FreeCAD Composite Workbench

This is a workbench for FreeCAD to support design and structural analysis of thin composite laminate structures.

This is very much a work in progress. A lot is subject to change or refactoring. Lots of code needs unit testing and handling input errors.

This requires a modified version of FreeCAD, mainly to support FEM analysis. https://github.com/jwharington/FreeCAD/tree/fem-orthotropic

Composite material composition

FibreCompositeLamina

• Element for fibre composite
• Classical theory for fibre reinforced material properties
• Various material fabrics (uni, bidirectional etc)

HomogeneousLamina

• Element for homogeneous (one part) core material
• May be orthotropic or isotropic

Laminate

• Element for homogeneous (single part) layered composites
• Classical Laminate Theory merging of laminates
• Symmetric (odd, even) and non-symmetric layups

CompositeLaminate

• Elements for fibre reinforced composites

Composite structure

CompositeShell

• Construction of shells in laminate materials
• LCS varies across the laminate shell by draping material
• Visualisation of fibre orientation across the part
• Visualisation of fabric draping strains across the part

Seam

• Tool for creating seam/overlap/transition regions

Stiffener

• Tool for constructing stiffeners with custom profiles

Fibre orientation

AlignFibreLCS

• Tool for aligning zero fibres

TransferLCS

• Tool for managing fibre orientations across cut lines like seams

WrapLCS

• Tool for managing fibre orientations around edges with matching fibre orientation

Manufacturing

TexturePlan

• Construction of aligned texture plans for layup

PartPlane

• Some preliminary work on constructing part lines/planes

Mould

• Some preliminary work on constructing moulds

Works in progress

Dart

• Tool for cutting darts and creating seam/overlap/transition regions

Analysis tools:

• Analysis tools such as average fibre length, % of plies in each orientation

Finite element analysis:

• Local coordinate system with orthotropic materials in FreeCAD FEM solver
• Composite material support in FreeCAD FEM using Calculix solver
• Computation of FEM stress exposure factor calculations including stress/strain/Tsai-hill

TODO, notes

• Refactoring to allow use of lower-level code without FeaturePython objects/gui
• Design rules
• Hybrid (2 fibre material) fabrics
• Failure modes implement as plug in to FEM
• CompositeShell should have code sensitive to whether laminate is Fibre
• Seam detection and splitting when unwrap fails or high strain
  • Mesh_PolyCut
• Scale expand drape if positive linear strain .scale
• TexturePlan
  • add easement
  • add overlaps at darts?

Terminology:

• splice
• butt joint
• joint

https://compositematerialshub.com/bonded-joints/

use CreateLabels.py from FEM for displaying layers?

Testing with real FreeCAD

Most tests under freecad/Composites/compositestests use mocks and can run without a FreeCAD runtime. For integration testing inside a real FreeCAD process, run:

~/opt/FreeCAD-build/bin/FreeCADCmd -P /home/jmw/opt/FreeCAD-CompositesWB \
  freecad/Composites/compositestests/run_freecad_integration_tests.py

This runs test_integration_freecad.py and exits non-zero if a test fails.