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1.	Okda, Sherif, et al. (författare) Testing of the Aerodynamic Characteristics of an Inflatable Airfoil Section 2020 Ingår i: Journal of Aerospace Engineering. - 1943-5525 .- 0893-1321. ; 33:5 Tidskriftsartikel (refereegranskat)abstract Inflatable structures are characterized by being light and easy to manufacture and deploy. Hence, they find many applications in aerospace and aeronautical engineering. In this paper, an inflatable segment with a The National Advisory Committee for Aeronautics (NACA) 0021 airfoil cross-section is designed, fabricated, and tested. The geometrical accuracy of the manufactured inflatable segment is measured using laser scanning. Measurements show that the average normalized error of the chord length and thickness are 2.97% and 0.554%, respectively. The aerodynamic behavior of the inflatable segment is then tested in a wind tunnel at different wind speeds and angles of attack. Lift forces are measured using a six-component balance, while the drag forces are calculated from the wake measurements. The lift and drag coefficients of the inflatable section are compared to those of a standard NACA 0021 airfoil. Finally, flow visualization is examined at different angles of attack using two methods: smoke and tufts. Both methods show that flow separation starts at 15° and full stall occurs at 25°. Results indicate that inflatables can find more applications in the design and construction of aerodynamic structures, such as wings.
2.	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.
3.	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.
4.	Mahade, Satyapal, 1987-, et al. (författare) Incorporation of graphene nano platelets in suspension plasma sprayed alumina coatings for improved tribological properties 2021 Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 570 Tidskriftsartikel (refereegranskat)abstract Graphene possesses high fracture toughness and excellent lubrication properties, which can be exploited to enhance tribological performance of coating systems utilized to combat wear. In this work, suspension plasma spray (SPS) process was employed to deposit a composite, graphene nano-platelets (GNP) incorporated alumina coating. For comparison, monolithic alumina was also deposited utilizing identical spray conditions. The as-deposited coatings were characterized in detail for their microstructure, porosity content, hardness, fracture toughness and phase composition. Raman analysis of the as-deposited composite coating confirmed retention of GNP. The composite coating also showed good microstructural integrity, comparable porosity, higher fracture toughness and similar alumina phase composition as the monolithic alumina coating. The as-deposited coatings were subjected to dry sliding wear tests. The GNP incorporated composite coating showed lower CoF and lower specific wear rate than the pure alumina coating. Additionally, the counter surface also showed a lower wear rate in case of the composite coating. Post-wear analysis performed by SEM/EDS showed differences in the coating wear track and in the ball wear track of monolithic and composite coatings. Furthermore, Raman analysis in the wear track of composite coating confirmed the presence of GNP. The micro-indentation and wear test results indicate that the presence of GNP in the composite coating aided in improving fracture toughness, lowering CoF and specific wear rate compared to the monolithic coating. Results from this work demonstrated retention of GNP in an SPS processed coating, which can be further exploited to design superior wear-resistant coatings.
5.	Mirkhalaf, S. Mohsen, 1982, et al. (författare) A finite element based orientation averaging method for predicting elastic properties of short fiber reinforced composites 2020 Ingår i: Composites Part B-Engineering. - : Elsevier BV. - 1359-8368. ; 202 Tidskriftsartikel (refereegranskat)abstract Short fiber reinforced composites have a variety of micro-structural parameters that affect their macromechanical performance. A modeling methodology, capable of accommodating a broad range of these parameters, is desirable. This paper describes a micro-mechanical model which is developed using Finite Element Analysis and Orientation Averaging. The model is applicable to short fiber reinforced composites with a wide variety of micro-structural parameters such as arbitrary fiber volume fractions, fiber aspect ratios and fiber orientation distributions. In addition to the Voigt and Reuss assumptions, an interaction model is developed based on the self-consistent assumption. Comparisons with experimental results, and direct numerical simulations of Representative Volume Elements show the capability of the model for fair predictions.
6.	Forsgren, Lilian, 1990 (författare) Processing and properties of thermoplastic composites containing cellulose nanocrystals or wood-based cellulose fibres 2020 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.
7.	Shaikh, Abdul Shaafi, 1989, et al. (författare) On the effect of building platform material on laser-powder bed fusion of a Ni-base superalloy HAYNES® 282® 2023 Ingår i: European Journal of Materials. - : Informa UK Limited. - 2688-9277. ; 3:1 Tidskriftsartikel (refereegranskat)abstract Additive manufacturing (AM) by laser powder bed fusion (LPBF) involves melting of layers of powder onto a substrate, called a building platform. Due to cost or convenience considerations, building platform materials rarely match the LPBF material, especially for high temperature materials. To ensure tolerances in component geometries, AM components are often stress-relieved/heat-treated while still attached to the building platform. It is therefore important to understand the effect of dissimilar building platform materials on the properties of the built-up material. These effects may be particularly important for high performance materials such as Ni-base superalloys used for critical applications in the aerospace and energy industries. To investigate this effect, samples of a Ni-base superalloy HAYNES® 282® were built onto a carbon steel building platform in several configurations. The samples were removed from the building platform after heat treatment and subjected to detailed composition analysis and microstructural characterization to investigate the effect of the building platform material on the properties of the additively manufactured part. Room temperature and high temperature tensile testing were used to characterize the material. Results showed no risk of large-scale chemical composition change, or mechanical property degradation of built-up material from on-platform heat treatment.
