Method for characterizing a fibrous texture

Abstract

Method for characterizing a fibrous texture. A method for characterizing a fibrous texture (10) having a three-dimensional or multilayer weave following a determined weave pattern on a plurality of warp planes and on a plurality of weft planes comprises calculating an infiltration score of the fibrous texture corresponding to the ratio between a number of actual crossing points (P1, P2) between warp yarns of the warp yarn layer present on an external surface of the fibrous texture and weft yarns of weft yarn layers and a maximum number of theoretical crossing points on the external surface of the fibrous texture, each actual crossing point (P1, P2) corresponding to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn with respect to a weft yarn between two successive warp planes. Figure for the abstract: Fig. 2.

Description

Title of the invention: Method for characterizing a fibrous texture technical field

[0001] The invention relates to the characterization of fibrous textures comprising a three-dimensional or multilayer weave used to form fibrous reinforcements in composite materials. Previous technique

[0002] One application of the invention is the production of parts made of structural composite material, that is, structural parts reinforced with fibers and densified by a matrix. Composite materials make it possible to produce parts with a lower overall mass than the same parts when made of metallic material.

[0003] The invention relates more particularly to composite material parts manufactured from a fibrous reinforcement obtained at least in part by three-dimensional (3D) or multilayer weaving between a plurality of warp yarn layers and a plurality of weft yarn layers, the reinforcement being densified by chemical infiltration in the gas phase (CVI). A 3D weave may, for example, correspond to an interlock weave, while a multilayer weave may, for example, correspond to a multi-plain, multi-satin, or multi-twill weave.

[0004] Depending on the 3D or multilayer weave structure used to form the fibrous texture, the latter exhibits varying degrees of infiltration, that is, a greater or lesser capacity for the reactive gas used for CVI to penetrate the fiber. Infiltration depends in particular on the density of warp yarns passing through two or more weft layers within the thickness of the fibrous texture. Indeed, when a warp yarn connects two or more weft yarns, it creates a preferential path that facilitates the flow of gas within the fibrous texture.

[0005] Furthermore, in the case of a weave structure comprising a two-dimensional woven skin on the surface of a 3D or multilayer weave, the skin creates a densification gradient between the surface and the core of the fibrous texture with a faster densification on the surface which then blocks the surface porosity and prevents good densification at the core of the fibrous texture.

[0006] Furthermore, the number of contact points between the warp and weft yarns in a 3D or multilayer weave influences the deformability and bulk of a fibrous texture. A texture with a weave structure with many contact points is not very deformable and has little bulk, which poses problem during shaping in former, the preform does not completely fill the former's air gap.

[0007] There is, therefore, a need to be able to characterize a fibrous texture according to its infiltrability and possibly its capacity for deformation and its bulking. Description of the invention

[0008] To this end, the invention proposes a method for characterizing a fibrous texture intended to form a reinforcement for a part made of composite material, the fibrous texture having a three-dimensional or multi-layered weave between layers of warp yarns juxtaposed in the thickness of the fibrous texture and layers of weft yarns juxtaposed in the thickness of the fibrous texture, the fibrous texture further comprising on one of its external surfaces a skin having a two-dimensional weave and covering the three-dimensional or multi-layered weave, the fibrous texture having a weave structure determined on a plurality of warp planes and on a plurality of weft planes,the method comprising calculating a complex weave infiltration score of the fibrous texture corresponding to the ratio between a number of actual crossing points of interest between warp and weft yarns of the skin of the fibrous texture and a maximum number of theoretical crossing points on said skin, each actual crossing point of interest corresponding to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn of the skin with respect to a weft yarn between two successive warp planes, said warp yarn of the skin being located above a warp yarn of a layer of warp yarns underlying the warp yarn layer of the skin linking at least two layers of weft yarns in the thickness of the fibrous texture.

[0009] The method of the invention makes it possible to determine the infiltration capacity of a fibrous texture comprising a 2D skin on the surface and a 3D or multilayer weave structure at its core. This allows for the selection of weaves that will improve the densification by CVI at the core, thus enabling more homogeneous densification throughout the fibrous texture.

