I was thinking about trying some sewing for headphone covers and a strap. I can easily disassemble the existing materials and reverse engineer them. I would rather try to learn parametric iterative design of textiles and alter the fit of the pads based on a pattern. Anyone have any experience with this application?
It sounds like you are looking for more of a pattern designing tool. There are open source projects that might be more suited to this than freeCAD. Try searching online for “open source textile pattern software”
I can’t vouch for this program/project as I am not involved nor have I used it; but Velentina sounds like it is capable of doing what you mentioned.
The sketchers in freeCAD can be used to draw and constrain the patterns, and then print them to scale and cut them out to see how it works.
(Note I have not tried to print to scale from freeCAD specifically but I would imagine it is more then capable of doing so assuming your sketches are smaller then the paper you are printing on)
Of course freeCAD can be used to do the physical modeling but I am unaware of any tools that would specifically assist you for textile pattern designs. The closest tool that I am aware of is the sheet metal workbench.
Hopefully this was helpful.
Someone else might be able to suggest a freeCAD specific solution but this might help get you started.