8.	Koptyug, Andrey, 1956-, et al. (författare) Electron Beam Melting: from Shape Freedom to Materials Properties Control at Macro- and Microscale 2021 Ingår i: Proceedings of the THERMEC 2020, Graz, Austria. - : Trans Tech Publications. ; , s. 755-759 Konferensbidrag (refereegranskat)abstract Electron beam melting (EBM) is one of the constantly developing powder bed fusion (PBF) additive manufacturing technologies (AM) offering advanced control over the manufacturing process. Freedom of component shapes is one of the AM competitive advantages already used at industrial and semi- industrial scale. Development of the additive manufacturing today is targeting both widening of the available materials classes, and introducing new enabling modalities. Present research is related to the new possibilities in tailoring different material properties within additively manufactured components effectively adding “fourth dimension to the 3D-printing”. Specific examples are given in relation to the electron beam melting, but majority of the conclusions are valid for the laser-based PBF techniques as well. Through manipulating beam energy deposition it is possible to tailor quite different material properties selectively within each manufactured component, including effective material density as well as thermal, mechanical, electrical and acoustic properties. It is also possible to acquire by choice both metal-metal composite and completely alloyed material, when blends of precursor powder are used together with the beam energy manipulation.
9.	Liu, X., et al. (författare) Biomimetic Photonic Multiform Composite for High-Performance Radiative Cooling 2021 Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 9:22 Tidskriftsartikel (refereegranskat)abstract Nanostructures on bodies of biological inhabitants in severe environments can exhibit excellent thermoregulation, which provide inspirations for artificial radiative cooling materials. However, achieving both large-scale manufacturing and flexible form-compatibility to various applications needs remains as a formidable challenge. Here a biomimetic strategy is adopted to design a thermal photonic composite inspired by the previously unexplored golden cicada's evolutionarily optimized thermoregulatory ability. A microimprint combined with phase separation method is developed for fabricating a biomimetic photonic material made of porous polymer–ceramic composite profiled in microhumps. The composite demonstrates high solar reflectance (97.6%) and infrared emissivity (95.5%) in atmospheric window, which results in a cooling power of 78 W m−2 and a maximum subambient temperature drop of 6.6 °C at noon. Moreover, the technique facilitates multiform manufacturing of the composites beyond films, as demonstrated by additive printing into general 3D structures. This work offers biomimetic approach for developing high-performance thermal regulation materials and devices.
10.	Harr Martinsen, Kristoffer, 1990 (författare) Preparation and characterization of graphene/metal composites 2021 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Since the isolation of graphene in 2004, much research has been conducted to understand this novel material and how its properties can be utilized in different applications. One type of venture involves graphene as a reinforcing filler in metal matrix composites (MMC) which is becoming increasingly prevalent in the automotive and aerospace industries. Such composites combine the machinability and processing flexibility of metals with the unique properties of graphene. In fact, copper-graphene composites have demonstrated ameliorated mechanical strength with thermal conductivities elevated beyond pristine copper. However, the challenges that remain to commercialize copper-graphene composites are numerous. The most challengeable one is that graphene must be uniformly dispersed in the matrix and adhere to copper through an industrially scalable and affordable process. Moreover, the volume fraction of graphene must be efficiently controlled, lest superfluous amounts lead to structural detriment. In this regard, the emphasis of this study was to investigate a scalable and simple method to obtain such MMC via powder metallurgy. Specifically, gas atomized copper powder was functionalized with 3-aminopropyl-triethoxysilane (APTES) in toluene (APTES-Cu), resulting in a positively charged surface; then aqueously dispersed and negatively charged graphene oxide (GO) could then be self-assembled on the surface APTES@Cu via electrostatic interaction (Cu@APTES-Cu). The thickness of GO layers and morphology on the powder was controlled by modulating APTES grafting duration and APTES concentration in toluene. Cu@APTES-Cu powders were thermally annealed before compaction and sintering in inert atmosphere. The results show that surface modification of metal powders serves as a scalable and versatile approach to coat graphene on metal particles for the preparation of graphene/metal composites. Surface modification of copper with 0.2 vol% APTES in toluene for 30 minutes was sufficient to obtain composite powders with incomplete GO coating, which nonetheless demonstrated improved hardness. However, cold working of sintered composites was essential to densify the porous structure created by reduced GO during sintering. On the other hand, sintered composite samples that exhibited higher thermal conductivity than copper was obtained with higher APTES and GO loading. After thermal annealing, these thicker GO coatings were found to improve thermal conductivity in sintered composites by acting as thermal bridges between individual composite particles. Despite incomplete sintering of these composites, a 20% increase in thermal conductivity was attainable. Finally, both polarization scans and etching measurements in concentrated HCl and ammonium persulfate (APS) indicate that the GO coating decomposes on the outer surface during sintering. However, the reduced GO coating can retard corrosion of the internal composite structure by diffusion inhibition.
11.	Noè, C., et al. (författare) Frontal-Photopolymerization of Fully Biobased Epoxy Composites 2022 Ingår i: Macromolecular materials and engineering. - : Wiley. - 1438-7492 .- 1439-2054. ; 307:6, s. 2100864- Tidskriftsartikel (refereegranskat)abstract The radical-induced cationic frontal photopolymerization (RICFP) of fully biobased epoxy composites is successfully demonstrated. This curing strategy considerably reduces the curing time and improves the efficiency of the composite fabrication. Two different natural fiber fabrics made of cellulose and flax fibers are embedded in two epoxy matrices, one derived from vanillin (diglycidylether of vanillyl alcohol-DGEVA) and the other from petroleum (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate-CE). After RICFP the composites are characterized by means of dynamic mechanical thermal analysis and tensile tests. The mechanical properties improved with increasing fiber content, confirming a strong adhesion between the matrix and the reinforcing fiber fabrics, which is further evidenced by scanning electron microscopy analyses of the fracture surfaces. Furthermore, these fully bio-based composites possess comparable or even higher mechanical strength compared with the corresponding epoxy composites fabricated with conventional CE resin. A promising facile route to high-performing natural fiber-biobased epoxy resin composites is presented.
