Abstract:
A composite vehicle body panel includes a fiber reinforced plastic panel and a steel flange disposed in the fiber reinforced plastic panel and having an edge protruding outward from the fiber reinforced plastic panel beyond an outer edge of the fiber reinforced plastic panel. The composite vehicle body panel can be used in vehicle structures manufactured on standard vehicle productions lines, thereby easing vehicle manufacturing, improving productivity, and providing increased rigidity to the vehicle bodies. A method of manufacturing the composite vehicle body panel and a vehicle structure using the panel are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2012-0143880 filed in the Korean Intellectual Property Office on Dec. 11, 2012, the entire contents of which are incorporated herein by reference. 
       (a) TECHNICAL FIELD 
       [0002]    The present disclosure relates to a composite vehicle body panel, a manufacturing method thereof, and a vehicle body structure using the same. More particularly, the present disclosure relates to a composite vehicle body panel made of fiber reinforced plastic and steel, a method of manufacturing the composite vehicle body panel, and a vehicle body structure using the composite vehicle body panel. 
       (b) BACKGROUND 
       [0003]    Panels made of steel have generally been used as body panels of vehicles. Recently, however, Fiber Reinforced Plastic (FRP) is being used for making vehicle body panels having reduced weight. 
         [0004]    Referring to  FIGS. 1 and 2 , a fiber reinforced plastic panel  10  is used as a roof panel. The fiber reinforced plastic panel  10 , however, cannot be attached to a side steel vehicle body  20  by welding, such as spot welding or arc welding, and therefore must be attached by other mechanical fastening methods. 
         [0005]    That is, the fiber reinforced plastic panel  10  and the side steel vehicle body  20  are attached to each other by forming fastening holes at the flange of the side steel vehicle body  20  and at the flange of the fiber reinforced plastic panel  10 , which are supposed to be attached. The fiber reinforced plastic panel  10  is then arranged such that the flange of the panel  10  is on top of the flange of the side steel vehicle body  20 . The flanges are then bonded with an adhesive  30 , and then by inserting a rivet through the fastening holes, as shown in  FIG. 2 . 
         [0006]    Because vehicle bodies are generally assembled by welding on current vehicle manufacturing lines, the cost for manufacturing vehicle bodies requiring other assembly methods may increase manufacturing costs. For example, when a fiber reinforced plastic panel  10  and a side steel vehicle body  20  are attached together using mechanical methods such as the method described above, additional process steps for forming the fastening holes and applying and hardening the adhesive are required. The addition of such process steps increases the cost for manufacturing vehicle bodies. 
         [0007]    Further, the forming of a fastening hole in the fiber reinforced plastic panel  10  commonly causes delamination of the fiber reinforced plastic. In order to avoid such defects, the size of the fastening hole may need to be increased and/or the time allotted for forming the fastening hole may need to be increased. 
         [0008]    Further, the bonding strength provided by attaching the fiber reinforced plastic panel  10  to the side steel panel  20  with bolts and nuts is small in comparison with the strength provided by spot welding of the same diameter. Therefore, more attachment points (each including a bolt and nut) are required to fasten the fiber reinforced plastic panel  10  to the side steel panel  20  with bolts and nuts, as compared to when fastening methods using welding are used. 
         [0009]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that is not prior art in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0010]    The present disclosure has been made in an effort to provide a composite vehicle body panel that can be fastened to other portions of a vehicle body by welding, and to provide a manufacturing method thereof, and a vehicle body structure using the same. 
         [0011]    An exemplary embodiment of the present disclosure provides a composite vehicle body panel, which may include: a fiber reinforced plastic panel; and a steel flange disposed in the fiber reinforced plastic panel and having an edge protruding outward from the fiber reinforced plastic panel beyond an outer edge of the fiber reinforced plastic panel. 
         [0012]    The steel flange may have one or more fastening holes extending through the steel flange and filled by the fiber reinforced plastic panel. 
         [0013]    The steel flange may have a stepped portion formed at an angle along an outer edge of the steel flange to cause the outer edge of the steel flange to be stepped in the height direction with respect to a central portion of the steel flange. 
         [0014]    The steel flange may have one or more foaming portions formed as receiving grooves in the steel flange. 
         [0015]    A foamed plastic may be bonded to each foaming portion. 
