Abstract:
A method comprises laying up a fiber ply of reinforcing fibers and a metal foil layer in a full face-to-face relation. The fibers in the fiber ply are oriented in a single direction. The metal foil layer includes a plurality of metal foil strips separated by gaps. The metal foil layer has substantially the same length and width as the fiber ply. The method further comprises infusing resin into the layup, wherein the resin flows through the gaps and infuses into the fibers.

Description:
This is a divisional of U.S. Ser. No. 11/328,012 filed 9 Jan. 2006, now U.S. Pat. No. 8,636,963 issued 28 Jan. 2014. U.S. Ser. No. 11/328,012 is a divisional of U.S. Ser. No. 10/649,280 filed 27 Aug. 2003, which was abandoned. 
    
    
     BACKGROUND 
       FIG. 1  illustrates a conventional laminated fiber metal composite  20  including a body  22  having a plurality of fiber plies  24  and a plurality of metal foil sheets  26  stacked in face to face relation in a predetermined order and orientation. Each fiber ply  24  has a resin mixture (not shown) interspersed between a plurality of reinforcing fibers (not shown). Each metal foil sheet  26  is uninterrupted throughout its length and width and is sized and shaped similarly to the fiber plies  24 . Because the metal foil sheets  26  are generally solid, the resin mixture may need to be interspersed between the fibers of each fiber ply and/or positioned between the fiber plies prior to lamination, for example by prepregging the fibers, wet-winding each fiber ply, resin transfer molding, and/or resin film infusion. Fiber metal laminates such as the laminate  20  may be used for many different applications, such as armor systems, high performance automotive components, and high-performance aerospace components. 
     The solid metal foil sheet between adjacent pre-impregnated fiber plies can increase bearing strength and other properties. However, if it is desired to infuse resin into a dry preform of fiber plies using a resin infusion process, the metal foil sheet can inhibit resin flow, resulting in resin starved regions. 
     SUMMARY 
     According to an embodiment herein, a method comprises laying up a fiber ply of reinforcing fibers and a metal foil layer in a full face-to-face relation. The fibers in the fiber ply are oriented in a single direction. The metal foil layer includes a plurality of metal foil strips separated by gaps. The metal foil layer has substantially the same length and width as the fiber ply. The method further comprises infusing resin into the layup, wherein the resin flows through the gaps and infuses into the fibers. 
     These features and functions may be achieved independently in various embodiments or may be combined in other embodiments. Further details of the embodiments can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a portion of a conventional laminated fiber metal composite. 
         FIGS. 2-4  are illustrations of different metal foil sheets. 
         FIG. 5  is an illustration of a laminated fiber metal composite preform. 
         FIG. 6  is an illustration of an alternative laminated fiber metal composite preform. 
         FIG. 7  is an illustration of a laminated fiber metal composite body. 
         FIG. 8  is an illustration of an alternative laminated fiber metal composite preform. 
         FIG. 9  is an illustration of an alternative laminated fiber metal composite body. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  illustrates a metal foil sheet  100  used in making laminated fiber metal composite structures. The sheet  100  has a first face  102  and a second face  104  opposite the first face. Although the sheet  100  may have other thicknesses, in one embodiment the sheet has a thickness of between about 0.005 inches and about 0.015 inches. The metal foil sheet  100  extends a length  106  and a width  108  between a plurality of edges  110 . In one embodiment, the sheet  100  is made of titanium (e.g., Ti 15-3-3-3). In another embodiment, the sheet  100  is made of aluminum (e.g., T-6061). In yet another embodiment, the sheet  100  is a combination of two or more metals. The metal foil sheet  100  is perforated so it has a plurality of openings  112  extending through the sheet from the first face  102  to the second face  104 . The openings  112  may have a variety of shapes and sizes suitable to facilitate flow of a resin mixture therethrough. For example, in one embodiment, the openings  112  are generally circular. In alternative embodiments, the openings  112  may have other suitable shapes. For example, the openings may be generally diamond shaped as illustrated in  FIG. 3 , or generally square as illustrated in  FIG. 4 . Although the openings  112  may have other dimensions, in one circular opening embodiment, each opening has a diameter of about 0.01 inches. In another embodiment, the openings  112  each have a diameter of about 0.04 inches. In yet another embodiment, the openings  112  each have a diameter of between about 0.01 inches and about 0.04 inches. Furthermore, the metal foil sheet  100  may include a variety of differently shaped and/or sized openings  112 . It should be understood that the metal foil sheet  100  may have any number of the openings  112 , each having any size and shape suitable for facilitating the flow of a resin mixture through the sheet, regardless of whether such size and shape is explicitly mentioned herein. 
