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Träfflista för sökning "AMNE:(ENGINEERING AND TECHNOLOGY Materials Engineering Textile, Rubber and Polymeric Materials) "

Sökning: AMNE:(ENGINEERING AND TECHNOLOGY Materials Engineering Textile, Rubber and Polymeric Materials)

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1.
  • Mellin, Pelle, 1985-, et al. (författare)
  • Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production
  • 2016
  • Ingår i: Journal of Cleaner Production. - Sweden : Elsevier. - 0959-6526 .- 1879-1786. ; 139, s. 1224-1233
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, the health and environmental perspective of nano-materials has gained attention. Most previous work focused on Engineered Nanoparticles (ENP). This paper examines some recently introduced production routes in terms of generated nano-sized by-products. A discussion on the hazards of emitting such particles and fibers is included. Fine by-products were found in recycled metal powder after 3D printing by Selective Laser Melting (SLM). The process somehow generated small round metal particles (~1e2 mm) that are possibly carcinogenic and respirable, but not small enough to enter by skin-absorption. With preventive measures like closed handling and masks, any health related effects can be prevented. The composite manufacturing in particular generated ceramic and carbonaceous particles that are very small and respirable but do not appear to be intrinsically toxic. The smallest features in agglomerates were about 30 nm. Small particles and fibers that were not attached in agglomerates were found in a wide range of sizes, from 1 μm and upwards. Preventive measures like closed handling and masks are strongly recommended. In contrast, the more traditional production route of fabric production is investigated. Here, brushing residue and recycled wool from fabric production contained few nano-sized by-products.
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2.
  • Jönsson, Christina, et al. (författare)
  • Biocatalysis in the Recycling Landscape for Synthetic Polymers and Plastics towards Circular Textiles
  • 2021
  • Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 14:19, s. 4028-4040
  • Tidskriftsartikel (refereegranskat)abstract
    • Although recovery of fibers from used textiles with retained material quality is desired, separation of individual components from polymer blends used in today's complex textile materials is currently not available at viable scale. Biotechnology could provide a solution to this pressing problem by enabling selective depolymerization of recyclable fibers of natural and synthetic origin, to isolate constituents or even recover monomers. We compiled experimental data for biocatalytic polymer degradation with a focus on synthetic polymers with hydrolysable links and calculated conversion rates to explore this path The analysis emphasizes that we urgently need major research efforts: beyond cellulose-based fibers, biotechnological-assisted depolymerization of plastics so far only works for polyethylene terephthalate, with degradation of a few other relevant synthetic polymer chains being reported. In contrast, by analyzing market data and emerging trends for synthetic fibers in the textile industry, in combination with numbers from used garment collection and sorting plants, it was shown that the use of difficult-to-recycle blended materials is rapidly growing. If the lack of recycling technology and production trend for fiber blends remains, a volume of more than 3400 Mt of waste will have been accumulated by 2030. This work highlights the urgent need to transform the textile industry from a biocatalytic perspective.
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3.
  • Åkerfeldt, Maria, 1982, et al. (författare)
  • Textile piezoelectric sensors – melt spun bi-component poly(vinylidene fluoride) fibres with conductive cores and poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) coating as the outer electrode
  • 2014
  • Ingår i: Fashion and Textiles. - : Springer Science and Business Media LLC. - 2198-0802. ; 1:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The work presented here addresses the outer electroding of a fully textile piezoelectric strain sensor, consisting of bi-component fibre yarns of β-crystalline poly(vinylidene fluoride) (PVDF) sheath and conductive high density polyethylene (HDPE)/carbon black (CB) core as insertions in a woven textile, with conductive poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) coatings developed for textile applications. Two coatings, one with a polyurethane binder and one without, were compared for the application and evaluated as electrode material in piezoelectric testing, as well as tested for surface resistivity, tear strength, abrasion resistance and shear flexing. Both coatings served their function as the outer electrodes in the system and no difference in this regard was detected between them. Omission of the binder resulted in a surface resistivity one order of magnitude less, of 12.3 Ω/square, but the surface resistivity of these samples increased more upon abrasion than the samples coated with binder. The tear strength of the textile coated with binder decreased with one third compared to the uncoated substrate, whereas the tear strength of the coated textile without binder increased with the same amount. Surface resistivity measurements and scanning electron microscopy (SEM) images of the samples subjected to shear flexing showed that the coatings without the binder did not withstand this treatment, and that the samples with the binder managed this to a greater extent. In summary, both of the PEDOT:PSS coatings could be used as outer electrodes of the piezoelectric fibres, but inclusion of binder was found necessary for the durability of the coating.
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4.
  • Seoane, Fernando, et al. (författare)
  • Conductive Polymer Films as Textrodes for Biopotential Sensing
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Introduction: After several years of progresses in textile technology and wearable measurement instrumentation, applications of wearable textile-electronics systems are arising providing a stable background for commercial applications. So far, the available commercial solutions are centered on fitness applications and mostly based in the acquisition of heart rate through Textile Electrodes (Textrodes) based on metallic threads or on conductive rubber compounds. Methods and Materials: In this work a novel material approach is presented to produce Textrodes for acquisition of Electrocardiographic (ECG) signals using a conductive polypropylene (PP1386 from Premix, Finland) polymer material. The polymer was film extruded into thin films, and used as such in the Textrode. Conductive Polymer Films (CPF) have been used to produce Textrodes, and its measurement performance has been compared with the ECG signals obtained with commercial Textrode fabrics and conventional Ag/AgCl electrodes. In order to set up the same measurement conditions, a chest strap tailored to host the testing electrodes has been used. Results: The close resemblance of the ECG acquired with the textile fabric electrodes, the Ag/AgCl electrodes and the PP1386 CPF electrodes suggest that the Polymer Electrodes PP1386 are a feasible alternative to the current textile fabrics that use silver thread as conductive material and also to conductive rubber material. Discussion & Conclusion: The availability of the Conductive Polymer Electrode PP1386 in a film form allows the manufacturing of electrodes by conventional textile processes, like lamination or sewing, therefore facilitating the transition from lab prototyping to industrial manufacturing. Replacing the traditional silver thread as conductive element in the fabrication of Textrodes will definitely reduce the material cost per Textrode. Biocompatibility issues and manufacturability issues must be addressed but the exhibited functional performance is showing encouraging results.
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5.
  • Hosseini, Seyedehsan, 1994 (författare)
  • Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces. The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.
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6.
  • Lei, Yu, et al. (författare)
  • Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices
  • 2022
  • Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 2:6, s. 450-485
  • Forskningsöversikt (refereegranskat)abstract
    • Since the isolation of graphene in 2004, two-dimensional (2D) materials research has rapidly evolved into an entire subdiscipline in the physical sciences with a wide range of emergent applications. The unique 2D structure offers an open canvas to tailor and functionalize 2D materials through layer number, defects, morphology, moiré pattern, strain, and other control knobs. Through this review, we aim to highlight the most recent discoveries in the following topics: theory-guided synthesis for enhanced control of 2D morphologies, quality, yield, as well as insights toward novel 2D materials; defect engineering to control and understand the role of various defects, including in situ and ex situ methods; and properties and applications that are related to moiré engineering, strain engineering, and artificial intelligence. Finally, we also provide our perspective on the challenges and opportunities in this fascinating field.
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7.
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8.
