Abstract:
Reinforced structural assemblies and methods for forming such assemblies are disclosed. In one embodiment, a reinforced structural assembly includes an engagement portion having at least one projecting structure extending outwardly from the engaging structure, and a receiving portion having at least one recessed structure that slidably receives and fixably retains the projecting structure. In another embodiment, a method for constructing a reinforced structural assembly includes positioning at least one projecting structure on a first substrate, positioning at least one recessed structure on a second substrate. The at least one projecting structure and the at least one recessed structure are slidably coupled and fixably secured.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to materials construction, and more particularly to reinforced structural assemblies and methods for forming such assemblies.  
       BACKGROUND OF THE INVENTION  
       [0002]     Reinforced structures are widely used in many industries and in many diverse applications. For example, aircraft, spacecraft, terrestrial and marine vehicles often employ a variety of planar, curved and multiple-contoured reinforced structures. The foregoing reinforced structures generally include a lightweight core material that is positioned between a pair of spaced apart and generally parallel face sheets. Since the bending stiffness of the reinforced structure substantially increases as the core thickness is increased, such structures advantageously provide a lightweight and effective means for resisting bending loads.  
         [0003]     One commonly used reinforced structure includes an interconnected honeycomb core structure having a selected thickness that is positioned between the face sheets. Although the foregoing reinforced structure is effective in resisting high bending loads, some disadvantages nevertheless exist. For example, since the core material must be bonded to the face sheets by adhesives, brazing or other similar processes at many discrete locations, portions of the core material may be insufficiently bonded to the face sheets during fabrication of the structure that result in localized weaknesses within the structure. Moreover, if the structure sustains physical damage while in service, the structure is typically repaired by cutting the face sheets and the core material to remove the damaged portion. Repair procedures of this type may cause further debonding of the core material from the face sheets, which is not readily detectable by commonly used inspection procedures.  
         [0004]     Another commonly used reinforced structure employs a closed network of discrete ribs that extend between opposed and spaced apart face sheets. The ribs are generally coupled to the face sheets by fixedly positioning edges of the ribs into receiving grooves that are machined or otherwise formed in the face sheets. One example of the foregoing reinforced structure is the GRID-LOCK structural system available from Rohr, Inc. of Chula Vista Calif. Although the foregoing system addresses some of the shortcomings present in structures having a honeycomb core material, still other shortcomings are present. For example, the machined receiving grooves require a small diameter tool to form the elongated grooves, which is time consuming and generally increases the production costs associated with the fabrication of the reinforced structure. Moreover, the relatively thin ribs are typically positioned in relatively shallow receiving grooves that provide a limited bond contact area. Accordingly, such structures must include a relatively large number of ribs and/or thicker face sheets in order to provide the desired flexural strength.  
         [0005]     Accordingly, what is needed in the art is a lightweight reinforced structure that is conveniently and inexpensively fabricated, while providing high flexural rigidity.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention is directed to reinforced structural assemblies and methods for forming such assemblies. In one aspect, a reinforced structural assembly includes an engagement portion having at least one circumferential projecting structure extending outwardly from the engaging structure, and a receiving portion having at least one circumferential recessed structure that slidably receives and fixably retains the projecting structure.  
         [0007]     In another aspect, a method for constructing a reinforced structural assembly includes positioning at least one projecting structure on a first substrate, and positioning at least one circumferential recessed structure on a second substrate. The at least one circumferential projecting structure and the at least one circumferential recessed structure are slidably coupled and fixably secured. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     Preferred and alternate embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0009]      FIG. 1  is a partial plan view of the reinforced structural assembly according to an embodiment of the invention;  
         [0010]      FIG. 2  is an exploded, partial isometric view of the embodiment of  FIG. 1 ;  
         [0011]      FIGS. 3   a  and  3   b  are respective cross sectional views of portions of the embodiment of  FIG. 1 ;  
         [0012]      FIG. 4  is a partial cross sectional view of the embodiment of  FIG. 1 ;  
         [0013]      FIG. 5  is a partial isometric view of a reinforced structural assembly according to another embodiment of the invention;  
         [0014]      FIG. 6  is a partial cross sectional view of the embodiment of  FIG. 5 ; and  
         [0015]      FIG. 7  is a side elevation view of an aircraft having one or more of the disclosed embodiments of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0016]     The present invention relates to reinforced structural assemblies and methods for forming such assemblies. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1 through 7  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description.  
