Deformation and energy dissipation mechanisms of needle-punched nonwoven fabrics: A multiscale experimental analysis

Abstract

The deformation and energy dissipation processes in a needle-punched polyethylene nonwoven fabric were characterized in detail by a combination of experimental techniques (macroscopic mechanical tests, single fiber and multi fiber pull-out tests, optical microscopy, X-ray computed tomography and wide angle X-ray diffraction) that provided information of the dominant mechanisms at different length scales. The macroscopic mechanical tests showed that the nonwoven fabric presented an outstanding strength and energy absorption capacity. The mechanical behavior was highly anisotropic although the initial fiber and knot distribution was isotropic. The load was transferred to the fabric through a set of fibers linked to the entanglement points, which formed an active skeleton. The fraction of fibers in the skeleton depended on the orientation and it was controlled by the features of the entanglement points. Most of the strength and energy dissipation was provided by the progressive extraction of the fibers in the skeleton from the entanglement points and final fracture occurred by the total disentanglement of the fiber network in a given section at which the macroscopic deformation was localized. These findings provide the fundamental observations to develop microstructure-based continuum models for the mechanical behavior of needle-punched nonwoven fabrics.