Meso-scale deformation and damage in thermally bonded nonwovens

Abstract

Abstract:Thermal bonding is the fastest and cheapest technique for manufacturing nonwovens. Understanding mechanical behaviour of these materials, especially related to damage, can aid in design of products containing nonwoven parts. A finite-element model incorporating mechanical properties related to damage such as maximum stress and strain at failure of fabric's fibres would be a powerful design and optimization tool. In this study, polypropylene-based thermally bonded nonwovens manufactured at optimal processing conditions were used as a model system. A damage behaviour of the nonwoven fabric is governed by its single-fibre properties, which are obtained by conducting tensile tests over a wide range of strain rates. The fibres for the tests were extracted from the nonwoven fabric in a way that a single bond point was attached at both ends of each fibre. Additionally, similar tests were performed on unprocessed fibres, which form the nonwoven. Those experiments not only provided insight into damage mechanisms of fibres in thermally bonded nonwovens but also demonstrated a significant drop in magnitudes of failure stress and respective strain in fibres due to the bonding process. A novel technique was introduced in this study to develop damage criteria based on the deformation and fracture behaviour of a single fibre in a thermally bonded nonwoven fabric. The damage behaviour of a fibrous network within the thermally bonded fabric was simulated with a finite-element model consisting of a number of fibres attached to two neighbouring bond points. Additionally, various arrangements of fibres' orientation and material properties were implemented in the model to analyse the respective effects.

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

“…Before starting the modelling process, input parameters required for modelling of nonwovens, such as physical and mechanical properties of fibres, their orientation distribution, size, shape and pattern of bond points are determined by experimental characterisation of the material. The details of determination of these material properties are given in [13]. The process of development of the model starts with introduction of bond points; they are modelled according to their required shape, size and pattern.…”

“…The complete details of the process of development of nonwoven network are given elsewhere [13,14]. Following the morphological analysis of the fabric, the nonwoven model consists of two regions: bond points and fibrous matrix (Fig.…”

“…Mechanical and geometrical properties of the fibres and bond points obtained previously [13] were implemented in the developed model. The constituent fibres are made of polymer materials with nonlinear elastic-plastic and viscous properties.…”

“…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.…”

“…The first part of this paper describes the suggested parametric technique used for development of a finiteelement model. The statistical parameters that define the microstructure as well as mechanical properties such as single-fibre behaviour and failure criteria, investigated experimentally [13], were used for the development of a s. Mechanical performance of nonwovens was simulated using the developed models and validated with experimental data. Finally, conclusions based on the obtained results and applicability of the model to design nonwoven for specific application requirements are discussed.…”