Abstract:
A block including at least one glass ply at least partially covering an outer surface of a core made from composite material. A method for reinforcing a block made from a composite material, including a glass ply placed in a mould, such as to cover the base of the mould; the block is positioned in the mould; the edges of the glass ply are folded such that the glass ply is moulded to the outer edge of the block; the mould is closed with a cover; the block housed inside the mould is cured in an oven such as to polymerize the glass ply; and the glass-ply-covered block is recovered.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Stage of International Application No. PCT/FR2008/051770 International Filing Date, 1 Oct. 2008, which designated the United States of America, and which International Application was published under PCT Article 21 (s) as WO Publication No. WO2009/053573 A2 and which claims priority from, and the benefit of, French Application No. 200758207 filed on 11 Oct. 2007, the disclosures of which are incorporated herein by reference in their entireties. 
       BACKGROUND 
       [0002]    The aspects of the disclosed embodiments relate to a block in composite material which is reinforced in order to withstand impacts and other external stresses. The disclosed embodiments particularly relate to a block in composite material which is intended to be placed on the upper surface of an aircraft wing in order to restore the aerofoil section in the region where said wing is fixed to the aircraft fuselage. The disclosed embodiments relate also to a method for reinforcing a block in composite material. 
       SUMMARY 
       [0003]    It is currently known in many fields to replace some components, previously made of metallic material, with components in composite material, notably in order to reduce the total mass of the device provided with one or more of these components. Thus, in the aeronautical field, many components, such as beams, covering panel etc. are now made of composite material. If it enables to get good results from the point of view of the final aircraft mass, the components in composite material can sometimes have an insufficient resistance to the charges to be withstood or to the environmental stresses. 
         [0004]    It is notably the case when transition blocks are used in the region where an aircraft wing is fixed to said aircraft fuselage, and are intended to restore the aerofoil section of the wing in the fixation region. Such blocks in composite material are described in the patent FR 2 869 872. The transition block in composite material is located on the upper surface of the wing and is submitted to bad weather and to other external stresses. The transition block is made for example of a polymethacrylimid foam, that is hard and light, which facilitates its handling and installation on the upper surface of an aircraft wing. 
         [0005]    The external surface of said block in composite material remains however granular, even after the application of one or more protecting paint layer(s). 
         [0006]    Moreover, it frequently happens that the block in composite material is marked, indeed damaged, at the time of the fixation onto the aircraft wing. The block is often dented by the knee prints of the installation workers, by pots of paint used for covering the blocks etc. The dents on the external surface of the block tend to reduce the aerodynamic performance of the aircraft, which notably increases the fuel consumption of the aircraft. 
         [0007]    One aspect of the disclosed embodiments is to increase the resistance of a block in composite material, such as that used as a transition block at the junction between the wing and the fuselage of an aircraft. 
         [0008]    To this end, according to the disclosed embodiments, it is proposed to cover the block in composite material with one or more layer(s) of glass which conform(s) to the external profile of the block. The layers of glass are advantageously polymerized on the central mass in composite material. Thus, whatever its shape may be, the block is entirely covered with layers of glass which smooth the external surface and reinforce it against the external stresses. The disclosed embodiments aim at providing a method for reinforcing the block, wherein said block in composite material is covered with one or more layer(s) of glass. The method according to the disclosed embodiments uses a mould able to withstand high temperatures and to be dismounted in order to free the block once the layers of glass are polymerized on the central mass in composite material. 
         [0009]    An aspect of the disclosed embodiments is thus a block intended to be fixed to the supper surface of an aircraft wing, wherein it comprises a core in composite material and at least one folded layer of glass covering at least partially an external surface, or wall, of the core in composite material. 
         [0010]    According to embodiment examples of the block according to the disclosed embodiments, it is possible to provide all or part of the following additional characteristics:
       the block comprises three folded layers of glass superposed so that three successive layers are formed around the core in composite material;   the composite material forming the block core is a polymethacrylimid foam.       