[0010] According to a particular aspect of the method of the invention, the calculation of the complex armor infiltration score comprises the following steps:

[0011] 1) gridding of the skin surface of the fibrous texture into a plurality of square cells, each square cell corresponding to an intersection between a warp plane and a weft plane and comprising four vertices,

[0012] 2) identification, among the plurality of square cells, of deep-bonding cells in which a warp thread present beneath the warp thread layer of the skin binds to minus two layers of weft yarns in the thickness of the fibrous texture,

[0013] 3) determining for each vertex of a cell the presence or absence of a point of genuine intersection of interest,

[0014] 4) addition of the actual crossing points of interest determined in step 3).

[0015] According to another particular aspect of the process of the invention, the infiltrability score The complex armor Sm is calculated using the following formula: PciXPn if 3(i, j) such that P { (i, j) >2

[0016] where P ch is the number of chain planes PTr is the number of frame plans / is a function for identifying real-world crossing points of interest i is the current chain plan j is the current frame plan.

[0017] According to a particular feature of the method of the invention, it further comprises the calculation of a number of contact points between warp yarns and weft yarns in the fibrous texture, comprising the following steps: 1) Calculation for each warp yarn layer of warp yarns of a warp contact point value, the warp contact point value being determined according to the number of weft yarn layers traversed by the warp yarn in question, said calculation being repeated for each warp weave plane, 2) Calculation of a value for chain contact points per centimeter, 3) Calculation for each weft yarn layer of weft yarns of a weft contact point value, the weft contact point value being determined according to the number of warp yarn layers crossed by the weft yarn considered, said calculation being repeated for each weft weave plane, 4) Calculation of a contact point value per centimeter in the grid, 5) Adding the warp and weft contact point values ​​per centimeter calculated in steps 2) and 4) to obtain a number of contact points in the fibrous texture.

[0018] The process of the invention makes it possible to evaluate the deformation (flexibility) and bulking capacity of a fibrous texture according to its weave structure and thus determine whether or not it can be easily shaped.

[0019] The invention also relates to a method for characterizing a fibrous texture intended to form a reinforcement for a part made of composite material, the fibrous texture having a three-dimensional or multilayer weave between layers of warp yarns juxtaposed in the thickness of the fibrous texture and layers of weft yarns juxtaposed in the thickness of the fibrous texture, the three-dimensional weave or multilayer being present on external surfaces of the fibrous texture, the fibrous texture having a determined weave structure on a plurality of warp planes and on a plurality of weft planes, the process comprising the calculation of a single weave infiltration score of the fibrous texture corresponding to the ratio between a number of actual crossing points between warp yarns of the warp yarn layer present on an external surface of the fibrous texture and weft yarns of weft yarn layers and a maximum number of theoretical crossing points on the external surface of the fibrous texture, each actual crossing point corresponding to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn with respect to a weft yarn between two successive warp planes.

[0020] The process of the invention makes it possible to determine the infiltration capacity of a fibrous texture based on its 3D or multilayer weave structure, that is, the infiltration capacity of the fibrous texture by the reactive gas used for CVI. This allows for the selection of weaves that will improve core densification by CVI and thus enable more homogeneous densification across the entire fibrous texture.

[0021] According to a particular aspect of the method of the invention, the calculation of the simple armor infiltration score comprises the following steps:

[0022] 1) gridding of one of the external surfaces of the fibrous texture into a plurality of square cells, each square cell corresponding to an intersection between a warp plane and a weft plane and comprising four vertices,

[0023] 2) determining for each vertex of a cell the presence or absence of a point of actual crossing,

[0024] 3) addition of the actual crossing points determined during step 2).

[0025] According to another particular aspect of the method of the invention, the simple armor infiltration score Si is calculated with the following formula: 1 “Pc^Pt!

[0026] where Pch is the number of chain planes PTr is the number of frame plans / is a function for identifying real intersection points i is the current warp plane j is the current frame plane.

