# Problem: Estimating pressure of compressive garment

qwertypie
Basically, I'm working on a project to make active compression garments instead of passive. There are a few materials that can actuate with large recoverable strains, and I want to use them to create the compression. I need to estimate how much pressure they could create based on the recoverable strain they are capable of producing though. This would be either by constricting upon actuation or expanding upon actuation and the pressure being generated upon release of stimulus as the fibers try to return to normal, like with regular passive compression garments. I just need a rough estimate, or just the idea of how I would model this.

Mentor
Do you really think it's the radial growth and contraction of the fibers that causes the compression?

Are the fibers embedded in a matrix, or is it a fabric? Are the fibers single ply? What is the nature of the fabric weave>

qwertypie
Do you really think it's the radial growth and contraction of the fibers that causes the compression?

Are the fibers embedded in a matrix, or is it a fabric? Are the fibers single ply? What is the nature of the fabric weave>
It's using shape memory alloys. Just to have some numbers, an alloy called Nitinol can recover strains up to ~6% after a phase transition. Nasa developed a device for rock splitting that use modified nitinol expanding elements that were capable of generating stresses in excess of 1.5 GPa at only 2-3 percent corresponding strain. In the time waiting, I found an equation for hoop stress, equated the stress to the young's modulus of the material x the strain, and solved for pressure. But I imagine that's wildly inaccurate to the real situation, which would be a cross-hatched weave where the lateral fibers contain the SMA wires as a core and some cladding.

Mentor
You need to do biaxial stress-strain experiments on the woven fabric, or you need some sort of theoretical development to predict the biaxial stress-strain properties from the fiber geometry, the weave geometry, and the frictional characteristics of the fibers.