivets or clinch joints may be used to join the panels together. One problem with clinch joints is that the reinforcing fibers may break through the surface of the composite panel. Carbon or natural fiber reinforcing fibers may absorb moisture if they break through the surface of the composite panel. Fibers that absorb moisture can be objectionable because they may cause corrosion and may weaken the joints. Carbon fibers when exposed to moisture may cause galvanic corrosion when they come into contact with metal parts or fasteners. 
         [0005]    The above problems and other problems are addressed by this disclosure as summarized below. 
       SUMMARY 
       [0006]    According to one aspect of this disclosure, an assembly is provided that is joined by a clinch joint. The assembly comprises a first part including a first layer of resin reinforced with fibers and a second layer of resin applied to one side of the first layer of resin. A second part contacts the first layer of first part and is joined to the first part by the clinch joint. The clinch joint includes a pressed-out portion of the first part that is pressed into a clinching portion of the second panel with the second layer of resin containing the fibers in the first part. 
         [0007]    According to other aspects of this disclosure as it relates to the assembly, the first part may be formed in a compression molding process with the first layer being formed in a first step and the second layer being applied to the first layer after the first layer is formed. Alternatively, the first part may be formed in a compression molding process with the first layer and the second layer being formed in a single step. The second layer may be formed against a textured surface of a compression molding die that inhibits the fibers from entering the second layer. 
         [0008]    The second layer may be provided on a partial area on the one side of the first layer where the clinch joint joins the first part to the second part. A plurality of clinch joints may be formed to join the first part to the second part and the second layer may be provided on a plurality of partial areas on the one side of the first layer where the clinch joints join the first part to the second part. Alternatively, the second layer may be provided on the entire one side of the first layer. 
         [0009]    The fibers may be carbon fibers, glass fibers, talc, or natural fibers. The second part may be formed of steel, aluminum, magnesium, or composite resin. 
         [0010]    According to another aspect of this disclosure, a method is provided for forming a clinch joint for joining a plurality of panels. The method comprises molding a first part that includes a first layer of resin reinforced with fibers. A second layer of resin is molded onto one side of the first layer of resin. A second part is assembled to the first layer of first part and the first part is joined to the second part by pressing a pressed-out portion of the first part into a clinching portion of the second panel. The second layer of resin inhibits the fibers in the first layer from protruding from the first part in the area of the clinch joint. 
         [0011]    According to other aspects of the method, the molding steps may be performed in a compression molding process wherein the first layer is formed in a first step and the second layer is applied to the first layer in a second step after the first layer is formed. Alternatively, the molding steps may be performed in a compression molding process wherein the first layer and the second layer are formed in a single step, and wherein the second layer is formed against a textured surface of a compression molding die that inhibits the fibers from entering the second layer. 
         [0012]    The step of molding the second layer may further comprise molding the second layer to a partial area on the one side of the first layer where the clinch joint joins the first part to the second part. A plurality of clinch joints may be formed to join the first part to the second part and the step of molding the second layer may further comprise molding the second layer to a plurality of partial areas on the one side of the first layer where the clinch joints join the first part to the second part. Alternatively, the step of molding the second layer may further comprise molding the second layer on one entire side of the first layer. 
         [0013]    According to another aspect of this disclosure, an assembly including a first composite panel formed of a fiber reinforced resin that has no fibers in a predetermined intended clinch joint forming area. A clinch joint formed in the intended clinch joining area joins the first panel to a second panel and exposed fibers are avoided on the clinch joint. 
         [0014]    The above aspects and other aspects of this disclosure are described in greater detail below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a fragmentary perspective view of a prior art clinch joint joining a composite fiber reinforced panel to another panel. 
           [0016]      FIG. 2  is a cross-sectional view taken along the line  2 - 2  in  FIG. 1 . 
           [0017]      FIG. 3  is a fragmentary perspective view of a clinch joint joining a composite fiber reinforced panel to another panel in accordance with one aspect of this disclosure. 
           [0018]      FIG. 4  is a cross-sectional view taken along the line  4 - 4  in  FIG. 3 . 
           [0019]      FIG. 5  is a fragmentary perspective view of a plurality of clinch joints in a flange of a composite fiber reinforced panel that has a fiber-free coating of resin applied to one side being joined to a mating flange of another panel. 
           [0020]      FIG. 6  is a fragmentary perspective view of a plurality of clinch joints in a flange of a composite fiber reinforced panel that has a fiber-free coating of a resin applied to only selected portions of the flange being joined to a mating flange of another panel. 
           [0021]      FIGS. 7A and 7B  are fragmentary cross-sectional views of alternative embodiments of a first composite panel that has fiber reinforcements in resin except where a clinch joint is to be formed. 
           [0022]      FIGS. 8A and 8B  are fragmentary cross-sectional views of the panels shown in  FIGS. 7A and 7B , respectively, being joined to a second panel by a clinch joint. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention. 
         [0024]    Referring to  FIGS. 1 and 2 , a prior art clinch joint  10  is shown connecting a fiber reinforced composite panel  12  to a substrate panel  14 . The panels  12 ,  14  are partially shown in  FIGS. 1 and 2 . The clinch joint  10  would in most cases be located in a flange area of a larger panel. 
