Abstract:
A laminated reinforced member that provides bending and stiffening support and that includes metal reinforcing sheets, and a method of making the member. Metal reinforcing sheets at connection locations eliminate the need for additional external connection reinforcements for engaging connectors.

Description:
RELATED APPLICATIONS 
       [0001]    [Not Applicable] 
       FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    [Not Applicable] 
       MICROFICHE/COPYRIGHT REFERENCE 
       [0003]    [Not Applicable] 
       FIELD 
       [0004]    This disclosure relates to reinforcement of laminated composite members. Various embodiments relate to fiber reinforced laminated composite stiffening and bending members. 
       BACKGROUND 
       [0005]    Carbon fiber reinforced plastic (“CFRP”) is widely used to provide structural members having a high strength to weight ratio. Carbon fiber reinforced plastics are fabricated from polymeric composites including thermosetting or thermoplastic polymer (“resin”) matrix within which are embedded carbon fibers. CFRP structural members may be formed by layers of fiber reinforced sheets and then bonding the sheets to form a composite member. These composites are widely used for aircraft structures, for example, the fuselage, wings, and other components of the aircraft&#39;s outer shell. These composites may be reinforced by thin metal sheets between layers of the composite member to enhance structural integrity of the member. 
         [0006]    CFRP is also used to form bending and stiffening members for structures such as aircraft. Bending and stiffening members are typically elongate members formed to have a cross section that resists bending about axes lying in the cross section. I sections, T sections and C sections are examples of such members. Forming such members of laminated CFRP sheets provides a member having advantageous strength along the member for bending and stiffening. However, applying loads to such members at connections such as to other members or components presents difficulties. 
         [0007]    CFRP members provide significant strength along the directions lying along the sheets that comprise the member. However the strength of such members through their thickness, a direction from sheet to sheet, is primarily the strength of the bonds between sheets and the strength of the plastic matrix of sheets that support fibers. Those strengths are orders of magnitude less than the strength of the fiber reinforced sheet in directions along which fibers extend. This low through thickness strength presents problems at connections to bending and stiffening members. Such connections can be by conventional connectors such as bolts or rivets extending through an opening that extends in a through thickness direction of the CFRP member. Loads applied to the CFRP member by such connectors can damage the CFRP member by causing delamination of sheets forming the member or damage to the matrix within which the fibers are embedded. Such damage typically occurs in regions where the load path changes direction from one plane to another plane that is inclined to said one plane (e.g. the radius detail when transitioning from a flange to a web). 
         [0008]      FIG. 1  shows known reinforcements for connection to an I section CFRP member  10 . The member  10  is formed by two separated generally parallel flanges  14  and  16  that are connected by a web  12  extending between and generally perpendicular to the flanges  14  and  16 .  FIG. 1  illustrates two connection reinforcements, radius block  22  and angle fitting  26 . Radius block  22  and angle fitting  26  strengthen connections to the member  10  through the flange  16  from a surface  17  that faces oppositely from the flange  14 . The connectors  24  and  28  extend through the flange  16  to connect to a component or member adjacent to the surface  17 . 
         [0009]    The connector  24  includes a section that overlies the radius block  22  and another section that extends through the radius block  22  and the flange  16 . The radius block  22  is positioned adjacent to a surface of the flange  16  opposite the surface  17  to distribute any load applied through the connector  24  to the flange  16 . The connectors  28  similarly extend through the angle fitting  26  and the flange  16 . In addition, the angle fitting  26  extends adjacent to the web  12  and connectors  30  extend through the angle fitting  26  and the web  12  to additionally reinforce the flange  16  to web  12  integrity of the member  10  and to transfer load from the connectors  28  to the web  12 . 
         [0010]    Radius blocks, angle fittings and similar connection reinforcements for applying loadings to CFRP members provides needed connection strength for CFRP members. Such connection reinforcements are additional parts that must be positioned and secured during assembly of structures that include connections to bending or stiffening members such as member  10 . These additional parts and the effort required for their assembly into a structure adds cost to structures that include bending or stiffening members such as member  10  and adds effort to assembly of those structures. 
       BRIEF SUMMARY 
       [0011]    In one aspect, laminated bending and stiffening members are described that are fabricated to support connection loads that are applied by connectors without external reinforcing members such as radius blocks and angle fittings. 
         [0012]    In another aspect, laminated carbon fiber reinforced plastic bending and stiffening members are described that are fabricated to support loads applied by connectors that engage the member without external reinforcing members and to transfer load to sections of the member adjacent to the location at which the connector engages the member. 