     The plurality of openings  112  may be arranged on the metal foil sheet  100  in any suitable pattern for facilitating the flow of a resin mixture through the sheet. For example, as illustrated in  FIG. 2  the plurality of openings  112  are arranged in a series of rows  114  spaced generally evenly along the sheet length  106 , wherein each row has a plurality of the openings spaced generally evenly along a portion of the sheet width  108 .  FIG. 3  illustrates another exemplary pattern for the openings  112 . In one embodiment, the openings  112  are spaced generally evenly apart on the sheet  100  by, for example, between about 0.25 inches and about 2.0 inches. In another embodiment, the openings  112  are spaced apart by varying distances. The plurality of openings  112  may be each spaced from adjacent openings by any suitable distance, and additionally the plurality of openings may be arranged on the sheet  100  in other patterns not specifically discussed and/or illustrated herein. 
     The plurality of openings  112  may be formed within the sheet using any suitable manufacturing process. For example, in one embodiment the openings  112  are formed by directing a pulsed laser at the metal foil sheet  100 . 
     As illustrated in  FIG. 5 , at least one metal foil sheet  100  is stacked together with a plurality of fiber plies  150  in face to face relation and in a predetermined order and orientation to form a fiber metal composite preform  152 . Similar to the conventional laminated fiber metal composite  20  ( FIG. 1 ), each fiber ply  150  has a plurality of reinforcing fibers  154 . In one embodiment, the reinforcing fibers  154  are fiberglass. In another embodiment, the reinforcing fibers  154  are carbon fibers. In yet another embodiment, the reinforcing fibers  154  are aramid fibers. The reinforcing fibers  154  may be any suitable fiber or combination of different fibers. Further, the fibers  154  of each ply may be oriented in one common direction or in a plurality of directions. In the embodiment illustrated in  FIG. 5 , the preform  152  includes a plurality of metal foil sheets  100 , and more specifically includes two perforated metal foil sheets having the plurality of fiber plies  150  positioned between them, and another perforated sheet positioned between two adjacent fiber plies of the plurality of fiber plies. As will be appreciated by those skilled in the art, the fiber plies  150  may be oriented so the fibers of each ply extend in a single common direction or they may be oriented in other directions to provide desired strength and stiffness for the finished body. Additionally, as illustrated in  FIG. 6 , the plurality of fiber plies  150  may be positioned within the preform  152  between a perforated metal foil sheet  100  and a non-perforated metal foil sheet (e.g., the metal foil sheet  26  illustrated in  FIG. 1 ), and the preform may also include a perforated metal foil sheet positioned between two adjacent fiber plies of the plurality of fiber plies. However, the preform  152  may include any number of metal foil sheets whether perforated or non-perforated, such that the preform  152  includes a perforated metal foil sheet  100  having a face (e.g., the first face  102 ) positioned adjacent a fiber ply  150 . Furthermore, the fiber metal composite preform  152  may include a variety of metal foil sheets, whether perforated or non-perforated, formed from different metals and/or metal alloys. 
