Abstract:
An improved monument structure combining an integrated construction system with carbon fiber reinforced composites to form an exoskeleton chassis. The chassis includes an above work deck subassembly, a below work deck subassembly, and a rear service wall subassembly, each respective subassembly is formed using carbon fiber reinforced composites (CFRC) pre-impregnated panel skins. The subassemblies are reinforced with a unidirectional carbon fiber.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 61/616,904, filed Mar. 28, 2012, incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Commercial passenger carrying airplanes commonly have storage or compartment structures (frequently referred to by the generic name “monuments”) installed on the aircraft. These structures are used in a variety of ways, such as storage of clothing and other passenger belongings, electronic entertainment centers, sleeping quarters for the officers and cabin crew, purser work stations, bar units, lavatories, and galleys used to provide in-flight catering meal service to the passengers. Traditionally, these monuments have been manufactured using multi-layered lightweight assemblies known as “sandwich panels” of Nomex® or Kevlar® cores, with resin pre impregnated fiberglass skins forming the surface. Other types of composite panels are manufactured with foam, thermo-plastic or metallic core materials and with plastic or metallic outer skins. Aircraft monuments may alternatively be constructed entirely from flat sheet materials that are pre manufactured in a process using a multi-layer temperature controlled press, and/or from molds using an autoclave to provide both temperature and pressure for curing of the panel, part or section. 
     Following manufacture, these parts or sections have to undergo additional “pre or post processing” where they may be trimmed, cut and/or formed into the parts necessary to construct the monument. They will also commonly undergo secondary operations to have fixing points and/or locating holes installed in the form of “inserts” or “bobbins.” In the case of the former, they provide a means of attaching items to the panel, and rely on the injection of an adhesive around the fixing to form a plug that resists being pulled out through the skin when a load or force is applied to it. In the case of the latter, a through hole is provided for fixings that would otherwise damage the panel. 
     Items attached to the panels include wiring looms and electrical components, plumbing hoses, pipes and components, ventilation and air extraction duct, hose and component mountings, décor panels, hinges, back stops, galley insert equipment interfaces, access panels, ducts, sliders and draw runners, electronic entertainment devices, grilles, and general equipment retainers. 
     After the preparatory stages are complete, the monument is constructed by assembling the various parts, either by bonding the flat panels together to form a rigid structure with viscous liquid adhesives, or by combining the flat panels with pre manufactured (e.g. pre cured) molded parts to form the basic structure. These molded sections or flat panel sub-assemblies may also remain as removable (i.e. bolt on/bolt off parts). Likewise, adhesive bonded flat panels forming sub-assemblies or modules may be bolted together to form the complete structure. 
     Basic construction in all cases involves a post composite panel manufacturing process that relies on bonding using liquid adhesives for the panels forming the structure itself, the fixing points, through holes and mountings and/or the sub-assemblies, modules and moldings themselves. Further, secondary operations attaching various loose metallic and non-metallic parts to the basic structure, together with electrical, water and air systems are then undertaken. These separate processes add significantly to the cost and construction time, and require a high level of expert knowledge and operator skill. 
     Another issue with the current monument construction is the need for reinforcement. To reinforce a given monument structure, “C,” “U,” “H,” “F” and right angle as well as other shapes of section aluminum extrusions are commonly bonded to the edges of the panels for stiffness. Where local re-enforcement of the structure is required (for load bearing purposes), flat sheets of aluminum, typically 1/32″ to ⅛″ thick, are bonded to the panel to transfer the effects of localized stress to portions of the structure with higher load bearing capabilities. This type of additional localized reinforcement is commonly called a “doubler.” This practice adds significant weight to the Monument and requires another manufacturing process, adding the cost. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved monument structure combining an integrated construction system with carbon fiber reinforced composites to form an exoskeletal chassis that significantly reduces the build times, manufacturing skill level requirements, post processing activities, and overall weight of a given aircraft monument. New monument designs may be analyzed using finite element analysis to determine the maximum load that will be imposed on the improved structure, and then all local reinforcement requirements will be incorporated into the integrated structure as determined by the monument&#39;s worst case loading determination. 
