Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/06—Fibrous reinforcements only
  • B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
  • B29C70/16—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length
  • B29C70/22—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in at least two directions forming a two dimensional structure
  • B29C70/222—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in at least two directions forming a two dimensional structure the structure being shaped to form a three dimensional configuration
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F30/00—Computer-aided design [CAD]
  • G06F30/10—Geometric CAD

Definitions

• the present invention relates to the field of making parts in woven composite material, after shaping one or more folds of 2D or 3D fabric.
• a part made of woven composite material comprises a woven preform, serving as a reinforcement, and a polymer matrix, serving as a binder.
• the fibers of the woven preform are made of carbon fibers, glass, Kevlar or linen.
• the woven preform when the positioning of the fibers within the preform is not random but has two preferred directions, comprises two types of son forming a network: the warps (which extend along the weaving direction) and the wefts (which extend transversely to the weaving direction).
• the warps are often substantially parallel to each other and the wefts are often substantially parallel to each other.
• Warps and wefts generally cross at a substantially right angle.
• the chain-to-frame coordinate system is generally considered to be orthogonal. It is then convenient and common to consider that the equivalent homogeneous composite material is orthotropic. This is the case, for example, with preforms leaving the looms.
• certain offsetting angles can reach up to 45 °, with values more commonly between 0 ° and 25 °.
• a constitutive law of a material aims to model the behavior (states of strain and stress) of said material in function of different conditions applied to said material (traction, pressures, etc.) and is identified empirically by subjecting said material to tensile experiments, for example.
• the same material can follow several constitutive laws. However, the number of constitutive laws remaining valid when the orthogonality of the material is lost, decreases. This number even tends to cancel out when the laws in question are non-linear. In addition, the value of the shift angles is often inhomogeneous in the room. If there is an anisotropic constitutive law, the material parameters will then have to be identified for each offset angle since they will depend intrinsically on this value, which in practice is not feasible.
• a so-called unframed material is more flexible in the weft direction, and more rigid in the warp direction.
• a margin is provided for in the manufacture of the parts, that is to say that certain areas of certain parts are voluntarily oversized, such as for example housing flanges.
• the housing is dimensioned to take into account up to 60% loss of properties in the weft direction for an offset angle of 30 degrees of loss of properties, therefore said flange is designed to be about twice as thick as this. that it should be without framing. This induces a high rate of material waste and a significant addition of mass for the engine.
• the present applicant has therefore set himself the objective in particular of providing a method for producing a part in woven composite material making it possible to predict and take into account the shifting of the warp-weft mark during the shaping of the woven reinforcement of the part.
• the proposed technical solution makes it possible to take into account the different unframing angles from geometric considerations and to optimize the manufacture of the part by including (and more precisely taking into account) these different post-shaping unframing angles in the design and production of said part.
• This solution applies to all constitutive laws (linear as well as non-linear) without the need to reformulate them.
• the identification of the material parameters remains unchanged. Only the knowledge of the framing angel is required for its implementation. It therefore becomes easy to continuously vary the object "constitutive law" with the field of offsetting angles and thus anticipate the mechanical behavior of the woven material as a function of the offsetting angle. It is thus possible to adapt the offset angle during the production of the part, depending on the expected local mechanical properties.
• the manufacturing time and costs are shortened.
• the manufacturing time (with all the stages of modeling, designs, tests, etc.) can be shortened by at least 30% which positively impacts the cost, and the design of the final part in composite material meets expectations.
• the parts obtained are more efficient because it is no longer necessary to apply a random safety coefficient which involved significant additional material on the dimensions, mass and cost of the part.
• the life of the parts is better calculated and optimized.
• the method according to the invention may include one or more of the following characteristics, taken in isolation from each other or in combination with each other:
• the local natural frame of reference is defined as the frame of reference attached to the preferred directions of the fibers of the offset network, the local natural frame of reference being non-orthogonal in the presence of a non-zero offset angle,
• the natural local coordinate system is defined as a covariant local coordinate system and that the linked coordinate system is defined as the contravariant local coordinate system, dual of the natural local coordinate system, - the passage from the local coordinate system orthogonal to the natural local coordinate system is done by means of a passage matrix defined as:
• the general constitutive law is a linear elastic constitutive law and that the tangent operator is a tensor of elastic rigidities
• the part is a housing.