  • Jeong, Seung Hee, 1978- (författare)
  • Soft Intelligence : Liquids Matter in Compliant Microsystems
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Soft matter, here, liquids and polymers, have adaptability to a surrounding geometry. They intrinsically have advantageous characteristics from a mechanical perspective, such as flowing and wetting on surrounding surfaces, giving compliant, conformal and deformable behavior. From the behavior of soft matter for heterogeneous surfaces, compliant structures can be engineered as embedded liquid microstructures or patterned liquid microsystems for emerging compliant microsystems.Recently, skin electronics and soft robotics have been initiated as potential applications that can provide soft interfaces and interactions for a human-machine interface. To meet the design parameters, developing soft material engineering aimed at tuning material properties and smart processing techniques proper to them are to be highly encouraged. As promising candidates, Ga-based liquid alloys and silicone-based elastomers have been widely applied to proof-of-concept compliant structures.In this thesis, the liquid alloy was employed as a soft and stretchable electrical and thermal conductor (resistor), interconnect and filler in an elastomer structure. Printing-based liquid alloy patterning techniques have been developed with a batch-type, parallel processing scheme. As a simple solution, tape transfer masking was combined with a liquid alloy spraying technique, which provides robust processability. Silicone elastomers could be tunable for multi-functional building blocks by liquid or liquid-like soft solid inclusions. The liquid alloy and a polymer additive were introduced to the silicone elastomer by a simple mixing process. Heterogeneous material microstructures in elastomer networks successfully changed mechanical, thermal and surface properties.To realize a compliant microsystem, these ideas have in practice been useful in designing and fabricating soft and stretchable systems. Many different designs of the microsystems have been fabricated with the developed techniques and materials, and successfully evaluated under dynamic conditions. The compliant microsystems work as basic components to build up a whole system with soft materials and a processing technology for our emerging society.
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9.
  • Decrop, Deborah, et al. (författare)
  • Single-step manufacturing of femtoliter microwell arrays in a novel surface energy mimicking polymer
  • 2015
  • Ingår i: 18th International Conference on Solid-State Sensors, Actuators and Microsystems (IEEE TRANSDUCER 2015). - : IEEE.
  • Konferensbidrag (refereegranskat)abstract
    • We report a novel polymer material formulation and stamp-molding technique that enable rapid single-step manufacturing of hydrophilic-in-hydrophobic microwell arrays. We developed a modified thiol-ene-epoxy polymer (mOSTE+) formulation that mimics the surface energy of its mold during polymerization. The polymer inherits the surface energy from the mold through molecular self-assembly, in which functional monomers self-assemble at the interface between the liquid prepolymer and the mold surface. Combining this novel mOSTE+ material with a stamp-molding process leads to simultaneous surface energy mimicking and micro-structuring. This method was used to manufacture microwells with hydrophilic bottom and hydrophobic sidewall, depressed in a surrounding hydrophobic surface. The microwell arrays were successfully tested for the self-assembly of 62’000 femtoliter-droplets. Such femtoliter droplet arrays are useful for, e.g., digital ELISA and single cell/molecule analysis applications.
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10.
  • Kroon, Martin (författare)
  • An 8-chain Model for Rubber-like Materials Accounting for Non-affine Chain Deformations and Topological Constraints
  • 2011
  • Ingår i: Journal of elasticity. - : Springer Science and Business Media LLC. - 0374-3535 .- 1573-2681. ; 102:2, s. 99-116
  • Tidskriftsartikel (refereegranskat)abstract
    • Several industrial applications involve rubber and rubber-like materials, and it is important to be able to predict the constitutive response of these materials. In the present paper, a new constitutive model for rubber-like solids is proposed. The model is based on the 8-chain concept introduced by Arruda and Boyce (J. Mech. Phys. Solids 41, 389-412, 1993) to which two new components are added. Real polymer networks do not deform affinely, and in the proposed model this is accounted for by the inclusion of an elastic spring, acting in series with the representative polymer chain. Furthermore, real polymer chains are not completely free to move, which is modelled by imposing a topological constraint on the transverse motions of the representative polymer chain. The model contains five model parameters and these need to be determined on the basis of experimental data. Three: experimental studies from the literature were used to assess the proposed model. The model was able to reproduce experimental data performed under conditions of uniaxial tension, generalised plane deformation, and biaxial tension with an excellent accuracy. The strong predictive abilities together with the numerically efficient structure of the model make it suitable for implementation in a finite element context.
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11.
  • Pardon, Gaspard, 1983- (författare)
  • From Macro to Nano : Electrokinetic Transport and Surface Control
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Today, the growing and aging population, and the rise of new global threats on human health puts an increasing demand on the healthcare system and calls for preventive actions. To make existing medical treatments more efficient and widely accessible and to prevent the emergence of new threats such as drug-resistant bacteria, improved diagnostic technologies are needed. Potential solutions to address these medical challenges could come from the development of novel lab-on-chip (LoC) for point-of-care (PoC) diagnostics.At the same time, the increasing demand for sustainable energy calls for the development of novel approaches for energy conversion and storage systems (ECS), to which micro- and nanotechnologies could also contribute.This thesis has for objective to contribute to these developments and presents the results of interdisciplinary research at the crossing of three disciplines of physics and engineering: electrokinetic transport in fluids, manufacturing of micro- and nanofluidic systems, and surface control and modification. By combining knowledge from each of these disciplines, novel solutions and functionalities were developed at the macro-, micro- and nanoscale, towards applications in PoC diagnostics and ECS systems.At the macroscale, electrokinetic transport was applied to the development of a novel PoC sampler for the efficient capture of exhaled breath aerosol onto a microfluidic platform.At the microscale, several methods for polymer micromanufacturing and surface modification were developed. Using direct photolithography in off-stoichiometry thiol-ene (OSTE) polymers, a novel manufacturing method for mold-free rapid prototyping of microfluidic devices was developed. An investigation of the photolithography of OSTE polymers revealed that a novel photopatterning mechanism arises from the off-stoichiometric polymer formulation. Using photografting on OSTE surfaces, a novel surface modification method was developed for the photopatterning of the surface energy. Finally, a novel method was developed for single-step microstructuring and micropatterning of surface energy, using a molecular self-alignment process resulting in spontaneous mimicking, in the replica, of the surface energy of the mold.At the nanoscale, several solutions for the study of electrokinetic transport toward selective biofiltration and energy conversion were developed. A novel, comprehensive model was developed for electrostatic gating of the electrokinetic transport in nanofluidics. A novel method for the manufacturing of electrostatically-gated nanofluidic membranes was developed, using atomic layer deposition (ALD) in deep anodic alumina oxide (AAO) nanopores. Finally, a preliminary investigation of the nanopatterning of OSTE polymers was performed for the manufacturing of polymer nanofluidic devices.
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12.
  • Henrysson, Erica, 1987, et al. (författare)
  • Conceptual Design and Analysis of Membrane Structures
  • 2016
  • Ingår i: Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • In this work one approach for formfinding and analysing tension membranestructures is described. Focus has been on the conceptual stage. For this the computersoftware SMART Form has been further developed, enabling the possibility to do real-timeformfinding and analysis of fabric structures. The software is based on a method where theorthotropic membrane is modeled with a triangular mesh, where the mass is lumped on thenodes. As a computational tool dynamic relaxation is used to find the static equilibriumconfiguration for the structure. The advantage with this is that there is no need for formulationand manipulation of matrices common in the finite element method.
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13.
  • Hosseini, Seyedehsan, 1994, et al. (författare)
  • Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene
  • 2024
  • Ingår i: Polymer Composites. - 1548-0569 .- 0272-8397. ; 45:1, s. 825-835
  • Tidskriftsartikel (refereegranskat)abstract
    • Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.
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14.