12.	Kuzminova, Yulia O., et al. (författare) Structural and mechanical properties of the additive manufactured CrFeCoNi(Al,Ti) high-entropy alloys produced using powder blends 2023 Ingår i: Materialia. - : Elsevier. - 2589-1529. ; 32 Tidskriftsartikel (refereegranskat)abstract High-entropy Alloys (HEAs) are considered prospective materials demonstrating the new approach of alloy design creating new compositions for harsh conditions. However, searching for alloy chemical composition providing the best material properties is a costly process. Additive manufacturing (AM) can be an effective technique for adjusting the alloy composition by using several initial materials. The powder bed fusion (PBF) AM process allows the printing of solid parts using powder blends. In the present study, the CrFeCoNi(Al,Ti) HEAs were printed by the PBF technique using the blends of three powders. The structural and phase investigations revealed the chemical inhomogeneity in the materials that led to the new phase formations affecting the mechanical characteristics. The high-temperature annealing at 1200 °C can be considered a post-treatment process for the printed alloys as a homogenization process while the annealing at a lower temperature of 800 °C initiates the decomposition of the initially formed f.c.c. phase.
13.	Xu, Johanna, 1989, et al. (författare) A multicell structural battery composite laminate 2022 Ingår i: EcoMat. - : Wiley. - 2567-3173. ; In Press Tidskriftsartikel (refereegranskat)abstract Multifunctional materials facilitate lightweight and slender structural solutions for numerous applications. In transportation, construction materials that can act as a battery, and store electrical energy, will contribute to realization of highly energy efficient vehicles and aircraft. Herein, a multicell structural battery composite laminate, with three state-of-the-art structural battery composite cells connected in series is demonstrated. The experimental results show that the capacity of the structural battery composite cells is only moderately affected by tensile loading up to 0.36% strain. The multicell structural battery laminate is made embedding the three connected structural battery composite cells between carbon fiber/glass fiber composite face sheets. Electrochemical performance of the multicell structural battery is demonstrated experimentally. High charge transfer resistance for the pack as well as the individual cells is reported. Mechanical performance of the structural battery laminate is estimated by classical laminate theory. Computed engineering in-plane moduli for the multicell structural battery laminate are on par with conventional glass fiber composite multiaxial laminates.
14.	Duan, Shanghong, 1992, et al. (författare) Determination of transverse and shear moduli of single carbon fibres 2020 Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 158C, s. 772-782 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.
15.	Johansen, Marcus, 1994, et al. (författare) Mapping nitrogen heteroatoms in carbon fibres using atom probe tomography and photoelectron spectroscopy 2021 Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 179, s. 20-27 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.
16.	Johansen, Marcus, 1994 (författare) Microstructure of Carbon Fibres for Multifunctional Composites: 3D Distribution and Configuration of Atoms 2021 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.
17.	Amiandamhen, Stephen, 1983-, et al. (författare) Recycling sawmilling wood chips, biomass combustion residues, and tyre fibres into cement-bonded composites : Properties of composites and life cycle analysis 2021 Ingår i: Construction and Building Materials. - : Elsevier Ltd. - 0950-0618 .- 1879-0526. ; 297 Tidskriftsartikel (refereegranskat)abstract This study investigated the properties and sustainability of cement-bonded composites containing industrial residues such as wood chips, tyre fibres and biomass combustion residues, i.e. bottom ash (BA) and fly ash (FA). The effect of cement-to-raw material (wood/tyre fibre) ratio (C/RM) and the aggregate content (BA and FA) on thermal and mechanical properties of the composites were investigated. Scanning electron microscopy (SEM) and life cycle analysis (LCA) were also conducted. The results revealed that as the aggregate content increased in wood composites, the mechanical properties also increased. The mean thermal conductivity and volumetric heat capacity of tyre composite samples were 0.37 W/mK and 1.2 MJ/m3K respectively, while the respective values for wood composite samples were 0.29 W/mK and 0.81 MJ/m3K. SEM analysis showed adequate bonding between wood/tyre fibres and cement matrix. LCA revealed that the materials share of the total primary energy use was about 60% for all analysed composites. © 2021 The Author(s)
18.	Mastantuoni, Gabriella G. (författare) Engineering of lignin in wood towards functional materials 2023 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Through 270 million years of evolution, the finely tuned hierarchical structure of wood has been optimized for efficient nutrient transport and exceptional mechanical stability. Its distinctive orthotropic constitution can provide inspiration and design opportunities for the development of novel functional materials. In recent years, top-down modification approaches have adapted the wood structure for innovative applications, utilizing the hierarchical arrangement at different length scales. In doing so, preserving the structural integrity is of the essence.This thesis explores new top-down modification techniques for the functionalization and structural control of wood-based materials. With the intent of better preserving and utilizing the natural wood organization and native components, two different modification routes were explored on softwood Scots pine: complete lignin removal and in-situ lignin modification. Complete delignification was achieved through preventive crosslinking of the polysaccharide matrix, enhancing intercellular adhesion between tracheids and preventing the disintegration of the cellular arrangement after lignin removal. The second approach focused on chemical modification of lignin by sulfonation as an alternative to complete lignin removal, resulting in wood templates of high negative charge up to 375 µmol g-1 and with well-preserved residual lignin. Hot compression of the delignified wood veneers produced thin wood films with high optical transmittance of 71 % alongside exceptional tensile strength of 449 MPa and Young’s modulus of 50 GPa. Densification of lignin-retaining wood veneers yielded strong and transparent thin films with UV blocking ability. Additionally, these densified films could be easily recycled into discrete wood fibers. The integration of conductive polymers including poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and polypyrrole in in-situ sulfonated wood resulted in bio-composites with high conductivity up to 203 S m-1 and high pseudo-capacitance up to 38 mF cm-2, indicating that tailoring the wood chemistry and activating the redox activity of lignin by sulfonation are important strategies for the fabrication of composites with potential for sustainable energy applications. By tailoring both wood chemistry and morphology, a wood foam with unique microstructure, enhanced permeability, along with high ultimate strength of 9 MPa and Young’s modulus of 364 MPa was obtained. When combined with the conductive polymer PEDOT:PSS, the composite demonstrated uniform conductivity of 215 S m-1 and mechanoresponsive electrical resistance, showing promise in sensing and mechanoresponsive devices.Therefore, in-situ engineering of lignin proved to be a versatile toolkit to obtain wood templates of improved permeability and porosity, greater compliance to densification, and enhanced compatibility with conductive polymers.