• the invention also relates to a ply of a dry woven (3D) preform, comprising a network of fibers, said network having locally, at least one zone in which it is not orthogonal, this zone having been defined by the method described. above.
• the ply may constitute a preform as mentioned above or a plurality of associated plies, for example by contact, may constitute such a preform.
• the invention finally relates to a turbomachine part made of woven composite material produced by shaping a woven preform comprising a network of fibers impregnated with a polymer matrix, said network having, before shaping the preform, at least an area in which it is not orthonormal, this area having been defined by the method described above.
• FIG. 1 is a front view of a conventional loom for weaving a woven preform
• FIG. 2 is a schematic sectional view of a woven preform before shaping said preform
• FIG. 3 is a turbomachine blade produced by means of shaping and matrix impregnation of a preform as illustrated in the previous figures,
• FIG. 4a is a schematic view of the deformations of the network of the preform once shaped
• FIG. 4b is a view similar to that of Figure 4a, but the variations of the angle of shift a are indicated numerically
• - Figure 5 is a schematic view of the change in the angle of offsetting a before and after shaping of the preform
• FIG. 6 is an illustration of a set of landmarks based on the orthonormal local coordinate system according to the invention.
• FIG. 7 is a schematic summary of the first four steps of the process according to the invention.
• FIG. 8 is a series of turbomachine blades schematized and produced by means of the method according to the present invention.
• the method proposed in the present invention consists in, first of all, modeling the part 10 to be manufactured, for example a fan blade of a turbomachine.
• the modeling is carried out using, for example, a computer-assisted finite element method calculation software equipping said computer.
• This part 10 is made from the shaping of a woven preform 12.
• This woven preform 12 comprises woven fibers and is conventionally, as illustrated in FIG. 1, woven on a loom making it possible to obtain either a preform from a single ply or ply, or from several plies or plies. which are arranged together to constitute a shaped preform.
• the ply (s) which form the preform are said to be dry. Indeed, the ply (s) are not yet impregnated with a matrix intended to densify the woven preform.
• the preform 12 thus presents a set of fibers woven in two preferred directions substantially perpendicular to each other, as can be seen in FIG. 1.
• This set of chains 16a and frames 16b therefore forms a substantially orthogonal network 18, as can be seen in FIG. 2.
• the woven preform 12 is then shaped (as visible in FIG. 3) to give, after matrix impregnation and baking, the part 10.
• the shaping is typically carried out in an injection mold in which the matrix is injected.
• FIGS. 4a and 4b it can be seen that this shaping of the preform 12 induces a series of deformations of the network 18.
• the network 18 is no longer orthogonal: it is framed. That is to say that an offset angle has appeared between the initial direction (pre-shaping) and the final direction (post-shaping) of the fibers frame 16b (see Figure 5).
• the weft fibers 16b of the network 18 are no longer perpendicular to the weaving direction 17.
• FIG. 4b shows that the offset angle a varies locally along the surface of the part. 10.
• FIG. 5 thus shows the evolution of the network 18 before shaping of the preform 12 (zone Zi - orthonormal) and after shaping of the preform 2 (zone Z 2 - offset).
• the preform 12 is conventionally impregnated with a polymer matrix, then baked in an autoclave, to form the part 10 of woven composite material 14.
• a composite material is defined as being a woven preform 12. impregnated with polymer matrix.
• This woven composite material 14 has known mechanical properties. These mechanical properties are expressed by a known general constitutive law L. It can for example be a linear elastic constitutive law. It is important to note that the constitutive law mentioned here characterizes the behavior of the woven composite material 14 (preform and matrix), and not of the preform itself.
• the mechanical behavior of a woven composite material 14 is influenced by the offset angles a. Likewise, the mechanical behavior of a woven composite material is different from that of a preform (dry fiber reinforcement).
• unframe woven composite material 14 is used to refer to a woven composite material 14 in which the woven preform 12 has a network 18 of fibers with a non-zero offset angle ⁇ .
