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In service, hydraulic flow is usually perpendicular to the plane of electrospun fiber mats for water filtration, inducing an out-of-plane deformation. In this paper, we have investigated the out-of-plane deformation response of wet electrospun polyacrylonitrile fiber mats with distinct average constituent fiber diameters of 232 ± 36 nm, 727 ± 148 nm and 1017 ± 80 nm, but with nominally similar thicknesses and areal densities using the classical bulge testing technique. The resultant pressure-deflection relationships are incompatible with constitutive models for out-of-plane deformation of continuum materials. Rather, the fiber mats exhibited a one-half dependence ( p ∼ h 1 2 ) governed by fiber deflection, and pressure asymptote indicative of steady-state fluid percolation, but influenced by the mats areal densities. In addition, the apparent bending rigidity increased with increasing fiber diameter. In the range tested for fiber mats with average fiber size of 232 nm, increase in mat thickness did not noticeably alter measured rigidities, although evidence of slight increase in pressure asymptote is observed. Cyclic flow rate tests provided evidence of good recoverability as well as minimal topological modifications. |
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