Abstract:
The present disclosure provides a method for manufacturing a preform made of reinforcement fibers woven in a longitudinal direction. The preform is impregnated with resin in order to form an elongated element having a variable transverse cross-section. In one form, the method includes the step of simultaneously including a reduction (or increase) in width and an increase (or reduction) in height. The variable cross-section includes, along the length thereof, a consistent number (c) of continuous warp threads arranged in layers. The method for reducing width includes carrying out a change in weave, adding additional weft threads, and simultaneously drawing the teeth of the longitudinal beater reed closer together so as to increase the number of layers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/FR2016/050304, filed on Feb. 10, 2016, which claims priority to and the benefit of FR 15/51072 filed on Feb. 10, 2015. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to a method for manufacturing a woven dry preform intended to be infiltrated with resin to form composite materials, as well as a profile made of composite materials comprising a preform carried out according to such a method. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    In order to carry out resistant and lightweight structural elements, particularly in the aeronautical field, it is known to prepare a textile preform from dry fibers, in particular carbon fibers, which is then impregnated with a resin in a tooling, following a method called “LCM” (Liquid Composite Molding) method. 
         [0005]    The fluid resin here carries out a complete impregnation of the preform, and the tooling allows a shaping of this assembly. After curing to polymerize the resin, there is obtained an element comprising fibers whose density and orientation are adjusted in order to obtain high mechanical resistance characteristics, adapted to the forces applied to this part. 
         [0006]    Particularly, it is possible to produce parts including an elongated shape along a longitudinal direction, having an evolutive variable transverse section. 
         [0007]    For example, a rear frame of a thrust reverser cascade for a turbojet engine constitutes an elongated part comprising a constant flat section forming substantially a belt, having at each end its two lateral flanges folded so as to form a yoke including two parallel wings. A transverse drilling of the wings receives an axis allowing, in the longitudinal direction, a clamping traction on the ends. 
         [0008]    In the case of an elongated part having a flat section which, in the length, changes the plane to reach 90°, a known solution consists in flat-draping two-dimensional fabric plies, then in deforming this assembly by twisting it along a quarter turn to carry out progressively the change of plane. 
         [0009]    However, for this solution, the cutting and the manipulation of a multitude of narrow and slender fabric plies can cause problems of losses of wicks at the edge of plies, and of significant deformations of these plies. In addition, the deformation of the plies can also lead to local disorientations of the fibers, which are not controllable if they are inside the part. 
         [0010]    Moreover, the dimensions of such a part with finished sides leaving the molding are difficult to obtain, and in most cases, it is necessary to carry out a machining after the polymerization, which is expensive. 
         [0011]    Another solution for carrying out a change of section consists in manufacturing a multi-layer preform of a ribbon type, then in increasing the number of layers locally and progressively by a successive addition of warp and weft yarns. 
         [0012]    There is thus obtained a single preform including a local thickening where warp yarns are added successively. However, the absence of continuity of these added yarns greatly reduces the mechanical strength of the assembly, in the areas of variation of the number of yarns. 
       SUMMARY 
       [0013]    The present disclosure provides a method for manufacturing a fibrous preform woven along a longitudinal direction, provided to be impregnated with resin in order to form a longilineal element having an evolutive transverse section, comprising simultaneously a reduction (or conversely an increase) in the width and an increase (or conversely a reduction) in the height, this evolutive section including, lengthwise, warp yarns in constant number which are continuous, disposed in height following layers, remarkable in that, for a reduction in the width, it performs a change of weave introducing additional weft yarns which thus increase the number of layers, and simultaneously it tightens the teeth of the longitudinal settling comb to reduce the space between the columns of warp yarns, and conversely for an increase in the width, it reduces the number of weft yarns which decreases the number of layers and simultaneously it spreads the teeth of the comb. 
         [0014]    An advantage of this method of weaving is that we obtain, in a single operation, a preform containing a fully finished progressive area of variation, comprising continuous warp yarns over the entire length of this variation. This preform allows a reduced labor time during its implementation, as well as a high mechanical resistance in the longitudinal direction. 
         [0015]    The woven preform according to the present disclosure can also include one or more of the following characteristics, which can be combined with one another. 
         [0016]    Particularly, the manufacturing method can, from a reinforcement having a defined number of layers of superimposed warp yarns, change the weaving pattern by inserting thereby a double number of weft yarns, and then carry out a tightening of the teeth of the comb in order to obtain a double number of superimposed layers having a width reduced substantially by half. 
         [0017]    Advantageously, each weft yarn takes, on each layer of warp yarns, one yarn out of four which it leaves on the other side, the yarns taken on each layer being superimposed between the different layers. 
         [0018]    Particularly, the method can take sixteen warp yarns between two teeth of the comb. 
