| 1. |
- Lindberg, Siv M, et al.
(författare)
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A product semantic study of the influence of the sense of touch on the evaluation of wood-based materials
- 2013
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 52, s. 300-307
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Tidskriftsartikel (refereegranskat)abstract
- Based on product semantics, this study investigated how the tactile attributes of wood and wood-based composites are perceived and interpreted semantically. The wood-based samples included ash, birch, elm, oak, pine, OSB (oriented strand board), two wood pulp-reinforced polylactide composites, Comp A and B and one wood-fiber reinforced polypropene composite, Comp C. The subjects rated the samples by the descriptive words natural, exclusive, eco-. friendly, rough, inexpensive, reliable, warm, modern, snug and solid. The most significant differences between the samples were found for roughness and for the descriptors, reliable, natural and solid. A principal component analysis yielded three attributes based on the tactile perceptions: reliable, old-. fashioned and smooth. The solid wood pieces were perceived as natural and oak was perceived as being exclusive. The composite materials presented a greater variation in terms of perceived attributes than the wood specimens.
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| 2. |
- Chen, Zhe, et al.
(författare)
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Nano-scale characterization of white layer in broached Inconel 718
- 2017
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - Amsterdam : Elsevier BV. - 0921-5093 .- 1873-4936. ; 684, s. 373-384
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Tidskriftsartikel (refereegranskat)abstract
- The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.
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| 3. |
- Duan, Shanghong, 1992, et al.
(författare)
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Determination of transverse and shear moduli of single carbon fibres
- 2020
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 158C, s. 772-782
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Tidskriftsartikel (refereegranskat)abstract
- Carbon fibres are extensively used for their high specific mechanical properties. Exploiting their high axial stiffness and strength, they are employed to reinforce polymer matrix materials in advanced composites. However, carbon fibres are not isotropic. Data of the elastic properties in the other directions of the fibres are still largely unknown. Furthermore, standardised methods to characterise these properties are lacking. In the present work, we propose a methodology to determine the transverse and shear moduli of single carbon fibres. An experimental procedure is developed to fabricate high-quality, flat fibre cross-sections in both longitudinal and transverse directions using Focused Ion Beam, which gives full control of the specimen geometry. Indentation modulus on those surfaces are obtained using both Atomic Force Microscopy (AFM) and nanoindentation tests. Hysteresis was found to occur in the nanoindentation tests. The hysteresis response was due to nano-buckling and reversible shear deformation of the carbon crystals. For this reason, indentation tests using AFM is recommended. From the AFM indentation tests the transverse and shear moduli of three different carbon fibres (IMS65, T800 and M60J) are successfully determined.
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| 4. |
- Johansen, Marcus, 1994, et al.
(författare)
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Mapping nitrogen heteroatoms in carbon fibres using atom probe tomography and photoelectron spectroscopy
- 2021
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 179, s. 20-27
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Tidskriftsartikel (refereegranskat)abstract
- Carbon fibres show great potential as multifunctional negative electrode for novel structural battery composites – a rechargeable electrochemical cell with structural function. The electrochemical performance of carbon materials can be enhanced with nitrogen heteroatoms, which conveniently are inherent in polyacrylonitrile (PAN)-based carbon fibres. However, it is not fully understood how the electrochemical performance is governed by microstructure and composition of the carbon fibres, particularly the distribution and chemical states of nitrogen heteroatoms. Here we reveal the atom-by-atom three-dimensional spatial distribution and the chemical states of nitrogen in three PAN-carbon fibre types (M60J, T800 and IMS65), using atom probe tomography (APT) and synchrotron hard X-ray photoelectron spectroscopy (HAXPES), and correlate the results to electrochemical performance. The findings pave the way for future tailoring of carbon fibre microstructure for multifunctional applications.
