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EP-4552816-B1 - METHOD OF MANUFACTURING Y-SHAPED STRINGERS AND DOUBLE Y-SHAPED SPARS MADE OF COMPOSITE MATERIAL

EP4552816B1EP 4552816 B1EP4552816 B1EP 4552816B1EP-4552816-B1

Inventors

  • JARA RODELGO, ALVARO
  • GONZALEZ ANTOHI, Miguel
  • DE LA PUERTA VALLEJO, Mikel

Dates

Publication Date
20260513
Application Date
20231107

Claims (15)

  1. Method for manufacturing a Y-shaped stringer (100) made of composite material, the Y-shaped stringer (100) comprising a stringer web (110) having a cross-section in a I-shape, lower flanges (130a, 130b), a first opened triangular-shaped cross-section structure (120) comprising first and second lower vertices (120a, 120b) respectively joined to the lower flanges (130a, 130b) and an upper vertex (120c) connected to a first end of the stringer web (110), wherein the first opened triangular-shaped cross-section structure (120) and the stringer web (110) form a cross-section in a Y-shape, the method comprising: - placing composite material onto first mold (A) and a second mold (B) that each comprises a molding curvature (X) having an angle β = 360º - α , wherein α is a working angle formed in a joint between the first opened triangular-shaped cross-section structure (120) and the lower flanges (130a, 130b), wherein α has a value between 100 to 165°; - placing composite material onto a third mold (C); - closing the first mold (A) and the second mold (B) with the third mold (C) to obtain a closed mold that contains a Y-shaped preform (100a); and curing the Y-shaped preform (100a) with an autoclave cycle to obtain the Y-shaped stringer (100).
  2. The method according to claim 1, further comprising cutting the Y-shaped stringer (100).
  3. The method according to claims 1 or 2, wherein curing the Y-shaped preform (100a) with an autoclave cycle comprises curing the Y-shaped preform (100a) at 180 degrees Celsius or less.
  4. The method according to claims 1 to 3, further comprising placing a rowing (D1, D2) in between the first mold (A) and the second mold (B).
  5. The method according to claims 1 to 4, further comprising: - obtaining the first mold (A), the second mold (B) and the third mold (C) with 3D printing.
  6. The method according to any of the previous claims, further comprising establishing the lower flanges (130a, 130b) in a perpendicular direction to the stringer web (110) with the shape of the first mold (A), the second mold (B) and the third mold (C).
  7. The method according to any of the previous claims, further comprising: - using carbon fiber with thermoset or thermoplastic resin or glass fiber with thermoset or thermoplastic resin as composite material.
  8. The method according to the previous claims, further comprising establishing vertical fins (140) in a parallel direction to the stringer web (110) with the shape of the first mold (A), the second mold (B) and the third mold (C).
  9. The method according to claims 1 to 7, further comprising connecting a cap (150) to a second end of the stringer web (110) that provides the stringer web (110) with a cross-section in a T-shape or in a L-shape or in a J-shape.
  10. The method according to the previous claim, wherein the cap (150) comprises: - a first layer comprising composite laminates that wrap the lower flanges (130a, 130b), the stringer web (110), wherein a 70% of the total composite laminates from the first layer are oriented at a load angle +/-45°, wherein the load angle is the angle of the load with respect to the Y-shaped stringer reference axis; - a second layer comprising composite laminates that can be established on top of the first layer wherein a 70% of the total composite laminates of the second layer are oriented at a load angle 0°. - a third layer comprising composite laminates that can be established on top of the second one, wherein a 70% of the total composite laminates from the third layer are oriented at a load angle +/-45°.
  11. Use of the Y-shaped stringer (100) according to any of the preceding claims as stiffener for a panel (1010) of an aircraft by joining the lower flanges (130a, 130b) to the panel (1010) of the aircraft by cocuring or cobounding.
  12. Method for manufacturing a double Y-shaped cross-section spar (300) comprising at least a spar web, lower spar flanges, upper spar flanges and a first cross-section opened triangular-shaped spar structure and a second cross-section opened triangular-shaped spar structure, the method comprising: connecting a second end of the stringer web (110) of a Y-shaped stringer (100) to a second end of a second stringer web (210) of a second Y-shaped stringer (200) each obtained by the method according to claims 1 to 8; or connecting the cap (150) of the Y-shaped stringer (100) to a second cap of a second Y-shaped stringer (200) each obtained by the method according to claims 8 to 9.
  13. Method for manufacturing a torsion box (2000) for an aircraft comprising a plurality of double Y-shaped cross-section spars (300) obtained by the method according to the previous claim and a first panel (1010) and a second panel (1020), the method comprising: - placing at least the plurality of double Y-shaped cross-section spars (300) in between first molds (E), wherein the first molds (E) are associated with at least the shape of the spar web, and the lower spar flanges and the upper spar flanges; - placing second molds (F) onto the first cross-section opened triangular-shaped spar structure and onto the second cross-section opened triangular-shaped spar structure; - placing composite material at least onto the second molds (F); - closing the first molds (E) and the second molds (F) with third molds (G) to obtain a closed mold that contains a torsion box preform (300a), wherein the third molds (G) are associated with at least the shape of the first panel (1010) of the torsion box (2000) and the shape of the second panel (1020) of the torsion box (2000) of the aircraft, and - curing the torsion box preform (300a) with an autoclave cycle to obtain the torsion box (2000).
  14. The method according to claim 13, further comprising cutting the torsion box (2000).
  15. The method according to claims 13 or 14, wherein curing the torsion box preform with an autoclave cycle comprises curing the torsion box preform at 180 degrees Celsius or less.