         [0019]    From a weaving of an upstream flat preform comprising initial width and height, the method can carry out an evolutive section having downstream a width and a final height substantially equal respectively to the height and the initial width. A profile is obtained, having a rotation of its section over 90°. 
         [0020]    Advantageously, for some applications, comprising, for example, a final drilling, the method includes a following step for depositing reinforcing fibers on flat faces of a flat section being located close to the evolutive section. In particular, the contour of a drilling can be reinforced. 
         [0021]    Particularly, the reinforcing fibers provided for reinforcing a drilling of the flat section, can have two crossed orientations substantially by +/−45° relative to the warp yarns or a concentric orientation relative to this drilling. 
         [0022]    The method can also include, during the weaving, a debanding operation of a portion of the constant section close to the evolutive section, carrying out a median section to form a fork. Thus, a yoke comprising a high mechanical resistance is easily carried out. 
         [0023]    The present disclosure further provides a composite material profile formed from a preform receiving an injected resin which is carried out with a method comprising any one of the preceding characteristics. 
         [0024]    Particularly, the profile can constitute a structural element integrated in a turbojet engine nacelle and having an evolutive section. 
         [0025]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0026]    In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
           [0027]      FIG. 1  shows a rear frame of turbojet engine, comprising two ends including an evolutive section carried out with a method according to the teachings of the present disclosure; 
           [0028]      FIG. 2  is a drawing of an evolutive section carried out with a method according to the present disclosure; 
           [0029]      FIG. 3  is a diagram showing in cross section successively different steps of weaving the horizontal flat portion upstream of the evolutive section according to the present disclosure; 
           [0030]      FIGS. 4A and 4B  are diagrams showing successively the different steps of weaving the first portion of the evolutive section according to the present disclosure; 
           [0031]      FIG. 5  is a diagram showing successively the different steps of weaving the second portion of the evolutive section according to the present disclosure; 
           [0032]      FIG. 6  illustrates a reinforcing type on a flat section comprising a drilling according to one form of the present disclosure; 
           [0033]      FIG. 7  illustrates a reinforcing type on a flat section comprising a drilling according to another form of the present disclosure; 
           [0034]      FIG. 8  shows the production of a fork-type fitting according to the present disclosure; and 
           [0035]      FIG. 9  shows the production of two successive inverted evolutive sections according to the present disclosure. 
       
    
    
       [0036]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
       DETAILED DESCRIPTION 
       [0037]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0038]      FIG. 1  shows a rear frame of the thrust reverser cascade  2  for a turbojet engine nacelle. In a bypass turbojet engine, a circular peripheral flow path surrounds the reactor to conduct cold air of propulsion. In a braking mode of the aircraft, this flow path is closed by shutters to deflect the flow radially outwards, by passing through thrust reverser cascades which directs it forward by generating a braking force. 
         [0039]    The rear frame  2  is a fixed belt made of composite materials, disposed at the rear of the thrust reverser cascades, including a flat constant longitudinal section  4  ending at each end  6  by two lateral flanges  8  bent at 90°, forming a yoke comprising a drilling receiving a transverse fixing axis  10 . 
         [0040]    For its fixation, a high tension is applied on the rear frame by exerting a traction on the transverse axis  10 , which is transmitted by the lateral flanges  8  to the flat section  4 , without risk of rupture. Particularly, it is desired to carry out an evolutive section in order to switch progressively from the flat section  4  to the end section comprising the flanges  8 , including a significant traction resistance. 
         [0041]      FIG. 2  shows a preform woven with an advance of the warp yarns following the longitudinal direction indicated by the arrow denoted “AV”, comprising a flat horizontal upstream portion  22 , followed by an evolutive section  20  which progressively reduces the width and simultaneously increases the height, to reach a vertical flat downstream portion  24  having the section of the upstream portion rotated by 90°. 
         [0042]    The evolutive section  20  includes a first portion A beginning immediately after the horizontal upstream portion  22  which is about the first third of the length of this section, and a second portion B which is about the second third of this length. 
         [0043]      FIG. 3  schematically shows the successive operations of forming the horizontal flat upstream portion  22 , comprising continuous warp yarns c, and weft yarns t inserted successively into these operations. 
         [0044]    The first operation  30  includes the production of two similar layers of warp yarns c following two planes, having the yarns which are superimposed two by two. The teeth of a longitudinal compaction comb of the weft yarns t after their insertions, aligned following the axes P, receive eight warp yarns c of each layer between two teeth. 
         [0045]    The second operation  32  includes the opening of a shed  50  forming the transverse passage provided to receive a weft yarn, by lifting one warp yarn c 1  out of two of the upper layer. 
         [0046]    The third operation  34  includes the passage of a weft yarn t 1  in the shed  50 , following the direction indicated by the arrow T. 
