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J Llorca - One of the best experts on this subject based on the ideXlab platform.
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deformation and energy dissipation mechanisms of needle punched Nonwoven Fabrics a multiscale experimental analysis
International Journal of Solids and Structures, 2015Co-Authors: F Martinezhergueta, Alvaro Ridruejo, Carlos Gonzalez, J LlorcaAbstract:Abstract The deformation and energy dissipation processes in a needle-punched polyethylene Nonwoven fabric were characterized in detail by a combination of experimental techniques (macroscopic mechanical tests, single fiber and multi fiber pull-out tests, optical microscopy, X-ray computed tomography and wide angle X-ray diffraction) that provided information of the dominant mechanisms at different length scales. The macroscopic mechanical tests showed that the Nonwoven fabric presented an outstanding strength and energy absorption capacity. The mechanical behavior was highly anisotropic although the initial fiber and knot distribution was isotropic. The load was transferred to the fabric through a set of fibers linked to the entanglement points, which formed an active skeleton. The fraction of fibers in the skeleton depended on the orientation and it was controlled by the features of the entanglement points. Most of the strength and energy dissipation was provided by the progressive extraction of the fibers in the skeleton from the entanglement points and final fracture occurred by the total disentanglement of the fiber network in a given section at which the macroscopic deformation was localized. These findings provide the fundamental observations to develop microstructure-based continuum models for the mechanical behavior of needle-punched Nonwoven Fabrics.
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inverse notch sensitivity cracks can make Nonwoven Fabrics stronger
Journal of The Mechanics and Physics of Solids, 2015Co-Authors: Alvaro Ridruejo, Rafael Jubera, Carlos Gonzalez, J LlorcaAbstract:Abstract The strength of materials is always reduced in the presence of notches and cracks and this phenomenon – known as notch sensitivity – is critical in structural design. Good structural materials (ductile metals, elastomers) tend to be notch insensitive, which was considered to be the optimum behavior. Here, we report that inverse notch insensitivity (where the failure stress of the notched specimen is higher than that of the unnotched counterpart) can be achieved in polypropylene Nonwoven Fabrics. This behavior is only possible because of the peculiar microstructure of Nonwoven Fabrics, in which fracture of interfiber bonds provides a source of non-linear deformation and leads to a change in the network topology. The former facilitates crack tip blunting, spreading damage in the ligament, while the re-orientation of the fibers perpendicular to the notch plane strengthens the material and improves the maximum load bearing capability.
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a constitutive model for the in plane mechanical behavior of Nonwoven Fabrics
International Journal of Solids and Structures, 2012Co-Authors: Alvaro Ridruejo, Carlos Gonzalez, J LlorcaAbstract:Abstract A constitutive model is presented for the in-plane mechanical behavior of Nonwoven Fabrics. The model is developed within the context of the finite element method and provides the constitutive response for a mesodomain of the fabric corresponding to the area associated to a finite element. The model is built upon the ensemble of three blocks, namely fabric, fibers and damage. The continuum tensorial formulation of the fabric response rigorously takes into account the effect of fiber rotation for large strains and includes the nonlinear fiber behavior. In addition, the various damage mechanisms experimentally observed (bond and fiber fracture, interfiber friction and fiber pull-out) are included in a phenomenological way and the random nature of these materials is also taken into account by means of a Monte Carlo lottery to determine the damage thresholds. The model results are validated with recent experimental results on the tensile response of smooth and notched specimens of a polypropylene Nonwoven fabric.
Weidong Yu - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation on the thermal protective performance of Nonwoven Fabrics made of high-performance fibers
Journal of Thermal Analysis and Calorimetry, 2015Co-Authors: Zhenglin Xu, Wenbin Li, Weidong YuAbstract:In this study, the thermal protective performance of Nonwoven Fabrics made of Nomex (polyisophthaloyl metaphenylene diamine), PPS (polyphenylene sulfide), P84 (polyimide), and basalt fibers was investigated. The objective was to determine the influence of fiber type, thickness of fabric, and wet on the thermal protective performance of Nonwoven fabric. The thermal resistances of different Nonwoven Fabrics were measured using a dry hot plate instrument, the basalt Nonwoven Fabrics had a highest thermal resistance in all fabric, and the thermal resistance of Nonwoven fabric increased with the increase in thickness. The six Nonwoven Fabrics were exposed to a hot environment for a few minutes by using a self-designed apparatus. The test results showed that the Nonwoven Fabrics made with basalt fiber exhibited the best thermal protective performance, and the thermal protective abilities of Nonwoven Fabrics increased with fabric thickness. Interestingly, Nonwoven Fabrics with added water were found to be able to keep the fabric surface lower temperature compared to dry Fabrics when exposed to a hot environment, indicating the excellent thermal protective performance of wet Nonwoven Fabrics.
