@article{sozumert_farukh_sabuncuoglu_demirci_acar_pourdeyhimi_silberschmidt_2018, title={Deformation and damage of random fibrous networks}, volume={184}, ISSN={0020-7683}, url={http://dx.doi.org/10.1016/J.IJSOLSTR.2018.12.012}, DOI={10.1016/j.ijsolstr.2018.12.012}, abstractNote={Fibrous networks are encountered in various natural and synthetic materials. Typically, they have random microstructures with complex patterns of fibre distribution. This microstructure, together with significant (in many cases) stretchability of such networks, results in a non-trivial load-transfer mechanism, different from that of continuous media. The aim of this study is to investigate evolution of local deformation, damage and fracture processes in fibrous networks. In order to do this, together with extensive experiments, discontinuous finite-element (FE) models with direct incorporation of microstructural features were developed using a parametric approach for specimens with various dimensions and different types of notches. These models, mimicking a microstructure of the selected fibrous network, were loaded by stretching along a principal direction. Discontinuous FE models provided data not only on a global response of the specimens but also on levels of stresses and strains in each fibre, forming the network. An effect of a notch shape on evolution of fibre strains as well as mechanisms and patterns of damage was investigated using experimental data and simulation results, assessing also toughness of specimens. Strain distribution over selected paths were tracked in notched specimens to quantify strain distributions in the vicinity of notch tips. The growth and patterns of local damage due to axial stretching obtained in advanced numerical simulations with the developed FE models demonstrated a good agreement with experimental observations.}, journal={International Journal of Solids and Structures}, publisher={Elsevier BV}, author={Sozumert, Emrah and Farukh, Farukh and Sabuncuoglu, Baris and Demirci, Emrah and Acar, Memis and Pourdeyhimi, Behnam and Silberschmidt, Vadim V.}, year={2018}, month={Dec}, pages={233–247} }
 @article{sozumert_farukh_sabuncuoglu_demirci_acar_pourdeyhimi_silberschmidt_2017, title={Notches in fibrous materials: micro-mechanisms of deformation and damage}, volume={6}, ISSN={["2452-3216"]}, DOI={10.1016/j.prostr.2017.11.026}, abstractNote={Fibrous networks are ubiquitous structures for many natural materials, such as bones and bacterial cellulose, and artificial ones (e.g. polymer-based nonwovens). Mechanical behaviour of these networks are of interest to researchers since it deviates significantly from that of traditional materials treated usually within the framework of continuum mechanics. The main reason for this difference is a discontinuous character of networks with randomly distributed fibres (that can be also curved) resulting in complex scenarios of fibre-to-fibre interactions in the process of their deformation. This also affects a character of load transfer, characterised by spatial non-uniformity and localisation. A discontinuous nature of fibrous networks results in their non-trivial failure character and, more specifically, evolution of failure caused by notches. In order to investigate these mechanisms, various notches are introduced both into real-life specimens used in experimentation and discontinuous finite-element (FE) models specially developed (Farukh et al., 2014a; Hou et al., 2009, 2011a; Sabuncuoglu et al, 2013) to mimic the microstructure of fibrous networks. The specimens were tested under tensile loading in one of the principal directions, with FE-based simulations emulating this regime. The effect of notch shape on damage mechanisms, effective material toughness and damage patterns was investigated using the obtained experimental and numerical methods. The developed discontinuous model with direct introduction of microstructural features of fibrous networks allowed assessment of strain distribution over selected paths in them in order to obtain strain profiles in the vicinity of notch tips. Additionally, evolution of damage calculated in advanced numerical simulations demonstrated a good agreement with images from experiments.}, journal={XXVII INTERNATIONAL CONFERENCE: MATHEMATICAL AND COMPUTER SIMULATION IN MECHANICS OF SOLIDS AND STRUCTURES - FUNDAMENTALS OF STATIC AND DYNAMIC FRACTURE (MCM 2017)}, author={Sozumert, Emrah and Farukh, Farukh and Sabuncuoglu, Baris and Demirci, Emrah and Acar, Memis and Pourdeyhimi, Behnam and Silberschmidt, Vadim V.}, year={2017}, pages={168–173} }
 @article{sozumert_farukh_demirci_acar_pourdeyhimi_silberschmidt_2015, title={Damage mechanisms of random fibrous networks}, volume={628}, ISSN={["1742-6596"]}, DOI={10.1088/1742-6596/628/1/012093}, abstractNote={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 behaviourof 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 fibresobtained 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.}, journal={11TH INTERNATIONAL CONFERENCE ON DAMAGE ASSESSMENT OF STRUCTURES (DAMAS 2015)}, author={Sozumert, E. and Farukh, F. and Demirci, E. and Acar, M. and Pourdeyhimi, B. and Silberschmidt, V. V.}, year={2015} }
 @article{farukh_demirci_sabuncuoglu_acar_pourdeyhimi_silberschmidt_2013, title={Characterisation and numerical modelling of complex deformation behaviour in thermally bonded nonwovens}, volume={71}, ISSN={["1879-0801"]}, DOI={10.1016/j.commatsci.2013.01.007}, abstractNote={A complex time-dependent deformation and damage behaviour in polymer-based nonwovens are analysed under conditions of multi-stage uniaxial loading. Elastic–plastic and viscous properties of a polypropylene-based fabric are obtained by series of tensile, creep and relaxation tests performed on single fibres extracted from the studied fabric. These properties are implemented in a finite-element (FE) model of nonwoven with direct introduction of fibres according to their actual orientation distribution in order to simulate the rate-dependent deformation up to the onset of damage in thermally bonded nonwovens. The predictions of FE simulations are compared with the experimental data of multi-stage deformation tensile tests and a good agreement is obtained including the mechanisms of deformation. Due to direct modelling of fibres based on their actual orientation distribution and implementation of viscous properties, the model could be extended to other types of polymer-based random fibrous networks.}, journal={COMPUTATIONAL MATERIALS SCIENCE}, author={Farukh, Farukh and Demirci, Emrah and Sabuncuoglu, Baris and Acar, Memis and Pourdeyhimi, Behnam and Silberschmidt, Vadim V.}, year={2013}, month={Apr}, pages={165–171} }