     The construction of the monument of the present invention calls for designing the lay-up of a composite panel sandwich to include integral localized reinforcement, capable of handling the stress loads imposed on the structure without the need for additional supplementary metallic reinforcement. All fixing points (which include both floating and fixed potted inserts), through holes, brackets, back stops for cart that prevent rearward movement, wear strip bases (rub and bump strips) trolley wheel guides, GAIN interface points, ducts, electrical routing channels and other secondary process items, are incorporated in the primary manufacturing process. 
     The primary manufacturing process consists of a modular, reversed molding system utilizing carbon fiber reinforced composite pre impregnated skins (referred to as CFRCs) with or without a core structure, and localized reinforcement of unidirectional carbon fiber (referred to as UD fiber) that are applicable to the structural requirements and loadings of the particular monument. Where applicable, previously manufactured I and H beams are incorporated into the structure to provide high strength reinforcement. The molds may or may not be modular in construction, depending on the type of monument being constructed, and will have a specific construction applicable to their intended function. 
     Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings, which illustrate, by way of example, the operation of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevated, perspective view of a first embodiment of the monument structure of the present invention; 
         FIG. 2  is a partially exploded, elevated, perspective view of the embodiment of  FIG. 1 ; 
         FIG. 3  is a perspective view of the above work deck sub-assembly of the embodiment of  FIG. 1 ; 
         FIG. 3A  is an enlarged, perspective view of the way in which the compartments of the above work deck are formed; 
         FIG. 3B  is a cross-sectional view of an intersection of the panels in the sub-assemblies of the present invention; 
         FIG. 4  is a perspective view of the below work deck sub-assembly of the embodiment of  FIG. 1 ; 
         FIG. 4A  is a cross-sectional view of the mating of the above work deck and below work deck sub-assemblies; 
         FIG. 5  is an enlarged, perspective view of the bump strip carrier for the below work deck sub-assembly of  FIG. 4 ; 
         FIG. 6  is an enlarged, perspective view of an integrated floor attachment device of the sub-assembly of  FIG. 4 ; 
         FIG. 7  is a perspective, front view of the rear service wall of the monument structure; and 
         FIG. 8  is an enlarged, perspective view of a composite roof attachment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  illustrate a first preferred composite aircraft monument in the form of a refrigerated center line galley  10  that comprises three main chassis sub-assemblies, a below work deck area (BWD)  12 , an above work deck area (AWD)  14 , and a removable, one piece rear service wall (RSW)  16 . The AWD section  14  provides compartments  18  as required for galley inserts, or GAINs, such as coolers, ovens, coffee brewers, and the like to be installed. The AWD section  14  compartments  18  also provide space for meal boxes or standard units (SUs), and miscellaneous storage in the same way, together with compartment door hinge and latch locations, if so required. On top of the above work deck area  14  is a pair of composite ceiling mounts  20  for attaching the monument  10  from above to the ceiling or supporting structure of the airframe. 
     The compartments  18  of the above work deck  14  are defined by panels  22  as shown in  FIG. 3 , that is formed of previously manufactured flat CFRC-faced panels integrated into the structure using slots  28  at the intersection of the horizontal shelves  24  and the vertical walls  26  (See  FIG. 3A ). The shelves  24  and walls  26  are formed using a wet lay process where layers  30  of material are placed in a mold in over a wet lay  32 , and the walls  26  and shelves  24  are then integrated into the assembly using additional UD reinforcing plies  34  (see  FIG. 3B ). When formed in this manner, the panels need no additional secondary stiffening, and separate metallic edge members are not required, although the edges of the panel may be sealed with a lightweight plastic extrusion. The edges may also be covered with overlapped panel skin plies  38 . The “B” surface  30 , i.e. the finished molded surface opposite the usual orientation of the lay-up, of the AWD molding preferably either provides the upper section of the air ducting for a chiller in the work deck (“CIWD”) air chiller fed system, or provides for a CIWD line replacement unit (“LRU”) chiller module. Non-chilled galleys that may not have this provision for ductwork may instead have a structure for other items such as sliding tables. In a preferred embodiment, the whole AWD section  14  is cured as a single and complete integrated structural sub-assembly. 