         [0013]    In still another aspect, laminated bending and stiffening members are described that include reinforcing layers within the member that provide strength to support loads that are applied to the member. 
         [0014]    In yet another aspect, a method is provided for fabricating laminated members in configurations that are used for bending and stiffening members and that include reinforcing layers within the member. 
         [0015]    In an additional aspect, a method is provided for fabricating laminated members in configurations that are used for bending and stiffening members and that provide strength to transfer load from connectors to the member without external reinforcements such as radius blocks and angle fittings. 
         [0016]    In yet an additional aspect, forming metal sheets to the shape of a portion of a CFRP member at which a connector engages the member is described as well as laminating the metal sheets into the CFRP member to reinforce the member. 
         [0017]    In still an additional aspect, forming metal sheets to the shape of a portion of a CFRP member at which a connector engages the member and the shape of one or more adjacent sections of the CFRP member is described and laminating the metal sheets into the CFRP member to reinforce the member at the connector location and to reinforce the transition to adjacent sections of the CFRP member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  illustrates a prior art I section member with a radius block and an angle fitting for connection reinforcement. 
           [0019]      FIG. 2  shows bending and stiffening members that may embody the invention. 
           [0020]      FIG. 3  is a cross section of a flange and a portion of an adjacent web of a C-shaped section. 
           [0021]      FIG. 4  is a cross section of another configuration of a flange and a portion of an adjacent web of a C-shaped section. 
           [0022]      FIG. 5  is a perspective view of a C-shaped member and lay up form for fabricating the member. 
           [0023]      FIG. 6  is a cross section of a T-shaped section. 
           [0024]      FIG. 7  is a cross section of a component of the T-shaped section shown by  FIG. 6 . 
           [0025]      FIG. 8  is a perspective view of an I-shaped member formed of components of the member and a lay up form for fabricating the member. 
           [0026]      FIG. 9  is a cross section of a welded T-shaped metal reinforcement for a member. 
           [0027]      FIG. 10  is a cross section of a T-shaped member including the reinforcement shown by  FIG. 9 . 
           [0028]      FIG. 11  is a cross section of an extruded T-shaped metal reinforcement for a laminated member. 
           [0029]      FIG. 12  is a cross section of a laminated T-shaped member including the reinforcement shown by  FIG. 11  as well as further reinforcement. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0030]    The described embodiments concern support of loads applied by laminated members, including loads applied by connectors. In particular, bending or stiffening members formed of laminated fiber reinforced sheets and by thin metal sheets are described. Metal sheets may be provided within a bending and stiffening member at a location at which a connector extends through the member. The thin metal sheets extend from the connector to strengthen the laminated bending or stiffening member to carry loads applied by the connector. 
         [0031]    The various embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which such embodiments are shown. The various embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are examples which have the full scope indicated by the claims. Like reference numbers refer to like elements throughout. 
         [0032]      FIG. 2  shows four bending and stiffening members having different cross sections that may be formed by laminated carbon fiber reinforced sheets. Member  32  is a member having a C-shaped cross section and member  34  is a member having a Hat-shaped cross section. Member  36  is a member having an I-shaped cross section and member  38  is a member having a T-shaped cross section. Members  32  and  34  may be formed as a single component as described below. Members  36  and  38  may be formed from multiple components as also described below. 
         [0033]      FIG. 3  is a cross section of a portion  40  of a member having a C-shaped cross section such as member  32 .  FIG. 3  shows a flange  42  that extends along a flange direction from an outer side  48  to a web section  44  where the portion  40  bends approximately 90 degrees so that the web section  44  extends generally perpendicular to the flange  42  to a web section  46  that continues from and along the direction of the section  44 . 
         [0034]    The sections  42 ,  44  and  46  include layers of carbon fiber reinforced plies  66 . The carbon fiber reinforced plies  66  extend from outer side  48  of the flange  42  through the flange  42 , through the web section  44  and continue through the web section  46 . The CFRP plies  66  are between 0.005 and 0.010 inches thick and may be tape or fabric and may also be impregnated with a thermoset or thermoplastic adhesive matrix. The flange  42  and web section  44  also include titanium sheets  68  that extend from the outer side  48  along the flange  42  and into the web section  44 . The titanium sheets  68  are between 0.004 and 0.020 inches thick. This range of thickness provides favorable lamination to CFRP sheets. The titanium sheets  68  bend with the member to extend through the flange  42  and along the web section  44 . As shown by  FIG. 3 , each titanium sheet  68  is positioned at least between two carbon fiber reinforced plies  66  and extends through the flange  42  into the web section  44 . The titanium sheets  68  extend from the flange  42  progressively greater distances along the web  44  as their distance from the outer side  48  increases. The web section  44  decreases in width along the flange direction as distance from the flange  42  increases as number of titanium sheets  68  at the location decreases. The width of the web section  46  remains constant as it is comprised only of the carbon fiber reinforced plies  66 . 
