Abstract:
A system for transmitting stresses at the intersection between a reinforcing frame and a stiffener in a fuselage and to a method for producing one such system. An aircraft fuselage includes stiffeners interrupted by reinforcing frames. At aforementioned interruptions, the stresses experienced by the stiffeners must be transmitted despite the presence of the reinforcing frames. Known solutions are difficult to manufacture and install and do not provide a simple stress transmission path when produced solely from composite materials. In order to solve this problem, the disclosed embodiments include the creation of battens that cover the ends of consecutive sections of a stiffener and the skin of the fuselage, extending under the reinforcing frame in order to join aforementioned two consecutive sections.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Stage of International Application No. PCT/FR2008/051630 International Filing Date, 12 Sep. 2008, which designated the United States of America, and which International Application was published under PCT Article 21 (s) as WO Publication No. WO2009/050357 A2 and which claims priority from, and the benefit of, French Application No. 200758418 filed on 18 Oct. 2007, the disclosures of which are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    The aspects of the disclosed embodiments relate to an aircraft comprising stiffener edge junctions and to a method for producing one such aircraft. More specifically, the disclosed embodiments relate to a system for transmitting stresses at the intersection between a reinforcing frame and a stiffener in a fuselage and a method for producing one such system. The purpose of the disclosed embodiments is to route stresses efficiently between two consecutive sections of an aircraft&#39;s stiffener. Such a stiffener normally passes through a reinforcing frame in a fuselage of an aircraft. The disclosed embodiments also aim to allow for a simple production and installation of means for routing for stiffeners with an omega-shaped profile. 
         [0003]    An aircraft&#39;s fuselage comprises several fuselage plated mounted together to form the fuselage. The fuselage plates have several stiffeners. The stiffeners are arranged in the form of raised ribs with respect to the said plates. The stiffeners extend over the plates, in the fuselage, along a longitudinal axis of the fuselage. In addition, such a fuselage includes reinforcing frames, particularly located at the junctions of the fuselage plates. These reinforcing plates are located perpendicularly along the longitudinal axis of the fuselage. In a fuselage, there are therefore many areas where the reinforcing frames and the stiffeners intersect. 
         [0004]    At an intersection between a stiffener and a reinforcing frame, the stiffener is interrupted in order to give priority to the reinforcing frame. Such a stiffener is therefore arranged in the form of multiple stiffener sections. Said sections are aligned and separated from each other by the presence of reinforcing frames. However, in order to play its role correctly in the fuselage of a device, the stress that a stiffener endures must be transmitted from one stiffener section to another, despite the presence of interruptions. 
         [0005]    It is known in the prior art, in the metal domain, to add brackets to the ends of the stiffener sections to allow continuity in the transmission of stress, despite the presence of reinforcing frames. Such brackets are supported on each side of the reinforcing frame and transmit stress from one stiffener section to the next section through the reinforcing frame, thereby ensuring a continuity of stress along a simple path. 
         [0006]    However, such brackets are difficult to manufacture for a stiffener with an omega-shaped transverse profile. By an omega transversal profile, this means a stiffener having two sole plates extending parallel to the fuselage plates and continuously from the nearest ends of the two sole plates, with a stiffener head connecting these two sole plates together. Such a head is arranged in the form of a sail whose profile is trapezoidal or curved. In a transverse cross-section, both sole plates associated with the head give the stiffener a capital omega ( 0 ) shape. 
         [0007]    In addition, the brackets cannot be produced entirely from composite materials. The presence of metallic elements is necessary for the production of the brackets. However, the presence of metallic elements causes corrosion problems, weight problems, and thermal problems in the fuselage. 
         [0008]    It is also known from the prior art, in the metal and composite domains, to create double folds in the plate&#39;s skin. Such double folds help to increase the rigidity of the plate. The purpose of these folds is to transmit stress from one stiffener section to another, despite the presence of reinforcing frames. The skin covers the inner wall of the fuselage plates. Such folds are formed by creating an additional layer under the skin before the interruption of the stiffener. This additional layers drains stress from a stiffener section before the stiffener is interrupted and transmits it to the stiffener&#39;s next section. For this, a fold wing passes under the reinforcing frame and continues under the end of the following stiffener section to transmit stress effectively. 
