Damage mechanisms of random fibrous networks

Abstract

Abstract. Fibrous networks are ubiquitous: they can be found in various engineering applications as well as in biological tissues. Due to complexity of their random microstructure, anisotropic properties and large deformation, their modelling is challenging. Though, there are numerous studies in literature focusing either on numerical simulations of fibrous networks or explaining their damage mechanisms at micro or meso-scale, the respective models usually do not include actual random microstructure and failure mechanisms. The microstructure of fibrous networks, together with highly non-linear mechanical behaviour of their fibres, is a key to initiation of damage, its spatial localization and ultimate failure [1]. Numerical models available in literature are not capable of elucidating actual microstructure of the material and, hence, its influence on damage processes in fibrous networks. To emulate a real-life microstructure in a developed finite-element model, an orientation distribution function for fibres obtained from X-ray micro computed-tomography images was considered to provide actual alignment of fibres. To validate the suggested model, notched and unnotched rectangular specimens were experimentally tested. A good correlation between the experimental data and simulation results was observed. This study revealed a significant effect of a notch on damage evolution. IntroductionFibrous materials are commonly found around us . Despite their extensive use in many products including automotive, hygiene, health applications, understanding of their mechanical properties and performance is not simple due to complexity of their microstructure. This complexity stems from manufacturing processes, non-trivial mechanical behaviour of constituent fibres and their random distribution in the microstructure of the material.Although some of those networks are man-made, such as, cellulose, papers and most of nonwovens, some are natural. Some of these materials are composed of fibrous network layers as in elastomeric fibrous scaffolds used in engineered soft tissues [2][3]. A main source of constituent fibres is natural or synthetic polymers [3]. As a result, these fibres might show time-dependent and/or non-linear mechanical behaviour, i.e. elasto-plasticity or visco-plasticity [3].The first attempt to model microstructured nonwoven materials was made by Liao et al [4] with the model based on discontinous modelling approach. The model was composed of many discrete cell elements, each representing a number of fibres. The orientation distribution of fibres in real fabrics was partially reflected in the model. Also, fibre-to-fibre interactions (friction or contacts between fibres) in the model were not included, and a partial account of fibre orientation, the model did not reproduce the actual deformation mechanisms and

Effect of areal density and fiber orientation on the deformation of thermomechanical bonds in a nonwoven fabric

“…Many mechanical models have been proposed to describe the material behavior of the thermomechanically bonded nonwovens. In the models for nonwovens, the bonds are treated as rigid bodies or as composites whose properties are calculated from bicomponent virgin fiber properties . The rigid body assumption on the bonds leads to inaccurate predictions due to the significant strain experienced by the bonds .…”

Biaxial properties of individual bonds in thermomechanically bonded nonwoven fabrics

“…In order to gain insight into the deformation mechanisms, uniaxial tensile tests are commonly performed on coupons of nonwovens with dimensions of the order of centimeters. [8][9][10][11][12] The deformation of individual bonds within the specimens has been observed, but never quantified. Nanjundappa and Bhat 13 studied individual bonds within a nonwoven specimen, analyzing the effect of bonding temperature on the failure mechanism of individual bonds.…”