Because the optical fiber and mattress membrane are very thin,
the lateral (shearing and bending) stiffnesses of the fiber and mattress cover are negligible.
Since the mattress cover is easy to wrinkle,
the in-plane stiffness of the cover may also be ignored.
This assumption makes it possible to perform only one FEA
for a given body pressure distribution
during the whole optimization process
since a change in placement of the fiber optic cable will not change the deformed shape of the mattress surface.
This makes using a global searching GA possible.