         [0009]    However, the presence of such fold wings under the stiffener implies a variation in the thickness of the skin where the stiffener is attached. It is difficult to produce a stiffener with an omega-shaped transverse profile that adapts to this variation in the thickness of the skin. In addition, the routing of stress from one stiffener section to another is complex, which results in a lower quality transmission of stress compared to the brackets. 
       SUMMARY 
       [0010]    The purpose of the disclosed embodiments is therefore to provide a device that can effectively route stress between two sections of a stiffener, without an excessive loss of stress, and that can be made from composite materials while being simple to manufacture and install. 
         [0011]    To achieve a continuity of stress in all of the stiffener sections, despite the presence of reinforcing frames, the disclosed embodiments provide for the addition of parts connecting the ends of consecutive sections of a stiffener. More specifically, the disclosed embodiments provide for the presence of battens covering the skin and the ends of the stiffener sections. Such a batten avoids the creation of folds in the skin and therefore the presence of thickness variations in the skin under the stiffener. 
         [0012]    In addition, the disclosed embodiments provide for such a batten to join two consecutive stiffen sections by extending under the reinforcing frame. Such a junction, associated to the stiffener covering, ensures that stress is routed efficiently, without an excessive loss of stress. Moreover, such a batten can easily be created from composite materials, thereby avoiding problems related to the presence of metallic elements. 
         [0013]    Finally, such a batten is arranged simply, which facilitates its production and installation in the fuselage. 
         [0014]    The disclosed embodiments therefore relate to an aircraft comprising: fuselage plates; a stiffener with an omega-shaped transverse profile, said stiffener extending on a fuselage plate or on a skin along a longitudinal axis of the fuselage; a reinforcing frame located on a plane perpendicular to the longitudinal axis of the fuselage, the stiffener being interrupted at the intersection of the plate with the reinforcing plate, the interruption of the stiffener separating said stiffener into two sections; at least one batten, this batten covering the ends of the stiffener sections, this batten joining two consecutive stiffener sections; characterized in that the batten is located between a plate and the reinforcing frame, said frame being supported against the batten. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The disclosed embodiments will be better understood upon reading the following description and studying the figures that accompany it. They are presented for illustrative purposes only and are not limiting to the disclosed embodiments. The figures show: 
           [0016]      FIG. 1 : A schematic perspective view of a part of fuselage; 
           [0017]      FIG. 2 : A schematic perspective view of a part of fuselage according to a first embodiment of the disclosed embodiments; 
           [0018]      FIG. 3 : A cross-sectional view of an intersection between a reinforcing frame and a stiffener according to the disclosed embodiments; 
           [0019]      FIG. 4 : A schematic perspective view of a part of fuselage according to a second embodiment of the disclosed embodiments; 
           [0020]      FIG. 5 : A cross-sectional view of a stiffener and a batten according to a third embodiment of the disclosed embodiments; 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  shows a schematic perspective view of a part of fuselage. Such a fuselage  1  has several segments  2  mounted together. These segments  2  are generally cylindrical in shape. Such a segment  2  has multiple fuselage plates  3  mounted together in order to form the cylindrical segment  2 . 
         [0022]    To ensure a certain solidarity to the structure, the fuselage  1  has at least one, or usually several, stiffener  4 . These stiffeners  4  extend parallel along a longitudinal axis  100  to the fuselage  1 . These stiffeners follow the inner wall of the fuselage  1 . 
         [0023]    In addition, such a fuselage  1  has at least one, or usually several, reinforcing frame  5 . These reinforcing frames are arranged in the form of beams, said beams having a sufficient height to ensure rigidity and prevent the fuselage from undergoing significant deformations. 
         [0024]    These reinforcing frames  5  follow the inner wall of the fuselage  1 . Such reinforcing frames  5  are located along planes perpendicular to the axis  100  of the fuselage  1 . The stiffeners  4  therefore extend along a perpendicular axis to the planes, along which extend reinforcing frames  5 . 