         [0016]    The steel flange may have one or more through-holes and a foaming portion may be formed along the edge of each of the through-holes. 
         [0017]    The steel flange may further have one or more foaming portions formed at edges of the teel flange and that extend across the steel flange in a width direction. 
         [0018]    Separation walls comprising continuous pieces of steel that extend across substantially the whole width of the steel flange can be disposed between the through-holes, and fastening holes may be disposed in the separation walls. 
         [0019]    Another exemplary embodiment of the present disclosure provides a method of manufacturing a composite vehicle body panel, which may include: manufacturing a steel panel; forming foaming portions and a stepped portion on the steel panel using a press; forming a steel flange with one or more fastening holes and one or more through-holes by punching the steel panel; manufacturing a foamed plastic in a shape that can be inserted into the foaming portions; inserting and bonding the foamed plastic into foaming portions; manufacturing a fiber reinforced plastic panel; and inserting the steel flange into a mold, mounting the fiber reinforced plastic panel onto the steel flange, and applying heat and pressure to form the composite vehicle body panel. 
         [0020]    The steel flange may have an edge protruding outward from the fiber reinforced plastic panel beyond an outer edge of the fiber reinforced plastic panel. 
         [0021]    The foaming portion may be formed as a receiving groove in the steel panel. 
         [0022]    The stepped portion may be formed at an angle along an outer edge of the steel plate to cause the outer edge of the steel plate to be stepped in the height direction with respect to a central portion of the steel plate. 
         [0023]    The steel panel may be a surface-treated steel plate and the fiber reinforced plastic panel is a fiber reinforced plastic panel using carbon fiber. 
         [0024]    Yet another exemplary embodiment of the present disclosure provides a method of manufacturing a composite vehicle body panel, which may include: manufacturing a steel panel; forming foaming portions and a stepped portion on the steel panel using a press; forming a steel flange with one or more fastening holes and one or more through-holes by punching the steel panel; manufacturing a foamed plastic in a shape that can be inserted into the foaming portions; inserting and bonding the foamed plastic into the foaming portions; and spraying and hardening discontinuous fiber and resin on the steel flange. 
         [0025]    Another exemplary embodiment of the present disclosure provides a vehicle body structure including a vehicle side body panel and a composite vehicle body panel that is welded to an upper edge of the vehicle side body panel to function as a roof panel. 
         [0026]    According to a composite vehicle body panel, a manufacturing method thereof, and a vehicle by structure using the same of an exemplary embodiment of the present disclosure, a steel flange made of steel is disposed in and integrally combined with a fiber reinforced plastic panel, thereby forming a composite vehicle body panel. 
         [0027]    Therefore, since the steel flange of the composite vehicle body panel can be welded to other portions of a vehicle body, assembly productivity of the vehicle body can be improved and the weight and cost can be reduced. 
         [0028]    It is possible to appropriately carry transverse load on the composite vehicle body panel by forming foaming portions on the steel flange and forming a step along edges of the steel flange and disposing the steel flange within the fiber reinforced plastic. It is possible to suppress delamination of the fiber reinforced plastic and appropriately carry vertical load by forming holes in the steel flange and filling the holes with the fiber reinforced plastic. The composite vehicle body panel has the increased strength because of the combined strengths of the steel flange and of the fiber reinforced plastic. 
         [0029]    By welding the composite vehicle body panel to a side vehicle body made of steel, load is appropriately transmitted and distributed when the vehicle is hit on the side or rolls over. The safety of passengers of the vehicle is thereby improved. 
         [0030]    When the composite vehicle body panel is formed by combining a steel flange with a CFRP using carbon fiber and a surface-treated steel sheet, it is possible to prevent galvanic corrosion between the carbon fiber and the steel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a perspective view showing a vehicle body including a fiber reinforced plastic panel used as a vehicle body panel. 
           [0032]      FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 . 
           [0033]      FIG. 3  is a perspective view showing a vehicle body including a composite vehicle body panel, according to an exemplary embodiment of the present disclosure. 
           [0034]      FIG. 4  is a cross-sectional view taken along line B-B in  FIG. 3 . 
           [0035]      FIG. 5  is a perspective view showing a steel panel for manufacturing a composite vehicle body panel according to an exemplary embodiment of the present disclosure. 