  • Nyflött, Åsa, 1986- (författare)
  • Structure-Performance Relations of Oxygen Barriers for Food Packaging
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Food packaging should ensure the safety and quality of food, minimize spoilage and provide an easy way of storing and handling it. Barrier coatings are generally used to meet the demands placed on fibre-based food packages, as these have the ability to regulate the amount of gases that can enter them. Some gases are detrimental to food quality: oxygen, for example, initiates lipid oxidation in fatty foods. Using both experimental data and computer modelling, this thesis explains some aspects of how the structure of barrier coatings influences the mass transport of oxygen with the aim of obtaining essential knowledge that can be used to optimize the performance of barriers.Barrier coatings are produced from polyvinyl alcohol and kaolin blends that are coated onto a polymeric support. The chemical and physical structures of these barriers were characterized according to their influence on permeability in various climates. At a low concentration of kaolin, the crystallinity of polyvinyl alcohol decreased; in the thinner films, the kaolin particles were orientated in the basal plane of the barrier coating. The experimental results indicated a complex interplay between the polymer and the filler with respect to permeability.A computer model for permeability incorporating theories for the filled polymeric layer to include the polymer crystallinity, addition of filler, filler aspect ratio and surrounding moisture was developed. The model shows that mass transport was affected by the aspect ratio of the clay in combination with the clay concentration, as well as the polymer crystallinity. The combined model agreed with the experiments, showing that it is possible to combine different theories into one model that can be used to predict the mass transport.Four barrier coatings: polyethylene, ethylene vinyl alcohol + kaolin, latex + kaolin and starch were evaluated using the parameters of greenhouse gas emissions and product costs. After the production of the barrier material, the coating process and the end-of-life handling scenarios were analysed, it emerged that starch had the lowest environmental impact and latex + kaolin had the highest.
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15.
  • Jeong, Seung Hee, 1978-, et al. (författare)
  • Stretchable Thermoelectric Generators Metallized with Liquid Alloy
  • 2017
  • Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:18, s. 15791-15797
  • Tidskriftsartikel (refereegranskat)abstract
    • Conventional thermoelectric generators (TEGs) are normally hard, rigid, and flat. However, most objects have curvy surfaces, which require soft and even stretchable TEGs for maximizing efficiency of thermal energy harvesting. Here, soft and stretchable TEGs using conventional rigid Bi2Te3 pellets metallized with a liquid alloy is reported. The fabrication is implemented by means of a tailored layer-by-layer fabrication process. The STEGs exhibit an output power density of 40.6 ?W/cm2 at room temperature. The STEGs are operational after being mechanically stretched-and-released more than 1000 times, thanks to the compliant contact between the liquid alloy interconnects and the rigid pellets. The demonstrated interconnect scheme will provide a new route to the development of soft and stretchable energy-harvesting avenues for a variety of emerging electronic applications.
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16.
  • Townsend, Philip, 1991, et al. (författare)
  • Stochastic modelling of 3D fiber structures imaged with X-ray microtomography
  • 2021
  • Ingår i: Computational materials science. - : Elsevier B.V.. - 0927-0256 .- 1879-0801. ; 194
  • Tidskriftsartikel (refereegranskat)abstract
    • Many products incorporate into their design fibrous material with particular levels of permeability as a way to control the retention and flow of liquid. The production and experimental testing of these materials can be expensive and time consuming, particularly if it needs to be optimised to a desired level of absorbency. We consider a parametric virtual fiber model as a replacement for the real material to facilitate studying the relationship between structure and properties in a cheaper and more convenient manner. 3D image data sets of a sample fibrous material are obtained using X-ray microtomography and the individual fibers isolated. The segmented fibers are used to estimate the parameters of a 3D stochastic model for generating softcore virtual fiber structures. We use several spatial measures to show the consistency between the real and virtual structures, and demonstrate with lattice Boltzmann simulations that our virtual structure has good agreement with respect to the permeability of the physical material. © 2021 The Author(s)
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17.
  • Eriksson, Siw, et al. (författare)
  • Three-dimensional Fabrics as Medical Textiles
  • 2015
  • Ingår i: Advances in 3D Textiles. - : Woodhead Publishing Limited. - 9781782422143 - 9781782422198 ; , s. 305-340
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • The number of 3D textile applications in medicine is rapidly increasing as new technology and procedures are introduced in health care.  A first estimate of current medical applications of both general and 3D textiles is presented based on the medical devices classification system established by the US Food and Drug Administration. The textile specifics for these applications are covered from a textile technique perspective where the different 3D weaving as well as knitting, braiding and non-woven techniques are described and how their properties they can contribute in medical applications. In addition, emerging opportunities based on smart textiles as part of textile systems are described on a general level. The strong application areas of 3D medical textiles, i.e. wound management, vascular grafting and scaffolding for tissue engineering are covered in detail both from the medical and textiles perspective. Finally, some future lines of development are suggested and a short discussion on how new 3D textiles applications can be developed in close cooperation between the textile industry and the health care sector is presented.
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18.
  • Peterson, Joel, 1959-, et al. (författare)
  • Mechanical-Property-Based Comparison of Paper Yarn with Cotton, Viscose, and Polyester Yarns
  • 2021
  • Ingår i: Journal of Natural Fibers. - : Taylor & Francis Group. - 1544-0478 .- 1544-046X. ; 18:4, s. 492-501
  • Tidskriftsartikel (refereegranskat)abstract
    • Cotton and oil-based fibre consumption is highly problematic because the growth of these materials often requires fertilisers and toxic pesticides. Less environmentally damaging alternative fibres are urgently required. This study investigates Manila-hemp paper-yarn textile fabrics. Manila-hemp (abacá) is a species of banana grown as a commercial crop in the Philippines, Ecuador, and Costa Rica. Knitted structures of paper, cotton, viscose, and polyester yarns are tested and compared. Tensile strength tests are also performed. Paper yarn shows low shrinkage and no pilling, which are excellent characteristics for use in the textile and clothing industries. However, its poor handleability/knittability, high stiffness, and hard grip must be resolved for the widespread application of paper yarn in the textile industry in the future.
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19.
  • Pardon, Gaspard, 1983-, et al. (författare)
  • Simultaneous replication of hydrophilic and superhydrophobic micropatterns through area-selective monomer self-assembly
  • 2016
  • Ingår i: Advanced Materials Interfaces. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 3:17
  • Tidskriftsartikel (refereegranskat)abstract
    • The control and permanent modification of the surface properties of polymers is a critical enabler for many applications. Here, we demonstrate a strategy, which we call surface energy mimicking, for the spontaneous replication of micropatterns of surface energies ranging from hydrophilic to superhydrophobic from a mold to several replicas.We introduce surface energy mimicking, enabling spontaneous replication of micropatterns (2D and 2.5D) of different surface energies, and enabled by self-assembly of functional mimicking monomers within a polymer matrix. We demonstrate replication of surface energies ranging from hydrophilic to superhydrophobic, and self-assembly of picoliter-droplet arrays on replicated micropatterned arrays containing hydrophilic patches in a hydrophobic surface.
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20.
  • Gaska, Karolina, 1986, et al. (författare)
  • Gas Barrier, Thermal, Mechanical and Rheological Properties of Highly Aligned Graphene-LDPE Nanocomposites
  • 2017
  • Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:7, s. 294-
  • Tidskriftsartikel (refereegranskat)abstract
    • This contribution reports on properties of low-density polyethylene-based composites filled with different amounts of graphene nanoplatelets. The studied samples were prepared in the form of films by means of the precoating technique and single screw melt-extrusion, which yields a highly ordered arrangement of graphene flakes and results in a strong anisotropy of composites morphology. The performed tests of gas permeability reveal a drastic decrease of this property with increasing filler content. A clear correlation is found between permeability and free volume fraction in the material, the latter evaluated by means of positron annihilation spectroscopy. A strong anisotropy of the thermal conductivity is also achieved and the thermal conductivity along the extrusion direction for samples filled with 7.5 wt % of GnP (graphene nanoplatelets) reached 2.2 W/m·K. At the same time, when measured through a plane, a slight decrease of thermal conductivity is found. The use of GnP filler leads also to improvements of mechanical properties. The increase of Young’s modulus and tensile strength are reached as the composites become more brittle.
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21.
