Patent Publication Number: US-2023140261-A1

Title: Mold for manufacturing a turbine engine fan casing from a composite material

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the general field of manufacture of turbomachine casings, and more particularly to containment casings for aeronautical engine gas turbine fans. 
     In an aeronautical turbomachine, a fan casing fulfills several functions. The fan casing defines the air inlet stream of the turbomachine, supports an abradable material facing the tips of the blades of the fan, supports a possible sound wave absorption structure for the inlet acoustic treatment of the turbomachine, and incorporates or supports a containment shield. 
     The containment shield forms a trap retaining debris, such as ingested objects or fragments of damaged blades, projected by the effect of centrifugal force, in order to avoid these debris passing through the casing and reaching other parts of the aircraft. 
     It is known to construct the fan casing of composite material, and more particularly of organic matrix composite material. To this end, a fibrous texture is wound around a mandrel in order to form a fibrous preform having the shape of the casing to be manufactured. The fibrous preform is then densified by a matrix. 
     In order to accomplish the densification of the fibrous preform by the matrix, said fibrous preform is wound around an impregnation mandrel, then the counter-mold angular sectors are positioned around the impregnation mandrel in order to form the injection mold. A precursor material of the matrix is then injected into the mold so as to densify the fibrous preform with said precursor material of the matrix. Once the fibrous matrix is densified, the precursor material is polymerized. 
     Known for example is document WO2017/089680 which describes an injection mold for the manufacture of a fan casing of composite material which comprises a plurality of angular sectors positioned around an impregnation mandrel. 
     In document WO2017/089680, sealing between the different angular sectors is provided by T shaped parts which are attached by boltwork between each angular sector and which each compress a flat seal overlapping two adjacent angular sectors. 
     Such a solution has the disadvantage of requiring considerable handling time, particularly for screwing and unscrewing the boltwork attaching the T shaped part to the angular sectors. 
     Moreover, an injection mold of this type can encounter a stiffness problem, and particularly with stiffness at the connection between the angular sectors. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The present invention therefore has as its main goal to compensate a disadvantage of this type by proposing, according to a first aspect of the invention, a mold for the manufacture of a turbomachine fan casing of composite material, and more precisely of organic matrix composite material, comprising:
         a mandrel around which a fibrous preform of the fan casing is intended to be wound;   a plurality of counter-mold angular sectors assembled on the external contour of the mandrel, which are intended to close the mold and to compact the fibrous preform wound on the mandrel;
 
characterized in that each angular sector comprises, on the one hand, a first lateral flange which is positioned at a first end of the angular sectors and, on the other hand, a second lateral flange which is positioned at a second end of the angular sectors and which is opposite to the first end, the first lateral flange and the second lateral flange being configured to cooperate respectively with the second lateral flange and the first lateral flange of the adjacent angular sectors,
 
at least one angular sector comprising a first groove formed in at least one of the first lateral flange and the second lateral flange, a first seal being positioned in said first groove, said first seal being configured to be compressed between the first lateral flange and the second lateral flange of two adjacent angular sectors.
       

     The mold can also comprise the following additional features, which can be taken alone or in combination according to technically possible combinations:
         each angular sector comprises a front flange and a rear flange which are configured to cooperate respectively with an upstream flange and a downstream flange of the mandrel, the upstream flange and the downstream flange comprising respectively a second groove and a third groove, a second seal and a third seal being respectively positioned in the second groove and the third groove, said second seal being configured to be compressed between the upstream flange of the mandrel and the front flange of the angular sectors, said third seal being configured to be compressed between the downstream flange of the mandrel and the rear flange of the angular sectors, the first groove leading, on the one hand, into the second groove and, on the other hand, into the third groove;   the mold comprises a first group of angular sectors for which the first groove is formed on the first lateral flange and on the second lateral flange, and a second group of angular sectors for which the first lateral flange and the second lateral flange are smooth, one angular sector of the first group being positioned between two angular sectors of the second group;   the first groove is formed on the first flange of each angular sector;   the first groove comprises an undulated shape;   the first groove is crenelated, the first groove comprising, on the one hand, a plurality of slots directed radially inward and, on the other hand, a plurality of slots directed radially outward;   the first flange and the second flange of the angular sectors comprise bores, each angular sector being attached to an adjacent angular sector by boltwork positioned, on the one hand, in the bores of the first lateral flange of the angular sector and, on the other hand, in the bores of the second lateral flange of the adjacent angular sector;   the slots directed radially outward are positioned between two bores;   the first seal is made of elastomer, for example a cold-vulcanizing elastomer.       