         [0017]      FIG. 1  is a partial plan view of the reinforced structural assembly  10  according to an embodiment of the invention, which shows respective disengaged portions of the assembly  10 . The assembly  10  includes a receiving portion  12  having at least one recessed structure  14 , and an engagement portion  16  having at least one projecting structure  18  configured to engage the recessed structure  14  of the receiving portion  12 . The receiving portion  12  includes a supporting substrate  20  that is fixedly coupled to the recessed structures  14 . Similarly, the engagement portion  16  also includes a supporting substrate  22  that is fixedly coupled to the projecting structures  18 . Accordingly, when the projecting structure  18  is received into the recessed structure  14 , the respective supporting substrates  20  and  22  form opposing external sides of the reinforced structural assembly  10 , which may form a portion of a structural panel, such as a floor panel or a wing panel for an aircraft, or other similar structures.  
         [0018]     In some embodiments, the receiving portion  12  and the engagement portion  16  may be formed from any suitable, substantially rigid material, which may include any ferrous material, or alternately any non-ferrous material, such as aluminum, a stainless alloy or titanium. The receiving portion  12  and the engagement portion  16  may also be formed from selected polymeric materials, which may also include polymeric materials that are reinforced by fiber elements embedded in the polymeric material, such as carbon fibers, or other like materials. The receiving portion  12  and the engagement portion  16  may also be formed as composite structures, wherein the recessed structure  14  and the projecting structure  18  are formed as separate elements and then fixedly positioned onto respective supporting substrates  20  and  22  by a variety well-known material joining methods. For example, when the recessed structure  14  and the supporting substrate  20  are comprised of a metal, the structure  14  and the substrate  20  may be joined by various fusion processes, such as welding or brazing. Similarly, the projecting structure  18  and the supporting structure  22  may also be joined by a fusion process when the projecting structure  18  and the supporting substrate  22  are formed from a metal. Alternately, when the recessed structure  14 , the projecting structure  18  and the respective supporting substrates  20  and  22  are formed from a polymeric material, a suitable adhesive material may be employed to bond the recessed structure  14  to the substrate  20  and the projecting structure  18  to the substrate  22 .  
         [0019]     Still referring to  FIG. 1 , the recessed structure  14  and the projecting structure  18  are depicted as having a rectangular and closed planform shape, so that the projecting structure “telescopes” (or is slidably received) into the recessed structure  14  during fabrication of the assembly  10 . It is understood, however, that the recessed structure  14  and the projecting structure  18  may have any regular polygonal shape in planform, and may further also be circular. In the embodiment shown in  FIG. 1 , the projecting structure  18  includes corners  24  having a radius that is greater than the corners  26  in the recessed structure  14 . This feature permits the recessed portion  14  to receive the projecting structure  18  without experiencing excessive binding or interference, which advantageously assists in fabricating the assembly  10 .  
         [0020]      FIG. 2  is an exploded, partial isometric view of the assembly  10  of  FIG. 1 , which will be used to describe the assembly  10  in greater detail. The recessed structure  14  further includes at least one recess  28  formed in an interior portion of the recessed structure  14  that assists the recessed structure  14  to retain the projecting structure  18  when the structure  18  is positioned within the recessed structure  14 . Accordingly, the recess  28  may be used to retain a volume of an adhesive material, such as an epoxy resin, that is applied to the interior portion of the recessed structure  14 . Alternately, the recess  28  may also be used to retain a portion of a brazing alloy that may be used to fixably join the projecting structure  18  to the recessed portion  14 . Although the recess  28  is shown as a longitudinal groove that extends partially along the interior portion of the recessed structure  14 , it is understood that the recess  28  may have a variety of other shapes and orientations. For example, the recess  28  may have a serpentine or saw tooth shape. Moreover, the recess  28  may extend around substantially the entire interior portion of the recessed structure  14 . Alternately, the recess  28  may extend about only a portion of the interior portion of the recessed structure  14 . The projecting structure  18  includes a relatively smooth outer portion that abuts the recess  28  in the interior portion of the recessed structure  14  when the receiving portion  12  is joined to the engagement portion  16 . The recessed portion  14  and the projecting structure  18  are generally configured to minimize the amount of the adhesive material between the recessed portion  14  and the projecting structure  18 , so that the adhesive material is substantially retained within the recess  28 .  