[0027] According to a particular feature of the process of the invention, it further comprises the calculation of a number of contact points between warp yarns and weft yarns in the fibrous texture, comprising the following steps: 1) Calculation for each warp thread of warp thread layers with a value of warp contact points, the value of warp contact points being determined according to the number of weft yarn layers crossed by the warp yarn considered, said calculation being repeated for each warp weave plane, 2) calculation of a value of warp contact points per centimeter, 3) calculation for each weft yarn layer of weft yarns of a value of weft contact points, the value of weft contact points being determined according to the number of warp yarn layers crossed by the weft yarn considered, said calculation being repeated for each weft weave plane, 4) calculation of a value of weft contact points per centimeter, 5) addition of the warp and weft contact point values ​​per centimeter calculated in steps 2) and 4) so ​​as to obtain a number of contact points in the fibrous texture.

[0028] The method of the invention also makes it possible to evaluate the deformation (flexibility) and bulking capacity of a fibrous texture as a function of its weave structure and thus determine whether or not it can be easily shaped. Brief description of the drawings

[0029] [Fig. 1A-1R] Figures IA to IR illustrate successive planes of a woven fabric of a fibrous texture with three-dimensional core weave and two-dimensional skin weave,

[0030] [Fig.2] Fig.2 illustrates a grid of one of the external surfaces of a fibrous texture having the weave structure of figures IA to 1H used for calculating an infiltrability score according to a method of the invention,

[0031] [Fig.3] [Fig.3] illustrates four theoretical intersection points of a cell of the grid of [Fig.2],

[0032] [Fig. 4] [Fig. 4] illustrates an example of assigning contact point values ​​in a 3D woven fibrous texture according to a method of the invention. Description of embodiments

[0033] The invention relates to the characterization of any fibrous texture having a three-dimensional (3D) or multilayer weave between a plurality of warp yarn layers and a plurality of weft yarn layers, intended to form a fibrous reinforcement for a composite material part, the fibrous texture being at least partially consolidated or densified by chemical infiltration in gaseous mode (CVI). The fibrous texture is intended to form the fibrous reinforcement of a composite material part, in particular, but not exclusively, a ceramic matrix composite (CMC) part, i.e., comprising a fibrous reinforcement, for example, of carbon or ceramic fibers densified by a matrix that is at least partially ceramic.

[0034] By "three-dimensional weaving" or "3D weaving", we mean here a weaving method in which at least some of the warp yarns link weft yarns over several weft layers such as for example an "interlock weave" in which each warp layer links several weft layers with all the yarns in the same warp column having the same movement in the plane of the weave.

[0035] The term "multilayer weave" here refers to a 3D weave with several weft layers, the basic weave of each layer being equivalent to a conventional 2D fabric weave, such as plain weave, satin weave, or twill weave, but with certain points of the weave that bind the weft layers together. Known examples of multilayer weave weaves are multiplain weave, multisatin weave, and multitwill weave.

[0036] A 3D or multilayer weave structure defines how the warp yarns interlace with the weft yarns and vice versa, according to an elementary pattern for each plane of the weave structure. The weave pattern is defined on a plurality of warp cross-section planes, also called warp planes, which show the path of the warp yarns relative to the weft yarns (represented in cross-section) through the thickness of a fibrous texture for a given column of warp yarns, i.e., the path of one warp yarn for each layer of warp yarns, and on a plurality of weft cross-section planes, also called weft planes, which show the path of the weft yarns relative to the warp yarns (represented in cross-section) through the thickness of a fibrous texture for a given column of weft yarns, i.e., the path of one weft yarn for each layer of weft yarns.The warp and weft planes are repeated in order throughout the weaving of the fibrous texture. Figure 2 shows an example of a multilayer weave whose representative pattern is defined on eight warp planes.