Description

Object of the invention The present invention refers to method of manufacturing stringers and spars made of composite material, particularly stringers used in the aerospace industry having a Y-shape and spars having a double Y-shape cross-section. The stringers according to the present invention can be applied as stiffeners in any part of the airframe of the aircraft. The spars according to the present invention can be used as spars for the airframe of the aircraft, in particular, for torsion boxes of the aircraft. Background of the invention CA2619767A1 relates to a stringer which is made from a composite material, and which is used to stiffen composite panels, particularly those used in the aeronautical industry. The stringer is formed by a base which is used to join the same to the panel and a structural element which is equipped with a structural reinforcement at the end opposite the base, said structural reinforcement being made from high-modulus unidirectional fibers of the same material as the stringer or of another compatible material. The existing "double T"-section and the "omega"-section stringers have a limited momentum of inertia, and may suffer from buckling and post-buckling, as well as from torsional behavior. Furthermore, other manufacturing requirements such as weight savings and cost savings are beneficial to improve the existing stringers. EP3095691A1 relates to a multi-spar torsion box structure comprising a plurality of spars of composite material arranged to form a multi-cell structure with two or more cells extending span-wise one after the other in the torsion box, and upper and lower skin covers of composite material respectively joined to upper and lower surfaces of the multi-cell structure. The existing "double T"-section and the "omega"-section spars used in multi-spar torsion box structures have a limited momentum of inertia, and may suffer from buckling and post-buckling, as well as from torsional behavior. Furthermore, other manufacturing requirements such as weight savings and cost savings are beneficial to improve the existing spars and torsion boxes. The present invention satisfies these demands and solves the drawbacks of the current existing stringers used as stiffeners and spars used in multi-spar torsion box structures. US2015183503A1 relates to a manufacturing method is disclosed for manufacturing of a composite stiffening element, including: arranging composite laminates partially between caul plates and mold halves, and partially between a movable upper sandwich plate and a movable lower sandwich plate, moving the upper and lower sandwich plates together and moving the assembly formed by the first caul plate and the first mold half and the assembly formed by the second caul plate and the second mold half, and joining and co-curing the composite laminates to make up the composite stiffening element. A composite stiffening element is also disclosed. Description of the invention The present invention proposes a first manufacturing method to obtain a composite material stringer (carbon fiber or glass fiber with thermoset or thermoplastic resin) that can be used as stiffener for (preferably composite) panels formed by joining the base or flanges of the stringer and the panel. The proposed stringer comprises a structural cross-section that has a shape in Y. This shape is specified in the present description as a Y-shape and can correspond to the total or a part of the structural cross-section. The proposed stringer is indicated in the present description as a Y-shaped stringer. The Y-shaped stringer according to the present invention comprises two structural elements: an opened triangular-shaped cross-section structure followed by a stringer web that provides a Y-shape. The Y-shaped or Y-section stringer made of composite material has various benefits such as better structural efficiency, less wrinkles when manufacturing due to high angles, no corrosion and better Non-Destructive Testing, NDT process. The Y-shaped stringer can have various shapes and can comprise vertical fins and a cap with different variations. The use of composite materials for this purpose enhances the actual stringer properties, as well as the inspections and repairability. The Y-shaped stringer according to the present invention provides an optimization of the "double T"-section and the "omega"-section stringers existing in the art. Advantageously, the proposed Y-shaped stringer increases the momentum of inertia, enhances the buckling and post-buckling behavior, as well as the torsional behavior, and provides a new shape been resulting in the most efficient of the shapes. Furthermore, the Y-section optimizes the disposition of stringers due to the wider effective surface of the feet, which implies weight savings, cost savings and a higher ROI. Furthermore, the present invention proposes another manufacturing method to obtain a double Y-shaped cross-section spar by connecting two Y-shaped stringers o