         [0025]    To give priority to the reinforcing frames  5 , the stiffeners  4  are interrupted at each intersection with a reinforcing frame  5 . A stiffener  4  is therefore divided into multiple sections  6 . A section  6  of a stiffener  4  is therefore either a section  6  at the beginning or end of the stiffener  4 , starting at the beginning or the end of the stiffener  4  and stopping just before a reinforcing frame  5 , or a stiffener  4  section  6  located between two reinforcing frames  5 . 
         [0026]    The fuselage  1  can have a skin  7 , which covers all or part of the inner wall of the fuselage  1 , which is the inner wall of the plates  3 . In this case, the stiffeners  4  can be attached to the skin  7  instead of being attached directly to the plates  3 . 
         [0027]      FIG. 2  shows a schematic perspective view of a part of fuselage  1  according to a first embodiment of the disclosed embodiments. In a transverse cross-section, a stiffener  4  is omega-shaped. More specifically, a stiffener  4  has a head support  8  and a head  9 . The head support  8  extends laterally from each site of the head  9  of a stiffener  4 . The head support  8  has a first sole plate  10  extending from one side of the head  9  and a second sole plate  11  extending from the opposite side of the first sole plate  10  of the head  9 . The first sole plate  10  and the second sole plate  11  extend parallel to the surface of a skin  7  covering the inner wall of the fuselage  1 . 
         [0028]    The head  9  has two sides and a top. A first side  12  forms an inclined plane relative to the first sole plate  10 . This first side  12  connects the first sole plate  10  to the top  13  of the head  9 . The top  13  of the head  9  forms a surface parallel to the skin  7  located between the first sole plate  10  and the second sole plate  11 . According to the variant of the disclosed embodiments shown in  FIG. 2 , the width of the top  13  is less than the distance separating the two sole plates  10  and  11 . According to other variants of the disclosed embodiments, this width can be greater than or equal to this distance. 
         [0029]    The second side  14  forms an inclined plane relative to the second sole plate  11 . This second side  14  connects the second sole plate  11  to the top  13  of the head  9 . The first sole plate  10 , the first side  12 , the top  13  of the head  9 , the second side  14 , and the second sole plate  11  give the stiffener  4  an omega-shaped transverse profile. However, this shape can also be achieved if the head  9  only has one curved plate connecting the first sole plate  10  and the second sole plate  11 . 
         [0030]    According to the disclosed embodiments, the fuselage  1  has battens  15 . There is a batten  15  located at each intersection between a reinforcing frame  5  and a stiffener  4 . Such a batten  15  is located between the skin  7  and the reinforcing frame  5 . More specifically, such a batten covers the skin  7  at the intersection between a reinforcing frame  5  and a stiffener  4 . This batten  15  forms the junction between two consecutive sections  6  of a stiffener  4 , the reinforcing frame  5  being supported on this batten  15 . 
         [0031]    The batten  15  covers the ends  16  of two consecutive sections  6  of a stiffener  4 . More specifically, this batten  15  has a blade  17  extending by covering a sole plate  10  and a wall  18  extending by covering a side  12  of the stiffener head. 
         [0032]    Such a batten  15  keeps folds from forming in the skin  7 . This absence of folds facilitates the installation of the stiffeners  4  at the intersections between the stiffeners  4  and the reinforcing frames  5 . In addition, this batten  15  provides for an efficient routing of stress between two consecutive sections  6 . 
         [0033]    Moreover, such battens  15  can be made entirely from composite materials, without the presence of metal parts. Such battens  15  prevent thermal problems and corrosion related to the presence of metal parts. 
         [0034]    According to the disclosed embodiments, after the interruption of the stiffener  4 , the battens  15  extend laterally so as to form together a flat and continuous surface  19  that supports the reinforcing frame  5  over its entire surface. The battens  15  have no thickness variations under the reinforcing frame  5 . This lack of thickness variation provides for a simple installation of the reinforcing frame  5  in the fuselage  1  while ensuring its stable support. 
         [0035]    The disclosed embodiments have multiple possible embodiments for the battens  15 . 
         [0036]    A first embodiment provides for a blade  17  from a first batten  20  to cover a first sole plate  10  on the first end  21  of a first section  22  of a stiffener  4 . A wall  18  from the first batten  20  also covers a first side  12  of the head  9  from this first end  21 . 