  • Kroon, Martin (författare)
  • Steady-state crack growth in rubber-like solids
  • 2011
  • Ingår i: International Journal of Fracture. - : Springer Science and Business Media LLC. - 0376-9429 .- 1573-2673. ; 169:1, s. 49-60
  • Tidskriftsartikel (refereegranskat)abstract
    • The fracture toughness of rubber-like materials depends on several factors. First there is the surface energy required to create new crack surface at the crack tip. Second, a significant amount of energy is dissipated through viscoelastic processes in the bulk material around the crack tip. Third, if the crack propagates very rapidly, inertia effects will come into play and contribute to the fracture toughness. In the present study, a computational framework for studying high-speed crack growth in rubber-like solids under conditions of steady-state is proposed. Effects of inertia, viscoelasticity and finite strains are included. The main purpose of the study is to study the contribution of viscoelastic dissipation to the total work of fracture required to propagate a crack in a rubber-like solid. The model was fully able to predict experimental results in terms of the local surface energy at the crack tip and the total energy release rate at different crack speeds. In addition, the predicted distributions of stress and dissipation around the propagating crack tip are presented.
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22.
  • Rasel, H., et al. (författare)
  • New bio-based plastics, from a non-edible plant oil side-stream, for film extrusion
  • 2014
  • Ingår i: 19th IAPRI World Conference on Packaging 2014. - : Victoria University. - 9781510821316 ; , s. 586-590
  • Konferensbidrag (refereegranskat)abstract
    • Renewable sourced PET, PA, PE, starch blends, etc, are fastly growing due to the processability and final performance, that is similar to their petroleum derived options. A bit in the shadow of the development of these plastics, development is ongoing on another group of plastics, made directly of the side-streams of agricultural products: oil plant residues and proteins. They can be used in edible applications but not all of them are suitable for food or forage. Industrial oilseed meal from crambe abyssinica contains relatively high levels of protein that is not suitable for human or animal consumption due to the presence of anti-nutritional compounds. This paper presents research on crambe meal as a base for new plastics, developed to extrude continuous, flexible plastic films based on crambe meal, blended with vital wheat gluten as an elastic component and urea as a protein denaturant. The effect of process parameters, such as screw speed, die temperature and pressure, and the effect of components were studied with regards to the final performance of the film extrudates. E.g. mechanical properties, oxygen permeability and moisture content were determined and surface and cross-section morphologies were examined with electron microscopy. The results showed that crambe-based blends can be extruded as continuous, flexible plastic films, which exhibit barrier properties towards oxygen. Recipes and methods for pelletizing of master batches for post-converting (e.g. extrusion or compression molding) were successfully developed. Addition of a renewable plasticizer improved the extrusion performance and resulted in less hygroscopic films, which further showed the overall highest tensile strength while the extensibility was nearly unaffected. The results provide a first basis to further develop the process and the blend towards potential industrial applications, for example as packaging materials to trays, pots and similar type of packages.
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23.
  • Andersson, Johanna, 1984 (författare)
  • Surface tension-driven flow in soft porous materials — An investigation of the mechanism of capillary flow in microchannels of hydrogels
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Spontaneous spreading of liquids in porous materials is of great industrial relevance and occurs in, for example, diapers, fabrics, paper or paint. Often, it is necessary to manipulate the spreading rate of liquids to result in the desired mass transport, for example to soak up large liquid volumes, as in a diaper. To do this, it is necessary to know the precise mechanism of surface tension driven flow. However, the process is complex and so are the porous materials in terms of both chemical composition and geometry. The mathematical and physical description of the process is often limited to specific cases – for example, the well-known Lucas-Washburn equation describes the speed of a meniscus in capillaries with circular cross-section in a hard material without interconnections. The objective of this thesis is to deepen the understanding of the mechanism with which a liquid spreads in a soft porous material only driven by surface tension. To this end, the liquid dynamics of water and water-based liquids were investigated in various model systems which are similar to porous 3D materials. In an alginate gel, capillaries with circular cross-sections were produced and the spreading rate of water was determined and compared to existing models. Using a method, which involves 3D printing, it was possible to fabricate open channels with rectangular cross-sections in the same alginate gel. The liquid spreading in these channels in geometries of branched channel systems was investigated. The results revealed that the spreading rate in capillaries of circular cross-sections in soft materials was much slower than that anticipated in existing models, which describe hard materials. In open channels of rectangular cross-sections, the presence of side channels slowed down the meniscus in the main channel; the meniscus stopped when it encountered junctions. The stop duration was longer when the side channels were longer, when they were wider, and when their tilting angle was low with respect to the main channel. An analysis of the volume flow indicated that those geometries that had long side channels but are few in number, resulted in faster volume flow. In a porous 3D material, this suggests that the interconnectivity could decrease the volume flow rate. Finally, a calcium alginate gel with straight-aligned pores was produced and characterised as an example of optimal liquid transport. The outcome of this thesis can be used to adjust the geometrical design of porous materials to result in desired liquid transport properties. The stiffness of the material may influence the liquid transport. The thesis also contributes to the discussion on how the liquid takes selective pathways in porous materials.
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24.
  • Lund, Anja (författare)
  • Melt spun piezoelectric textile fibres : an experimental study
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Melt Spun Piezoelectric Textile Fibres - an Experimental Study ANJA LUND Department of Materials and Manufacturing Technology Chalmers University of Technology ABSTRACT The manufacturing and characterisation of piezoelectric textile fibres are described in this thesis. A piezoelectric material is one that generates an electric voltage when deformed, a property which exists in a number of materials. The polymer with the strongest known piezoelectric effect today is poly(vinylidene fluoride) (PVDF), however it must be processed under certain conditions to become piezoelectric. This study shows that piezoelectric bicomponent PVDF-based fibres can be produced by melt spinning, which is a common and relatively simple fibre spinning method. The melt spinning process must include cold drawing, as this introduces a polar crystalline structure in the polymer. The fibres must also be electroded, which is done by producing bicomponent fibres with a core-and-sheath structure. The core is electrically conductive and constitutes an inner electrode consisting of a carbon black/polymer compound, whereas the sheath is PVDF and constitutes the piezoelectric component. Being sensitive to both deformation and temperature changes, these fibres are anticipated to be useful in a number of sensor applications. The flexibility and small size of the fibres makes it possible to include them as miniature-sensors in structures or garment without affecting the shape or comfort.
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25.
  • Muneer, Faraz, et al. (författare)
  • Preparation, Properties, Protein Cross-Linking and Biodegradability of Plasticizer-Solvent Free Hemp Fibre Reinforced Wheat Gluten, Glutenin, and Gliadin Composites
  • 2014
  • Ingår i: BioResources. - : BioResources. - 1930-2126. ; 9:3, s. 5246-5261
  • Tidskriftsartikel (refereegranskat)abstract
    • The present study is aimed at evaluating the use of plant-based polymers and fibres for the production of sustainable biocomposites. For the first time, plasticiser/solvent-free hemp fibre-reinforced wheat gluten and hemp-gliadin and glutenin composites were obtained by compression moulding at different temperatures. The plasticiser/solvent-free sample preparation method developed in this study facilitated the use of a powdered protein matrix with a mat of randomly oriented hemp fibres. The tensile and protein cross-linking properties, as well as the biodegradability, were investigated. The addition of hemp fibre to the protein matrix increased the E-modulus by 20 to 60% at 130 degrees C. An increase in moulding temperature from 110 to 130 degrees C resulted in an increase in maximum stress due to the formation of intermolecular bonds between protein chains. The gliadin composites had higher E-modulus and maximum stress and showed a larger increase in protein polymerisation with increased temperature compared to the gluten in composites. A comparison of tensile properties revealed that the composites were stiffer and stronger compared to several similarly produced biobased composites. The composites were found to be fully biodegradable under a simulated soil environment after 180 days. Biocomposites produced in the present study were found to be environmentally friendly with fairly good mechanical properties.
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26.