[0037] CVI treatment is a well-known process for densifying porous preforms to produce parts made of CMC composite material. The preform(s) to be densified are placed in a reaction chamber of a CVI installation where they are heated. A reactive gas containing one or more gaseous precursors of the matrix material is introduced into the reaction chamber. The temperature and pressure in the installation are adjusted to allow the reactive gas to diffuse within the porosity of the preforms and form a deposit of the matrix material by decomposition of one or more components of the reactive gas or by reaction between several components, these components forming the matrix precursor. Such a process is described, in particular, in US patent 9,845,534.

[0038] The characterization method of the invention comprises calculating an infiltration score for a fibrous texture, which makes it possible to determine a representative value of its potential for infiltration by the gas or gases used for CVI. As described in detail below, the method of the invention proposes to calculate a score The "simple armor infiltration" method determines a representative value of the infiltration potential of a 3D or multilayer woven armor when it is present on the external surfaces of the fibrous texture, i.e., those directly accessible to the reactive gas of the CVI (Controlled Insulation Composite System). The invention further proposes to calculate a "complex armor infiltration" score, which determines a representative value of the infiltration potential of a woven armor comprising an inner part or core formed by a 3D or multilayer weave and an outer part or skin with a two-dimensional weave covering the 3D or multilayer weave.

[0039] As explained below, the "simple weave infiltration score" corresponds to the ratio between a number of actual crossing points between warp yarns of the warp yarn layer present on an external surface of the fibrous texture and weft yarns of weft yarn layers and a maximum number of theoretical crossing points on the external surface of the fibrous texture, while the "complex weave infiltration score" corresponds to the ratio between a number of actual crossing points near an underlying deep bond, called "points of interest", between warp yarns and weft yarns of the skin of the fibrous texture and a maximum number of theoretical crossing points on said skin.

[0040] An example of calculating an infiltration score for a fibrous texture illustrated in Figures IA to IR is now described. Figures IA to IR represent eight successive warp planes CH1 to CH18 of a weave structure of a fibrous texture 10 obtained by 3D core weaving 12 and two-dimensional skin weaving 14, 16. The representative pattern of the weave of the fibrous texture 10 is defined on eighteen warp and weft planes. The fibrous structure 10 comprises five layers of warp yarns Ci to C5 and five layers of weft yarns Ti to T5.

[0041] The calculation of the infiltration score begins by dividing one of the external surfaces of the fibrous texture 10, here the surface of the fibrous texture 10 comprising the skin 16, into a plurality of square cells as shown in [Fig. 2]. Each square cell corresponds to an intersection between a warp plane CH1 to CH18 and a weft plane TRI to TRI8. The square cells of the grid represent the behavior of the warp yarn Cn to Cn8 of the warp yarn layer Ci of the skin 16 respectively on the eight warp planes CH1 to CH18 and weft planes TRI to TR18. For example, the warp yarn Cn visible on the warp plane CH1 of [Fig. 1A] is represented in [Fig. 2] in the left column from bottom to top of the figure, and so on for the warp yarns Ci2 to Cn8 from left to right in [Fig. 2].The black square cells represent warp threads visible on the surface of the fibrous texture, while the white square cells represent weft threads visible on the surface of the fibrous texture.

[0042] In the following explanation of the calculation of the infiltration score, we generalize by denoting PCh as the number of warp planes, and Ptr as the number of weft planes. We also denote Cch as the number of warp layers, and Ctr as the number of weft layers. In the example in Figures IA to IR, Cch = Ctr.

[0043] Denoting z as the current warp plane, j as the current weft plane, and Pk(p) as the position of warp thread k, defined by the number of frames locally above thread k (thread 1 being the surface thread), the value of the cell C(i, j) is obtained by the following formula: 0 if Pi(i, j) = 0 1 C(ij) = . ' 1 7 l IstPi (f,j) >0 J for 1 < i < PCh and for 1 < i < PTr

[0044] The cells in black on figure 2 therefore correspond to the cells (kj) for which C (i, j) =0, and the cells in white therefore correspond to the cells (i, j) for which C (i, j) = 1.