19.	Johansen, Marcus, 1994 (författare) Atoms in Lithiated Carbon Fibres 2023 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Carbon fibres are key constituents of structural batteries, in which electrochemical energy storage and mechanical load bearing are merged in one multifunctional device. Here carbon fibres simultaneously act as structural reinforcement by carrying load and as battery electrode by hosting lithium (Li)-ions in its microstructure. However, conventional carbon fibres are not designed to be multifunctional. To enable carbon fibres with optimised multifunctional capabilities, a fundamental understanding of their microstructure, chemical information and interaction with Li is required. In this thesis, mass spectrometry and electron spectroscopy techniques are developed and used to elucidate the atomic distribution, configuration, and interaction in commercial carbon fibres used in structural batteries. Here the methodology of analysing Li in carbon fibres with atom probe tomography (APT) and Auger electron spectroscopy (AES) is demonstrated. Synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES) reveals that certain chemical states of N heteroatoms, pyridinic and pyrrolic, are connected to enhanced electrochemical performance of carbon fibres. AES shows that: Li distributes throughout the entire carbon fibre; the amount of trapped Li is higher and concentrated towards the centre of the fibre at increased discharge rates; Li is initially inserted in amorphous domains and with increased states of lithiation in crystalline domains; and Li plating can occur on individual fibres without spreading to adjacent fibres. APT on lithiated carbon fibres shows that: the distribution of Li is independent of the distribution of N heteroatoms; trapped Li is distributed uniformly in all domains; and Li agglomerates at elevated states of lithiation. The work presented in this thesis paves the way for analysis of carbon-based battery materials with APT and AES. Furthermore, the work unveils much of the interplay between carbon fibre and Li and deepens the understanding of the design parameters for tailoring multifunctional carbon fibres used in improved structural batteries.
20.	Akbarpour, Sahar, et al. (författare) Enhancing the performance of bolted joints in composites by use of patched steel or titanium inserts 2021 Rapport (övrigt vetenskapligt/konstnärligt)abstract A new insert concept that interlaces metal inserts into composite laminates has earlier been shown to improve the relatively poor bearing strength of holes in fibre reinforced polymer composites, and it is here further and more thoroughly investigated. The concept was invented to increase the efficiency of joints with mechanical fasteners in composite materials and this work presents experiments on double bolt joints with inserts made of either stainless steel or a titanium (Ti) alloy. In particular the work compares different implementations of the insert concept by reinforcing one or two holes in double bolt joints, and the effect of using different metals in the inserts. Some complementary tests on pin-loaded specimens and open hole tensile specimens are also performed and compared, also with some results reported previously. Considerable improvements in the bearing load capacity, i.e. 50%-60% or 35%-45%, is attained. The open-hole tensile strength is also improved considerably (almost 30%) when the holes are reinforced with Ti inserts. The fact that the inserts can improve not only the bearing strength but also the performance in open-hole tension implies that the Ti inserts bring nothing but positive effects to the strength of the joints. The test results from single-shear double-bolt specimens with inserts at one hole showed improved strengths of 30% and 20% for specimens with steel and Ti inserts, respectively. Finally, an impressive strength improvement of 40-45% is achieved for single-shear double-bolt specimens having both holes reinforced with inserts of either steel or Ti.
21.	Mentges, N., et al. (författare) Micromechanical modelling of short fibre composites considering fibre length distributions 2023 Ingår i: Composites Part B-Engineering. - 1359-8368. ; 264 Tidskriftsartikel (refereegranskat)abstract Mechanical response of short fibre composites is varying locally with respect to the microstructural constitution of the material, which in turn is a consequence of flow conditions during manufacturing. This local constitution is described by local fibre volume content, local fibre orientation distribution and local fibre length distribution. For short fibre reinforced plastics, both distributions are affected by flow conditions during an injection moulding process. Current material models for predicting the homogenised material response account for the local volume fraction and local fibre orientation distribution. Fibre length distribution, however, is usually approximated with a single average fibre length. To investigate the effects of fibre length distribution on the elasto-plastic response of short fibre composites, a micromechanical Orientation Averaging model has been extended. Two methods are presented in this work. In the first method, an additional averaging scheme over the fibre length distribution is included. In the second method, a novel representative fibre length is presented based on a stiffness-weighted average. The predictionsobtained from these methods are then compared and evaluated against experimental results of uniaxial tensile tests taken from literature. Good agreements are found using both methods. However, for the investigated behaviour, using a representative fibre length is still beneficial due to the superior computational performance.
22.	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.