     According to a second aspect, the invention proposes a manufacturing method of a turbomachine fan casing of composite material with the mold according to any one of the preceding features, the method comprising the following steps:
         winding a fibrous preform of the fan casing around the mandrel;   assembling the plurality of counter-mold angular sectors on the external contour of the mandrel by attaching the first lateral flange of the angular sectors to the second lateral flange of an adjacent angular sector;   densifying the fibrous preform by injection of a precursor material of a matrix of the composite material into the mold;   polymerizing the precursor material to obtain the matrix of the composite material;   withdrawing the plurality of angular sectors;   de-molding the fan casing.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will be revealed by the description made below, with reference to the appended drawings that illustrate an exemplary embodiment free of any limiting character. In these figures: 
         FIG.  1    is a schematic view of a mold for manufacturing of a turbomachine fan casing of composite material; 
         FIG.  2    is a schematic view of the cooperation between the adjacent angular sectors of the mold of  FIG.  1   ; 
         FIG.  3   a    is a more precise view of the zone A of  FIG.  2   , the seal not being shown; 
         FIG.  3   b    is a more precise view of the zone B of  FIG.  2   , the seal not being shown; 
         FIG.  4    shows schematically the different steps of a manufacturing method of a fan casing of composite material. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As illustrated in  FIGS.  1 ,  2 ,  3  and  4   , a mold  1  for manufacturing a turbomachine fan casing of composite material comprises a mandrel  2  around which a fibrous preform of the fan casing is wound. 
     The mold  1  is intended to be used for impregnation by an RTM (“Resin Transfer Molding”) type process of the fibrous preform. 
     The fibrous preform can be created by two-dimensional weaving of fibers (2D weaving) or preferably by three-dimensional weaving of fibers (3D weaving). 
     What is meant here by “three-dimensional weaving” or “3D weaving” or “multilayer weaving” is a weaving mode by which at least some of the weft thread connect the warp threads over several layers of warp, or conversely, according to a weave corresponding to a weaving pattern, said weaving pattern being able to be selected in particular among one of the following weaving patterns: interlock, multi-plain, multi-satin and multi-twill. 
     What is meant here by “two-dimensional weaving” or “2D weaving” is a conventional weaving mode by which each warp thread passes from one side to the other of threads of a single weft layer. 
     The fibrous preform can be created from carbon fibers, from glass fibers, from aramid fibers, or even from ceramic fibers. 
     The outer wall of the mandrel  2  around which the fibrous preform is wound has a profile which corresponds to the profile of the fan casing to be manufactured. 
     The mold  1  also comprises a plurality of counter-mold angular sectors  3  which are assembled removably on the external contour of the mandrel  2 . Once assembled on the external contour of the mandrel  2 , the angular sectors  3  close the mold  1  and compress the fibrous preform. 
     The compression of the fibrous preform by the angular sectors  3  allows compacting the preform to the desire thickness and to obtain the desired volume density of fibers in the fan casing. 
     In order to attach the angular sectors  3  to the mandrel  2 , the mandrel  2  comprises an upstream flange  21  positioned at a front end of the mandrel  2 , and a downstream flange  22  positioned at a rear end of the mandrel  2 , and each angular sector  3  comprises, on the one hand, a front flange  31  which is configured to cooperate with the upstream flange  21 , and on the other hand a rear flange  32  which is configured to cooperate with the downstream flange  22 . 
     In the variant illustrated in  FIGS.  1  to  4   , the front flange  31  and the rear flange  32  of the angular sectors  3  are respectively attached to the upstream flange  21  and the downstream flange  22  by boltwork which is positioned in the bores formed in said front flange  31 , rear flange  32 , upstream flange  21  and downstream flange  22 . 
     Moreover, the angular sectors  3  are attached to one another, each angular sector  3  being attached to the two angular sectors adjacent to it. 
     Each angular sector  3  comprises a first lateral flange  33  which is positioned at the first end of the angular sectors  3  and a second lateral flange  34  which is positioned at a second end of said angular sectors  3 , the second end being opposite to the first end. 
     For each angular sector  3 , the first lateral flange  33  is configured to cooperate with the second lateral flange  34  of the adjacent angular sector  3 , and thus the second lateral flange  34  is configured to cooperate with the first lateral flange  33  of the other adjacent angular sector  3 . 
     Thus, to attach the plurality of angular sectors  3  to the contour of the mandrel  2 , each angular sector  3  is attached to the following elements:
         the front flange  31  of the angular sector  3  is attached to the upstream flange  21  of the mandrel  2 ;   the rear flange  32  of the angular sector  3  is attached to the downstream flange  22  of the mandrel;   the first lateral flange  33  of the angular sector  3  is attached to the second lateral flange  34  of the first adjacent angular sector  3 ;   the second lateral flange  34  of the angular sector  3  is attached to the first lateral flange  33  of the second adjacent angular sector  3 .       