[0045] For example, the value of the cells C(kj) in the left column of [Fig.2] from bottom to top is 01,1) = 1 (weft yarn over warp yarn Cn), 01,2) = 1 (weft yarn over warp yarn Ci2), 01,3) = 1 (weft yarn over warp yarn Cn), 01,4) = 0 (weft yarn under warp yarn CM), 01,5) = 0 (weft yarn under warp yarn Ci5), 01,6) = 0 (weft yarn under warp yarn Ci6), C(7,7) = 1 (weft yarn over warp yarn Ci7), 01,8) = 1 (weft yarn over warp yarn C[8], 01,9) = 1 (weft yarn over warp yarn Ci9), 01,10) = 0 (weft yarn below warp yarn Cno), 01,11) = 0 (weft yarn below warp yarn Cm), 0.1,12) = 0 (weft yarn below warp yarn Cm), 0.1,13) = 1 (weft yarn above warp yarn Cm), 0.1,14) = 1 (weft yarn above warp yarn Cn4), 0.1,15) = 1 (weft yarn above warp yarn Cn5), 0.1.16) = 0 (weft yarn below warp yarn Cn6), 0.1.17) = 0 (weft yarn below warp yarn Cm) 0.1.18) = 0 (weft yarn below warp yarn Cm). .

[0046] Each square cell has four vertices, each corresponding to a theoretical crossing point between a warp yarn and a weft yarn.

[0047] Figure 3 illustrates the four theoretical crossing points of a square cell C(k,fp). For a given cell C(i,j), the theoretical crossing points between a warp yarn and a weft yarn are identified at the vertices of the square cells as shown below, with the following boundary assumption:

[0048] Point (-^, = Point (Pch+^, j + y), forl <j<Ptr Point (-1, j-1) = Point (Pch + j, jy), for 1 < j < Ptr Point (i + ^, -j) - Point (i + ^, Ptr + ^), for l <i<PCh Point (i-^, - 2 ) “P°int (z " 4 ?tr + 2 )’ Pour 1 -z-?Ch Cellule ( -1, j) = Cellule (PCh, j), pour 1 < j < Ptr Cellule (i, -1) = Cellule (i, Ptr) , pour 0< i<PC h

[0049] It is thus possible to determine the maximum number of crossing points theoretical on the external surface of the fibrous texture.

[0050] The function f defined below allows us to isolate the actual crossing points, represented by Pi and P2 in Figure 2, from among all the theoretical crossing points on a given cell (f, j):

[0051] For \ <i<PCh-\ et l^j<PTr [°°52] eC 1 ; IX ; iUhz|cO <j^ JV""' j~ 2 / -J Vz+2' J ■“ / - „ . I 0 smon

[0053] The actual warp and frame crossing points are those for which the function f equals 1.

[0054] Each actual crossing point corresponds to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn with respect to a weft yarn between two successive warp planes

[0055] In the case of a 3D or multilayer weave armor present directly on the external surfaces of the fibrous texture, i.e. without a two-dimensional skin on its surface, all the real isolated crossing points on the surface of the fibrous texture are added together as described above, and then the number of real crossing points found is divided by the maximum number of theoretical crossing points on the external surface of the fibrous texture to calculate a simple armor infiltration score.

[0056] The simple armor infiltration score, noted as 5'1, can be calculated using the following formula:

[0057] ,

[0058] where P ch is the number of chain planes Ph is the number of frame planes / is a function for identifying real crossing points i is the current warp plane j is the current frame plane

[0059] By way of example, if we consider that [Fig.2] represents the surface of a texture fibrous without the two-dimensional skin, namely that the warp threads present in the first layer of warp threads already make deep bonds, the simple armor infiltration score would be 216 / 324 = 0.67.