         [0025]    The stippling in  FIG. 1  is provided to denote exposed fibers  16  that are exposed in the course of forming the clinch joint  10 . Fibers from the fiber reinforced panel  12  may extend into the clinch joint  10 , as shown in  FIG. 2 . The exposed fibers  16  may absorb moisture and lead to a reduction in the holding force of the clinch joint  10 . The fibers, especially if they are carbon fibers, may also result in galvanic corrosion as water or other moisture absorbed by the fibers  16  comes into contact with metal parts or fasteners. 
         [0026]    Referring to  FIGS. 3 and 4 , an improved clinch joint  20  is shown that is directed to solving the problem of exposed fibers in the clinch joint  10  described with reference to  FIGS. 1 and 2 . The improved clinch joint  20  is formed in an encased fiber reinforced composite part  22 , or first part. The first part  22  is connected to a substrate panel  24 , or second part, by the clinch joint  20 . The fiber reinforced part  22  includes a layer  25  that is reinforced with fibers  26 . This layer  25  is also referred to in this disclosure as a first layer. The layer reinforced with fibers  26  may be reinforced with carbon fibers, glass fibers, natural fibers, or talc that are encased in a resin composition. 
         [0027]    A neat resin layer  28 , or second layer, forms part of the fiber reinforced composite part  22 . The neat resin layer  28  consists essentially of the resin used to form the fiber reinforced composite part  22 . 
         [0028]    The fiber reinforced composite part  22  is preferably formed in a compression molding operation in a compression molding die. The compression molding die may include a textured surface on the surface facing the resin layer  28 . The textured surface may function to exclude fibers from the layer reinforced with fibers  26  and thereby form the neat resin layer  28 . Compression molding tools for forming fiber reinforced composite parts are well known and such tools are also well known that include a textured surface for esthetics. 
         [0029]    The improved clinch joint  20  includes a pressed out portion  30  formed in the fiber reinforced composite part  22 . The pressed out portion  30  is pressed into a clinching portion  32  formed in the substrate panel  24 . The neat resin layer  28  encases the fibers  26  that would otherwise be exposed during the clinching operation in the pressed out portion  30  and provides the desired fiber-free smooth interior surface  36  of the clinch joint  20 . By encasing the fibers  26  with the neat resin layer  28 , the tendency of any fibers  26  to become exposed within the clinch joint  20  is eliminated or at least minimized and thereby reduces the chance of moisture being absorbed by the fibers  26  in the layer  25  reinforced by the fibers  26 . 
         [0030]    The neat resin layer  28  is preferably 0.5 to 1.5 mm thick. The thickness of the encased fiber reinforced composite part  22  is preferably 0.5 to 6 mm thick and typically from 2.5 to 3 mm thick. The substrate panel  24  is preferably 0.5 to 6 mm thick and typically between 2.5 to 3 mm thick. The substrate layer is preferably metal such as aluminum, steel, magnesium, or may also be another fiber reinforced composite part. 
         [0031]    Referring to  FIG. 5 , an assembly  40  is partially shown that includes an inner panel  42  and an outer panel  44  that are joined together by an inner flange  46  and an outer flange  48 . As shown in  FIG. 5 , the resin layer  28  is provided on the top surface and is indicated by shading stripes extending across the entire top surface to denote a smooth resin surface. A plurality of clinch joints  20  are shown connecting the inner flange  46  to the outer flange  48  with the inner flange clinching a pressed out portion  30  of the outer flange  48 . 
         [0032]    Referring to  FIG. 6 , an assembly  40  is shown that includes an inner panel  42  that is married to an outer panel  44 . An inner flange  46  of the inner panel  42  is connected by a clinch joint  20  to the outer flange  48  of the outer panel  44 . A partial area  50  of the outer flange  48  is provided with a textured surface  52 . The textured surface  52  is formed in the compression molding operation by providing an orange peel textured surface on the surface of the compression molding die that forms the textured surface  52  on the outer flange  48 . Other types of textured surfaces may also be formed in the compression molding operation. 
         [0033]    Referring to  FIGS. 7A and 7B , alternative embodiments of a composite panel  60  are illustrated that are formed of a polymeric resin  62  and reinforced with fiber reinforcements  64  in  FIG. 7A . In  FIG. 7B , a fiber mat  65  is shown embedded in the resin  62  to illustrate an alternative to the loose fibers  64 . An intended clinch joint location  66  consists essentially of pure or neat resin  62 . The surrounding portions of the panel  60  include the fiber reinforcements  64  or fiber mat  65 . While discontinuous, or loose fiber reinforcements  64  may be used, a woven mat of fiber having cut-outs in the intended clinch joint locations  66  may be easier to process. The woven mat  65  also may be braided or stitched continuous fiber reinforcements  64 . 
         [0034]    Referring to  FIGS. 8A and 8B , the composite panels  60  are illustrated after a clinch joint  68  is formed to join the composite panel  60  and a second panel  70 . The composite panel  60  includes a pressed out portion  72  that is received in a clinching portion  74  of the second panel  70 . The clinch joint  68  does not have any exposed fibers because no fiber reinforcements  64  (in  FIG. 8A ) or fiber mat  65  (shown in  FIG. 8B ) are disposed in the intended clinch joint locations  66 . 
         [0035]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.