           [0036]      FIG. 6  is a perspective view showing a steel panel shaped by a press and used to manufacture a composite vehicle body panel according to an exemplary embodiment of the present disclosure. 
           [0037]      FIG. 7  is a perspective view showing a steel flange according to an exemplary embodiment of the present disclosure. 
           [0038]      FIG. 8  is a perspective view showing foamed plastic for use in manufacturing a composite vehicle body panel according to an exemplary embodiment of the present disclosure. 
           [0039]      FIG. 9  is a perspective view showing the foamed plastic disposed on the steel flange to manufacture a composite vehicle body panel according to an exemplary embodiment of the present disclosure. 
           [0040]      FIG. 10  is a perspective view showing a composite vehicle body panel according to an exemplary embodiment of the present disclosure. 
           [0041]      FIG. 11  is a cross-sectional view taken along line C-C in  FIG. 10 . 
           [0042]      FIG. 12  is a cross-sectional view taken along line D-D in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    Exemplary embodiments of the present disclosure will be described hereafter in detail with reference to the accompanying drawings. 
         [0044]    Referring to  FIGS. 3 and 4 , a composite vehicle body panel  100  according to an exemplary embodiment of the present disclosure is used as a roof panel and welded to the upper edge of a vehicle side body  110  made of steel, thereby forming a portion of a vehicle body. 
         [0045]    The composite vehicle body panel  100  may, more generally, be used as a vehicle body panel other than a roof panel. 
         [0046]    The composite vehicle body panel  100  includes a fiber reinforced plastic panel  102  and a steel flange  104 . The composite vehicle body panel  100  is assembled by inserting the steel flange  104  into the fiber reinforced plastic panel  102 . 
         [0047]    The steel flange  104  is larger in width and length than the fiber reinforced plastic panel  102 . As such, an outer edge  104   a  of the steel flange  104  protrudes outward beyond an outer edge of the fiber reinforced plastic panel  102  when the steel flange  104  and the fiber reinforced plastic panel  102  are assembled. 
         [0048]    During assembly of the vehicle body, the outer edge  104   a  of the steel flange  104  is placed on the side vehicle body  110  and then fastened thereto by welding  120  such as spot welding or arc welding. 
         [0049]    Therefore, joint stiffness of the joint between the composite vehicle body panel  100  and the side vehicle body  110  is improved, and it is not required to add a specific combination process in the assembly line of vehicles. 
         [0050]    When a vehicle having a vehicle body including a composite vehicle body panel  100  such as the one described above is hit on the side or rolls over, load applied to the composite vehicle body panel  100  is appropriately transmitted and distributed to the side vehicle body  110  through the steel flange  104 . Because of the transmitting and distributing of the load, safety of passengers in the vehicle is improved as compared to vehicles in which the body structure only uses a fiber reinforced plastic panel. 
         [0051]    Referring to  FIGS. 5 and 10 , the composite vehicle body panel  100  according to an exemplary embodiment of the present disclosure can be manufactured through the following steps. 
         [0052]    As shown in  FIG. 5 , a steel panel  1041  made of steel or a surface-treated steel panel is manufactured in a substantially rectangular shape and structure. 
         [0053]    In the surface-treated steel panel, for example, when a zinc-fusing alloy steel plate is used as the steel panel and the composite vehicle body panel  100  is made of CFRP (Carbon-fiber-reinforced plastic), it is possible to suppress corrosion (galvanic corrosion) due to a potential difference between the carbon fiber and the steel. 
         [0054]    As shown in  FIG. 6 , a formed steel panel  1042  is manufactured by shaping the steel panel  1041  with a press. The formed steel panel  1042  can be formed to have a foaming portion  104   b  and a stepped portion  104   c , as shown in  FIG. 11 , when the steel panel  1041  is shaped by the press. The foaming portion  104   b  and stepped portion  104   c  may increase joint stiffness with the fiber reinforced plastic panel  110 . 
         [0055]    The foaming portion  104   b  serves to appropriately carry transverse load that is applied to the composite vehicle body panel  100 . The stepped portion  104   c  serves to suppress lateral slippage such that slippage does not occur between the steel flange  104  and the fiber reinforced plastic panel  102  when transverse load is applied to the composite vehicle body panel  100 . 
         [0056]    The foaming portion  104   b  can be implemented by forming a receiving groove in the steel flange  104 , the receiving groove having a downward concave shape. 