23.	Svenningsson, Leo, 1990, et al. (författare) Disassociated molecular orientation distributions of a composite cellulose–lignin carbon fiber precursor : A study by rotor synchronized NMR spectroscopy and X-ray scattering 2021 Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 254 Tidskriftsartikel (refereegranskat)abstract Cellulose–lignin composite carbon fibers have shown to be a potential environmentally benign alternative to the traditional polyacrylonitrile precursor. With the associated cost reduction, cellulose–lignin carbon fibers are an attractive light-weight material for, e.g. wind power and automobile manufacturing. The carbon fiber tenacity, tensile modulus and creep resistance is in part determined by the carbon content and the molecular orientation distribution of the precursor. This work disassociates the molecular orientation of different components in cellulose–lignin composite fibers using rotor-synchronized solid-state nuclear magnetic resonance spectroscopy and X-ray scattering. Our results show that lignin is completely disordered, in a mechanically stretched cellulose–lignin composite fiber, while the cellulose is ordered. In contrast, the native spruce wood raw material displays both oriented lignin and cellulose. The current processes for fabricating a cellulose–lignin composite fiber cannot regain the oriented lignin as observed from the native wood. © 2020 The Author(s)
24.	Sciegaj, Adam, et al. (författare) Textile reinforced concrete members subjected to tension, bending, and in-plane loads: Experimental study and numerical analyses 2023 Ingår i: Construction and Building Materials. - 0950-0618. ; 408 Tidskriftsartikel (refereegranskat)abstract Textile reinforced concrete has raised increasing research interest during the last years, mainly due to its potential to be used for freeform shell structures involving complex load situations. Yet, most experimental work has focused on test setups with primarily uniaxial loading. In the current work, such setups are complemented with a novel test setup of deep beams, including in-plane bending and shear. Further, nonlinear finite element analyses were carried out, applying an earlier calibrated bond-slip relation and efficiency factors for strength and stiffness of the textile reinforcement. It was found that the structural behaviour in terms of the overall stiffness, ultimate load and deformation, number of cracks, and total (summed) crack width, could be described with reasonably good accuracy. The inclusion of a calibrated efficiency factor for the stiffness of the yarn was shown to be vital. Moreover, it was shown to be important to weaken and randomise the material properties of the concrete at the location of transverse yarns, to trigger localisation (cracking) in the numerical model.
25.	Akbarpour, Sahar, et al. (författare) Experimental investigation and numerical analysis of multi-material interfaces related to a composite joint concept 2021 Rapport (övrigt vetenskapligt/konstnärligt)abstract An insert concept for reinforcing bolt-holes with high strength metals was previously introduced by the authors, where inserts are anchored in composite laminates through interlacement of composite plies and thin metal patches. The resulting finger-joints must be strong enough to avoid composite-metal debonding happening before bearing failure at the bolt-hole. The strength of the composite-metal interfaces is thus crucial for successful implementation of the insert concept. The paper presents an experimental study investigating the strength of various interface geometries between a prepreg composite material and stainless steel or titanium alloy inserts. In addition to the experimental work, finite element simulations are performed to analyse the stresses at the interfaces. The results indicate that the stress concentrations at multi-material corner points govern the failure and that the strength can be enhanced by expedient design.
26.	Pupurs, Andrejs, et al. (författare) Digital Image Correlation (DIC) Validation of Engineering Approaches for Bending Stiffness Determination of Damaged Laminates 2022 Ingår i: Applied Composite Materials. - : Springer Science and Business Media B.V.. - 0929-189X .- 1573-4897. ; 29, s. 1937-1958 Tidskriftsartikel (refereegranskat)abstract During the last decade new models for bending stiffness prediction of damaged composite laminates have been proposed in the literature advancing the earlier developed engineering approaches in accuracy and in complexity. However, experimental data for validation of complex analytical or engineering models are almost non-existent in the literature. In the present work a detailed experimental study was performed to investigate the bending stiffness reduction of composite cross-ply laminates with evolving micro-damage. Intralaminar cracks and local delaminations in the bottom surface 90-degree layer of carbon/epoxy and glass/epoxy cross-ply laminates were introduced in 4-point bending tests. Digital Image correlation (DIC) technique was used to experimentally determine the midplane curvature. The accuracy of beam theory for bending stiffness determination was assessed. The measured bending stiffness reduction with respect to transverse crack density was also compared with FEM predictions. The results show that the beam theory gives slightly underestimated curvature at low deflections, whereas at large deflections the beam theory overestimates the curvature and the moment–curvature relation becomes nonlinear. Nevertheless, the overall agreement between beam theory and DIC-based results is still very good, which leads to conclude that beam theory based data reduction schemes have sufficient accuracy for predicting bending stiffness even for highly damaged laminates. © 2022, The Author(s)
27.	Talebi, Nasrin, 1992, et al. (författare) CRACK INITIATION CRITERIA FOR DEFORMED ANISOTROPIC R260 RAIL STEEL 2022 Ingår i: CM 2022 - 12th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Conference Proceedings. ; , s. 857-864 Konferensbidrag (refereegranskat)abstract Rail material selection and maintenance planning require accurate material failure criteria. While many of these criteria consider low-cycle fatigue of virgin materials, rail failure is known to occur after severe plastic deformations. It is, therefore, relevant to consider the applicability of such criteria during large plastic deformations. In this study, we simulate previously performed high-shear tension-torsion experiments using finite strain theory to evaluate the local stresses and strains. Based on these results, failure criteria are calibrated and validated. The Jiang-Sehitoglu criterion accurately fits and predicts failure. However, the identified parameter values are different from literature values for similar materials.
28.	Williams Portal, Natalie, et al. (författare) Analysis of tensile behavior of recycled aggregate concrete using acoustic emission technique 2020 Ingår i: RILEM Technical Letters. - Bagneux, France : RILEM Publications SARL. - 2518-0231. ; 5, s. 131-140 Tidskriftsartikel (refereegranskat)abstract Recycled concrete aggregate (RCA) was processed from reinforced concrete edge beams sourced from a demolished bridge in Sweden. This material replaced different ratios of coarse aggregate in a benchmark concrete. The tensile behavior of the developed concrete mixes was characterized via monotonic and cyclic uniaxial tensile tests performed on notched cylinders. Such tensile tests allow for the quantification of the fracture energy and softening behavior of the concrete. Moreover, acoustic emission (AE) measurements were conducted in conjunction with the cyclic tests to characterize e.g. micro‐crack initiation and development, as well as crack localization. The tensile behavior of the various materials was found to be similar with minimal variation in the results. However, the softening behavior suggests that the RCA materials are slightly more brittle compared to both the mother and benchmark materials, which could be indicative of differences in the interface transition zones. The corresponding AE measurements also indicated similarities between the micro‐crack initiation and development for these mixes. It can be constituted that if the concrete used to produce RCA is of high quality and from one source, the resulting RAC will have adequate tensile properties with minimal variation, despite the aggregate replacement ratio. © The Author(s) 2020.