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| 5. |
- Johansen, Marcus, 1994
(författare)
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Microstructure of Carbon Fibres for Multifunctional Composites: 3D Distribution and Configuration of Atoms
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lightweight energy storage is a must for increased driving range of electric vehicles. “Mass-less” energy storage can be achieved by directly storing energy in structural components. In such multifunctional devices called structural composite batteries, carbon fibres carry mechanical load and simultaneously act as negative battery electrode by hosting lithium ions in its microstructure. Little is known of how the microstructure of carbon fibres is optimised for multifunctionality, and deeper understanding of the configuration and the distribution of atoms in carbon fibres is needed. Here synchrotron hard X-ray photoelectron spectroscopy and atom probe tomography are used to reveal the chemical states and three-dimensional distribution of atoms in commercial carbon fibres. This thesis presents the first ever guide for how to perform atom probe tomography on carbon fibres, and the first ever three-dimensional atomic reconstruction of a carbon fibre. The results show that the chemical states and distribution of nitrogen heteroatoms in carbon fibres affect the electrochemical performance of the fibres. Carbon fibres performed electrochemically better with higher amount of nitrogen with pyridinic and pyrrolic configurations. Additionally, the nitrogen concentration varies throughout the carbon fibre, which may suggest that the electrochemical properties also vary throughout the carbon fibre. The knowledge provided by this thesis can lead to future carbon fibre designs with enhanced electrochemical performance for multifunctional applications.
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| 6. |
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| 7. |
- Forsgren, Lilian, 1990
(författare)
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Processing and properties of thermoplastic composites containing cellulose nanocrystals or wood-based cellulose fibres
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose nanocrystals (CNC) were surface modified with dialkylamines to increase the compatibility between the CNC and the polymeric matrix, and promising results were obtained, with a 300 % stiffness increase when the mixed dispersion was compression moulded on a laboratory scale. The manufacturing process was up-scaled using water-assisted mixing in a twin-screw extruder (TSE) followed by a second compounding step and injection moulding (IM). The composites were successfully produced using conventional melt-processing techniques but these did not show the same improvement in mechanical performance, probably due to the formation of CNC aggregates. There were indications of network formation when CNC was added, especially in the case of surface-modified CNC. Cellulose fibres and thermomechanical pulp were used as reinforcement in similar types of polymer matrices and the mixtures were similarly processed by TSE and IM. These materials were characterized with regard to appearance and durability. The discoloration of the composites due to excessive heat during processing did not significantly affect their mechanical properties, and the addition of the cellulose-based reinforcement to the polymer did not reduce its resistance to thermo-oxidative degradation compared to that of the pure matrix. In fact, the resistance to degradation was increased when lignin was present in the reinforcing element, showing a synergistic effect together with the added anti-oxidant. Superior properties were expected for the CNC composites compared to those of the larger cellulose fibre reinforcements, but in continuous production the stiffening effects were similar regardless of reinforcement type. These results confirm that the processing method and properties strongly affect the final properties of the composite.
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| 8. |
- Muneer, Faraz, et al.
(författare)
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Preparation, Properties, Protein Cross-Linking and Biodegradability of Plasticizer-Solvent Free Hemp Fibre Reinforced Wheat Gluten, Glutenin, and Gliadin Composites
- 2014
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 9:3, s. 5246-5261
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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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| 9. |
- Hosseini, Seyedehsan, 1994
(författare)
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Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
- 2023
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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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| 10. |
- Liu, Jun, et al.
(författare)
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Investigation of using limestone calcined clay cement (LC3) in engineered cementitious composites: The effect of propylene fibers and the curing system
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 2117-2144
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Tidskriftsartikel (refereegranskat)abstract
- Limestone calcined clay cement (LC3) is a new type of low-carbon cement that can reduce energy consumption and carbon dioxide emissions while meeting the performance requirements of ordinary cement. In this study, polypropylene (PP) fibers were mixed into limestone calcined clay cement-based materials to make new low-carbon ECCs. In this study, a total of 24 sets of specimens were designed for 4 groups of curing ages and 6 types of mix ratios. The compressive load–displacement data were measured the compressive curve characteristics were analyzed then, a compressive constitutive model of the composites was deduced and obtained. Through XRD, SEM-EDS and MIP experiments, the reasons and laws of the compressive strength ranges of adding PP fibers and LC3 to engineered cementitious composites (LC3-PP-ECCs) are further explained from the perspective of the pore size, microstructures and hydration products. The results show that, after 28 days, the compressive strength values of LC3-PP-ECCs generally decreases with increasing PP fiber content and the combined effect of PP fibers and hydration products causes the compressive strength of LC3-ECCs with 0.5% PP fibers to drop sharply. In addition, the specimens showed better properties in terms of toughness, ductility and energy absorption. However, in the microstructures, the addition of PP fibers will cause more internal defects and flaws. This results of this study can provide some theoretical experience and technical support for the engineering application of LC3-ECCs.
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