     To form a laminated fiber metal composite body, such as the laminated fiber metal composite body portion illustrated in  FIG. 7  and generally designated by the reference numeral  200 , the fiber metal composite preform  152  ( FIG. 5 ) is infused with a resin mixture and laminated to bond the plurality of fiber plies  150  and the metal foil sheet(s)  100  together. In one embodiment, the body  200  is cured after lamination to facilitate bonding the plurality of fiber plies  150  and the metal foil sheets(s)  100  together. More specifically, a resin infusion process is used to infuse the resin mixture into the preform  152  such that the resin mixture flows through the plurality of fiber plies  150  and the openings  112  ( FIG. 5 ) within the metal foil sheet(s)  100 . As the resin mixture flows through the fiber plies  150  and the metal foil sheet(s)  100 , the resin mixture intersperses between the plurality of fiber plies, and more specifically between the reinforcing fibers  154  of each fiber ply. A variety of resin infusion processes are suitable for infusing a resin mixture into the preform  152 , such as, for example, resin transfer molding, vacuum assisted resin transfer molding, seemann composites resin infusion molding process (SCRIMP®), and controlled atmospheric pressure resin infusion. SCRIMP is a federally registered trademark of TPI Technology, Inc of Warren, R.I. A mold may be used during stacking of the fiber plies  150  and the metal foil sheet(s)  100 , and during lamination of the preform  152 , to control a shape of the laminated fiber metal composite body  200 . 
     Reference is now made to  FIG. 8 , which illustrates a fiber-metal composite perform  352  including a plurality of fiber plies  350  and metal foil layers  356 . The metal foil layers  356  are stacked with the fiber plies  350  in a face-to-face relationship and in a predetermined order and orientation. 
     Similar to the laminated fiber metal composite  200  of  FIG. 7 , each fiber ply  350  has a plurality of reinforcing fibers  354  such as fiberglass, carbon fibers or aramid fibers. The reinforcing fibers  354  may be any suitable fiber or combination of different fibers. Further, the fibers  354  of each ply may be oriented in one common direction or in a plurality of directions. 
     Each metal foil layer  356  includes a plurality of metal foil strips  300 . Although the metal foil strips  300  may have other thicknesses, in one embodiment the strips  300  each have a thickness of between about 0.005 inches and about 0.015 inches. The thickness of each strip  300  may vary along its length and/or width. Further, some metal foil strips  300  may have different thicknesses from other strips  300 . In one embodiment, the strips  300  are made of titanium (e.g., TI 15-3-3-3). In another embodiment, the strips  300  are made of aluminum (e.g., T-6061). In another embodiment, the strips  300  are made of a combination of two or more metals. Although the metal foil strips  300  of  FIG. 8  are shown as being generally rectangular, the strips  300  of other embodiments may have a variety of shapes and sizes. 
     In the embodiment illustrated in  FIG. 8 , the metal foil strips  300  in each layer  356  are arranged in side by side relationship. The metal foil strips  300  are arranged side by side so that at least two adjacent strips  300  in each metal foil layer  356  are spaced by a gap  358 . In one embodiment, each of the metal foil strips  300  is spaced from adjacent strips by a gap  358 . The gaps  358  facilitate flow of resin mixture through the metal foil layer  356 , and more specifically through the gaps  358 . 
     Although the gaps  358  may have other widths  360 , in one embodiment each of the gaps  358  has a width  360  of between about 0.01 inches and about 0.05 inches. The gaps  358  may have varying widths  360  to facilitate flow of a resin mixture through the gaps  358 . Additionally, each metal foil layer  356  may include any number of metal foil strips  300 , and the strips  300  within each layer  356  may be spaced by gaps  358  having any suitable width  360 . The widths  360  may be identical within each layer  356 , vary within each layer  356 , vary from layer  356  to layer  356 , or be constant throughout the preform  352 . 
     Although the metal foil strips  300  may have other widths  362 , in one embodiment, the width  362  is between about 0.125 inches and about 2.0 inches. In one embodiment the strips  300  have varying widths  362 . For example, some or all of the metal foil strips  300  may have widths  362  that vary along their respective lengths. 
