System and method for determining the direction and spacing of fiber paths for a composite ply

Patent metadata

Field	Value
Publication number	US-10670394-B2
Application number	US-201715634837-A
Country	US
Kind code	B2
Filing date	Jun 27, 2017
Priority date	Jun 27, 2017
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

A method of determining fibers paths for a composite ply includes generating a triangulated surface of the composite ply, and defining a first unit vector field establishing a 0-degree direction for the triangulated surface. A second unit vector field is defined by rotating, through specified fiber angles measured relative to the 0-degree direction, the first unit vector field about surface normals of the triangulated surface. A third unit vector field representing a gradient direction of a potential function is defined by rotating the second unit vector field over 90° about the respective surface normals. The third unit vector field is scaled to create a non-unit vector field, and a first potential function is determined by performing a least-squares fit such that the direction and magnitude of the gradient best approximate the direction and the magnitude of the non-unit vector field. A normalization of the potential function uniformly distributes contour lines of the potential function across the triangulated surface. The contour lines are used as fiber paths for laying up courses of composite material to fabricate the composite ply.

First claim

What is claimed is:

1. A method of determining a direction and spacing of fiber paths for a composite ply of a composite layup given a surface definition and a fiber angle definition having one or more fiber angles, comprising the steps of:
generating an approximation of the surface, the approximation comprising a triangulated surface including a mesh of triangles, the composite ply having at least one of the following characteristics: the surface definition has a non-planar contour, the fiber angle definition comprises non-constant fiber angles;
defining on the triangulated surface a first unit vector field establishing a 0-degree direction for each one of the triangles, the 0-degree direction being the direction from which the one or more fiber angles are measured;
defining on the triangulated surface a second unit vector field by rotating, through the one or more fiber angles specified in the fiber angle definition, the first unit vector field about surface normals respectively corresponding to the triangles;
defining on the triangulated surface a third unit vector field comprising vectors each having a length of one and representing a direction of a gradient of a first potential function to be determined, the third unit vector field being defined on the triangulated surface by rotating the second unit vector field 90° about the respective surface normals in preparation for determining the first potential function, the direction of the gradient being perpendicular to the direction of the fiber paths to be defined as a result of determining the first potential function;
determining a magnitude function to scale the third unit vector field over the triangulated surface to create a non-unit vector field that enables solving for the first potential function in a manner accounting for an interdependence of direction and magnitude of the gradient, wherein determining the magnitude function comprises determining, for each vector in the third unit vector field, a length that represents a relative spacing of the fiber paths, and searching all non-zero lengths of the vectors of the non-unit vector field and selecting the vectors of non-zero length that make a curl of the non-unit vector field as small as possible, wherein the selected vectors of non-zero length correspond to the magnitude function;
determining the first potential function by performing a least-squares fit of the direction and magnitude of the gradient of the first potential function to the direction and magnitude of the non-unit vector field, the first potential function having contour lines that comprise epuipotential lines which are aligned with the second unit vector field;
performing a normalization of the first potential function by applying a scaling function to the first potential function such that the contour lines are uniformly distributed across the triangulated surface; and
using the contour lines of the normalized potential function as fiber paths for laying up courses of composite material along the fiber paths to fabricate the composite ply.

2. The method of claim 1 , further including the step of:
determining a second potential function that improves alignment of the contour lines with the second unit vector field by minimizing deviation between the direction of the non-unit vector field and the gradient direction of the first potential function, while also adjusting the magnitude function scaling the third unit vector field.

3. The method of claim 1 , further including the step of:
determining a third potential function that improves alignment of the contour lines with the second unit vector field by minimizing only deviation between the direction of the third unit vector field and the gradient direction of the first potential function.

4. The method of claim 1 , wherein, in the step of defining the second unit vector field on the triangulated surface:
the fiber angle definition comprises constant ply angles.

5. The method of claim 1 , further including:
smoothing the first potential function by minimizing variation in the magnitude of the gradient of the first potential function.

6. The method of claim 1 , wherein the contour lines are disconnected across the triangulated surface and, after determining the first potential function, the method further includes:
partitioning the surface approximation into regions along contour lines of the first potential function such that all contour lines within each region are connected.

7. The method of claim 1 , wherein the step of performing a normalization of the first potential function comprises:
applying a scaling function to the first potential function to adjust values of the first potential function such that an inverse of the magnitude of the gradient along each contour line is on average equivalent to a head width of an automated fiber placement machine.

8. The method of claim 1 , wherein the step of performing a normalization of the first potential function comprises:
applying a scaling function to the first potential function to adjust values of the first potential function such that an inverse of the minimum magnitude of the gradient along each contour line is not greater than a head width of an automated fiber placement machine to avoid gaps between adjacent courses.

9. The method of claim 1 , wherein the contour lines of the normalized potential function have a spacing, the method further including the step of:
adjusting a width of one or more of the courses to be less than the spacing between the contour lines to avoid overlapping of adjacent courses.

10. A method of determining a direction and spacing of fiber paths for a composite ply of a composite layup given a surface definition and a fiber angle definition having one or more fiber angles, comprising the steps of:
generating an approximation of the surface, the approximation comprising a triangulated surface including a mesh of triangles, the composite ply having at least one of the following characteristics: the surface definition has a non-planar contour, the fiber angle definition comprises non-constant fiber angles;
defining on the triangulated surface a first unit vector field establishing a 0-degree direction for each one of the triangles, the 0-degree direction being the direction from which the one or more fiber angles are measured;
defining on the triangulated surface a second unit vector field by rotating, through the one or more fiber angles specified in the fiber angle definition, the first unit vector field about surface normals respectively corresponding to the triangles;
defining on the triangulated surface a third unit vector field comprising vectors each having a length of one and representing a direction of a gradient of a first potential function to be determined, the third unit vector field being defined on the triangulated surface by rotating the second unit vector field 90° about the respective surface normals in preparation for determining the first potential function, the direction of the gradient being perpendicular to the direction of the fiber paths to be defined as a result of determining the first potential function;
determining a magnitude function to scale the third unit vector field over the triangulated surface to create a non-unit vector field that enables solving for the first potential function in a manner accounting for an interdependence of direction and magnitude of the gradient, wherein determining the magnitude function comprises determining, for each vector in the third unit vector field, a length that represents a relative spacing of the fiber paths, and searching all non-zero lengths of the vectors of the non-unit vector field and selecting the vectors of non-zero length t

Assignees

• Boeing Co

Inventors

• Winfree Troy
• Blom-Schieber Adriana Willempje

Classifications

• B29C70/382

  Automated fiber placement [AFP] · CPC title

• G06F30/20 Primary

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

• B29C70/54

  Component parts, details or accessories; Auxiliary operations {, e.g. feeding or storage of prepregs or SMC after impregnation or during ageing} · CPC title

• G01N33/367 Primary

  Fabric or woven textiles · CPC title

• B29K2105/0881

  unidirectional · CPC title