Symbol	Description
$d_1$	inner fiber diameter
$d_2$	outer fiber diameter
$P_1$	pressure inside the fiber
$P_2$	pressure outside the fiber
$\delta$	selective layer thickness
${\sigma }_r$	radial stress
${\sigma }_{\theta }$	circumferential stress
$r$	cylinder radius
$u$	displacement vector
$C$	integration constant
$\epsilon$	relative elongation (strain)
$\sigma$	stress
$E$	Young’s modulus
$\mu$	Poisson’s ratio
${\epsilon }_r$	radial strain
${\epsilon }_{\theta }$	circumferential strain
$\tilde{\rho }$	the density of the porous material
${\rho }_s$	density of dense matter
$L$	cell size
$t$	the thickness of the cell’s edges
$\tilde{E}$	Young’s modulus of porous material
$E_s$	Young’s modulus of dense matter