 
         [0013]    The disclosed embodiments relate also a method for reinforcing a block in composite material, wherein it comprises the following steps:
       a first lower folded layer of glass is placed into a mould, in order to cover a mould bottom and in order that the edges of the lower folded layer of glass project from the lateral walls of said mould;   the block is placed into the mould, with the external side facing the outside of the mould.   the lower folded layer of glass is folded over the block, so that the folded layer of glass conforms to the external profile of the block;   the mould is closed by means a cover;   the block in the mould is fired in an oven in order to polymerize the folded layer of glass;   the block covered with the folded layer of glass is removed.       
 
         [0020]    According to some embodiment examples of the method according to the disclosed embodiments, it is possible to implement all or part of the following additional steps:
       a second lower folded layer of glass is placed into the mould in order to cover the first lower folded layer of glass; a third lower folded layer of glass is placed in the same way over the second lower folded layer of glass; the third lower folded layer of glass is leveled at the joint plane; the three lower folded layers of glass are successively folded over the external side of the block. In the case when the dimensions of the block and of the mould are strictly superior to the dimensions of the folded strips of glass used, a number of strips are used in an adjacent arrangement in the mould in order to form a given folded layer of glass;   the external side of the bloc is covered with a first upper folded layer of glass before placing said block into the mould. Thus, if the dimensions of the lower folded layers of glass are not sufficient for covering the entire surface of the block core, the external side of said core is covered with the upper folded layer(s) of glass, whereas the internal side and the lateral walls of said block core are covered with the lower folded layers of glass;   the block is fired in an oven in which the temperature is progressively increased at a rate of 2° C./min until the temperature level of 150° C.+/−20° C. is reached; the temperature level is maintained for 2 hours, +/−15 min;   a mould with a bottom on which four lateral walls and a removable cover are mounted, is used; after the firing step, the cover and the four lateral walls are removed from the mould in order to remove the block covered with folded layers of glass.       
 
         [0025]    The disclosed embodiments will be better understood from the following description and from the accompanying figures. These figures are given as an indicative, but non-limitative illustration of the disclosed embodiments. In the figures: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a schematic representation of a first example of a block in composite material which can be covered with folded layers of glass according to the disclosed embodiments; 
           [0027]      FIG. 2  is a schematic representation of a second example of a block in composite material which can be covered with folded layers of glass according to the disclosed embodiments; 
           [0028]      FIGS. 3A ,  3 B and  3 C represent three sectional enlargements of the block in  FIG. 2 , at the front tip, a central section and a back section, respectively; 
           [0029]      FIG. 4  is a schematic representation of a cross section of a mould used for implementing the method according to the disclosed embodiments; 
           [0030]      FIG. 5  is a schematic representation of a cross section of the mould according to the disclosed embodiments in which the block to be covered with folded layers of glass is placed. 
       
    
    
       [0031]    In the examples described below, it is referred only to transition blocks to be fixed to the upper surface of an aircraft wing in order to facilitate the passage of a joint from the means for fixing of the wing to the aircraft fuselage to the upper surface of said wing. Of course, the disclosed embodiments can also be applied to any other kind of block in composite material, whatever its dimensions may be. 
         [0032]    Such a transition block can have a length of several tenths of meters and a thickness which varies from one end of the block to the other. “Length” means the dimension of said block extending parallel to the longitudinal axis of the block. “Thickness” means the dimension of the block extending vertically to a plane in which the block extends. 
         [0033]    Afterwards, “external side” means the block side facing the outside of the mould and “internal side” means the block side in contact with the mould bottom. On the other hand, in use, the external side of the block is fixed to the upper surface of the aircraft wing, and the internal side is submitted to external stresses. 
       DETAILED DESCRIPTION 
       [0034]    In  FIG. 1  it is represented a first example of the block  1  in composite material, which is intended to be fixed to the upper surface of an aircraft wing. 