         [0035]      FIG. 4  is a cross section of a portion  50  of a C-shaped section such as member  32 .  FIG. 4  shows a flange  42  that extends along a flange direction from an outer side  48  to a web section  74  where the member bends approximately 90 degrees so that the web section  74  extends generally perpendicular to the flange  42  to a web section  76  that continues from and along the direction of the section  74 . The sections  42 ,  74  and  76  include laminated layers of carbon fiber reinforced plies  66  that extend from the outer side  48  through the flange  42 , the web section  74  and the web section  76 . As shown by  FIG. 4 , titanium sheets  68  extend from the outer side  48  through the flange  42  and web section  74 . The titanium sheets  68  bend with the portion  50  to extend along the web section  74  away from the flange  42 . The titanium sheets  68  extend from the flange  42  progressively greater distances along the web  74  as their distance from the outer side  48  increases. Beginning near the farthest extent of a titanium sheet  68  along the web section  74 , a carbon fiber reinforced ply  66  is positioned adjacent to the titanium sheet  78  and extends along the web sections  74  and  76 . As shown by  FIG. 4 , the carbon fiber reinforced plies  66  that form part of the flange  42  and web section  74  extend from outer side  48  through the flange  42 , the web section  74  and continue through the web section  76 . The web section  74  remains approximately the same width as distance from the flange  42  increases due to carbon fiber plies  66  that continue along the flange sections  74  and  76  extending from the titanium sheets  68 . 
         [0036]    The titanium sheets  68  of the portion  40  shown by  FIG. 3  are positioned between two carbon fiber reinforced plies  66 . The titanium sheets  68  of the portion  50  shown by  FIG. 4  are positioned adjacent to one or more titanium sheets  68 . An adhesive film is applied between adjacent titanium sheets  68  of the portion  50  shown by  FIG. 4 . 
         [0037]      FIG. 5  shows a C-shaped channel member  32  positioned within a formed support  78  that is shaped to support the member  32 . The member  32  is a laminated member that may be formed of carbon fiber reinforced plies  66  and titanium sheets  68 . The member  32  is formed in the support  78  by a lay-up process. The titanium sheets  68  are formed to the bent configuration shown by  FIGS. 3 and 4  and are then degreased. A sol-gel procedure is then applied to the titanium sheets. A layer of primer is applied to the bent titanium sheets if storage for any duration is required. The carbon fiber reinforced plies  66  and bent titanium sheets  68  are placed in the formed support  78  adjacent to each other as described above. The lay-up process includes application of the adhesive that is used to form the reinforced plies  66  between adjacent plies  66 . For configurations such as that of portion  50  shown by  FIG. 4  in which titanium sheets  68  are adjacent to each other, an adhesive film is applied between adjacent titanium sheets  68 . After the plies  66  and titanium sheets  68  are layed up to the configuration described above, they are vacuum bagged and cured at an appropriate elevated temperature and under surrounding pressure to cure the resin of the plies  66  and to bond the plies  66  and the titanium sheets  68 . The curing process creates a unitary composite member. 
         [0038]      FIG. 6  shows a cross section of a CFRP member  80  forming a T shaped section having a flange  82  joined to a web  84 . The flange  82  extends in a width direction from a first outer side  92  to a second outer side  94 . The flange  82  forms a top surface  96  that extends from the first outer side  92  to the second outer side  94 . The web  84  extends from the flange  82  oppositely from the flange top surface  96 . 
         [0039]    The T-shaped member  80  is formed by four components, an outer flange section  102 , two angle sections  104  and  106  and a gap filling noodle  108 . The outer flange section  102  extends from the first outer side  92  to the second outer side  94  and from the flange top surface  96  to form a portion of the flange  82  extending from the flange top surface  96  toward the web  84 . The angle section  104  has a flange section  112  that forms a section of the flange  82  that extends from the first outer side  92  to the web  84  and then bends to extend from the flange  82  oppositely from the flange top surface  96  to form a section of the web  84 . The flange section  112  is adjacent to the outer flange section  102  such that the flange section  112  and the outer flange section  102  together form the flange adjacent to the first outer side  92 . The angle section  106  has a flange section  122  that forms a section of the flange  82  that extends from the second outer side  94  to the web  84  and then bends to extend from the flange  82  oppositely from the flange top surface  96  to form a section of the web  84 . The flange section  122  is adjacent to the outer flange section  102  such that the flange section  122  and the outer flange section  102  together form the flange adjacent to the second outer side  94 . The angle sections  104  and  106  meet each other adjacent to the flange outer section  102  and extend adjacent to each other to form the web  84 . The flange outer section  102  and the angle sections  104  and  106  bound a void at the location adjacent to the angle section bends. The noodle  108  is adjacent to the flange outer section  102  and the angle sections  104  and  106  to fill that void. The noodle  108  may be formed of adhesive filler or adhesive filler in combination with rolled up fibers. Alternatively, the noodle may be formed of a low-density foam. 