     The fact that the angular sectors  3  are directly attached to one another, and not with an intermediate part positioned between each angular sector, allows reinforcing the stiffness of the mold  1  at the connection between the angular sectors  3 , and thus limits the deformation of the mold at the connection between the angular sectors  3 . 
     In order to attach the first lateral flange  33  and the second lateral flange  34 , said first lateral flange  33  and second lateral flange  34  comprise bores  35  which allow the passage of boltwork. 
     In order to ensure sealing between the different angular sectors  3 , a first groove  36  is formed in at least one of the first lateral flange  33  and the second lateral flange  34 . 
     More precisely, the first groove  36  is formed in the flat portion of the first lateral flanges  33  and/or of the second lateral flange  34  which is supported against the complementary flat portion of the second lateral flange  34  or of the first lateral flange  33  of the adjacent angular sector  3 . 
     A first seal  5  is positioned inside the first groove  36 , said first seal  5  thus being compressed between, on the one hand, the first lateral flange  33 , and on the other hand the second lateral flange  34 , thus allowing sealing the connection between the angular sectors  3 . The first seal  5  is not shown in  FIGS.  3   a  and  3   b    so as to leave the first groove  36  visible. 
     The first seal  5  can be made of an elastomer which is a material suited to the stresses encountered by the first seal  5 , and particularly a cold-vulcanizing (or RTV for “Room Temperature Vulcanizing”) elastomer, such as for example a cold-vulcanizing silicone, thus offering good resistance to the stresses to which the first seal  5  is subjected, as well as simplicity of use. 
     In the variant embodiment illustrated in  FIG.  2   , the first groove  36  is not formed on all the angular sectors  3 , but rather on only part of said angular sectors  3 . 
     More precisely, in the variant illustrated in  FIG.  2   , the mold  1  one comprises, on the one hand, a first group of angular sectors  3  for which a first groove  36  is formed both on the first lateral flange  33  and on the second lateral flange  34 , and on the other hand a second group of angular sectors  3  for which the first lateral flange  33  and the second lateral flange  34  are smooth, i.e. the first lateral flange  33  and the second lateral flange  34  have no first groove  36 . 
     One angular sector  3  of the first group is positioned between two angular sectors  3  of the second group. Thus, in this variant, the sealing between the different angular sectors  3  is obtained in the following manner;
         the first seal  5  positioned in the first groove  36  formed in the first lateral flange  33  of the angular sectors  3  of the first group is compressed between, on the one hand, the first lateral flange  33  of the angular sectors  3  of the first group and, on the other hand, the second lateral flange  34  of the angular sectors  3  of the second group;   the first seal  5  positioned in the first groove  36  formed in the second lateral flange  34  of the angular sectors  3  of the first group is compressed between, on the one hand, the second lateral flange  34  of the angular sectors  3  of the first group and, on the other hand, the first lateral flange  33  of the angular sectors  3  of the second group.       

