Numerical analysis of progressive damage in nonwoven fibrous networks under tension

Understanding a mechanical behaviour of polymer-based nonwoven materials that include large-strain deformation and damage can help to evaluate a response of nonwoven fibrous networks to various loading conditions. Here, a nonwoven felt made by thermal bonding of polypropylene fibres was used as a model system. Its deformation and damage behaviour was analysed by means of experimental assessment of damage evolution based on single-fibre failure and finite-element simulations. Tensile tests of nonwoven fabrics were carried out to characterise their damage behaviour under in-plane mechanical loading. It was found that progressive failure of fibres led to localization of damage initiation and propagation, ultimately resulting in failure of the nonwoven felt. To obtain the criteria that control the onset and propagation of damage in these materials, tensile tests on single fibres, extracted from the felt with bond points attached to their ends, were performed. A finite-element model was developed to study damage initiation and propagation in nonwovens. In the model, structural randomness of a nonwoven fibrous network was implemented by means of direct introduction of fibres according to the orientation distribution function. The evolution of damage in the network was controlled by a single-fibre failure criterion obtained experimentally. The proposed numerical model not only captured the macroscopic response of the felt successfully but also reproduced the underlying mechanisms involved in deformation and damage of nonwovens.