Wrinkle reduction in formed composite laminates

Patent metadata

Field	Value
Publication number	US-10449754-B2
Application number	US-201615194986-A
Country	US
Kind code	B2
Filing date	Jun 28, 2016
Priority date	Jun 28, 2016
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

Wrinkling of a contoured composite laminate part during forming to contour is reduced by using laminate plies having off-angle reinforcing fibers that provide the part with primary axial strength along a major axis of loading.

First claim

What is claimed is:

1. A method of making a composite laminate part exhibiting reduced wrinkling, and having a desired contour along a major axis of loading:
laying up a substantially flat stack of fiber plies each having a unidirectional fiber orientation, wherein the substantially flat stack of fiber plies is devoid of 0° plies, wherein at least some of the plies provide the part with primary axial stiffness along the major axis of loading, including orienting the plies providing the primary axial stiffness at off-angles relative to the major axis of loading;
forming the stack to a desired cross sectional shape; and
forming the stack to the desired contour along the major axis of loading, wherein during the forming, strain on the plies providing the primary axial stiffness is reduced by their off-angle orientation.

2. The method of claim 1 , wherein the plies providing primary axial stiffness are oriented at off-angles within ranges of approximately +5° to +30°, and approximately −5° to −30°.

3. The method of claim 1 , wherein laying up the flat stack includes orienting all of the plies in the stack at angles greater than approximately ±5° relative to the major axis of loading.

4. The method of claim 1 , wherein orienting the plies is performed such that that fibers in the plies providing primary axial stiffness transition along their length during the forming of the desired contour from a compressive state to a neutral state, and from a neutral state to a tensile state.

5. The method of claim 1 , further comprising:
calculating thickness values for the plies;
performing discrete ply thickness integer optimization;
filtering the results of calculating thickness values for the plies and the discrete ply thickness integer optimization; and
optimizing the shape and stacking sequence of the plies.

6. A method of making a contoured composite laminate part having a high aspect ratio, a major axis of loading and a plurality of zones along its length respectively having desired stiffnesses, comprising:
selecting a set of fiber angles for plies of unidirectional reinforcing fibers, wherein the plies of unidirectional reinforcing fibers are devoid of 0° plies;
determining, for each of the fiber angles, a number of plies in each of the zones required to provide a desired set of in-plane laminate properties in the zone;
determining a shape and stacking sequence of the plies;
laying up the plies into a flat stack using the stacking sequence; and
forming the flat stack into the shape of the contoured composite laminate part.

7. The method of claim 6 , wherein:
determining the fiber angles includes selecting a plurality of possible combinations of fiber angles, and
determining a number of plies in each of the zones required to provide a desired set of in-plane laminate properties in the zone is performed for each of the possible combinations of angles.

8. The method of claim 7 , wherein:
determining the fiber angles includes eliminating certain of the possible combinations of fiber angles using a set of composite laminate design rules.

9. The method of claim 6 , wherein the set of fiber angles include fiber orientations relative to the major axis of loading of θ1, θ2, θ3, where 0<θ1<θ2≤θ3≤90°.

10. The method of claim 6 , wherein:
θ2−θ1≤45°, and

θ3−θ2≤45°.

11. The method of claim 9 , wherein θ 1 is selected to be between approximately 5° and 30°.

12. The method of claim 7 , wherein:
determining the number of plies in each of the zones includes limiting the number of plies to a discrete value by performing discrete ply thickness integer optimization.

13. The method of claim 12 , wherein determining the number of plies in each of the zones includes filtering the results of the discrete ply thickness integer optimization based on an allowed deviation of effective laminate properties from the desired set of in-plane laminate properties.

14. A method of making a composite laminate stiffener having a major axis of loading, and contoured both longitudinally and transversely, comprising:
laying up a substantially flat stack of fiber plies each having a unidirectional fiber orientation, wherein the substantially flat stack of fiber plies is devoid of 0° plies, wherein at least some of the plies provide the stiffener with primary axial stiffness along the major axis of loading, including orienting the plies providing the primary axial stiffness at off-angles relative to the major axis of loading;
forming the stack to desired transverse and longitudinal contours, wherein during the forming the fibers in plies providing the stiffener with primary axial stiffness transition along their lengths from a compression state, to a neutral state, and from the neutral state to a tensile state; and
wherein during the forming, strain on the plies providing the primary axial stiffness is reduced by their off-angle orientation.

15. The method of claim 14 , wherein the off-angle orientations of the plies providing the primary axial stiffness reduces the length to which the fibers of the plies are compressed and causes a portion of the compression is converted to shear deformation.

16. The method of claim 14 , wherein the composite laminate stiffener is a stringer having a hat shape in cross-section, including a cap, a pair of webs and a pair of flanges, and wherein during forming:
the fibers in the plies at the cap are in the compression state,

the fibers in the plies in the webs are in the neutral state, and
the fibers in the flanges are in the tensile state.

17. The method of claim 14 , wherein fibers in the plies providing the primary axial stiffness are shorter in length than the length of the composite laminate stiffener whereby transverse slip between the plies occurs during forming which reduces compression of the fibers.

18. The method of claim 14 , wherein orienting the plies providing the primary axial stiffness at off-angles reduces the compression loading on the fibers in the plies during the forming.

19. The method of claim 14 , wherein composite laminate stiffener is an existing stiffener design, and the method further comprises:
determining continuous ply thickness values for various ply angle combinations that match the stiffness and thickness of the existing stiffener design;
performing discrete ply thickness integer optimization, including calculating a number of plies with discrete ply thicknesses;
filtering the results of the ply thickness integer optimization, wherein a laminate design is selected that best reduces wrinkles during the forming; and
generating layup information, including determining ply shapes and the stacking sequence conforming to a desired set of stacking sequence and manufacturability rules.

20. The method of claim 14 , wherein the composite laminate stiffener includes a plurality of zones along its length respectively having differing stiffness requirements, and the method further comprises:
selecting orientations of the plies and a number of plies per orientation for each of the zones; and
then, after selecting the orientations and the number of plies per orientation, selecting shapes of the plies in each of the zones.

21. A method of forming a composite laminate stiffener having a primary axis of loading, comprising:
laying up a flat composite laminate stack of plies of reinforcing fibers, wherein the flat composite laminate stack of plies of reinforcing fibers are devoid of 0° plies;
forming the composite laminate stack such that the f

Assignees

• Boeing Co

Inventors

• Blom-Schieber Adriana Willempje

Classifications

• B29L2031/001

  Profiled members, e.g. beams, sections · CPC title

• B29C70/34

  and shaping or impregnating by compression {, i.e. combined with compressing after the lay-up operation} · CPC title

• G06F2113/26

  Composites · CPC title

• G06F2113/24

  Sheet material · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title