         [0037]    At the interruption in the first section  22  of the stiffener  4 , the first batten  20  extends laterally, or perpendicularly at the axis  100  of the fuselage to cover the skin  7  on a width  35  extending between a longitudinal axis  101  of the stiffener  4  to the middle of a strip, with width  23 , separating two side by side stiffeners  4 . In addition, parallel to the axis  100  of the fuselage  1 , the first batten  20  extends under the reinforcing frame  5  to reach a second section  24  of the stiffener  4  that is consecutive to the first section  22 . This first batten  22  forms the junction between the first end  21  and a second end  25 , respectively, of the first section  22  and the second section  24 . 
         [0038]    At the start of the second section  24  of the stiffener  4 , the width of the first batten  20  is reduced. The first batten  20  therefore covers the end  25  of this second section  24  in the same way that it covers the end  21  of the first section  22 , meaning that a blade  17  from the first batten  20  covers a first sole plate  10  and a wall  18  from the first batten  20  covers a first side  12  of the end  25 . 
         [0039]    In this embodiment of the disclosed embodiments, the first batten  20  and a second batten  26  are located on either side of a single stiffener  4 . The second sole plate  11  and the second side  14  of the head  9  are respectively covered by a blade and a wall  18  from the second batten  26 . This second batten  26  extends symmetrically to the first batten  20  relative to a plane of symmetry from the stiffener  4 . 
         [0040]      FIG. 3  shows a cross-sectional view of an intersection between a reinforcing frame and a stiffener according to the disclosed embodiments. At a reinforcing frame  5 , the stiffener  4  is interrupted; it is therefore divided into sections ( 22 ,  24 ). The ends  21  and  25  of said sections are equipped with battens  15 . All of the battens  15  then cover the entirety of the skin  7 , or the fuselage plates  3 , between two sections  22  and  24  of the stiffeners  4 , on the entire support surface of the reinforcing frame  5 . 
         [0041]      FIG. 4  shows a schematic perspective view of a part of fuselage according to a second embodiment of the disclosed embodiments. This second embodiment brings together, in a single batten  27 , the two battens  20  and  26  shown in  FIG. 2 . This batten  27  covers the ends  21  and  25  of the stiffener  4  in the same way as the battens  20  and  26  together. In addition, this batten  27  covers the same surface of skin  7 , or plate  3 , as the battens  20  and  26  together. 
         [0042]      FIG. 5  shows a cross-sectional view of a stiffener and a batten according to a third embodiment of the disclosed embodiments. According to this embodiment, a batten  28  covers a first sole plate  10  and a first side  12  of a first stiffener  29 . This same batten  28  also covers a second sole plate  11  and a second side  14  of a second stiffener  30 . The first stiffener  29  and the second stiffener  30  are arranged parallel to each other and side by side in the fuselage  1 . Such a batten  28  covers the same surface of skin  7  as a batten  20  of a first stiffener  29  associated to a second batten  26  of a second stiffener  30 , according to the first embodiment of the disclosed embodiments, described above. 
         [0043]    Such battens  15  may be located at the ends  16  of the stiffener  4 , uninterrupted by the presence of a reinforcing frame  5 , or at the start or at the end of a stiffener  4 . These battens equip the ends of a stiffener  4 . These battens at the beginning and end of a stiffener cover an end  16  of a section  6  of a stiffener  4  corresponding to the beginning or end of a stiffener  4  and stop on the skin  7 , or the fuselage plate  3 , without forming a junction with another end  16  of another section  6 . These beginning and end battens are used to drain stress in the stiffener  4  at the beginning of a stiffener  4  or to distribute stress from the stiffener  4 . 
         [0044]    The disclosed embodiments also provide for two variants of routing stress. 
         [0045]    In a first variant,  FIG. 2 , the sole plates  10  and  11  of a stiffener  4  are interrupted farther from the reinforcing frame  5  than the stiffener head  9 . This interruption in the sole plates  10  and  11  farther from the reinforcing frame  5  than the end of the head  9  of the stiffener  4  allows stress to be discharged from the stiffener  4  in the batten  15 , said discharge being carried out first by the sole plates  10  and  11 , then by the sides  12  and  14  of the head  9  of the stiffener  4 , and finally by the top  13  of the head  9  of the stiffener  4 . 
