Creating a Producibility for Braiding

Click Producibility for Braiding and select a ply with 2 loops.
See Creating Plies for Braiding for more information.
Composites Braiding checks that the ply is tubular and has one start and one end contour.
If the ply is valid, its name is displayed in the dialog box.

Select a Propagation Type
By default, Braiding (Geometrical) is proposed.

Still in the Home tab, select the Braid Path i.e. the travel path of the braiding head.
It is usually the centerline of the components, and must be a single curve.

It must cover the entire surface, and even more to define a starting and finishing length. Either select an existing braid path. Its name is displayed in the dialog box. Or click Generate. The braid path is created as Centerline under a body named after the ply, after the Stacking node. The curve representing the braid path is smoothed to avoid sharp bumps that reduce the quality of the resulting braid. The name of the braid path is displayed in the dialog box. The default values of the Machining Parameters are updated. Select the Show Path check box at the bottom of the dialog box to display the braid head path as a pair of helices. You can thus check the consistency of the guide diameter and speed values. Anticlockwise and clockwise tows are displayed in different colors.

It is very important to avoid sharp corners on the guide path.

Specify an orientation curve that allows the rotation of the braiding tool relatively to the component.
Selecting an orientation curve adds a head angle in the speed table.
If you do not specify an orientation curve, the Z-Axis is taken as the starting position of the mandrel.
Optional: Select the Reverse direction check box.

Enter the values of the Machining Parameters.

Starting Length: Distance before the start of the ply, where the simulation starts. Its default value is 50 mm. Finishing Length: Distance after the end of the ply, where the simulation ends. Its default value is 50 mm. Guide Diameter: Internal diameter of the guide. Its default value is 1.5 times the Maximum Diameter. However, try to follow the practice of manufacturing and use a guide ring that is a close fit to the component. Using an overly large ring can cause convergence issues with the solution on parts with curvature. Carrier Rotation Speed: Rotation speed of the braiding machine. Mandrel Speed: Average speed of the mandrel. Either Enter a fixed value. Or click ... to specify variable mandrel speeds.

In the Edit Mandrel Speed dialog box

Editing the mandrel speed splits the braid axially into multiple segments, with a constant speed over each segment. You can edit the position between each segment, defining the theoretical contact position on the surface. Enter a Target Angle. By default it is the ply angle, usually 45°. Enter a Segment Spacing, i.e. the distance between two consecutive segments. Click Create to create the variable speeds. Based on a calculation of the braiding simulation that includes the effect of the lead of the carrier over the contact point, a nominal speed is calculated analytically. After a simulation is run, the average angle at each position is calculated and the difference to the Target Angle stored as an Angle Correction. They are displayed in the 3D viewer and in the dialog box. You can update the Angle Correction column with the results from the Results tab: The difference between the average simulated angle and the target angle is used to estimate the correction angle. Click Import to import them from a xml or a csv file. Click Clear to erase existing values. Right-click anywhere in the table to add or delete rows. Once the speeds are created, click Optimize Speed. Optimize Speed recomputes the speed by adding the Angle Correction to the Target Angle. Using this "reverse engineering" process, you can determine an optimized speed profile to achieve an angle profile. Checks are done to inform of possible problems and propose actions.

Go to the Material tab to update material parameters and click Estimate Thickness.

The complete braiding material consists of braid tows wound in a clockwise and anticlockwise directions around the mandrel, and optional axial tows. By default, the braid tow material is set to the material referenced by the ply, with the original width and thickness appended to the material label. The material parameters of tow width and thickness can be overridden to investigate the sensitivity of results to material parameters. The number of braiding tows, typically between 18 and 36, is half the number of carriers. If the Axial Tow Ratio is set to 1, the number of axial tows is equal to the number of clockwise tows and equal to the number of anti-clockwise tows. Braid Tow Material: Taken from the materials defined in the Composites Parameters. Num Braiding Tows: Number of braiding tows in each direction, defined by the braiding machine, and equal to half the carriers of the machine. By default, it is set to 18. Braiding Tow Width: Nominal cured width at the expected fiber volume fraction. By default, it is the width of the selected material, but it is editable. Braiding Tow Thickness: Nominal cured thickness at the expected fiber volume fraction. By default, it is the thickness of the selected material, but it is editable. Axial Tow Ratio: Ratio of axial tows/braid tows. Possible value are: 1 for tri-axial braid 0 for bi-axial braid (Axial Tow Material, Axial Tow Width, Axial Tow Thickness are disabled). Axial Tow Material: Taken from the materials defined in the Composites Parameters. Axial Tow Width: Nominal cured width at the expected fiber volume fraction. By default, it is the width of the selected material, but it is editable.  Axial Tow Thickness: Nominal cured thickness at the expected fiber volume fraction. By default, it is the thickness of the selected material, but it is editable. Fiber Volume Fraction: Fiber volume fraction to use to compute the thickness. Estimate Dimensions: Thickness information for cross-sections along the mandrel is computed (minimum, maximum and mean values). The computation is based on the target braid angle, tow dimension, number of tows and local perimeter of the mandrel. The range of perimeters is displayed, for an early indication of the suitability of the design for use as a mandrel in braiding.

In the Thickness Update tab, select the Thickness update check box to activate it.
It adjusts the height of the surface to take underlying braid layers into account
(using the thickness defined for the material, not the effective one).
This is a quick method. For a greater accuracy, use the mandrel generation tool.
It uses a thickness derived from braid simulations of the underlying layers.