• unframed woven composite material 14 means a woven composite material 14 of which the woven preform 12 has an unframed network 18.
• the orientations of the fibers 16a, 16b of the network 18 can be expressed by decomposition on the vectors of a base.
• a basis of a vector space V is a free family of vectors of V which generates V.
• This general constitutive law L can be classically composed of tensors having coordinates in the base Bi considered as numerical values.
• the offset base B 2 is no longer orthogonal in the presence of offset.
• the shaping of the preform 12 woven from the part 10 to be produced is modeled so as to locally predict the deformations and the angles of shifting a of the network 18 of fibers 16a, 16b as a function of the shaping of the preform 12.
• this modeling is geometric and is obtained by a digital simulation of the shaping of the preform according to an improved thread algorithm. Then, the offsetting angles allow the part 10 to be modeled by the finite element method.
• the orthogonal local coordinate system Ri is defined with respect to the network 18 before shaping the preform 12.
• the natural local coordinate system R 2 is defined.
• This definition of the reference R 2 makes it possible to express a tensor of the stiffnesses C of the unframe woven composite material 14.
• this stiffness tensor C is conventionally defined in the local orthogonal coordinate system Ri.
• the components of the stiffness tensor C are known in the local orthogonal coordinate system Ri. Any stiffness tensor is obtained experimentally by experimental tests on a woven composite material (in the form of a test tube) and in the local orthogonal coordinate system Ri (without shifting). Each stiffness tensor is linked to a defined material.
• a tensor of the deformations E in the orthogonal local coordinate system Ri
• the tensor of the deformations is provided by a person skilled in the art and / or preferably a software used to produce modeling by the finite element method.
• the strain tensor is known in the mathematical sense of the term.
• the tensor of the strains E is expressed in a related reference R 2 .
• the linked frame R 2 is defined with respect to the network of fibers.
• the expression or calculation is carried out by means of a passage matrix J T as can be seen in FIG. 7.
• this linked frame of reference R 2 is the contravariant local frame of reference R 2 , dual of the natural local frame of reference R2, called covariant benchmark.
• the constitutive law of the woven composite material is used to, by means of the tensors C and E, calculate a stress tensor p in the natural local coordinate system R2.
• the stress tensor p obtained above is expressed in the local orthogonal coordinate system Ri by means of a passage matrix J j .
• a tangent operator for a numerical resolution by the finite element method comprising components which are equal to those of the stiffness tensor previously expressed in the local orthogonal coordinate system Ri.
• the tangent operator is equal to C expressed in Ri.
• the expression of the tangent operator is more complex and depends on the nature of the nonlinearity.
• the local orthogonal coordinate system Ri represented in FIG. 6 by the two vectors dXi and dX2.
• the natural local frame of reference R 2 is the frame of reference attached to the preferred directions of the fibers 16a, 16b of the framed network 18.
• the natural local coordinate system R 2 is non-orthogonal in the presence of a non-zero shift angle a, that is to say when a is different from 0.
• marks a collection of reference elements, one of which is designated as the origin, these elements allowing to designate in a simple way any object of a given set.
• a coordinate system is used to define the coordinates of each point.
• the marks are for example used to represent data graphically.
• the shift angle a is thus defined as the angle formed between dM 2 and dX 2 (see FIG. 6).
• a linear map (also called linear operator or linear transformation but many authors reserve the word "transformation” for those which are bijective) is a map between two vector spaces on a field K or two moduli on a ring which respects the addition of vectors and scalar multiplication defined in these vector spaces or moduli, or, in other words, which "preserves linear combinations".
• This coordinate system changes with a, and is coincident with the orthogonal coordinate system Ri (represented by the vectors dXi and dX 2 in FIG. 6) when the offset angle a is zero.
• a dual reference R 2 This coordinate system is defined as the dual coordinate system of the natural local coordinate system R 2 .
• This dual reference R 2 is associated with a so-called contravariant base B 2 (represented by the vectors dM 1 and dM 2 in FIG. 6).