  • Frischknecht, Rolf, et al. (författare)
  • Comparative Life Cycle Assessment of Geosyhnthetics versus Conventional filter layer
  • 2013
  • Ingår i: Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering. - 9782859784744 ; 4, s. 3203-3206
  • Konferensbidrag (refereegranskat)abstract
    • Geosynthetics made from plastics can replace filter layers made of gravel. In this article goal and scope, basic data and the results of a comparative life cycle assessment of gravel and geosynthetics based filter layers are described. The filter layers of a road made of 30 cm gravel and a filter geosynthetic, respectively, form the basis for the comparison. The filter layers have the same technical performance and the same life time of 30 years. The product system includes the supply of the raw materials, the manufacture of the geotextiles and the extraction of mineral resources, the construction of the road filter, its use and its end of life phase. The life cycle assessment reveals that the geosynthetics based filter layer causes lower environmental impacts per square metre. The cumulative greenhouse gas emissions amount to 7.8 kg CO2-eq (mineral filter) and to 0.81 kg CO2-eq (geosynthetic filter). The variation of the thickness of the gravel based filter layer confirms the lower environmental impacts of a geosynthetics based filter layer. Environmental impacts of the geosynthetic production are dominated by the raw material provision (plastic granulate) and electricity consumption during manufacturing.
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27.
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28.
  • Åkerfeldt, Maria (författare)
  • Studies of electrically conductive textile coatings with PEDOT:PSS
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This study investigates electrically conductive coatings of textiles, obtained with a direct coating and the addition of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) dispersion to a thickened polyurethane (PU)-based formulation. Textiles with enhanced electrical conductivity have potential applications in antistatic, electrostatic discharge protective, electromagnetic interference shielding, sensoric and temperature-regulating products. The composition of the coating formulation will have a large impact on the obtained coated textiles. Firstly, the amount solids (polymer content) of the components will affect the shear viscosity which is amongst other important for the level of penetration of the coating. In this work, different coating formulations have been studied with steady state shear viscometry. It was found that the viscosity during knife coating to a large extent could be controlled by the addition of a hydrophobically modified ethoxylated urethane (HEUR) rheology modifier. Secondly, the level of conductivity will depend on the amount conductive material, in this case PEDOT:PSS, that is present in the coating, indicating percolation behaviour of the system. Conductivity was evaluated with two-point and four-point surface resistivity measurements. Addition of a high-boiling solvent, i.e. ethylene glycol, was however imperative for low surface resistivity. Thirdly, tear strength measurements, performed with the dynamic pendulum method, and investigations of bending rigidity, with the Kawabata evaluation system for fabrics, KES-F-2, showed that samples coated with formulations containing larger amounts of PEDOT:PSS and ethylene glycol were significantly softer and more ductile than samples coated with formulations containing more binder. A decrease in surface resistivity could also be obtained by increasing the amount deposited coating on the substrate. This decrease was however counteracted by the concurrent increase of insulating binder polymers in the coating. The increased coating deposit resulted in stiffer samples with lower tear strength due to increased brittleness. The influence of kinetics during film formation on the surface resistivity was also studied but was found to be close to insignificant. Abrasion resistance was investigated for all samples with a modified Martindale method and the samples showed less impact from this than expected.
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29.
  • Hu, Enyi, et al. (författare)
  • Junction and energy band on novel semiconductor-based fuel cells
  • 2021
  • Ingår i: iScience. - : Elsevier BV. - 2589-0042. ; 24:3
  • Forskningsöversikt (refereegranskat)abstract
    • Fuel cells are highly efficient and green power sources. The typical membrane electrode assembly is necessary for common electrochemical devices. Recent research and development in solid oxide fuel cells have opened up many new opportunities based on the semiconductor or its heterostructure materials. Semiconductor-based fuel cells (SBFCs) realize the fuel cell functionality in a much more straightforward way. This work aims to discuss new strategies and scientific principles of SBFCs by reviewing various novel junction types/interfaces, i.e., bulk and planar p-n junction, Schottky junction, and n-i type interface contact. New designing methodologies of SBFCs from energy band/alignment and built-in electric field (BIEF), which block the internal electronic transport while assisting interfacial superionic transport and subsequently enhance device performance, are comprehensively reviewed. This work highlights the recent advances of SBFCs and provides new methodology and understanding with significant importance for both fundamental and applied R&D on new-generation fuel cell materials and technologies.
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30.
  • Wallbaum, Holger, 1967, et al. (författare)
  • Environmental benefits by using construction methods with geosynthetics
  • 2014
  • Ingår i: 10th International Conference on Geosynthetics, ICG 2014. - 9783981395396
  • Konferensbidrag (refereegranskat)abstract
    • Geosynthetic materials are used in many different applications in the civil and underground engineering. In most cases, the use of geosynthetic material replaces the use of other materials. On behalf of the European Association for Geosynthetic Manufacturers (EAGM) the authors quantified the environmental performance of commonly applied construction materials (such as concrete, cement, lime or gravel) versus geosynthetics. To this end a set of comparative life cycle assessment studies are carried out, according to the ISO 14040 and 14044 standards, concentrating on various application cases, namely filtration, foundation stabilised road, landfill construction and slope retention. The environmental performance of geosynthetics is compared to the performance of competing construction materials used. The environmental impacts of the full life cycle of the four cases show overall the following results:• A filter using a geosynthetic layer causes lower impacts compared to a conventional gravel based filter layer with regard to all impact category indicators investigated.• A conventional road causes higher impacts compared to a road reinforced with geosynthetics with regard to all impact category indicators.• A geosynthetic drainage layer causes lower environmental impacts compared to a gravel based drainage layer in all impact categories considered except land competition which is about the same in both cases.• A geosynthetic reinforced wall causes lower environmental impacts compared to a reinforced concrete wall in all impact categories considered.
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31.
  • Zubritskaya, Irina, 1984, et al. (författare)
  • Dynamically Tunable Optical Cavities with Embedded Nematic Liquid Crystalline Networks
  • 2023
  • Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:13
  • Tidskriftsartikel (refereegranskat)abstract
    • Tunable metal–insulator–metal (MIM) Fabry–Pérot (FP) cavities that can dynamically control light enable novel sensing, imaging and display applications. However, the realization of dynamic cavities incorporating stimuli-responsive materials poses a significant engineering challenge. Current approaches rely on refractive index modulation and suffer from low dynamic tunability, high losses, and limited spectral ranges, and require liquid and hazardous materials for operation. To overcome these challenges, a new tuning mechanism employing reversible mechanical adaptations of a polymer network is proposed, and dynamic tuning of optical resonances is demonstrated. Solid-state temperature-responsive optical coatings are developed by preparing a monodomain nematic liquid crystalline network (LCN) and are incorporated between metallic mirrors to form active optical microcavities. LCN microcavities offer large, reversible and highly linear spectral tuning of FP resonances reaching wavelength-shifts up to 40 nm via thermomechanical actuation while featuring outstanding repeatability and precision over more than 100 heating–cooling cycles. This degree of tunability allows for reversible switching between the reflective and the absorbing states of the device over the entire visible and near-infrared spectral regions, reaching large changes in reflectance with modulation efficiency ΔR = 79%.
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32.
  • Barletta, Ilaria Giovanna, 1988, et al. (författare)
  • Climate implications of water-free dyeing of biofibers (ClimaDYE)
  • 2017
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • This document illustrates the project outputs of the Climate-KIC funded project “ClimaDYE”. The purpose of the project is to estimate environmental and in particular climate implications of a water-free dyeing technology using supercritical CO2 (scCO2) and to evaluate the business case for it. The outputs of the ClimaDYE project are three: 1. an economic and environmental evaluation of scCO2 dyeing of polyester (PES) fabric against two alternative dyeing technologies 2. an estimation of environmental impact of scCO2 dyeing of biofibers, to be confirmed by future physical tests on biofibers 3. a list of business opportunities for PES and biofibers dyeing with scCO2, to be confirmed by future physical tests on biofibers.As a result, this deliverable is to be considered as a blend of a feasibility study and a comparative study. This document contains the main analyses being done to obtain the project outputs mentioned above, and the project results in relation to the three outputs.
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33.