[0060] In the case of a weave comprising an inner part or core formed by a 3D or multilayer weave and an outer part or skin having a two-dimensional weave and covering the 3D or multilayer weave, as shown in Figures IA to IR and 2, the cells where a deep bonding point exists are first identified. A deep bonding point corresponds to a warp yarn from a layer of warp yarns underlying the warp yarn layer of the skin that binds at least two layers of weft yarns within the thickness of the fibrous texture. The cells where a deep bonding point exists are represented with a point Lpa or Lpd in [Fig. 2], Lpa corresponding to an upward deep bonding point and Lpd corresponding to a downward deep bonding point.To do this, simply look at the behavior of the warp yarn C2i to C28 (figures IA to IR), warp plane by warp plane, and identify the positions where two or more weft layers are linked.

[0061] The cells (i, for which there is a depth link point are identified by the values ​​+1 or -1 in the output of the following function:

[0062] psz l <P2(zj) <2 £(h. / j= 1szP2(zJ)>2 . - 1 sî P2(i, j) <1

[0063] Cells (z, j) for which g(i, j) = 1 are identified by an Lpd point (downward linkage) (Figure 2). Cells (z, j) for which g(i, j) = -1 are identified by an Lpa point (upward linkage) ([Fig. 2]).

[0064] Once this identification has been carried out, the function h defined below makes it possible to distinguish, among the real crossing points, the real crossing points of interest represented by Pi on the [Fig.2].

[0065] For 1 < i < PCh and 1 < j < PTr h 0'4' JA ) = / 04' >4 ) xmin( kU J) I + k0'- j) I + \s(p J-01 + kG-i J-0 h U

[0066] The actual crossing points of interest are those that are close to a deep binding of a warp yarn in the fibrous texture. In other words, each actual crossing point of interest Pi corresponds to a change in relative position in the direction of the thickness of the fibrous texture of a skin warp yarn with respect to a weft yarn between two successive warp planes, the considered skin warp yarn being located above a warp yarn of a layer of warp yarns underlying the skin warp yarn layer binding at least two layers of weft yarns in the thickness of the fibrous texture

[0067] The actual crossing points of interest between the warp and weft threads of the skin These are the points for which the function h equals 1 (h=0 for the others). This can be determined by examining the four cells adjacent to each of these points.

[0068] The "multilayer infiltration" score, denoted Sm, can be calculated using the following formula: yPc"yPT'h ( M 1 if 3(i, j) such that (i, j) > 2 O m — 2 C7t tr S! otherwise

[0069] where Pch is the number of chain planes PTr is the number of frame plans h is a function for identifying real crossing points of interest, i is the current warp plane, j is the current frame plane

[0070] The infiltration score of the weave structure shown in Figures IA to IR is 0.22, obtained on the basis of the number of Pi points present in [Fig. 2] divided by the maximum number of theoretical crossing points on the external surface of the fibrous texture, i.e., 72 / 324. The fibrous texture having the weave structure defined in Figures IA to IR has an unsatisfactory infiltration score because it is less than 0.67.

[0071] Calculating the number of contact points between warp and weft yarns allows for the evaluation of the deformation (flexibility) and bulking capacity of a fibrous texture.

[0072] The calculation of the number of contact points for the warp yarns of the fibrous texture begins by calculating, for each warp yarn in the warp yarn layers of the fibrous texture, a warp contact point value. A contact point corresponds to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn in a warp plane of the weave of the fibrous texture. The value of a warp contact point is determined based on the number of weft yarn layers traversed by a given warp yarn corresponding to a depth of the bonding point in the weft yarn layer(s), the calculation being repeated for each warp weave plane. As illustrated in the example in [Fig. 4], the warp yarn Ca has two contact points. A value of 1 is assigned to the first contact point of the warp yarn Ca on the left in [Fig. 4].4] since the warp yarn Ca passes through a layer of weft yarns Ta here. A value of 2 is assigned to the second point of contact of the warp yarn Ca on the right in [Fig.4] since the warp yarn Ca passes through two layers of weft yarns Ta and Tb here. Similarly, the warp yarn Cb has two points of contact to which a value of 1 is assigned respectively (first point of contact of the warp yarn Cb on the left in [Fig.4]) since the warp yarn Cb passes through a layer of weft yarns Tb here and a value of 2 (second point of contact of the warp yarn Cb on the right in [Fig.4]). Since the warp yarn Cb passes through two layers of weft yarns Tb and Te, the warp yarn Ca has two points of contact. We assign a value of 1 to each of the two points of contact of the warp yarn Ce, since the yarn Ce passes through a single layer of weft yarns Te twice.

