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# Composite with inclusion (stitch): analytical model?

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## Composite with inclusion (stitch): analytical model?

(OP)
Hello there,

I am currently developing a numerical model to simulate the behaviour of carbon/epoxy composite plates containing stitches (with thin metallic wires). I am looking for an analytical solution allowing me to validate my model. The case is simple: a square composite plate (the square shape is in the x-y plane) containing an insertion in z-direction (through-thickness). The z-inclusion represents one stitch. The plate is forced to elongate of 1% of its length in the x direction. I would like to calculate (analytically) the stress or strain distribution along the through-the-thickness inclusion. I am very familiar with composite materials equations, but I am fairly new with inclusion theories such Timoshenko's or Eshelby's. Could anyone help me to orient my search to find a suitable analytical model?

### RE: Composite with inclusion (stitch): analytical model?

Are you referring to pins or stitching where the wire loops? A lot of work has been done on Z-pinning using carbon fiber pins to arrest delamination failures. Stitching with kevlar and other threads has also been looked at. Stitching causes a rather significant reduction in compression strength. From what I can recall the undamaged compression strength is about 80% of unstitched material. However, the compression strength after impact damage is higher with stitching. These have been interesting ideas but I don't know of any real life applications.
Sorry, I can't help you with any analysis theories.

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