Press the required icon to define the type of computation: Constant Thickness Core Sampling User or Automatic Constant Offset Select the elements to process: Full Stacking or Ply group only.

In the Advanced Parameters tab:

The braid calculation is done on a facetted mesh extracted from the geometry.
The Tessellation Sag and Step control the tessellation on which the simulation is run.
The Sag represents the maximum distance from the surface to an element, while the Step limits the maximum size of an element.
Fiber Interaction invokes algorithms to account for the interaction between fibers in an empirical way, stabilizing the simulation.
The Centerline Orientation options force the guide to follow the centerline, or to keep a constant alignment with the tangent at the midpoint.

Enter the required values:

Axial Step: Defines the maximum length of steps when exporting the piecewise linear mandrel path curve. Tessellation Sag: Distance between the mesh and the surface used to generate the tessellation used in the simulation and exported in the layup file. Tessellation Step: Maximum allowed length of an element used to generate the tessellation used in the simulation and exported in the layup file. Setting a smaller value gives a better approximation to the component shape, at the expense of slower simulation. Select the Fiber interactions check box to check the interactions between fibers at each crossing point, and reposition the fiber. However, it is more time consuming. Using this means that where fibers cross over other fibers, they are pulled towards the surface. Select the Pertub Helix check box to compute perturbation effects. The braiding simulation assumes the fibre between the guide ring and the mandrel is straight. However, the tow does not follow a straight line from guide ring to mandrel, but a curved (segmented) path due to the contact with the fibres going in the opposite direction. With a cylindrical mandrel, this curvature is the same at all points around the mandrel. With non-cylindrical mandrels the curvature varies, related in some way to the distance between the mandrel and the guide ring. A quick solution to the problem is to calculate the amount by which the tow angles need to be adjusted to account for the varying frictional affects when the mandrel is not cylindrical based on the variation in number of fibres crossed and use this to correct the fibre angles. A scaling factor is added to tune the magnitude of the effect as it depends on surface finish of the fibres, which is not accounted for in the calculations. If the check box is not selected or if the value is 0, perturbation effects are not calculated. A value of 1 uses the values as calculated. Select the Centerline orientation, i.e. how the brading machine is set up to work: Follow braid path tangent (default option). Use this option if there is a large curvature on the mandrel as a whole. Follow braid path midpoint: With this option, the mandrel is translated without being rotated. To be used when there are sharp direction changes in the component, causing the tow threads to overlap. However, the total change of direction of the centerline must remain small.

Click Preview.

then go to the Results tab to manage the results.
Results are updated dynamically when input variables are modified.

From the list, select the Result to check: Axial Deviation Clockwise Deviation Anticlockwise Deviation Clockwise Angle Anticlockwise Angle Coverage Separation Thickness Concavity Pertub Ratio allows to adjust the scaling factor to get the desired effect on large aspect ratio mandrels. Perimeter (Requires Ruled surface Display). No Result Define the Warning and Limit values. Warning defines the value for the yellow band. Limit defines the value for the red band. Select the elements where the results are displayed (multi-selection is allowed). Clockwise tow Anticlockwise tow Axial tow Surface Labels Ruled surface

Click Producibility Inspection.

Create points where you want to retrieve braided fiber results. Multi-selection is available. Click Apply. Braided fiber results are displayed in the Inspection Analysis dialog box. They can be considered as core samples for producibility results. For each point, you can retrieve the material, total thickness, expected and actual direction and the delta between them, as well as the local rosette. The results can be exported.

Select an additional action:

Export guide path: Data from the centreline and speed table are written to an XML file to drive braid machines Export to Layup: Writes out the standard layup file that can be used to transfer Composites definitions to other packages. It creates a balanced ply by writing 5 layers – ½ clockwise, ½ anti, axial, ½ anti, ½ clockwise. Fiber directions are taken from the simulated ones. Export results as a .csv file for locations along the guide path. The values are the average for a ring of points at each location along the guide path. Inspect Angles exports the variation in angle around the perimeter at a chosen location on the mandrel to allow comparison of simulation with experimental results. Select a point. It is projected onto the closest point on the centerline. A plane normal to the centerline is created at this point. A line is created at the intersection of the plane with the mandrel surface. 100 points are created on this line. Or a line. 100 equally spaced points are created on this line, then projected on the mandrel surface. A set of 100 closest points is created on the surface. Enter the storage path to export the result .csv file. It looks like this. Note: Point gives the position of 100 evenly spaced points around the perimeter. Coordinate Point Ratio CW Ratio ACW Clock-wise Anti-Clock-wise Perturbed Clock-wise Perturbed Anti-Clock-wise (376.843 19.910 -13.811) 1 0.779 0.779 -48.002 45.82 0 0 (376.843 19.518 -15.228) 2 0.853 0.853 -46.544 45.975 0 0 (376.843 18.864 -16.544) 3 0.855 0.855 -45.38 46.107 0 0

Enter a name of a geometrical set, and press Keep all visible fibers to do so.

The graphic lines used for the preview are stored as geometrical lines, in three sets: Braiding fibers Clockwise tow Braiding fibers Anticlockwise tow Braiding fibers Axial tow Each set contains the lines, one for each head.

When you are done, click OK to validate and exit the command.