[0073] More generally, when a warp yarn passes through n layers of weft yarns, this corresponds to a point of contact to which the value n is assigned.

[0074] A value is assigned to all identified contact points for warp yarns of all warp yarn layers, i.e. for each warp yarn present in each warp plane of the weave weave of the fibrous texture.

[0075] The calculation of the number of contact points then involves calculating a value for warp contact points per centimeter. For this purpose, the weft yarn count, corresponding to the number of weft yarns per centimeter, also called "weft count per centimeter," is calculated to obtain a figure for the number of contact points per centimeter. To manage the weft counts, an average contact weighting is calculated for a layer and multiplied by the number of yarns per cm in each direction.

[0076] The steps described above are also carried out for the weft yarns of the fibrous texture, namely:

[0077] - Calculation for each weft yarn of the weft yarn layers of the fibrous texture of a value of contact points in the weft (a contact point corresponds to a change in relative position in the direction of the thickness of the fibrous texture of a weft yarn in a weft plane of the weave of the fibrous texture) according to the method described above for warp yarns,

[0078] - calculation of a value of contact points in the grid per centimeter, the texture of the warp threads, corresponding to the number of warp threads per centimeter also called "count per centimeter", in order to obtain a figure of the number of contact points per centimeter.

[0079] The warp and weft contact point values ​​per centimeter previously calculated are then added together to obtain a number of contact points in the fibrous texture.

[0080] The number of contact points in a fibrous texture can be calculated using the following formula:

[0081] / y - Nch xC x ------- + Ntr x D x (Ptr .v Cch) (Pch x Cïr)

[0082] With:

[0083] N: Total number of contact points

[0084] Nch: Number of contact points in the chain per plane (counted according to the principle above)

[0085] Ntr: Number of contact points in the Frame per plane (counted according to the principle above)

[0086] C = Count (number of warp threads per cm)

[0087] D = Weft thread count (Number of weft threads per cm)

[0088] Pch = Number of shots in Chain

[0089] Ptr = Number of frames in frame

[0090] Cch = Number of Chain Layers

[0091] Ctr = Number of frame layers

[0092] Based on this calculation formula, it is therefore possible to count the number of contact points on new armors, and thus to estimate their behavior in terms of bulking and deformability relative to each other.

[0093] The number of contact points calculated for the fibrous texture having the weave structure defined in figures IA to IR is 65.

Claims

Demands

1. A method for characterizing a fibrous texture (10) intended to form a reinforcement for a part made of composite material, the fibrous texture having a three-dimensional or multilayer weave (12) between layers of warp yarns (C1-C5) juxtaposed in the thickness of the fibrous texture and layers of weft yarns (T1-T5) juxtaposed in the thickness of the fibrous texture, the fibrous texture further comprising on one of its external surfaces a skin (16) having a two-dimensional weave and covering the three-dimensional or multilayer weave (12), the fibrous texture having a weave structure determined on a plurality of warp planes (CH1-CH18) and on a plurality of weft planes,the method comprising calculating a complex weave infiltration score of the fibrous texture corresponding to the ratio between a number of actual crossing points of interest (PI) between warp yarns and weft yarns of the skin of the fibrous texture and a maximum number of theoretical crossing points on said skin, each actual crossing point of interest (PI) corresponding to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn of the skin with respect to a weft yarn between two successive warp planes, said warp yarn of the skin being located above a warp yarn of a layer of warp yarns underlying the warp yarn layer of the skin linking at least two layers of weft yarns in the thickness of the fibrous texture.