  • Åkerfeldt, Maria, 1982, et al. (författare)
  • Textile sensing glove with piezoelectric PVDF fibers and printed electrodes of PEDOT:PSS
  • 2015
  • Ingår i: Textile Research Journal. - : SAGE Publications. - 0040-5175 .- 1746-7748. ; 85:17, s. 1789-1799
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of an entirely polymer-based motion sensing glove with possible applications, for example, in physical rehabilitation is described. The importance of comfort for the wearer and the possibility to clean the glove in normal laundering processes were important aspects in the development. The glove is all textile and manufactured using materials and methods suitable for standard textile industry processes. For the first time, melt-spun piezoelectric poly(vinylidene fluoride) (PVDF) fibers with conductive cores were machine embroidered onto a textile glove to function as a sensor element. Electrodes and electrical interconnections were constituted by a screen printed conductive poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) formulation. The screen printing of the interconnections was shown to be a reliable method for reproducible material deposition, resulting in an average surface resistivity value of 57/square. A repeated strain of 10% only influenced the resistance of the interconnections initially and to a very limited extent. The influence of washing on the electrical resistance of the printed interconnections was also studied; after 15 wash cycles the average surface resistivity was still below 500/square, which was deemed sufficient for the polymeric sensor system to remain functional during long-term use. Sensor data from the glove was also successfully used as input to a microcontroller running a robot gripper, in order to demonstrate its potential applications.
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34.
  • Kroon, Martin (författare)
  • Energy release rates in rubber during dynamic crack propagation
  • 2014
  • Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 51:25-26, s. 4419-4426
  • Tidskriftsartikel (refereegranskat)abstract
    • The theoretical understanding of the fracture mechanics of rubber is not as well developed as for other engineering materials, such as metals. The present study is intended to further the understanding of the dissipative processes that take place in rubber in the vicinity of a propagating crack tip. This dissipation contributes significantly to the total fracture toughness of the rubber and is therefore of great interest from a fracture mechanics point of view. To study this, a computational framework for analysing high-speed crack growth in a biaxially stretched rubber under plane stress is therefore formulated. The main purpose is to investigate the energy release rates required for crack propagation under different modes of biaxial stretching. The results show, that inertia comes into play when the crack speed exceeds about 50 m/s. The total work of fracture by far exceeds the surface energy consumed at the very crack tip, and the difference must be attributed to dissipative damage processes in the vicinity of the crack tip. The size of this damage/dissipation zone is expected to be a few millimetres.
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35.
  • Elmukashfi, Elsiddig, et al. (författare)
  • Numerical analysis of dynamic crack propagation in biaxially strained rubber sheets
  • 2014
  • Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944 .- 1873-7315. ; 124, s. 1-17
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper proposes a computational framework for dynamic crack propagation in rubber in which a nonlinear finite element analysis using cohesive zone modeling approach is used. A suddenly initiated crack at the center of biaxially stretched sheet problem is studied under plane stress conditions. A transient dynamic analysis using implicit time integration scheme is performed. In the constitutive modeling, the continuum is characterized by finite-viscoelasticity theory and coupled with the fracture processes using a cohesive zone model. This computational framework was introduced previously by the present authors (Elmukashfi and Kroon, 2012). In the current work, the use of a rate-dependent cohesive model is examined in addition to investigation of generalized biaxial loading cases. A Kelvin-Voigt element is used to describe the rate-dependent cohesive model wherein the spring is described by a bilinear law and dashpot with a constant viscosity is adopted. An explicit integration is used to incorporate the rate-dependent cohesive model in the finite element environment. A parametric study over the cohesive viscosity is performed and the steady crack propagation velocity is evaluated and compared with experimental data. It appears that the viscosity varies with the crack speed. Further, the total work of fracture is estimated using rate-independent cohesive law such that the strength of the cohesive zone is assumed to be constant and the separation work per unit area is determined form the experimental data. The results show that fracture-related processes, i.e. creation of new surfaces, cavitation and crystallization; contribute to the total work of fracture in a contradictory manner.
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36.
  • Elmukashfi, Elsiddig, et al. (författare)
  • Numerical analysis of dynamic crack propagation in rubber
  • 2012
  • Ingår i: International Journal of Fracture. - : Springer Science and Business Media LLC. - 0376-9429 .- 1573-2673. ; 177:2, s. 163-178
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present paper, dynamic crack propagation in rubber is analyzed numerically using the finite element method. The problem of a suddenly initiated crack at the center of stretched sheet is studied under plane stress conditions. A nonlinear finite element analysis using implicit time integration scheme is used. The bulk material behavior is described by finite-viscoelasticity theory and the fracture separation process is characterized using a cohesive zone model with a bilinear traction-separation law. Hence, the numerical model is able to model and predict the different contributions to the fracture toughness, i.e. the surface energy, viscoelastic dissipation, and inertia effects. The separation work per unit area and the strength of the cohesive zone have been parameterized, and their influence on the separation process has been investigated. A steadily propagating crack is obtained and the corresponding crack tip position and velocity history as well as the steady crack propagation velocity are evaluated and compared with experimental data. A minimum threshold stretch of 3.0 is required for crack propagation. The numerical model is able to predict the dynamic crack growth. It appears that the strength and the surface energy vary with the crack speed. Finally, the maximum principal stretch and stress distribution around steadily propagation crack tip suggest that crystallization and cavity formation may take place.
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37.
  • Kroon, Martin (författare)
  • A constitutive framework for modelling thin incompressible viscoelastic materials under plane stress in the finite strain regime
  • 2011
  • Ingår i: Mechanics of time-dependant materials. - : Springer Science and Business Media LLC. - 1385-2000 .- 1573-2738. ; 15:4, s. 389-406
  • Tidskriftsartikel (refereegranskat)abstract
    • Rubbers and soft biological tissues may undergo large deformations and are also viscoelastic. The formulation of constitutive models for these materials poses special challenges. In several applications, especially in biomechanics, these materials are also relatively thin, implying that in-plane stresses dominate and that plane stress may therefore be assumed. In the present paper, a constitutive model for viscoelastic materials in the finite strain regime and under the assumption of plane stress is proposed. It is assumed that the relaxation behaviour in the direction of plane stress can be treated separately, which makes it possible to formulate evolution laws for the plastic strains on explicit form at the same time as incompressibility is fulfilled. Experimental results from biomechanics (dynamic inflation of dog aorta) and rubber mechanics (biaxial stretching of rubber sheets) were used to assess the proposed model. The assessment clearly indicates that the model is fully able to predict the experimental outcome for these types of material.
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38.
  • Kroon, Martin (författare)
  • An asymptotic analysis of dynamic crack growth in rubber
  • 2011
  • Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944 .- 1873-7315. ; 78:17, s. 3111-3122
  • Tidskriftsartikel (refereegranskat)abstract
    • Asymptotic analyses of the mechanical fields in front of stationary and propagating cracks are important for several reasons. For example, they facilitate the understanding of the mechanical and physical state in front of crack tips, and they enable prediction of crack growth. Furthermore, efficient modelling of arbitrary crack growth by use of XFEM (extended finite element method) requires accurate knowledge of the asymptotic crack tip fields. The present study focuses on the asymptotic fields in front of a crack that propagates dynamically in rubber. Static analyses of this type of problem have been made in previous studies. In order to be able to compare the present results with these earlier studies, the constitutive model from Knowles and Sternberg (J. Elast. 3: 67-107, 1973) was adopted. It is assumed that viscoelastic stresses become negligible compared with the singular elastic stresses close to the crack tip. The present analysis shows that in materials with a significant hardening, the inertia term in the equations of motion becomes negligible in the asymptotic analysis. However, for a neoHookean type of model, inertia comes into play and causes a maximum theoretical crack speed that equals the shear wave speed.
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39.
