Strength of fibres in low-density thermally bonded nonwovens: An experimental investigation

Journal of Composite Materials

Pourdeyhimi

et al. 2020

Calendered nonwovens, formed by polymeric fibres, are three-phase heterogeneous materials, comprising a fibrous matrix, bond-areas and interface regions. As a result, two main factors of anisotropy can be identified. The first one is ascribable to a random fibrous microstructure, with the second one related to orientation of a bond pattern. This paper focuses on the first type of anisotropy in thin and thick nonwovens under uniaxial tensile loading. Individual and combined effects of anisotropy and strain rate were studied by conducting uniaxial tensile tests in various loading directions (0°, 30°, 45°, 60° and 90° with regard to the main fabric’s direction) and strain rate (0.01, 0.1 and 0.5 s−1). Fabrics exhibited an initial linear elastic response, followed by nonlinear strain hardening up to necking and final softening. The studied allowed assessment of the extent the effects of loading direction (anisotropy), planar density and strain rate on the mechanical response of the calendered fabrics. The evidence supported the conclusion that anisotropy is the most crucial factor, also delineating the balance between the fabric’s load-bearing capacity and extension level along various directions. The strain rate produced a marked effect on the fibre’s response, with increased stress at higher strain rate while this effect in the fabric was small. The results demonstrated the differences of the mechanical behaviour of fabrics from that of their constituent fibres.

Section: Mechanical Behaviour Of Fibressupporting

confidence: 76%

Anisotropic mechanical behaviour of calendered nonwoven fabrics: Strain-rate dependency

Cucumazzo

Journal of Composite Materials

Pourdeyhimi

et al. 2020

“…The constituent fibres are made of polymer materials with nonlinear elastic-plastic and viscous properties. A single-fibre failure criterion based on experimental data [13,17] was used to simulate damage initiation and propagation in nonwovens. The developed model captured the random, anisotropic nature of the fabric, based on explicit introduction of fibres, reproduced its main deformation and damage mechanisms observed experimentally.…”

Section: Finite-element Modelmentioning

confidence: 99%

Mechanical behaviour of nonwovens: Analysis of effect of manufacturing parameters with parametric computational model

Farukh

Computational Materials Science

Sabuncuoğlu

et al. 2014

Self Cite

Abstract:A deformation behaviour of, and damage in, polymer-based thermally bonded nonwovens was studied with a parametric finite-element model. Microstructure of the studied nonwoven was modelled by direct introduction of fibres and bond points, employing a subroutine-based parametric technique. This technique helped to implement variations in dimensional characteristics of structural entities related with manufacturing of these materials. Following experimental observations, a realistic orientation distribution of fibres and single-fibre failure criteria were included into the model. The developed model was demonstrated to be a very useful tool not only for predicting effects of parameters related to manufacturing of nonwovens or of specimen size on a macroscopic response of the nonwoven but also for getting an insight into deformation mechanisms and damage localization in its structure.

“…It was also revealed [16][17][18][19] that fibres even made of the same material demonstrate distinct deformation and failure behaviours before and after their manufacturing process. Thus, individual fibres were extracted from the fabric and tested to assess their material properties.…”

Section: Single Fibre Testsmentioning

confidence: 98%

Damage mechanisms of random fibrous networks

Sozumert

Farukh

et al. 2015

J. Phys.: Conf. Ser.

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