         [0035]    The block  1  comprises a beveled end  2 , a second end  3  opposite the chamfered end  2  being a right end. Moreover, as it appears from the cross view I-I, the thickness E, e of the block  1  decreases widthwise. “Width” means the dimension of the block  1  which extends transversely to the longitudinal axis A of the block  1 . 
         [0036]    In  FIG. 2  it is represented a second example of a transition block  10 , said block  10  having a constant thickness, but a width I, I′ which decreases from the first end  11  to a second end  12 , both ends being right ends, in contrast with a beveled end. 
         [0037]    The block  10  comprises a core  13  in composite material covered with at least one folded layer of glass, which increases the resistance of the block  10  to external stresses. 
         [0038]    In the method according to the disclosed embodiments, any block can be covered with one or more folded layer(s) of glass, whatever its dimensions, form etc. may be. 
         [0039]    To this end, according to the method of the disclosed embodiments, it is used a mould such as represented in  FIG. 4 . 
         [0040]    The mould  100  comprises a bottom, or base  101 , the internal side  102  of which is intended to receive the block  10 . “Internal side” means the side in an internal volume V of the mould  100 . Said mould  100  comprises otherwise four lateral walls  103  (only two lateral left and right walls are visible in  FIG. 4 ), said lateral walls  103  being removable in order to be dismounted from the bottom  101 . Moreover, the mould  100  comprises a cover  104  able to be sealed on the upper ends  105  of the lateral walls  103  in order to hermetically close the internal volume V of the mould  100 . 
         [0041]    The internal volume V of the mould  10  is able to receive the block  10 . 
         [0042]    According to the method of the disclosed embodiments, a first lower folded layer of glass  14  is placed at the beginning against the internal wall  102  of the bottom  101  of the mould  100 . The first lower folded layer of glass  14  conforms to the profile of the mould  100  and covers the bottom  102  and the lateral walls  103  as far as the ends  105 . More precisely, the external edges  15  of the first lower folded layer of glass are placed side by side against the ends  105  of the lateral walls  103 . the first lower folded layer of glass  15  is the layer intended to be in contact with the outside with respect to the foam core  13  which it surrounds. 
         [0043]    Then a second lower folded layer of glass  116  is placed over the first lower folded layer of glass  14 . the edges  17  of the second lower folded layer of glass  16  cover the external edges  15  of the first lower folded layer of glass  14 . 
         [0044]    Then, a third lower folded layer of glass  18  is placed over the second lower folded layer of glass which it surrounds. 
         [0045]    The external edges  19  of the third lower folded layer of glass  18  are leveled at the ends  105  of the lateral walls  103  of the mould  100 . An excessive thickness at the external side  21  of the core  13  of the block  10  is thus avoided because the edges  15 ,  17 ,  19  of the folded layers of glass  14 ,  16 ,  18  are folded against said external side  21 . 
         [0046]    The core  13  in composite material of the bock  10  is placed into the internal volume V of the mould  100  so that the internal side  20  of said core  13  in composite material is placed against the internal wall  102  of the bottom  101  of the mould  100 . 
         [0047]    In the example represented in  FIG. 5 , the external side  21  of the core  13  in composite material has been first covered with three superposed upper folded layers of glass  22 . It enables to assure a tightness at the core  103  of the block  10  while guaranteeing that the entire surface of the core  103  is covered with at least one folded layer of glass. Indeed, if the external side  21  of the core  13  in composite material is not covered with its own folded layers of glass and if the dimensions of the lower folded layers of glass are not sufficient, it is possible that a central portion of the core  13  of the block  10  is not covered once the lower folded layers of glass are folded over the external side of the core  13  of the block  10 . 
         [0048]    Of course, the upper folded layers of glass  22  can be placed on the external side  21  of the core  13  in composite material only when this core has been placed into the mould  100  and before the edges  19 ,  17 ,  15  of the lower folded layers  14 ,  16 ,  18  are folded over said external side  21 , even after folding said edges  19 ,  17 ,  15  over said external side  21 . 