     In the embodiment illustrated in  FIG. 8 , the preform  352  includes a first metal foil layer  356 , a first stack of three fiber plies  350  on the first metal foil layer  356 , a second metal foil layer  356  on the first stack of fiber plies  350 , a second stack of fiber plies  350  on the second metal foil layer  356 , and a third metal foil layer  356  on the second stack of fiber plies  350 . The fiber plies  350  may be oriented so the fibers of each ply  560  extend in a single common direction or they may be oriented in other directions to provide desired strength and stiffness for the finished body. 
     The plurality of strips  300  may be arranged within each layer  356  in any suitable pattern. Further, the pattern in which the strips  300  are arranged may vary from layer to layer or be similar for each layer. For example, as illustrated in  FIG. 8  the plurality of strips  300  in each layer  356  may extend longitudinally along a length of the preform  352 . Alternatively, the plurality of strips  300  in one or more layers  356  may extend transversely across a width of the preform  352 . As an example of another configuration, a plurality of strips  300  may extend diagonally across the preform  352 , a plurality of strips  300  may be woven together, and/or a plurality of strips  300  may overlap one another in a criss-cross pattern. Additionally, a plurality of glass fibers (not shown) may be woven around one or more of the strips  300  to control the gaps  358  between the strips and control the position of the strips within the preform  352 , regardless of the pattern in which the strips  300  are arranged. The plurality of strips  300  in each layer  356  may be arranged in other patterns not specifically discussed and/or illustrated herein, such that the strips  300  in each layer  356  are arranged in any suitable pattern facilitating the flow of a resin mixture through the metal foil layer  356 . 
     In some embodiments of a preform, the plurality of fiber plies  350  may be positioned between a metal foil layer  356  and a metal foil sheet (e.g., the metal foil sheet  26  illustrated in  FIG. 1  or the perforated metal foil sheet  100  illustrated in  FIG. 2 ), and a layer of metal foil strips may be positioned between two adjacent fiber plies of the plurality of fiber plies. Such a preform may include any number of metal foil layers  356 , and additionally may include any number of metal foil sheets (whether perforated or non-perforated) such that the preform includes a layer of metal foil strips  300  positioned adjacent a fiber ply  350 . Furthermore, the preform may include a variety of metal foil strips  300 , and that these strips  300  may be arranged in the same layer  356  or different layers. Still further, the strips  300  may be formed from different metals and/or metal alloys. 
     To form a laminated fiber metal composite body, generally designated by  400  in  FIG. 9 , the fiber metal composite preform  352  ( FIG. 8 ) is infused with a resin mixture and laminated to bond the plurality of fiber plies  350  to the metal foil layer(s)  356 . In one embodiment, the body  400  is cured after lamination to facilitate bonding the plurality of fiber plies  350  to the metal foil layer(s)  356 . More specifically, a resin infusion process is used to infuse the resin mixture into the preform  352  such that the resin mixture flows through the plurality of fiber plies  350  and the gaps  358  ( FIG. 8 ) in the metal foil layer(s)  356 . As the resin mixture flows through the fiber plies  350  and the metal foil layer(s)  356 , the resin mixture intersperses between the plurality of fiber plies  350 , and more specifically between the reinforcing fibers  354  of each fiber ply  350 . A variety of resin infusion processes are suitable for infusing a resin mixture into the preform  352 , such as, for example, resin transfer molding, vacuum assisted resin transfer molding, SCRIMP®, and controlled atmospheric pressure resin infusion. A mold may be used when stacking the fiber plies  350  and the metal foil layer(s)  356 , and during lamination of the preform  352 , to control a shape of the laminated fiber metal composite body  400 . 
     The above-described perforated metal foil sheet and layer of metal foil strips are cost-effective and reliable for facilitating infusion of a resin mixture into a fiber metal composite without generally sacrificing the bearing strength of the composite. More specifically, during a resin infusion process, resin flows through the perforations in the metal foil sheet and/or the gaps in the metal foil layer, and intersperses between a plurality of fiber plies stacked together with the metal foil sheet and/or the metal foil layer. As a result, a conventional resin infusion process may be used during lamination without the need to prepreg the fibers, wet-wind the fiber plies, and/or insert thin sheets of resin between the fiber plies prior to lamination.