         [0046]    According to this first variant, the interruption of a batten  15 , or the point to which a batten  15  covers the end  16  of a stiffener  4 , is closer to the reinforcing frame  5  on the sides  12  and  14  of a head  9  than on the sole plates  10  and  11 . The wall  18  of a batten  15  then undergoes a significant reduction in its coverage surface on the sides of the head  9  of a stiffener closer to the reinforcing frames  5  than the interruption of the blade  17 . This wall  18  therefore extends after this reduction in the form of a reduced wall  31  pressed on a low surface of a side of a stiffener  4  to the full interruption of the batten  15 . The blade  17  and the reduced wall  31  are interrupted at the same level. 
         [0047]    In a second variant,  FIG. 4 , the head  9  of the stiffener  4  is interrupted farther from the reinforcing frame  5  than the sole plates  10  and  11  of the stiffener  4 . In this variant, the interruption of the head  9  of the stiffener  4  is formed along an inclined plane relative to the top  13 . According to this variant of the disclosed embodiments, the batten  15 , in addition to covering the sole plates  10  and  11  of a stiffener  4  and the sides  12  and  14  of a head  9  of a stiffener  4 , cover a part  32  of the inclined plane in the interruption of the head  9  of the stiffener  4 . Therefore, the stiffener  15  has a stop  33  that extends by covering the head  9  of the stiffener  4 , according to the interruption plane of inclination of the head  9  of the stiffener  4  by resting on the head  9 . 
         [0048]    According to this variant of the disclosed embodiments, stress is discharged from the stiffener  4  in the batten  15  first by the top  13  of the head  9  of the stiffener  4 , then by the sides  12  and  14  of the head  9 , and finally by the sole plates  10  and  11  of the stiffener  4 . 
         [0049]    In this second variant, the interruption of a batten  15  on one end  16  of a section  6  of a stiffener  4  is closer to the reinforcing frame  5  on the sole plates  10  and  11  than on the sides  12  and  14  of a head  9 . The wall  18  then extends farther from the reinforcing frame  5  than the blade  17 . 
         [0050]    In addition, the disclosed embodiments can provide for the batten  15  to have a means for maintaining the alignment of the two consecutive stiffener sections  5  interrupted by a reinforcing frame  5 . 
         [0051]    In the second variant, meaning the variant where the sole plates  10  and  11  of the stiffeners  4  are interrupted closer to the reinforcing frame  5  than the head  9  of the stiffener  4 , the disclosed embodiments provide that an area  34  of the wall  18  has a lesser thickness at the end of the head  9 . Such a weak area  34  allows the wall  18  to fold lightly in order to maintain an alignment of the various sections  6  of the stiffener  4 . When installing the various sections  6  of a stiffener  4 , it is often difficult to maintain a perfect alignment of the sections  6 . 
         [0052]    According to the disclosed embodiments, the advantage of such a batten  15  also comes from the way the batten  15  is built. Many manufacturing and installation methods can be used to produce a batten  15  according to the disclosed embodiments. 
         [0053]    Therefore, a batten  15  made from composite materials and a skin  7  according to the disclosed embodiments can be made together and at the same time. Similarly, such a batten  15  made from composite materials and stiffeners  4  according to the disclosed embodiments can be made together and at the same time. Another solution consists of making the batten  15  separately from the stiffeners  4  and attaching it to the stiffener  4  and the skin  7  later. The battens  15  can, for example, be glued to a polymer skin  7  or even bolted to the stiffeners  4  and the skin  7 . 
         [0054]    According to the disclosed embodiments, the embodiments and batten variants described above can be combined. Therefore, a stiffener can, for example, be covered on one side by a batten  20  according to the first embodiment, while its other side is covered by a stiffener  28  according to the third embodiment. It is also possible to combine variants. For example, a stiffener can have a first sole plate  10  interrupted closer to the reinforcing frame  5  than the head  9 , the head  9  itself being interrupted closer to the reinforcing frame  5  than the second sole plate  11 .