2. A method according to claim 1, wherein the calculation of the complex weave infiltration score comprises the following steps: 1) dividing the skin surface of the fibrous texture into a plurality of square cells, each square cell corresponding to an intersection between a warp plane and a weft plane and having four vertices, 2) identifying, among the plurality of square cells, deep-bonding cells in which a warp yarn present under the warp yarn layer of the skin binds at least two layers of weft yarns in the thickness of the fibrous texture, 3) determining for each vertex of a cell the presence or absence of an actual crossing point of interest, 4) adding the actual crossing points of interest determined in step 3).

3. A method according to claim 2, wherein the complex armor infiltration score Sm is calculated with the following formula: (i-~i--i Sm=' p xP , such that where Pch is the number of warp planes, PTr is the number of weft planes, / is a function for identifying real crossover points of interest, i is the current warp plane, and j is the current weft plane

4. A method according to any one of claims 1 to 3, further comprising calculating the number of contact points between warp and weft yarns in the fibrous texture, comprising the following steps: 1) calculating, for each warp yarn layer, the warp yarn layer value, the warp yarn layer value being determined as a function of the number of weft yarn layers traversed by the warp yarn in question, said calculation being repeated for each warp weave plane, 2) calculating a warp yarn layer value per centimeter, 3) calculating, for each weft yarn layer, the weft yarn layer value, the weft yarn layer value being determined as a function of the number of warp yarn layers traversed by the weft yarn in question, said calculation being repeated for each weft weave plane,4) Calculation of a contact point value per centimeter in the weft, 5) addition of the warp and weft contact point values ​​per centimeter calculated in steps 2) and 4) in order to obtain a number of contact points in the fibrous texture.

5. A method for characterizing a fibrous texture (10) intended to form a reinforcement for a part made of composite material, the fibrous texture having a three-dimensional or multilayer weave between layers of warp yarns (C1-C5) juxtaposed in the thickness of the fibrous texture and layers of weft yarns (T1-T5) juxtaposed in the thickness of the fibrous texture, the three-dimensional or multilayer weave being present on external surfaces of the fibrous texture, the fibrous texture having a weave structure determined on a plurality of warp planes (CH1-CH18) and on a plurality of weft planes. weft, the process comprising the calculation of a simple weave infiltration score of the fibrous texture corresponding to the ratio between a number of actual crossing points (PI, P2) between warp yarns of the warp yarn layer present on an external surface of the fibrous texture and weft yarns of weft yarn layers and a maximum number of theoretical crossing points on the external surface of the fibrous texture, each actual crossing point (PI, P2) corresponding to a change in relative position in the direction of the thickness of the fibrous texture of a warp yarn with respect to a weft yarn between two successive warp planes.

6. A method according to claim 5, wherein the calculation of the single weave infiltration score comprises the following steps: 1) dividing one of the external surfaces of the fibrous texture into a plurality of square cells, each square cell corresponding to an intersection between a warp plane and a weft plane and having four vertices, 2) determining for each vertex of a cell the presence or absence of an actual crossing point, 3) adding the actual crossing points determined in step 2).

7. A method according to claim 6, wherein the single-armor infiltration score Si is calculated with the following formula: ôi“ Pcl^Ptr where Pa is the number of warp planes, PTr is the number of weft planes, l is a function for identifying actual crossover points, i is the current warp plane, and j is the current weft plane.

8. A method according to any one of claims 5 to 7, further comprising calculating the number of contact points between warp and weft yarns in the fibrous texture, comprising the following steps: 1) calculating, for each warp yarn layer, a value of warp contact points, the value of warp contact points being determined as a function of the number of weft yarn layers traversed by the warp yarn in question, said calculation being repeated for each warp weave plane, 2) calculating a value of warp contact points per centimeter, 3) Calculation for each weft yarn layer of weft yarns of a weft contact point value, the weft contact point value being determined according to the number of warp yarn layers crossed by the weft yarn considered, said calculation being repeated for each weft weave plane, 4) Calculation of a contact point value per centimeter in the grid, 5) Adding the warp and weft contact point values ​​per centimeter calculated in steps 2) and 4) to obtain a number of contact points in the fibrous texture.

Images