     According to another possible variant, the first groove  36  can be formed on the first lateral flange  33  of each angular sector  3 , so that the first seal  5  is compressed between the first lateral flange  33  and the second lateral flange  34 , the second lateral flange  34 , for its part, being smooth. It should be noted that, equivalently, the first groove  36  can be formed in the second lateral flange  34  of each angular sector  3  while the first lateral flange  33  is smooth. By “smooth” it is also understood here that the first lateral flange  33  or the second lateral flange  34  does not have the first groove  36 . 
     In order to ensure the sealing between the mandrel  2  and the angular sectors  3 , the upstream flange  21  of the mandrel  2  comprises a second groove  23  and the downstream flange  22  of the mandrel  2  comprises a third groove  24 . 
     The second groove  23  is an annular groove which runs on the contour of the upstream flange  21 , and more precisely on the flat surface of the upstream flange  21  which comes into contact with the complementary flat surface of the front flange  31  of the angular sectors  3 . 
     The third groove  24  is also an annular groove which runs on the contour of the downstream flange  22 , and more precisely on the flat surface of the downstream flange  22  which comes into contact with the complementary flat surface of the rear flange  32  of the angular sectors  3 . 
     A second seal  6  is positioned inside the second groove  23 , and a third seal  7  is positioned inside the third groove  24 . 
     The second seal  6  is configured to be compressed between the upstream flange  21  of the mandrel  2  and the front flange  31  of the angular sectors  3 , thus allowing ensuring the sealing of the attachment between the upstream flange  21  of the mandrel  2  and the front flange  31  of the angular sectors  3 . 
     The third seal  7  is, for its part, configured to be compressed between the downstream flange  22  off the mandrel  2  and the rear flange  32  of the angular sectors  3 , thus allowing ensuring the sealing of the attachment between the downstream flange  22  of the mandrel  2  and the rear flange  32  of the angular sectors  3 . 
     The second seal  6  and the third seal  7  can be made of elastomer, which is a material suited to the stresses encountered by the second seal  6  and the third seal  7 . The second seal  6  and the third seal  7  can be made of cold-vulcanizing (or RTV for “room temperature vulcanizing”) elastomer, and particularly of cold-vulcanizing silicone. 
     As shown in detail in  FIGS.  3   a  and  3   b   , when an angular sector  3  is attached to the mandrel  2 , the first groove  36  formed in the first lateral flange  34  leads, on the one hand, into the third groove  23  formed in the upstream flange  21 , and on the other hand into the third groove  24  formed in the downstream flange  22 . 
     The fact that the first groove  36  leads into the second groove  23  and the third groove  24  allows ensuring the continuity of the sealing. 
     Moreover, as illustrated in  FIG.  2   , the first groove  36  comprises an undulated shape, thus allowing limiting the risk of the first seal  5  leaving said first groove  36 . 
     The undulated shape of the first groove  36  is advantageously a crenelated shape, said first groove  36  comprising slots directed radially inward, and slots directed radially outward. A crenelated shape of this type allows limiting the risk of the first seal  5  leaving the first groove  36 . 
     It is understood here that slot directed radially inward means a portion of the first groove  36  in which the first groove  36  approaches the mandrel  2 , and slot directed radially outward means here a portion of the first groove  36  in which the first groove  36  go away from the mandrel  2 . 
     As illustrated in  FIG.  2   , the slots directed radially outward from the first groove  36  can be advantageously positioned between two bores  35 . 
     The mold  1  can be used in order to implement the manufacturing method of the fan casing of composite material as illustrated in  FIG.  4   , the method comprising the following steps:
         E 1 : winding the fan casing fibrous preform around the mandrel  2 ;   E 2 : assembling the plurality of counter-mold angular sectors  3  on the exterior contour of the mandrel  2  by attaching the first lateral flange  33  of the angular sectors  3  to the second lateral flange  34  of an adjacent angular segment  3 . The angular sectors  3  are also attached to the mandrel  2  by attaching the front  31  and rear  32  flanges of the sectors  3  to the upstream  21  and downstream  22  flanges of the mandrel  2 ;   E 3 : densifying the fibrous preform by injection of a precursor material of a matrix of the composite material into the mold  1 , the mold  1  comprising injection openings for the injection of said precursor material;   E 4 : polymerizing the precursor material to obtain the matrix of the composite material;   E 5 : withdrawing the plurality of angular sectors  3 , this step being accomplished by decoupling the first lateral flanges  33  from the second lateral flanges  34 , the front flanges  31  from the upstream flange  21 , as well as the rear flanges  32  from the downstream flange  32 ;   E 6 : de-molding the fan casing.