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Fractal calculation of air permeability of Nonwoven Fabrics
Journal of The Textile Institute, 2012Co-Authors: Wenfang Song, Weidong YuAbstract:A fractal permeability model for Nonwoven Fabrics is developed based on the fractal characteristics of pores within them. The fractal permeability is found to be related to pore area fractal dimension, tortuosity fractal dimension, size of fibers, the maximum and minimum pore sizes, fabric thickness, and the effective porosity of a medium. To verify the validity of the proposed model, experimental work was conducted on a set of Nonwoven Fabrics, and the predicted air permeability was compared with the experimental results. Good concordance was found between them. Meantime, the model was also compared with the existing models and is proved to be more accurate.
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evaluation of thermal protective performance of basalt fiber Nonwoven Fabrics
Journal of Thermal Analysis and Calorimetry, 2010Co-Authors: Weidong YuAbstract:Thermal insulation and fire protection have been a point of interest and discussion for several decades. Due to its excellent performances, basalt fiber has been widely used in the fields of thermal insulation and fire protection. The morphological structure and thermal stability of continuous basalt fiber were analysed using CH-2 projection microscope, scanning electron microscope (SEM) and thermogravimetry (TG). In order to evaluate the thermal radiation protective performance when exposed to fire environment, the spectral reflectances of Nonwoven Fabrics with different thicknesses were evaluated by ultraviolet-visible-near infrared (UV–Vis–NIR) spectrophotometer analysis. The jointly analysis of TG and UV–Vis–NIR spectrophotometer revealed that the basalt fiber exhibits good thermal stability, and the Nonwoven Fabrics present excellent thermal protective performance.
AM Cottenden - One of the best experts on this subject based on the ideXlab platform.
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a study of friction mechanisms between a surrogate skin lorica soft and Nonwoven Fabrics
Journal of The Mechanical Behavior of Biomedical Materials, 2013Co-Authors: David J Cottenden, AM CottendenAbstract:Hygiene products such as incontinence pads bring Nonwoven Fabrics into contact with users' skin, which can cause damage in various ways, including the Nonwoven abrading the skin by friction. The aim of the work described here was to develop and use methods for understanding the origin of friction between Nonwoven Fabrics and skin by relating measured normal and friction forces to the nature and area of the contact (fibre footprint) between them. The method development work reported here used a skin surrogate (Lorica Soft) in place of skin for reproducibility. The work was primarily experimental in nature, and involved two separate approaches. In the first, a microscope with a shallow depth of field was used to determine the length of Nonwoven fibre in contact with a facing surface as a function of pressure, from which the contact area could be inferred; and, in the second, friction between chosen Nonwoven Fabrics and Lorica Soft was measured at a variety of anatomically relevant pressures (0.25-32.1kPa) and speeds (0.05-5mms(-1)). Both techniques were extensively validated, and showed reproducibility of about 5% in length and force, respectively. Straightforward inspection of the data for Lorica Soft against the Nonwovens showed that Amontons' law (with respect to load) was obeyed to high precision (R(2)>0.999 in all cases), though there was the suggestion of sub-linearity at low loads. More detailed consideration of the friction traces suggested that two different friction mechanisms are important, and comparison with the contact data suggests tentatively that they may correspond to adhesion between two different populations of contacts, one "rough" and one "smooth". This additional insight is a good illustration of how these techniques may prove valuable in studying other, similar interfaces. In particular, they could be used to investigate interfaces between Nonwovens and skin, which was the primary motivation for developing them.
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A study of friction mechanisms between a surrogate skin (lorica soft) and Nonwoven Fabrics
Journal of the Mechanical Behavior of Biomedical Materials, 2013Co-Authors: AM CottendenAbstract:Hygiene products such as incontinence pads bring Nonwoven Fabrics into contact with users' skin, which can cause damage in various ways, including the Nonwoven abrading the skin by friction. The aim of the work described here was to develop and use methods for understanding the origin of friction between Nonwoven Fabrics and skin by relating measured normal and friction forces to the nature and area of the contact (fibre footprint) between them. The method development work reported here used a skin surrogate (Lorica Soft) in place of skin for reproducibility. The work was primarily experimental in nature, and involved two separate approaches. In the first, a microscope with a shallow depth of field was used to determine the length of Nonwoven fibre in contact with a facing surface as a function of pressure, from which the contact area could be inferred; and, in the second, friction between chosen Nonwoven Fabrics and Lorica Soft was measured at a variety of anatomically relevant pressures (0.25-32.1kPa) and speeds (0.05-5mms). Both techniques were extensively validated, and showed reproducibility of about 5% in length and force, respectively. Straightforward inspection of the data for Lorica Soft against the Nonwovens showed that Amontons' law (with respect to load) was obeyed to high precision ( > 0.999 in all cases), though there was the suggestion of sub-linearity at low loads. More detailed consideration of the friction traces suggested that two different friction mechanisms are important, and comparison with the contact data suggests tentatively that they may correspond to adhesion between two different populations of contacts, one "rough" and one "smooth". This additional insight is a good illustration of how these techniques may prove valuable in studying other, similar interfaces. In particular, they could be used to investigate interfaces between Nonwovens and skin, which was the primary motivation for developing them. © 2013 Elsevier Ltd.