         [0047]    The fourth operation  36  includes the closing of the shed  50 , by lowering the lifted warp yarns c 1 . The fifth operation  38  shows the end of the closing of the shed  50 , the assembly of the warp yarns c, c 1  being disposed again following two layers. 
         [0048]    The sixth operation  40  includes the opening of a second shed  52  by lowering one warp yarn c 2  out of two of the lower layer, which is vertically offset relative to the warp yarn cl of the first layer which had been raised. 
         [0049]    The seventh operation  42  includes the passage of a weft yarn t 2  in the second shed  52 . 
         [0050]    The eighth operation  44  includes the closing of the second shed  52  by raising the lowered warp yarns c 2 . The ninth and last operation  46  shows the end of the closing of the second shed  52 , the assembly of the fabric returning on the two original planes. 
         [0051]    In addition, we have, after the passage of one or more weft yarn(s) t 1 , t 2 , a compaction operation of these yarns in the longitudinal direction, by the teeth of the comb disposed following the axes P. For this weaving operation of the constant upstream section  22 , the spacing of the teeth of the comb also remains constant. 
         [0052]    In general, the upstream portion  22  shown in this example with two layers can include a variable number of layers, with warp and weft yarns woven together according to a conventional interlock pattern allowing linking these layers of yarns together according to a defined pattern of layers. 
         [0053]      FIGS. 4A and 4B  show twenty-one successive operations of forming the first portion A of the evolutive section  20 , comprising continuous warp yarns c, and weft yarns t successively inserted into these operations. 
         [0054]    The first operation  60  is the recovery of the two identical layers of warp yarns c 1 , for the upper layer, and c 2 , for the lower layer, showing the yarns which are superimposed two by two. The teeth of the compaction comb of the weft yarns t after their insertions, aligned along the axes P, receive eight warp yarns c of each layer between two teeth. 
         [0055]    The second operation  62  includes the opening of a first shed  110  forming the transverse passage provided to receive a first weft yarn t 1 , by lifting one warp yarn c 1   a  out of four of the upper layer c 1 . 
         [0056]    The third operation  64  includes the passage of the first weft yarn t 1  into the first shed  110 , following the direction indicated by the arrow T. 
         [0057]    The fourth operation  66  includes the closing of the first shed  110 , by lowering the lifted warp yarns c 1   a.  The fifth operation  68  shows the end of the closing of the first shed  110 , the assembly of the warp yarns c 1 , c 2  being again disposed following two layers. 
         [0058]    The sixth operation  70  includes the opening of a second shed  112  by lifting the assembly of the warp yarns of the upper layer c 1 , except one yarn c 1   b  out of four being located close to a first yarn c 1   a  which has been lifted for the opening of the first shed  110 . 
         [0059]    The seventh  72 , eighth  74  and ninth  76  operations successively include, as above, the passage of the second weft yarn t 2 , the beginning of the closing of the second shed  112  and the end of this closing. The assembly of the warp yarns c 1 , c 2  are again disposed following two layers. 
         [0060]    The tenth operation  78  includes the opening of a third shed  114  comprising, as for the opening of the first shed  110 , the lifting of one warp yarn c 2   a  out of four of the lower layer c 2 , which is aligned with the warp yarn c 1   a  which has been lifted for this first shed. 
         [0061]    The eleventh  80 , twelfth  82 , and thirteenth  84  operations successively include, as above, the passage of the third weft yarn t 3 , the beginning of closing of the third shed  114  and the end of this closing. The assembly of the warp yarns c 1 , c 2  is again disposed following two layers. 
         [0062]    The fourteenth operation  86  includes the opening of a fourth shed  116  comprising, as for the opening of the second shed  112 , the lifting of the assembly of the warp yarns of the lower layer c 2 , except one yarn c 2   b  out of four being located next to a first yarn c 2   a  which has been lifted for the opening of the third shed  114 . 
         [0063]    The fifteenth  88 , sixteenth  90 , and seventeenth  92  operations successively include, as above, the passage of the fourth weft yarn t 4 , the beginning of closing of the fourth shed  116  and the end of this closing. The assembly of the warp yarns c 1 , c 2  is again disposed following two layers. 
         [0064]    For all the preceding operations, the longitudinal compaction of the weft yarns t is done with the comb preserving the same spacing of the teeth P. 
         [0065]    The eighteenth operation  94  has a lateral displacement of the warp yarns c 1 , c 1 ′, c 2 , c 2 ′ which, under the tension of the weft yarns t, naturally tend to move in height alternately one upwards and the next downwards, depending on their positions above or below the same weft yarn. 