  • Wysocki, Maciej, et al. (författare)
  • The out-of-plane behaviour of spread-tow fabrics
  • 2014
  • Ingår i: 16th European Conference on Composite Materials, ECCM 2014. - : European Conference on Composite Materials, ECCM. - 9780000000002
  • Konferensbidrag (refereegranskat)abstract
    • In this paper the constitutive compressive behaviour of nearly parallel spread-tow textile reinforcement is studied. The striking result of our analysis is that the spread-tow type of reinforcement should obey linear relation between force and deformation. This is in contrast to standard textile reinforcements that obey a power-law type of behaviour. To support the theoretical investigation we have developed an test rig who's chief purpose is to achieve compression between nearly perfectly parallel surfaces. This is achieved using a mechanical arrangement consisting of a ball-joint.
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40.
  • Öberg Månsson, Ingrid, 1991- (författare)
  • Electroanalytical devices with fluidic control using textile materials and methods
  • 2020
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis, written by Ingrid Öberg Månsson at KTH Royal Institute of Technology and entitled “Electroanalytical devices with fluidic control using textile materials and methods”, presents experimental studies on the development of textile based electronic devices and biosensors. One of the reasons why this is of interest is the growing demand for integrated smart products for wearable health monitoring or energy harvesting. To enable such products, new interdisciplinary fields arise combining traditional textile technology and electronics.Textile based devices have garnered much interest in recent years due to their innate ability to incorporate function directly into, for example, clothing or bandages by textile processes such as weaving, knitting or stitching. However, many modifications of yarns required for such applications are not available on an industrial scale. The major objective of this work has been to study how to achieve the performance necessary to create electronic textile devices by either coating yarns with conductive material or using commercially available conductive yarns that are functionalized to create sensing elements.Further, liquid transport within textile materials has been studied to be able to control the contact area between electrolyte and electrodes in electrochemical devices such as sensors and transistors. Yarns with specially designed cross-sections, traditionally used in sportswear to wick sweat away from the body and enhance evaporation, was used to transport electrolyte liquids to come in contact with yarn electrodes. The defined area of the junction where the fluidic yarn meets the conductive yarn was shown to increase stability of the measurements and the reproducibility between devices.The results presented in the two publications of this thesis as well as additional results presented in the thesis itself show the promising potential of using textile materials to integrate electronic and electrochemical functionality in our everyday life. This is shown by using basic textile materials and processing techniques to fabricate complex devices for various application areas such as sensors and diagnostics as well as electrical and energy harvesting components.
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41.
  • Lund, Anja, et al. (författare)
  • Piezoelectric polymeric bicomponent fibers produced by melt spinning
  • 2012
  • Ingår i: Journal of Applied Polymer Science. - : Wiley Periodicals, Inc.. - 0021-8995 .- 1097-4628. ; 126:2, s. 490-500
  • Tidskriftsartikel (refereegranskat)abstract
    • Melt spinning of a novel piezoelectric bicomponent fiber, with poly(vinylidene fluoride) as the electroactive sheath component, has been demonstrated. An electrically conductive compound of carbon black (CB) and high density polyethylene was used as core material, working as an inner electrode. A force sensor consisting of a number of fibers embedded in a soft CB/polyolefin elastomer matrix was manufactured for characterization. The fibers showed a clear piezoelectric effect, with a voltage output (peak-to-peak) of up to 40 mV under lateral compression. This continuous all-polymer piezoelectric fiber introduces new possibilities toward minimal single fiber sensors as well as large area sensors produced in standard industrial weaving machines.
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42.
  • He, Zhongxia Simon, 1984, et al. (författare)
  • A 90-140 GHz, High Power Frequency Source Packaged in a Self-aligned Waveguide Module
  • 2018
  • Ingår i: Asia Pacific Microwave Conference-Proceedings. - 9784902339451 ; 2018-November, s. 261-263
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents a solution for packaging monolithic microwave integrated circuit (MMIC) using commercially available liquid crystal polymer (LCP) substrate print circuit board. This package solution comprises of a novel self-aligned microstrip-to-waveguide transition design. For demonstration, an active frequency multiplier-by three MMIC at F-band (90-140 GHz) is packaged into a split-block waveguide module and tested. The circuit is implemented in a 250-nm InP double-heterostructure bipolar transistor technology with ft/fmax 350/650 GHz, respectively. The tripler module has measured output power of 10.6 dBm and a 3-dB output bandwidth of 36.3%, (90-130 GHz). Total power consumption is 156 mW at 2-dBm input power.
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43.
  • Biswas, Tuser, 1988-, et al. (författare)
  • Enzyme immobilization on textiles by inkjet printing for advanced applications
  • 2019
  • Konferensbidrag (refereegranskat)abstract
    • Immobilization of enzymes on textiles can impart a range of advanced applications e.g. anti-microbial, controlled release, drug delivery and bio-sensing (Wehrschütz-Sigl et al., 2010). Such applications enable minimal consumption, recovery, and reusability of these valuable bio-materials compared to their conventional textile applications in surface cleaning and finishing (Araujo et al., 2008). Methods used for immobilization can play important roles to ensure precise, flexible and contamination free application. Compared to many of the conventional methods of textile immobilization such as coating and screen-printing, digital inkjet technology offers many benefits for such advanced applications (Kan and Yuen, 2012). Among various inkjet technologies, drop-on-demand piezoelectric printing is a promising resource-efficient technology for enzyme immobilization.  The enzymes should retain high activity after the immobilization process. Various factors involved during inkjet printing (Saunders and Derby, 2014) and fabric characteristics (Mohamed et al., 2008) can influence this enzymatic activity. Factors concerning the inkjet procedure include rheology and ionic nature of ink along with the shear force and waveform generated inside a piezoelectric printhead (Magdassi, 2010). Factors dependent upon fabric characteristics include surface structure, pore size distribution, and binding mechanism (Nierstrasz and Warmoeskerken, 2003). In this work, we have studied the effects of inkjet procedures on enzymatic activity. Lysozyme being a stable and well-studied enzyme was chosen for our experiments. A Xennia Carnelian printer with a Dimatix QS10 industrial printhead was used for inkjetting. Lytic activity of lysozyme was studied by a UV-Vis spectrophotometer against decrease of Micrococcus lysodeikticus cell concentration at 450 nm. Results showed ca. 10-15% activity reduction of the jetted lysozyme ink. As all the ink and printer parameters were optimized, the probable reason for such reduction could be the effect of shear forces inside the printhead on three-dimensional conformation of lysozyme. In conclusion, our formulated lysozyme ink showed potential for printing textiles with probable activity reduction that require further investigation. 
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44.
  • Johannisson, Wilhelm, et al. (författare)
  • A screen-printing method for manufacturing of current collectors for structural batteries
  • 2021
  • Ingår i: Multifunctional Materials. - : IOP Publishing. - 2399-7532. ; 4:3, s. 035002-
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural carbon fibre composite batteries are a type of multifunctional batteries that combine the energy storage capability of a battery with the load-carrying ability of a structural material. To extract the current from the structural battery cell, current collectors are needed. However, current collectors are expensive, hard to connect to the electrode material and add mass to the system. Further, attaching the current collector to the carbon fibre electrode must not affect the electrochemical properties negatively or requires time-consuming, manual steps. This paper presents a proof-of-concept method for screen-printing of current collectors for structural carbon fibre composite batteries using silver conductive paste. Current collectors are screen-printed directly on spread carbon fibre tows and a polycarbonate carrier film. Experimental results show that the electrochemical performance of carbon fibre vs lithium metal half-cells with the screen-printed collectors is similar to reference half-cells using metal foil and silver adhered metal-foil collectors. The screen-printed current collectors fulfil the requirements for electrical conductivity, adhesion to the fibres and flexible handling of the fibre electrode. The screen-printing process is highly automatable and allows for cost-efficient upscaling to large scale manufacturing of arbitrary and complex current collector shapes. Hence, the screen-printing process shows a promising route to realization of high performing current collectors in structural batteries and potentially in other types of energy storage solutions.
  •  
45.