         [0021]     With reference briefly to  FIG. 3   a  and  FIG. 3   b , cross sections of the recessed structure  14  and the projecting structure  18  are shown, respectively. With reference first to  FIG. 3   a , the recess  28  may extend into the interior portion of the recessed portion  14  to a relatively shallow depth, which advantageously limits the amount of machining required within the recessed portion  14 . Further, the recess  28  may be formed so that the recess  28  includes a relatively large radius  29  on opposing sides of the recess  28 . Consequently, regions of elevated stress concentration are minimized. Although two recesses  28  are shown in  FIG. 3   b , it is understood that one, or more than two recesses  28  may be present. Turning now to  FIG. 3   b , the projecting structure  18  is relatively uniform in cross section so that the adhesive material is retained within the recess  28  of  FIG. 3   a  when the recessed structure  14  and the projecting structure  18  are substantially abutting, as shown in detail in  FIG. 4 . Although the projecting structure  18  is shown having a relatively uniform cross section, it is understood that the projecting structure  18  may include one or more recesses of the type shown in  FIG. 3   a . Alternately, and in other particular embodiments of the invention, the recess  28  may not be present in either the projecting structure  18  or the recessed structure  14 , so that the projecting structure  18  and the recessed structure  14  are fixably coupled by mechanical interference.  
         [0022]      FIG. 5  is a partial isometric view of a reinforced structural assembly  30  according to another embodiment of the invention. The assembly  30  includes a recessed structure  32  that is fixedly positioned on a supporting substrate  20 . The recessed structure  32  is configured to receive the projecting structure  18  of the engagement portion  16  of  FIG. 1  to form the assembly  30 . For clarity of illustration, the engagement portion  16  is not shown in  FIG. 5 . The recessed structure  32  includes at least one recess  28  that is formed in the interior of the recessed structure  32 . The recessed structure  32  further includes raised corner regions  34  that advantageously permit a thickness h of the recessed structure  32  to be increased so that the flexural stiffness of the assembly  30  may be increased while avoiding a significant increase in weight for the assembly  30 .  FIG. 6  is a partial side view of the assembly  30  that shows the projecting structure  18  of the engagement portion  16  of  FIG. 1  positioned in the recessed structure  32  of the assembly  30 . As shown therein, the thickness h may be altered for the recessed structure  32  without alteration of the engagement portion  16 . Accordingly, the flexural stiffness of the assembly  30  may be tailored to accommodate a selected application by alteration of only the recessed structure  32 . This feature advantageously permits a component inventory to be minimized since the recessed structure  32  may be easily reconfigured to provide various thicknesses h.  
         [0023]     Those skilled in the art will also readily recognize that the foregoing embodiments may be incorporated into a wide variety of different systems. Referring now in particular to  FIG. 7 , a side elevation view of an aircraft  300  having one or more of the disclosed embodiments of the present invention is shown. With the exception of the embodiments according to the present invention, the aircraft  300  includes components and subsystems generally known in the pertinent art, and in the interest of brevity, will not be described further. The aircraft  300  generally includes one or more propulsion units  302  that are coupled to wing assemblies  304 , or alternately, to a fuselage  306  or even other portions of the aircraft  300 . Additionally, the aircraft  300  also includes a tail assembly  308  and a landing assembly  310  coupled to the fuselage  306 . The aircraft  300  further includes other systems and subsystems generally required for the proper operation of the aircraft  300 . For example, the aircraft  300  includes a flight control system  312  (not shown in  FIG. 7 ), as well as a plurality of other electrical, mechanical and electromechanical systems that cooperatively perform a variety of tasks necessary for the operation of the aircraft  300 . Accordingly, the aircraft  300  is generally representative of a commercial passenger aircraft, which may include, for example, the 737, 747, 757, 767 and 777 commercial passenger aircraft available from The Boeing Company of Chicago, Ill. Although the aircraft  300  shown in  FIG. 7  generally shows a commercial passenger aircraft, it is understood that the various embodiments of the present invention may also be incorporated into flight vehicles of other types. Examples of such flight vehicles may include manned or even unmanned military aircraft, rotary wing aircraft, ballistic flight vehicles or orbital vehicle, as illustrated more fully in various descriptive volumes, such as Jane&#39;s All The World&#39;s Aircraft, available from Jane&#39;s Information Group, Ltd. of Coulsdon, Surrey, UK. Additionally, those skilled in the art will readily recognize that the various embodiments of the present invention may also be incorporated into terrestrial or even marine vehicles.  
         [0024]     With reference still to  FIG. 7 , the aircraft  300  may include one or more of the embodiments of the reinforced structural assembly  314  according to the present invention, which may be incorporated into various structural portions of the aircraft  300 . In addition, the various embodiments of the present invention may also be incorporated into the various systems and sub-systems of the aircraft  300 .  
         [0025]     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.