Carlos Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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deformation and energy dissipation mechanisms of needle punched Nonwoven Fabrics a multiscale experimental analysis
International Journal of Solids and Structures, 2015Co-Authors: F Martinezhergueta, Alvaro Ridruejo, Carlos Gonzalez, J LlorcaAbstract:Abstract The deformation and energy dissipation processes in a needle-punched polyethylene Nonwoven fabric were characterized in detail by a combination of experimental techniques (macroscopic mechanical tests, single fiber and multi fiber pull-out tests, optical microscopy, X-ray computed tomography and wide angle X-ray diffraction) that provided information of the dominant mechanisms at different length scales. The macroscopic mechanical tests showed that the Nonwoven fabric presented an outstanding strength and energy absorption capacity. The mechanical behavior was highly anisotropic although the initial fiber and knot distribution was isotropic. The load was transferred to the fabric through a set of fibers linked to the entanglement points, which formed an active skeleton. The fraction of fibers in the skeleton depended on the orientation and it was controlled by the features of the entanglement points. Most of the strength and energy dissipation was provided by the progressive extraction of the fibers in the skeleton from the entanglement points and final fracture occurred by the total disentanglement of the fiber network in a given section at which the macroscopic deformation was localized. These findings provide the fundamental observations to develop microstructure-based continuum models for the mechanical behavior of needle-punched Nonwoven Fabrics.
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inverse notch sensitivity cracks can make Nonwoven Fabrics stronger
Journal of The Mechanics and Physics of Solids, 2015Co-Authors: Alvaro Ridruejo, Rafael Jubera, Carlos Gonzalez, J LlorcaAbstract:Abstract The strength of materials is always reduced in the presence of notches and cracks and this phenomenon – known as notch sensitivity – is critical in structural design. Good structural materials (ductile metals, elastomers) tend to be notch insensitive, which was considered to be the optimum behavior. Here, we report that inverse notch insensitivity (where the failure stress of the notched specimen is higher than that of the unnotched counterpart) can be achieved in polypropylene Nonwoven Fabrics. This behavior is only possible because of the peculiar microstructure of Nonwoven Fabrics, in which fracture of interfiber bonds provides a source of non-linear deformation and leads to a change in the network topology. The former facilitates crack tip blunting, spreading damage in the ligament, while the re-orientation of the fibers perpendicular to the notch plane strengthens the material and improves the maximum load bearing capability.
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a constitutive model for the in plane mechanical behavior of Nonwoven Fabrics
International Journal of Solids and Structures, 2012Co-Authors: Alvaro Ridruejo, Carlos Gonzalez, J LlorcaAbstract:Abstract A constitutive model is presented for the in-plane mechanical behavior of Nonwoven Fabrics. The model is developed within the context of the finite element method and provides the constitutive response for a mesodomain of the fabric corresponding to the area associated to a finite element. The model is built upon the ensemble of three blocks, namely fabric, fibers and damage. The continuum tensorial formulation of the fabric response rigorously takes into account the effect of fiber rotation for large strains and includes the nonlinear fiber behavior. In addition, the various damage mechanisms experimentally observed (bond and fiber fracture, interfiber friction and fiber pull-out) are included in a phenomenological way and the random nature of these materials is also taken into account by means of a Monte Carlo lottery to determine the damage thresholds. The model results are validated with recent experimental results on the tensile response of smooth and notched specimens of a polypropylene Nonwoven fabric.
David J Cottenden - One of the best experts on this subject based on the ideXlab platform.
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a study of friction mechanisms between a surrogate skin lorica soft and Nonwoven Fabrics
Journal of The Mechanical Behavior of Biomedical Materials, 2013Co-Authors: David J Cottenden, AM CottendenAbstract:Hygiene products such as incontinence pads bring Nonwoven Fabrics into contact with users' skin, which can cause damage in various ways, including the Nonwoven abrading the skin by friction. The aim of the work described here was to develop and use methods for understanding the origin of friction between Nonwoven Fabrics and skin by relating measured normal and friction forces to the nature and area of the contact (fibre footprint) between them. The method development work reported here used a skin surrogate (Lorica Soft) in place of skin for reproducibility. The work was primarily experimental in nature, and involved two separate approaches. In the first, a microscope with a shallow depth of field was used to determine the length of Nonwoven fibre in contact with a facing surface as a function of pressure, from which the contact area could be inferred; and, in the second, friction between chosen Nonwoven Fabrics and Lorica Soft was measured at a variety of anatomically relevant pressures (0.25-32.1kPa) and speeds (0.05-5mms(-1)). Both techniques were extensively validated, and showed reproducibility of about 5% in length and force, respectively. Straightforward inspection of the data for Lorica Soft against the Nonwovens showed that Amontons' law (with respect to load) was obeyed to high precision (R(2)>0.999 in all cases), though there was the suggestion of sub-linearity at low loads. More detailed consideration of the friction traces suggested that two different friction mechanisms are important, and comparison with the contact data suggests tentatively that they may correspond to adhesion between two different populations of contacts, one "rough" and one "smooth". This additional insight is a good illustration of how these techniques may prove valuable in studying other, similar interfaces. In particular, they could be used to investigate interfaces between Nonwovens and skin, which was the primary motivation for developing them.