     On the upper surface  40  of the above work deck area  14  is a pair of horizontal channels  42  that can be used to adjustably position the monument  10  within the aircraft. Roof attachments  20  (see  FIG. 8 ) is formed of a high strength composite and have orthogonal plates  21 ,  23 , where plate  21  extends below a lower surface  23   a  such that plate  21  can slide within its channel  42  and be clamped or fastened in the desired location. The plate  23  then rests on the upper surface  40  of the above work deck  14  to stabilize the attachment. The roof attachment  20  can include a lug  25  that can be used to bolt, rivet, or otherwise secure the monument  10  to the upper airframe structure. 
     The BWD section  12  provides accommodation in the form of two large cabinets  50  for meal service carts or trolleys, storage compartments, waste container areas, trash compactor location, galley waste disposal units (GWDU) and/or miscellaneous stowage areas. Further, the below work deck section incorporates fixing and locating points, including integrated aircraft floor attachment devices  70  (see  FIG. 6 ), back stops  80 , cart dividers (T dividers)  85 , and rub and bump strip bases  90 . Divisions between the compartments are formed during the wet lay process or integrated into the assembly using additional UD reinforcing plies, as discussed above with respect to  FIG. 3 .  FIG. 5  shows a view of the rub and bump strip  90 , along with the back stop  80  to prevent the beverage cart (not shown) from extending too far into the cabinets  50 . 
       FIG. 6  illustrates an integrated floor attachment device  70  incorporated into the walls  210  of the below work deck section  12 . The floor attachment device  70  comprises two horseshoe shaped plates  120  having an outer radius along the perimeter and an inner radius along the inner edge. The two plates  120  are joined together along the inner radius by a rigid panel  130 , such that there is an arcuate gap between the two plates  120 , and between the rigid panel  130  and the outer radius of the two plates  120 . The connection of the two plates  120  to the rigid panel  130 , such as by welding for example, is sufficient to transfer loads from the panel  130  to the plates  120 . 
     At the base of the attachment device  70  are a pair of lugs  140  including a vertical channel  150  sized to receive a fastener (not shown). The lugs  140  are preferably positioned such that no more than half of the lug  140  is outside of the envelope of the two plates  120 . The two lugs  140  are formed from a common block, that also connects to the rigid panel  130 . The bottom edge of the plates  120  coincide with a bottom edge of the lugs  140  such that the attachment device  70  lays flush with a floor of the aircraft. Sandwiched between the monument walls is a composite panel core material  220  that forms the interior of the wall structure. At the base of the wall, between the panels  210 , is the floor attachment device  70  that is used to mount the wall to the floor of the aircraft. A space above the cylindrical lugs  140  can be used to insert and remove the fasteners, and the arch shape of the fitting contributes to the overall strength of the fitting. 
     In a preferred embodiment, the attachment device  70  is integrated in the wall structure of the monument  10  during the primary build phase, eliminating the need for a secondary operation and greatly improving the component strength and the ability of the structure to handle both static and dynamic loads. This is particularly important in a vehicle such as an aircraft, which is subject to dynamic loads on a consistent basis. The lugs  140  create a small offset that allow the monument structure to have a greater proportion of standardized parts while reducing the weight of the component as well as the footprint of the monument. In a non-metallic form, such as a composite or hardened plastic, the fitting  70  can be mass produced, very light, and resistant to corrosion. 
     As the panels of the above work deck  14  and below work deck  12  need no additional secondary stiffening, separate metallic edge members are not required; however, the edges of the panel may be sealed with a lightweight plastic extrusion  137  or use overlapped panel skin plies ( FIG. 4A ). The mating surface of the BWD&#39;s molding either provides the lower section of the air ducting for a CIWD air chiller fed system or provides for a CIWD LRU chiller module. Further, the whole BWD section  12  is preferably cured as a single and complete integrated structural sub assembly. Note the AWD  14  and BWD  12  sub assemblies have the provision of male and female attachment points to allow structural connection of the two halves. The alignment of the two mating sub-assemblies  12 , 14  share a common through-hole  131  that can be used to secure the two components. When the two mating surfaces are bolted together, a gap  133  is formed between the surfaces that can promote cooling or venting. 