         [0066]    During the weaving of the first portion A of the evolutive section  20 , a change in the weaving pattern, is performed, which allows a selection of the different warp yarns. This change results, among others, in the insertion of a larger number of weft yarns which, by their binding, allow to form a larger number of layers linked together. 
         [0067]    The nineteenth operation  96  has the lateral displacement of the warp yarns c 1 , c 1 ′, c 2 , c 2 ′ which continues in the same way, with a natural tendency to be aligned with each other to form four columns between two teeth of the comb P. A rearrangement of the warp yarns is observed under the tension of the weft yarn t, the latter naturally tend to move in height alternately one upwards and the other downwards, depending on their positions above or below the same weft yarn. 
         [0068]    Due to the new weaving pattern, binding less yarns together, the warp yarns have a natural tendency to be aligned with each other to form a column between two teeth of the comb P. 
         [0069]    The twentieth operation  98  has a tightening of the gap between the teeth of the comb P, indicated by the arrows F, which drives an approximation of the columns of warp yarns c together. 
         [0070]    The twenty-first and last operation  100  has, at the end of the approximation of the teeth of the comb P, spacings between these teeth which is reduced substantially by half. We obtain a woven reinforcement of four layers of warp yarns c comprising a density of warp yarns on surface similar to that of the two-layer starting fabric shown by the ninth operation  46  of  FIG. 3 , with a thickness which is doubled. 
         [0071]    There is thus a first evolution of the evolutive section  20 , comprising a width decreased by half and a doubled height. 
         [0072]    Particularly, it is desired to provide for the weaving of this type of preform, an automated weaving machine comprising an evolutive comb, capable of modifying, during the manufacturing, the spacing of its teeth. 
         [0073]      FIG. 5  summarizes three successive operations of forming the second portion B of the evolutive section  20 , from four layers of warp yarns c 1 , c 2 , c 3 , c 4  which come out from the first portion A. 
         [0074]    All the preceding operations, shown in  FIGS. 4A and 4B , with the four layers of warp yarns instead of two layers, are carried. First, in the first step  120 , as for the previous seventeenth operation  92 , we obtain four tightened layers comprising eight weft yarns each taking, on each layer, one warp yarn out of four, these warp yarns taken from the four layers being superimposed. 
         [0075]    Then, in the second step  122 , as for the previous nineteenth operation  96 , we obtain the natural lateral displacement of the warp yarns c 1 , ct, c 2 , c 2 ′, c 3 , c 3 ′, c 4 , c 4 ′ which are aligned with one another to form four columns between two teeth of the comb P. 
         [0076]    Finally, in the third and last step  124 , as for the twenty-first previous operation  100 , after a tightening of the gap between the teeth of the comb P decreased by two, we obtain eight layers having a density of warp yarns on surface similar to that of the start, with a width reduced by half and a doubled thickness. 
         [0077]    It is possible to continue in the same manner to form the following portion of the evolutive section  20  of the profile. At the end, when the final ratio of the height to the width is obtained, the downstream portion of the profile  24  is continued to be woven normally, with a number of layers which remains constant and a comb which preserves the same deviation between its teeth. 
         [0078]    A profile including good mechanical performance of the evolutive section in the longitudinal direction is obtained, the warp yarns being all continuous in this direction. In addition, the preform may be carried out on a machine allowing a weaving with finished sides, the subsequent cuttings and falls are reduced, the manufacturing costs of this preform are decreased. 
         [0079]      FIGS. 6 and 7  show an application of a preform of this type. The vertical downstream portion  24  of the finished part after polymerization of the resin, receives a transverse drilling  130  of fixing the end of the part. 
         [0080]      FIG. 6  particularly shows a reinforcement of the vertical downstream portion  24  around the drilling  130 , comprising the addition of each side of the preform, of a fabric plate also called a “patch”  132 , having yarns oriented at +/−45° relative to the longitudinal direction of the warp yarns, so as to complete the resistance in the different directions. 
         [0081]      FIG. 7  shows another reinforcement of the vertical downstream portion  24  around the drilling  130 , comprising the addition of each side of the preform, of a plate of fibers  134  oriented concentrically around this drilling. 
         [0082]      FIG. 8  has an debanding operation of the vertical downstream portion  24 , carrying out a vertical section in the median portion of this portion in order to form a fork. Particularly, there can be formed, from this fork, a yoke having on each face reinforcements of a transverse drilling, as shown in  FIG. 6  and  FIG. 7 , in particular to carry out the ends of the rear frame of the thrust reverser cascade shown in  FIG. 1 . 
         [0083]      FIG. 9  shows a preform comprising, downstream of the vertical flat portion  24 , a second portion of evolutive section  26  symmetrical to the first portion  20 , which carries out a decrease in height at the same time as an increase in the width, in order to obtain again a flat horizontal rear portion  28  similar to the front portion. 
         [0084]    The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.