         [0040]    The outer flange section  102  is formed by laminated layers of carbon fiber reinforced plies  66 . The CFRP plies  66  are between 0.005 and 0.010 inches thick and may be tape or fabric and are impregnated with a thermoset or thermoplastic adhesive matrix. 
         [0041]    The angle sections  104  and  106  are formed by laminated layers of carbon fiber reinforced plies  66  and, in the regions forming part of the flange  82  and the region of the web  84 , also formed of titanium sheets  68 . The titanium sheets  68  are between 0.004″ and 0.020″ thick. This range of thickness provides favorable lamination to CFRP sheets. As shown by  FIGS. 6 and 7 , the titanium sheets  68  extend from the first and second outer sides  92  and  94  through the flange sections  112  and  122  of the angle sections  104  and  106  respectively. The titanium sheets  68  bend with the angle sections  104  and  106  to extend along the web  84  away from the flange  82 . The titanium sheets  68  extend from the flange sections  112  and  122  in transition regions  114  and  124 , respectively. The carbon fiber reinforced plies  66  of the angle sections  104  and  106  extend from the first and second outer sides  92  and  94 , respectively through the flange sections  112  and  122 , respectively and then through the transition sections  114  and  124  respectively into sections  116  and  126  of the web  84 . As shown, each titanium sheet  68  of the angle sections  104  and  106  is positioned between two carbon fiber reinforced plies  66 . 
         [0042]    As shown by  FIGS. 6 and 7 , the titanium sheets  68  extend through the flange section  112  and  122 . Within each angle member  104  and  106  the titanium sheets  68  extend from the flange  82  progressively greater distances along the web  84  as their distance from the first outer side  92  and second outer side  94 , respectively, increases. Further, the distances that titanium sheets  68  extend along the web  84  from the flange  82  are the same for titanium sheets  68  that are the same distance from the first and second outer sides  92  and  94  to create the symmetric configuration shown by  FIG. 6  with the longest titanium sheets  68  positioned at the middle of the web  84 . As shown by  FIGS. 6 and 7 , the carbon fiber reinforced plies  66  that form part of the angle sections  104  and  106  respectively, extend from first and second outer sides  92  and  94  through the flange sections  112  and  122 , respectively, the transition sections  114  and  124 , respectively, and continue through the web sections  116  and  126 . The web  84  decreases in width along the direction between the first and second outer sides  92  and  94 , as distance from the flange  82  increases as number of titanium sheets at the location decreases. The width of the web  84  remains constant in the web sections  116  and  126  that are comprised only of the carbon fiber reinforced plies  66 . 
         [0043]    The T-shaped member  80  may be fabricated by a co-bonding process. The outer flange section  102  is pre-cured by laying up carbon fiber reinforced sheets  66  to form the outer flange section  102  and then pre-curing that section. The two angle sections  104  and  106  may be fabricated by forming titanium sheets  68  to the configuration as described above and as shown by  FIGS. 6 and 7 . The titanium sheets are prepared as described above by reference to C-shaped channel member  32 . The two angle sections  104  and  106  are then pre-cured to form individual components of the member  80 . The pre-cured outer flange section  102 , the angle sections  104  and  106 , and the noodle  108  are assembled and vacuum bagged. The assembly is then cured in an autoclave at elevated temperature and pressure to form a unitary composite member. 
         [0044]    An alternative to forming a member from multiple pre-cured components as described above is shown by  FIG. 8 .  FIG. 8  shows an I-section member  36  that is formed by two C-shaped members  132  and two outer flange sections  102 . Each member  132  is formed as similarly to member  32  as described above. Rather than a support such as  78  within which a member is formed, the two C-shaped members  132  are each formed around a tool  144  so that the web  134  and the flanges  136  and  138  of each member  132  are adjacent to the tool  144 . A surface of the web  134  faces oppositely from the tool  144 . The members  132  are placed adjacent to each other so that the surface of each member that faces oppositely from the tool  144  is adjacent to oppositely facing surface of the web  134  of the other member  132 . A noodle  108  is positioned adjacent to the members  132  between the oppositely extending flanges  136  and  138 . An outer flange section  102  is formed of carbon fiber reinforced plies  66  and is placed adjacent to the oppositely extending flanges  136  and  138 . The assembly is vacuum bagged and cured in an autoclave at elevated temperature and pressure. This procedure requires only one curing step to form a unitary composite member. 
