On the importance of fiber curvature to the elastic moduli of electrospun nonwoven fiber meshes

Abstract

Adequate mechanical integrity of nonwoven fabrics is generally a prerequisite for their practical usage. Nonwoven fiber mats of poly(trimethyl hexamethylene terephthalamide) (PA 6(3)T) with average fiber diameters from 0.1 to 3.6 microns were electrospun from solutions in dimethylformamide and formic acid and their in-plane mechanical response characterized. Two quantitative microstructure-based models that relate the Young’s moduli of these fabrics to those of the fibers are considered, one assuming straight fibers and the other allowing for curved fibers. It is found that the model allowing for curved fibers provides a quantitative relationship between the Young’s moduli of the mats and those of the fibers themselves. The governing factors that affect the mechanical properties of nonwoven mats are the porosity of the mats, the intrinsic fiber modulus, and the average fiber diameter, curvature (or “curl”) and distance between fiber-to-fiber junctions. Especially for submicron diameter fibers, both the intrinsic fiber properties and fiber curvature make important contributions to the mechanical behavior of their nonwoven fabrics.