         [0057]    The stepped portion  104   c  is formed at an angle along an outer edge of the steel flange  104  to cause the outer edge of the steel flange to be stepped in the height direction with respect to a central portion of the steel flange. 
         [0058]    As shown in  FIG. 7 , the steel flange  104  is completed by punching the formed steel panel  1042  with a trim mold. 
         [0059]    One or more fastening holes  104   d  are formed at positions located along outer edges  104   a  of the steel flange  104 , when the formed steel panel  1042  is punched by the trim mold. The fastening holes  104   d  are formed at predetermined intervals along the outer edges  104   a.    
         [0060]    By filling each fastening hole  104   d  with fiber reinforced plastic resin, as shown in  FIG. 12 , it is possible to increase the joint stiffness between the steel flange  104  and the fiber reinforced plastic panel  102 , to prevent delamination of the fiber reinforced plastic due to vertical load, and to reduce the manufacturing time by making resin injection smooth when manufacturing the fiber reinforced plastic panel  102 , using a carbon fiber sheet. 
         [0061]    The formed steel flange  104  is formed in the shape of a substantially rectangular panel with one or more through-holes  104   e  divided by separation walls  104   f , at predetermined intervals. The separation walls  104   f  are continuous pieces of steel that extend across substantially the whole width of the steel flange  104  between stepped portions  104   c  formed on both sides of the steel flange  104  (i.e., between stepped portions  104   c  that are positioned on both sides of the vehicle body). 
         [0062]    The foaming portion  104   b  is continuously formed along the edge of each of the through-holes  104   e . In addition, one or more foaming portions  104   b  are formed at the edges of both ends of the steel flange  104  and extend in the width direction across the steel flange  104 . The forming portions  104   b  are formed at edges of the steel flange  104  that are positioned towards the front and towards the rear of the vehicle body, and extend across substantially the whole width of the steel flange  104  between stepped portions  104   c  formed on both sides of the steel flange  104 . 
         [0063]    One or more fastening holes  104   d  may be formed on each of the separation walls  104   f  and may be formed at both left and right extremities of the foaming portions  104   b  that extend across substantially the whole width of the steel flange  104 . 
         [0064]    The position and the number of the fastening holes  104   d  may be appropriately selected and set to provide strength and reliability in the connection between the steel flange  104  and the fiber reinforced plastic panel  102 . 
         [0065]    As shown in  FIG. 8 , foamed plastics  106  are formed to fill the foaming portions  104   b . The foamed plastics  106  are inserted and bonded in the foaming portions  104   b , as shown in  FIG. 9 . 
         [0066]    The foamed plastics  106  can improve the quality of the external appearance, increase rigidity, and reduce the amount of material used in forming the fiber reinforced plastic panel  102 , when the foaming portions  104   b  of the steel flange  104  are covered with the fiber reinforced plastic panel  102 . 
         [0067]    The composite vehicle body panel  100  is formed, as shown in  FIG. 10 , by forming the fiber reinforced plastic panel  102  onto the steel flange  104 . A steel flange formed as described above, and having foamed plastics attached thereto, is inserted in a mold used for forming the fiber reinforced plastic panel  102 . That is, the forming is performed by inserting a steel flange  104  into a mold, mounting fiber reinforced plastic onto the top and the bottom of the steel flange  104 , and applying heat and pressure thereto. 
         [0068]    The composite vehicle body panel  100  can be manufactured by inserting and setting a steel flange  104  in a mold, putting a BMC (Bulk Molding Compound) made by mixing discontinuous fiber with resin into the mold, and applying heat and pressure. Alternatively, the composite vehicle body panel  100  can be manufactured using an RTM (Resin Transfer Molding) method of covering a steel flange  104  with an SMC (Sheet Molding Compound) or a carbon fiber sheet, injecting resin into a mold, and applying heat and pressure. The composite vehicle body panel  100  can further be manufactured by spraying discontinuous fiber and resin onto a steel flange  104  and hardening them. 
         [0069]    While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
       DESCRIPTION OF SYMBOLS 
       [0000]    
       
         
           
               100 : Composite vehicle body panel 
               102 : Fiber reinforced plastic panel 
               104 : Steel flange 
               106 : Foamed plastic 
               120 : Welding