• This dual frame of reference R 2 also changes with the offset angle a, and is also coincident with the local orthogonal coordinate system Ri when the offset angle a is zero.
• Step 1 the shaping of the woven reinforcement of the part 10 to be produced is modeled so as to locally predict the deformations and the angles of shifting a of the network 18 of fibers 16a, 16b as a function of the shaping of the preform 12.
• Stage 2 the components of the tensor of the rigidities of material C are supposed to be known and unchanged in the natural local coordinate system R 2 whatever the value of the angle of shifting a. The tensor C is thus expressed in the natural local coordinate system R 2 . (in summary, we construct the frames R2 and R 2 as a function of the offset angles a previously obtained and we express C)
• Stage 3 the tensor of the strains E is provided (by a person skilled in the art) at the input of the constitutive law L in the local orthogonal coordinate system Ri.
• the tensor E being expressed in the dual frame of reference R 2 and the tensor C being expressed in the natural local coordinate system R2, the tensors C and E are thus expressed in dual frames of reference from one another (R2 and R 2 ): their tensor product is therefore objective, within the meaning of the principle of objectivity of physical laws.
• One can thus calculate the components of the stress tensor p (p 0: E) in the covariant base B 2 of the natural local coordinate system R2.
• Step 5 numerical resolution using a tangent operator.
• the components of the tangent operator are calculated using the general constitutive law L. In the present case, these components are calculated in the local orthogonal coordinate system Ri.
• the tangent operator is equal to the tensor of the elastic rigidities and its components in the reference Ri are calculated by an operation of change of base applied to a tensor of order 4 of which the expression is as follows:
• C [v (p, q), v (r, s)] J T [p, i ⁇ .J T [q, j] .J T [r, k] .J T [s, l].
• the tensor of the rigidities C (which had already been expressed in the reference R2), is expressed in the local orthogonal reference Ri.
• This step is illustrated in Figure 7 by arrow number 4 which symbolizes the passage from the natural local coordinate system R2 to the orthogonal local coordinate system Ri.
• the last five steps of the process of the present application are thus:
• This adaptation of the weaving can be done by a local rearrangement of the directions of the and / or a localized modification of the thickness of the fibers 16a. , 16b and / or their spacing, for example.
• This adaptation is then fixed, before the impregnation of the preform with the polymer matrix. This makes it possible to retain the expected properties of the woven composite material 14 despite the shaping, and makes it possible to overcome the dimensional margins linked to the uncertainty on the mechanical properties of the woven composite material 14 after shaping of the preform 12.
• the loom is reconfigured to produce a fiber preform, the orientation of the weft and warp fibers of which makes it possible to anticipate the behavior of the woven composite material with offset angles.
• a difference is observed in the modal response of said part 10 (here a fan blade).
• the modal response is determined by subjecting the part to waves (eg sound): the vibrations of the part, in response to these waves, are measured via sensors and / or cameras.
• the vibratory propagations are different in the part as shown diagrammatically by lines in the blades drawn in figure 8.
• the vibratory response is differently in accordance with different modes and the part can thus be characterized in predictions of its sound. behavior in particular during aero-elastic stresses.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Geometry (AREA)
• Mechanical Engineering (AREA)
• Composite Materials (AREA)
• Chemical & Material Sciences (AREA)
• Computer Hardware Design (AREA)
• Mathematical Optimization (AREA)
• Pure & Applied Mathematics (AREA)
• Mathematical Analysis (AREA)
• Evolutionary Computation (AREA)
• General Engineering & Computer Science (AREA)
• Computational Mathematics (AREA)
• Woven Fabrics (AREA)
• Moulding By Coating Moulds (AREA)
• Reinforced Plastic Materials (AREA)
• Nonwoven Fabrics (AREA)

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• 2019
  • 2019-02-28 FR FR1902083A patent/FR3093297B1/fr active Active
• 2020
  • 2020-02-28 WO PCT/FR2020/050399 patent/WO2020174198A1/fr unknown
  • 2020-02-28 CN CN202080021964.8A patent/CN113573874B/zh active Active
  • 2020-02-28 US US17/433,490 patent/US20220134683A1/en active Pending
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