29.	Svenningsson, Leo, 1990 (författare) Molecular orientation in cellulose fibers and composites 2020 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The scope of this thesis is to quantitatively investigate the molecular orientation distribution of regenerated cellulose fibers and composites. The molecular orientation is known to affect macroscopic properties such as tensile strength of the fiber. In addition, the quality of a carbon fiber is, to a great extent, determined by the molecular orientation of the precursor. A plethora of techniques are paramount for materials characterization and a handful of these are suited for determination of molecular orientation. Since different methods have various experimental limitations, methodological awareness is crucial in the strive for quantitative data and in particular when cellulose fibers and other polymers are chemically modified, or a part of a composite. This work concerns three methods in order to investigate molecular orientation: rotor synchronized magic angle spinning solid-state nuclear magnetic resonance spectroscopy (ROSMAS), polarized Raman spectroscopy, and X-ray scattering. The latter is already a proven method for analyzing molecular orientation and was therefore used as a reference for the two first methods, which have never previously been applied on cellulose fibers. ROSMAS was used to investigate the chemical shift anisotropy, which relates to molecular orientation, on a bundle of Lyocell fibers. Polarized Raman spectroscopy was used to analyze the molecular orientation distribution from the Raman vibrational tensor on a single fiber. A new method was developed for polarized Raman spectroscopy by assuming a wrapped Lorentzian orientation distribution function, as measured from X-ray scattering patterns. The results from both ROSMAS and polarized Raman spectroscopy were in agreement with X-ray scattering on a highly oriented cellulose fiber bundle and on a single regenerated cellulose fiber, respectively, indicating that these methods are quantitative. The ROSMAS and X-ray methodologies were applied to a stretched fiber consisting of a regenerated cellulose-lignin composite intended as a carbon fiber precursor. Finally, ROSMAS was also used for determination of the complete chemical shift anisotropy in the molecular reference frame on regio-regular poly(3-hexylthiophene) fibers, in addition to elucidation of backbone and side chain orientation. In the grand perspective, resources have to be used efficiently to minimize environmental impact. Therefore, this work explores man-made environmentally benign cellulose alternatives to cotton and other polymers. These processes refine cellulose from plant life, typically trees, which can grow without pesticide on non-arable land.
30.	Xu, Yunsheng, et al. (författare) Methacrylated lignosulfonate as compatibilizer for flax fiber reinforced biocomposites with soybean-derived polyester matrix 2020 Ingår i: Composites Communications. - : Elsevier BV. - 2452-2139. Tidskriftsartikel (refereegranskat)abstract The poor adhesion between natural fibers and polymer matrix restricts the mechanical performance of natural fiber reinforced composites. Here, lignosulfonate was methacrylated and evaluated as a potential compatibilizer for flax fiber reinforced soybean-derived polyester thermosets. Significant improvement in both tensile and flexural properties of the fiber composites were achieved when the flax fiber mat was treated with methacrylated lignosulfonate solution. In particular, the flexural modulus and flexural strength more than doubled from 2.6 to 6.7 GPa and from 36 MPa to 76.8 MPa, respectively when the fibers were soaked in 5 wt % MLS solution. The SEM analysis revealed improved fiber-matrix interface and lower extent of fiber pull-out in the methacrylated lignosulfonate treated fiber composites, which correlates with the improved mechanical properties.
31.	Anthony, David B., et al. (författare) STRUCTURAL SUPERCAPACITOR COMPOSITE TECHNOLOGY DEMONSTRATOR 2022 Ingår i: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability. ; 5, s. 253-259 Konferensbidrag (refereegranskat)abstract Structural power composites, a class of multifunctional materials, have significant potential to facilitate lightweighting and accelerate widespread electrification in sustainable transportation. In civil aircraft, a bank of supercapacitors can provide power to open the doors in an emergency. Structural power composite fuselage components near the doors could provide this power and eliminate the mass and volume needed for the supercapacitors. To demonstrate this concept, we designed and manufactured a multifunctional component representative of a fuselage rib, which powered the opening and closing of a desktop scale composite aircraft door. This paper provides information about structural supercapacitor technology demonstrators, discusses the fabrication of this demonstrator and concludes by providing an insight into the future challenges that need to be addressed to realise structural power composite components.
32.	Iseri, Emre (författare) Microfluidic Compartmentalization for Smart Materials, Medical Diagnostics and Cell Therapy 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The organisation of fluids in small compartments is ubiquitous in nature, such as in the cellular composition of all life. This work explores several engineering avenues where microscale fluid compartmentalization can bring novel material properties or novel functionality in life sciences or medicine. Here, we introduce four unique compartmentalization methods: 1) 3D fluid self-organisation in microscaffolds (FLUID3EAMS), 2) 2D microcapillary arrays on a dipstick (Digital Dipstick), 3) a sliding microfluidic platform with cross-flow (Slip-X-Chip), and 4) compartmentalization by cutting of soft solid matter (Solidify & Cut). These methods were used in a wide range of applications. Within the area of smart materials, we applied FLUID3EAMS to synthesize materials with temperature-tuneable permeability and surface energy and to establish, in a well-controlled fashion, tissue-like materials in the form of 3D droplet interface bilayer networks. Solidify & Cut was used to form soft composites with a new type of magnetic behaviour, rotation-induced ferromagnetism, that allows easy reprogramming of the magnetization of magnetopolymers. Within the area of medical diagnostics, we applied Digital Dipstick to perform rapid digital bacterial culture in a dipstick format and obtained clinically relevant diagnostic results on samples from patients with a urinary tract infection. Furthermore, Slip-X-Chip enables particle concentration and washing as new functions in sliding microfluidic platforms, which significantly expands their potential application area. Finally, within the area of cell therapy, we explored the microencapsulation of high concentrations of therapeutic cells and presented a novel technique to fabricate core-shell microcapsules by exploiting the superior material properties of spider silk membranes.