         [0045]    An alternative construction of a T-section that may form a T-shaped member or web to flange sections of an I-shaped member is shown by  FIGS. 9 and 10 .  FIG. 9  shows a cross section of a welded titanium T section  150 . The T section  150  is formed by plates  152  and  156 . As shown by  FIG. 9 , the plate  152  extends from an end  151  to an end  153 . The plate  156  extends from an end  155  to an end  157 . The plate  156  is positioned so that the end  155  is adjacent to the plate  152  at a location between ends  151  and  153  and the plate  156  extends generally perpendicular to the plate  152 . The plate  156  is welded to the plate  152  at the end  155 . 
         [0046]      FIG. 10  shows a cross section of a T-shaped member  170  that includes the T section  150 . An outer flange section  102  extends adjacent to a surface of the plate  152  that faces oppositely from the plate  156  from the end  151  to the end  153 . The outer flange section  102  is formed by laminated layers of carbon fiber reinforced plies  66 . Angle portions  172  and  182  extend from the ends  151  and  153 , respectively to the plate  156  adjacent to a surface of the plate  152  that faces oppositely from the outer flange section  102 . The angle portions  172  and  182  include flange sections  174  and  184  that extend from the ends  151  and  153 , respectively, to the plate  156  and bend to form transitions sections  176  and  186 , respectively, that extend along the plate  156  generally perpendicular to and away from the plate  152 . The angle portions  172  and  182  are formed similarly to the angle sections  104  and  106  described above of layers of carbon fiber reinforced plies  66  and also formed of titanium sheets  68 . The titanium sheets  68  in the transition sections  176  and  186  that are close to the plate  156  extend a distance along the direction of the plate  156  that is greater than the distance that titanium sheets  68  that are farther from the plate  156  extend. Noodles  108  are positioned on either side of the plate  156  at the location that plate  156  is welded to plate  152  to fill a void between the plates  152 ,  156  and the angle sections  172  and  182 . The carbon fiber reinforced plies  66  of the angle sections  172  and  182  extend from the titanium sheets  68  to form a carbon fiber reinforced section  192 . The T-shaped member  170  may be formed as a single member so that it may be vacuum bagged and cured in an autoclave at elevated temperature and pressure to be cured in a single step to form a unitary member. 
         [0047]    An alternative construction of a T-section that may form a T-shaped member or web to flange sections of an I-shaped member is shown by  FIGS. 11 and 12 .  FIG. 11  shows a member  210  that has a T shaped cross section similar to that of T section  150  shown by  FIG. 9 . The T section  210  is extruded as a single member that forms a generally planar flange plate  212 , a generally planar web plate  216  that extends perpendicularly from the flange plate  212  and a transition section  214  between flange plate  212  and plate  216 . 
         [0048]      FIG. 12  shows a cross section of a T-shaped member  220  that includes the T section  210 . The member  220  is similar to member  170  shown by  FIG. 10  and described above. The member  220  includes member  210  having the transition section  214  that is formed to conform to adjacent angle sections  222  and  232  of the member  220 . No void is formed by the angle sections  222  and  232  and the member  210 , and noodles  108  are therefore not required to fill such a void. A single titanium sheet  68  extends through the angle sections  222  and  232 . The web section  242  includes carbon fiber reinforced plies  66  that are positioned on oppositely facing surfaces of the that section to extend from the angle sections  222  and  232 . The T-shaped member  220  may be formed as a single member so that it may be vacuum bagged and cured in an autoclave at elevated temperature and pressure to be cured in a single step to form a unitary member. 
         [0049]    After a member is formed according to the invention, holes are drilled through the member at locations at which titanium sheets have been positioned to accept bolts or other connectors. 
         [0050]    The present invention is not limited to use with any specific shape section. The invention can be adapted to a variety of structural members, and members may be made according to the invention in forms other than conventional structural shapes. Further, the number, shape, size and thickness of laminated metal sheets may be varied to attain a desired strength. Similarly, the metal from which sheets are formed and the materials that form the fiber reinforced sheets may be other than as described for the embodiments.