         [0049]    When the core  13  in composite material is placed in the internal volume V of the mould  100 , the external edges  9  of the third lower folded layer of glass  18  is folded against the external wall  21  of the core  13  and then against the external edges  17  of the second lower folded layer of glass  16  and finally against the external edges  15  of the first lower folded layer of glass  14 . 
         [0050]    The folded layers of glass  14 ,  16 ,  18 ,  22  are thus draped over the foam core  13  while conforming to the profile thereof. 
         [0051]    Before folding the lower folded layers of glass  14 ,  16 ,  18  over the external wall  21  of the core  13 , it is possible to cut all the angles of the folded layers of glass, or only some of them, with an angle of 45° in order to avoid an excessive overlapping of the folded layers of glass  14 ,  16 ,  18  which could locally lead to a damageable excessive thickness. 
         [0052]    The internal volume V of the mould  100  is then closed by means of the cover  104  which is fixed by any means to the lateral walls  103 . 
         [0053]    The mould  100  is then placed into an oven and heated up to 150° C. at a rate of 2° C./min and then the mould is left at this temperature level for two hours. 
         [0054]    The mould  100  is then removed from the oven and is left to cool down to 60° by natural convection. 
         [0055]    The mould  100  is opened in order to extract the block  10 . To that end, the lateral walls  103  are dismounted from the bottom  101  in order to easily remove the block  10  from said mould  100 . 
         [0056]      FIGS. 3A ,  3 B and  3 C show different cross views of the block  10  covered with folded layers of glass according to the disclosed embodiments. Of course, the block  10  can be covered with more or less folded layers of glass, according to the thickness of said folded layers and according to the purpose of the block. 
         [0057]    Thus, in  FIG. 3A , it is represented a longitudinal section of the front end  12  of the block  10 . 
         [0058]    Three upper folded layers of glass  22  cover the external wall  21  of the core  13  in composite material of the block  10  intended to be fixed to the upper surface of an aircraft wing. The three lower folded layers of glass  14 ,  16  and  18  conform to an external profile of the internal wall  20  of the core  13  in composite material, intended to be submitted to external stresses. At this end  12 , the upper folded layers covers the lower folded layers  14 ,  16 ,  18 , which enables to assure a tightness of the core  13  in composite material by means of the glass protection. 
         [0059]    In  FIG. 3B , it is represented a longitudinal section of the block  10  at some place of said block  10 . 
         [0060]    Thus, we can see the three upper folded layers  22  covering the external side  21  of the core  13  of the block  10 , as well as the three lower folded layers  14 ,  16 ,  18  covering the internal side  20  of said core  13 . 
         [0061]    In the example represented in  FIG. 3B , each folded layer of glass  14 ,  16 ,  18 ,  22  considered is formed by a number of bands of pre-impregnated fabric successively placed in the same plane. Of course, if the bands of pre-impregnated fabric used have sufficient dimensions, it is possible to use one band for each folded layer. However, in the case of a block  10  with big dimensions, the use of a number of bands of pre-impregnated fabric for forming a given folded layer of glass enables to facilitate the installation into the mould  100 : instead of handling only one band of pre-impregnated fabric with big dimensions for placing it against the bottom  102  of the mould  100  and against the lateral walls  103  of said mould, over the entire length of said mould, a number of small bands of pre-impregnated fabric are successively placed for covering the entire internal surface of the mould  100 . 
         [0062]    In  FIG. 3C , it is represented a cross section of the block  10  at some place of said block  10 , showing the core  13  in composite material surrounded with the succession of folded layers of glass  14 ,  16 ,  18  and  22  forming a tight protecting shell around said core  13 . 
         [0063]    In the particular case of transition blocks intended to be fixed to the upper surface of an aircraft wing, each folded layer of glass has advantageously a thickness of 0.2 mm+/−0.05 mm.