33.	Mathern, Alexandre, 1986, et al. (författare) A practical finite element modeling strategy to capture cracking and crushing behavior of reinforced concrete structures 2021 Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:3, s. 1-26 Tidskriftsartikel (refereegranskat)abstract Nonlinear finite element (FE) analysis of reinforced concrete (RC) structures is characterized by numerous modeling options and input parameters. To accurately model the nonlinear RC behavior involving concrete cracking in tension and crushing in compression, practitioners make different choices regarding the critical modeling issues, e.g., defining the concrete constitutive relations, assigning the bond between the concrete and the steel reinforcement, and solving problems related to convergence difficulties and mesh sensitivities. Thus, it is imperative to review the common modeling choices critically and develop a robust modeling strategy with consistency, reliability, and comparability. This paper proposes a modeling strategy and practical recommendations for the nonlinear FE analysis of RC structures based on parametric studies of critical modeling choices. The proposed modeling strategy aims at providing reliable predictions of flexural responses of RC members with a focus on concrete cracking behavior and crushing failure, which serve as the foundation for more complex modeling cases, e.g., RC beams bonded with fiber reinforced polymer (FRP) laminates. Additionally, herein, the implementation procedure for the proposed modeling strategy is comprehensively described with a focus on the critical modeling issues for RC structures. The proposed strategy is demonstrated through FE analyses of RC beams tested in four-point bending—one RC beam as reference and one beam externally bonded with a carbon-FRP (CFRP) laminate in its soffit. The simulated results agree well with experimental measurements regarding load-deformation relationship, cracking, flexural failure due to concrete crushing, and CFRP debonding initiated by intermediate cracks. The modeling strategy and recommendations presented herein are applicable to the nonlinear FE analysis of RC structures in general.
34.	Rempling, Rasmus, 1976, et al. (författare) Utmattning 2021 Ingår i: Betonghandbok material - Hårdnad betong, fysikaliska egenskaper och beständighet. - 9789179170882 ; , s. 485-510 Bokkapitel (övrigt vetenskapligt/konstnärligt)
35.	Olsson, Jens, 1985, et al. (författare) The numerical simulation of standard concrete tests and steel reinforcement using force flux peridynamics 2023 Ingår i: Structural Concrete. - : Wiley. - 1751-7648 .- 1464-4177. ; 24:2, s. 2071-2092 Tidskriftsartikel (refereegranskat)abstract Peridynamics is a numerical particle-based solid mechanics method that enables the simulation of brittle and quasi-brittle materials, as well as ductile materials. It allows cracking to appear spontaneously in the arms joining the particles and can therefore be used to simulate progressive fracture. In this article, we apply our version of peridynamics, which we call force flux peridynamics, to the simulation of concrete where the appearance of cracks plays an important role in the global mechanical properties. It is not difficult to modify the material parameters in peridynamics to achieve a given tensile strength or a given compressive strength. However, it is much more difficult to choose parameters which will model all the strength parameters of a material within the same model. When concrete fails in compression it may split or spall showing a complex relationship between compressive and tensile failure. We therefore set ourselves the simple task of producing a single peridynamics model which can predict the stiffness and strength behavior of concrete in standard compression and tension tests for which we chose the American Society for Testing and Materials standards for the cylinder compression test, the split cylinder test, and the modulus of rupture test. A parameter sensitivity study was performed based on the cylinder compression test to tune the key peridynamics parameters that determine the global material behavior. The compressive and tensile strengths were then determined from the combined simulation data. While the fracture modes, crack branching pattern and also the stress–strain curve show promising results, the maximum tensile strength was found to be significantly larger than physical experiments suggest. This is probably due to imperfections within real concrete at the interface between aggregate particles and cement paste and it shows that the detailed numerical modeling of the failure of concrete is highly complex with a large number of unknown material parameters.
36.	Montanari, Celine (författare) Transparent Wood Biocomposites for Sustainable Development 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Sustainable wood nanotechnologies that combine optical transmittance and mechanical performance are interesting for new functionalities utilizing transparency. Wood is a sophisticated bio-based material with a natural hierarchical, anisotropic and porous structure. The wood cellular structure can be functionalized at the micro and nanostructural level for the design of advanced functional materials. In recent years, the development of transparent wood biocomposites derived from delignified wood substrates have gained interest because they combine attractive structural properties with optical functionality. Nanostructural tailoring of transparent wood biocomposites is required to improve optical transmittance, mechanical performance, and to add new functionalities. In this thesis, environmentally friendly material components and green chemical processes have been developed for the fabrication of nanostructurally tailored transparent wood biocomposites.Mesoporous delignified wood substrates with preserved microstructure and cellulose microfibril alignment in the cell wall are used as reinforcement in transparent wood biocomposites. Chemical functionalization strategies using renewable maleic, itaconic and succinic anhydrides have been explored for molecular and nanostructural tailoring of delignified cell walls. Cyclic anhydride functionalization results in high degree of esterification, reduces moisture content in the wood substrate, improves monomer diffusion within the cell wall, and further enables interface tailoring at the molecular scale with possibility for covalent attachment with polymer matrix. Transparent wood biocomposites were prepared by methyl methacrylate monomer impregnation followed by in situ polymerization within the chemically modified wood substrates. The anhydride-functionalized transparent wood biocomposites have improved wood-polymer interfacial interactions, resulting in improved optical and mechanical properties. Moreover, a bio-based polymer matrix was designed from renewable limonene oxide and acrylic acid for the fabrication of fully bio-based transparent wood biocomposites. The bio-based monomer can diffuse into the cell wall, and the polymer phase is both refractive index-matched and covalently linked to the wood substrate. The bio-based transparent wood biocomposites are nanostructured and demonstrate superior optical transmittance, low haze, and excellent mechanical performance.Nanostructural functionalization using phase-change materials is also demonstrated for the design of transparent wood biocomposites that combine thermal energy storage, tunable optical properties, and load bearing functions. Molecular and nanoscale interactions in transparent wood biocomposites are critical as they contribute to the favorable distribution of the phase-change material across the wood structure, which is a key component in optimizing thermal energy storage capacity. Bio-based design of transparent wood is also explored for thermal energy storage applications. Low environmental impact is achieved by combining the use of bio-based resources with green processing routes. Environmentally friendly transparent wood nanotechnologies can compete with petroleum-based plastics in applications such as load-bearing transparent panel and energy saving.
