Constrained creep forming of contoured composite stiffeners

Patent metadata

Field	Value
Publication number	US-11518121-B2
Application number	US-201916600887-A
Country	US
Kind code	B2
Filing date	Oct 14, 2019
Priority date	Oct 14, 2019
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

A composite laminate stiffener is formed to contour with reduced ply wrinkling using constrained creep forming. The tooling apparatus is provided with flexible cauls which constrain the stiffener during the contour forming process. The creep forming is carried out at a slow enough rate so that friction or shear resistance between the resin and fibers of the plies remains low enough that slippage can occur and significant compression stresses are not generated rate, allowing relaxation of residual stresses in the stiffener.

First claim

What is claimed is:

1. A method of making a contoured composite laminate stiffener, comprising:
placing a composite charge on a die having a die cavity;
heating the composite charge;
producing a partially formed stiffener having a length and a cross-sectional shape by forcing the composite charge into the die cavity;
fully constraining all surfaces of the cross-sectional shape of the partially formed stiffener; and
creep forming the partially formed stiffener to a desired contour along the length while the partially formed stiffener is being fully constrained.

2. The method of claim 1 , wherein creep forming the partially formed stiffener is performed at a rate between approximately 0.0015 inches/second and approximately 0.006 inches/second.

3. The method of claim 1 , wherein the partially formed stiffener has sides and fully constraining all the surfaces of the cross-sectional shape of the partially formed stiffener includes applying a pressure to each of the sides.

4. The method of claim 3 , wherein the partially formed stiffener includes flange portions and fully constraining all the surfaces of the cross-sectional shape of the partially formed stiffener includes pressing the flange portions against the die.

5. The method of claim 3 , wherein:
forcing the composite charge into the die cavity is performed using a punch to punch the composite charge into the die cavity, and
applying the pressure to each of the sides is performed by using the die and the punch to apply the pressure.

6. The method of claim 1 , wherein:
fully constraining all the surfaces of the cross-sectional shape of the partially formed stiffener is performed using a pair of flexible cauls, and
creep forming the partially formed stiffener is performed using the pair of flexible cauls and includes flexing the pair of flexible cauls to the desired contour.

7. The method of claim 1 , wherein:
the composite charge comprises a polymer containing reinforcement fibers, and
creep forming the partially formed stiffener to the desired contour is performed at a rate that allows the reinforcement fibers to permanently deform.

8. A method of making a contoured fiber-reinforced composite laminate stiffener with reduced wrinkling, comprising:
placing a fiber-reinforced composite charge between an upper die and a lower die having a die cavity;
heating the fiber-reinforced composite charge;
producing a stiffener having a desired cross-sectional shape by forcing the fiber-reinforced composite charge into the die cavity using the upper die;
fully constraining all surfaces of the cross-sectional shape of the stiffener by using the upper die and the lower die to apply pressure to the stiffener; and
creep forming the stiffener to a contour while fully constraining the stiffener using the upper die and the lower die, wherein creep forming the stiffener to the contour produces residual stresses in the stiffener, and creep forming the stiffener to the contour is performed at a rate that allows relaxation of the residual stresses.

9. The method of claim 8 , wherein the stiffener has sides and fully constraining all the surfaces of the cross-sectional shape of the stiffener includes constraining the sides while creep forming the stiffener to the contour.

10. The method of claim 8 , wherein creep forming the stiffener to the contour includes contouring the upper die and the lower die.

11. The method of claim 8 , wherein fully constraining all the surfaces of the cross-sectional shape of the stiffener includes using the upper die to apply pressure to portions of the stiffener at spaced apart locations along a length of the stiffener while creep forming the stiffener to the contour.

12. The method of claim 8 , wherein the rate is between approximately 0.0015 inches/second and approximately 0.006 inches/second.

13. The method of claim 8 , wherein:
the lower die comprises a pair of flexible cauls and fully constraining all the surfaces of the cross-sectional shape of the stiffener is performed using the pair of flexible cauls, and
creep forming the stiffener is performed using the pair of flexible cauls as forming tools.

14. The method of claim 8 , wherein:
forcing the fiber-reinforced composite charge into the die cavity is performed using a punch on the upper die, and
fully constraining all the surfaces of the cross-sectional shape of the stiffener includes using the upper die to apply pressure to the fiber-reinforced composite charge.

15. A method of making a fiber-reinforced composite laminate stiffener having a length and a contour along its length, comprising:
placing a composite charge on a pair of flexible cauls arranged to form a die cavity therebetween;
heating the composite charge;
forming the composite charge into a stiffener having a desired cross-sectional shape by forcing the composite charge into the die cavity;
fully constraining all surfaces of the cross-sectional shape of the stiffener, including using the pair of flexible cauls to apply pressure to the stiffener; and
creep forming the stiffener to the contour using the pair of flexible cauls, including flexing the pair of flexible cauls as the pair of flexible cauls constrain the stiffener while creep forming the stiffener to the contour,
wherein creep forming the stiffener to the contour is performed at a rate causing irreversible deformation of the stiffener.

16. The method of claim 15 , wherein:
forcing the composite charge into the die cavity is performed using a punch, and
fully constraining all the surfaces of the cross-sectional shape of the stiffener includes using the punch to apply pressure to at least a portion of the stiffener.

17. The method of claim 16 , wherein using the punch to apply pressure to the stiffener includes applying the pressure at spaced apart locations along the length of the stiffener.

18. The method of claim 15 , further comprising:
installing the pair of flexible cauls on die support blocks, and
wherein creep forming the stiffener to the contour includes bending the pair of flexible cauls and the die support blocks to the contour.

19. The method of claim 15 , further comprising:
using the pair of flexible cauls to change the desired cross-sectional shape of the stiffener after creep forming the stiffener to the contour.

20. The method of claim 15 , wherein the rate is between approximately 0.0015 and approximately 0.006 inches/second.

Assignees

• Boeing Co

Inventors

• Saini Gagandeep
• Carlson Lisa Christina
• Willden Kurtis Shuldberg
• Smith Brian James
• Santiago Jonathan

Classifications

• B29K2063/00

  Use of {EP, i.e.} epoxy resins {or derivatives thereof}, as moulding material · CPC title

• B29D99/0014

  provided with ridges or ribs, e.g. joined ribs · CPC title

• B29C70/461

  Rigid movable compressing mould parts acting independently from opening or closing action of the main mould · CPC title

• B29C70/543 Primary

  Fixing the position or configuration of fibrous reinforcements before or during moulding (for non-woven fabrics D04H3/08) · CPC title

• B29C53/382

  using laminated sheets · CPC title