       FIG. 7  illustrates the rear service wall  16 , which preferably carries the majority of the galley electrical and plumbing service provisions. The RSW also provides the integrated chilled air ducting system (for both the AWD  14  and BWD  12  in the case of an air chiller supplied galley, and BWD only in the case of a chilled liquid supplied galley), and applicable galley insert retention and location provisions. The rear service wall  16  is also preferably cured as a single and complete integrated structural sub assembly. Wiring and plumbing components are mounted to the RSW  16  following the curing process. The RSW sub assembly may also have the provision of male and female attachment points to allow a structural connection to the two halves of the AWD and BWD sub assemblies. In a preferred embodiment, the rear service wall  16  includes a series of air vents  171  near the bottom of the RSW, where the vents  171  are located in recesses in the wall as shown in  FIG. 7 . The recesses extend vertically to a midpoint, where they funnel and consolidate into a single recess that vents through the top of the RSW  16 . This venting system allows air to circulate over the electrical system to prevent overheating, or to cool the backs of refrigeration units or other GAINs that require venting. 
     Although the above examples relate to one type of monument, i.e. a galley, the present intention is not limited in this manner and is applicable to the use and incorporation in the construction of other commercial aircraft monuments using the same or broadly similar methods. 
     The present invention is characterized in that the replacement of conventional pre-impregnated fiber glass panel skin materials with carbon fiber reinforced composites pre impregnated panel skin materials are used to form a structurally competent exoskeleton chassis that produces significant weight savings and strength advantages. The present invention also results in the elimination of a high percentage of cold bridges (caused by conduction through embedded metallic fixings, edge members, floor fittings, etc.) that are present between the exterior and the interior of refrigerated or chilled galley compartments, resulting in improved thermal insulation capabilities and lower cooling power requirements from the air or liquid chiller supplying the monument. 
     The present invention also leads to the elimination of a significant percentage of aircraft monument panel secondary processing operations, consisting of the provision of load bearing attachment points, through holes, locating points, access apertures, air ducting, reinforced beams, air craft attachment points, rub and bump strips, T dividers, back stops, etc., by integrating them into the primary molding operation. This results in a reduction in construction man hours, partial de-skilling of manufacturing processes, and significant weight saving advantages. 
     The present invention allows for the integration of chilled air distribution into the structure work deck area. Additionally, the combination of dry panel components, specific area reinforcements and pre manufactured CFRC parts incorporated into an integrated wet lay assembly lead to the formation of structural skeletal sub-assemblies. An advantage of the present invention is the elimination of the current requirement for metallic edge members for the purpose of stiffening and/or edge sealing of structural galley composite panels, through the use of CFRC panels with overwrapped skin or plastic capped edges. As set forth above, this provides significant cost and structure weight savings. 
     Another benefit of the present invention is the elimination of the use of supplementary localized metallic reinforcements. The present invention utilizes additional UD carbon plies (where required) to provide an integral integrated reinforcement solution, and results in significant manufacturing process time, and overall structure weight savings. The integration of major services into a single removable back panel for monuments, where electrical, plumbing, vacuum, refrigeration, CAX or ventilation systems are required, simplifies assembly and allows parallel flow line production. 
     Yet another feature of the present invention is the adoption of reverse molding to combine a wet/dry composite lay-up consisting of uncured materials, pre manufactured panels and composite components, to form an integrated primary manufacturing system. Additionally, the present invention&#39;s use of CFRCs significantly increases the strength of the monument for a given size while decreasing the structure weight. Also, the wet/dry molding system significantly reduces build times by integrating many secondary assembly operations into the primary manufacturing process. 
     A secondary benefit of the present invention is that the primary manufacturing process significantly reduces the volume of metallic parts in the structure, substantially reducing the weight. This also leads to the elimination of a significant volume of metallic cold bridges between the interior and exterior of chilled or refrigerated compartments, which reduces thermal losses and the energy required to achieve the specified compartment temperature. 
     Various features and embodiments of the present invention have been described herein, but the foregoing description is not intended to be limiting or exclusive. Rather, it would be apparent to one of ordinary skill in the art that various modifications would be readily available, and the present invention is intended to cover all such modifications and alternative embodiments.