  • Lund, Anja, et al. (författare)
  • Melt spinning of beta-phase poly(vinylidene fluoride) yarns with and without a conductive core
  • 2011
  • Ingår i: Journal of Applied Polymer Science. - : Wiley Periodicals, Inc.. - 0021-8995 .- 1097-4628. ; 120:2, s. 1080-1089
  • Tidskriftsartikel (refereegranskat)abstract
    • When poly(vinylidene fluoride) (PVDF) is to be used as a piezoelectric material, the processing must include the formation of polar β-phase crystallites, as well as the application of electrically conducting charge collectors, that is, electrodes. In this article, results from the melt spinning of PVDF yarns and a novel bicomponent PVDF-yarn with a conductive carbon black/polypropylene (CB/PP) core are presented. Melt spinning has been done under conditions typical for industrial large-scale fiber production. The effects on the resulting crystalline structure of varying the spinning velocity, draw rate, and draw temperature are discussed. The results show that, for maximum α-to-β phase transformation, cold drawing should take place at a temperature between 70 and 90°C, and both the draw ratio and the draw rate should be as high as possible. It was observed that the cold drawing necessary to form β-phase crystallinity simultaneously leads to a decrease in the core conductivity of the bicomponent yarns. In this work, the melt spinning of bicomponent fibers with high-β-phase PVDF in the sheath and a CB/PP core was successfully accomplished. The core material remained electrically conductive, paving the way for the use of a CB-polymer compound as inner electrode in the melt spinning of piezoelectric bicomponent fibers.
  •  
46.
  • Schellenberger, Steffen, 1981-, et al. (författare)
  • An Outdoor Aging Study to Investigate the Release of Per- And Polyfluoroalkyl Substances (PFAS) from Functional Textiles
  • 2022
  • Ingår i: Environmental Science and Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 56, s. 3471-
  • Tidskriftsartikel (refereegranskat)abstract
    • The emission of per- and polyfluoroalkyl substances (PFAS) from functional textiles was investigated via an outdoor weathering experiment in Sydney, Australia. Polyamide (PA) textile fabrics treated with different water-repellent, side-chain fluorinated polymers (SFPs) were exposed on a rooftop to multiple natural stressors, including direct sunlight, precipitation, wind, and heat for 6-months. After weathering, additional stress was applied to the fabrics through abrasion and washing. Textile characterization using a multiplatform analytical approach revealed loss of both PFAS-containing textile fragments (e.g., microfibers) as well as formation and loss of low molecular weight PFAS, both of which occurred throughout weathering. These changes were accompanied by a loss of color and water repellency of the textile. The potential formation of perfluoroalkyl acids (PFAAs) from mobile residuals was quantified by oxidative conversion of extracts from unweathered textiles. Each SFP-textile finish emitted a distinct PFAA pattern following weathering, and in some cases the concentrations exceeded regulatory limits for textiles. In addition to transformation of residual low molecular weight PFAA-precursors, release of polymeric PFAS from degradation and loss of textile fibers/particles contributed to overall PFAS emissions during weathering. © 2022 The Authors. 
  •  
47.
  • Carlstedt, David, 1984, et al. (författare)
  • Effects of state of charge on elastic properties of 3D structural battery composites
  • 2019
  • Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 169, s. 26-33
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of state of charge (SOC) on the elastic properties of 3D structural battery composites are studied. An analytical model based on micromechanical models is developed to estimate the effective elastic properties of 3D structural battery composite laminae at different SOC. A parametric study is performed to evaluate how different design parameters such as volume fraction of active materials, stiffness of constituents, type of positive electrode material, etc. affect the moduli of the composite lamina for extremes in SOC. Critical parameters and configurations resulting in large variations in elastic properties due to change in SOC are identified. As the extreme cases are of primary interest in structural design, the effective elastic properties are only estimated for the electrochemical states corresponding to discharged (SOC = 0) and fully charged (SOC = 1) battery. The change in SOC is simulated by varying the volume and elastic properties of the constituents based on data from literature. Parametric finite element (FE) models for square and hexagonal fibre packing arrangements are also analysed in the commercial FE software COMSOL and used to validate the analytical model. The present study shows that the transverse elastic properties E2 and G23 and the in-plane shear modulus G12 are strongly affected by the SOC while the longitudinal stiffness E1 is not. Fibre volume fraction and the properties of the coating (such as stiffness and Poisson's ratio) are identified as critical parameters that have significant impact on the effect of SOC on the effective elastic properties of the composite lamina. For configurations with fibre volume fraction Vf ≥ 0.4 and Young's modulus of the coating of 1 GPa or higher, the transverse properties E2 and G23 change more than 30% between extremes in SOC. Furthermore, for configurations with high volume fractions of electrode materials and coating properties approaching those of rubber the predicted change in transverse stiffness E2 is as high as +43%. This shows that it is crucial to take effects of SOC on the elastic properties into account when designing 3D structural battery composite components. © 2018 Elsevier Ltd
  •  
48.
  • Dahlbom, Maja, et al. (författare)
  • Sustainable clothing futures - Mapping of textile actors in sorting and recycling of textiles in Europe
  • 2023
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • This report is as a part of the research project Sustainable clothing futures, and have, through literature and market studies and interviews, identified actors working with sorting and recycling of textiles, with capacities of 560 000 tons and 1.3 million tons per year, respectively.In the interviews, it was clear that an up scale of the capacities is possible, but is depending on several factors, technological development amongst others.
  •  
49.
  • Lund, Anja, 1971, et al. (författare)
  • Electrically conducting fibres for e-textiles: An open playground for conjugated polymers and carbon nanomaterials
  • 2018
  • Ingår i: Materials Science and Engineering: R: Reports. - : Elsevier BV. - 0927-796X .- 1879-212X. ; 126, s. 1-29
  • Forskningsöversikt (refereegranskat)abstract
    • Conducting fibres and yams promise to become an essential part of the next generation of wearable electronics that seamlessly integrate electronic function into one of the most versatile and most widely used form of materials: textiles. This review explores the many types of conducting fibres and yarns that can be realised with conjugated polymers and carbon materials, including carbon black, carbon nanotubes and graphene. We discuss how the interplay of materials properties and the chosen processing technique lead to fibres with a wide range of electrical and mechanical properties. Depending on the choice of conjugated polymer, carbon nanotube, graphene, polymer blend, or nanocomposite the electrical conductivity can vary from less than 10(-3) to more than 10(3) S cm(-1), accompanied by an increase in Young's modulus from 10 s of MPa to 100 s of GPa. Further, we discuss how conducting fibres can be integrated into electronic textiles (e-textiles) through e.g. weaving and knitting. Then, we provide an overview of some of the envisaged functionalities, such as sensing, data processing and storage, as well as energy harvesting e.g. by using the piezoelectric, thermoelectric, triboelectric or photovoltaic effect. Finally, we critically discuss sustainability aspects such as the supply of materials, their toxicity, the embodied energy of fibre and textile production and recyclability, which currently are not adequately considered but must be taken into account to ready carbon based conducting fibres for truly practical e-textile applications.
  •  
50.
  • Lund, Anja, 1971, et al. (författare)
  • Roll-to-Roll Dyed Conducting Silk Yarns: A Versatile Material for E-Textile Devices
  • 2018
  • Ingår i: Advanced Materials Technologies. - : Wiley. - 2365-709X. ; 3:12
  • Tidskriftsartikel (refereegranskat)abstract
    • KGaA, Weinheim Textiles are a promising base material for flexible and wearable electronic applications such as sensors, actuators, and energy harvesters. An essential component in such electronic textiles (e-textiles) is electrically conducting yarns. Here, a continuous dyeing process is presented to convert an off-the-shelf silk sewing thread into a wash and wear resistant functional thread with a conductivity of about 70 S cm−1; a record high value for coated yarns. An aqueous ink based on the conducting polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is modified, to produce more than 100 m of dyed conducting threads, which are subsequently converted into e-textiles by both hand weaving and machine embroidery. The yarns are resistant to abrasion and wear, and can be machine washed at least 15 times with retained electronic properties. The woven fabric is used to design a capacitive touch sensor which functions as an e-textile keyboard.
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