37.	Venkatesh, Abhijit, 1989 (författare) Melt-processing and properties of thermoplastic composites based on ethylene-acrylic acid copolymer reinforced with wood nanocellulose 2020 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Composites reinforced with cellulose nanofibers (CNF), both modified and unmodified cellulose nanocrystals (CNC) and pulp fibers have been prepared through small-scale and large-scale methods. The composites were produced by water-assisted dispersion mixing, drying and compression moulding on the laboratory scale and by extrusion and injection moulding for the large-scale production. The compression-moulded composites were stiffer and stronger by a factor of more than 10 for the CNF or pulp-based samples (>50 wt%) and by a factor of 3 for the CNC-based composites (at 10 wt%). The addition of a lubricant to pulp-based fibers resulted in a behaviour similar to that of a compatibilizer at low concentrations and to that of both compatibilizer and lubricant at higher concentrations. However, when the processing was scaled up, the improvement in properties was much less for the CNF-based and CNC-based composites after being melt-processed via extrusion and injection moulding, despite the fact that they showed a percolated cellulose network. Although the scale-up was successful, aggregates were observed. These aggregates could be reduced to some extent by changing the process design and parameters. Water-assisted extrusion was also used to reduce the aggregation but there was little improvement in properties. It is suggested that the extent of melt flow in the processing method influences the final properties of the composites, despite the nanoscale reinforcement.
38.	Carlstedt, David, 1984 (författare) Computational modelling of structural battery composites 2022 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Batteries and surrounding structures (e.g. battery modules and packs) in electrical vehicles and devices are often designed in a way that prevents the electro-chemically active part of the battery cells from being exposed to mechanical loads during operation/service. This means that the energy storage capability is added as a monofunctional addition to the system (i.e. it only provides one functionality, storing energy). Hence, one of the main drawbacks of the existing technology is its energy storage to weight ratio, in terms of the complete system. A viable route to improve this ratio is to develop energy storage solutions with the ability to sustain mechanical loads. Indeed, by adding this additional functionality, such solutions offer significant system mass and volume savings and allow for innovative future design of electric vehicles and devices. The structural battery composite material is made from carbon fibre reinforced structural battery electrolyte (SBE), and exploits the multifunctional capability of the material constituents to facilitate electrical energy storage in structural components. Due to its inherent multifunctionality, the physical phenomena occurring within the material during operation will interact. Further, due to the fact that the studied material is intended to perform multiple functions some of the couplings between the physical processes are expected to be more pronounced, and critical to design, as compared to conventional batteries. Hence, to accurately predict and evaluate the combined performance of structural batteries, coupled multiphysics models are needed. In this thesis, a computational modelling framework to predict the coupled thermo-electro-chemo-mechanical performance of structural batteries is developed. The framework is utilized to study the essential couplings between the physical processes and numerical predictions are compared favourably with experimental data. It is shown that two-way coupling between the electro-chemical and mechanical processes is important to account for when evaluating the combined electro-chemo-mechanical performance of structural batteries. Further, it is shown that the convective contribution to the mass flux of ions in the SBE, as well as the thermal effects during operations are crucial to consider when evaluating the combined performance. Moreover, the framework is extended to study an electro-chemically driven actuator and sensor utilizing carbon fibre-SBE electrodes. Finally, in addition to the modelling work a laminated structural battery with unprecedented multifunctional (i.e. combined mechanical and electro-chemical) performance is manufactured and characterized, featuring an energy density of 24 Wh/kg and an elastic modulus of 25 GPa and tensile strength exceeding 300 MPa.
39.	Anilkumar, V., et al. (författare) Impact of heat treatment analysis on the wear behaviour of al-14.2si-0.3mg-tic composite using response surface methodology 2021 Ingår i: Tribology in Industry. - : Faculty of Engineering, University of Kragujevac. - 0354-8996 .- 2217-7965. ; 43:4, s. 590-602 Tidskriftsartikel (refereegranskat)abstract Al-14.2Si-0.3Mg Alloy reinforced with hard phased TiC coarse particulates (10 wt-%) was contrived using the liquid metallurgy route. The so fabricated aluminium metal matrix composites was made to undergo solutionising at 5250C for 12 hours in a heat treatment furnace and was subsequently water quenched to room temperature. The developed composite was then kept for age hardening at varying temperatures and time for enhanced tribological properties. A pin on disc Tribometer (ASTM-G99) was utilised to study the wear properties of the fabricated composite. Aging temperature (0C), applied load (N) and Aging time (hours) were chosen as the process parameters for analysing the material's resistance to wear. Using response surface methodology the influence of reinforcement in the wear properties of the composite was studied. The design of the regression equation was prepared and the impact of each experimental parameter was scrutinized. Results depict that with an increase in the aging temperature, aging time and load, there observed a variation in the materials wear properties. The worn-out surface of the metal matrix composite was then investigated with the help of the Scanning Electron Microscope (SEM).
40.	Liu, Jun, et al. (författare) Investigation of using limestone calcined clay cement (LC3) in engineered cementitious composites: The effect of propylene fibers and the curing system 2021 Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 2117-2144 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.
41.	Asp, Leif, 1966, et al. (författare) A structural battery and its multifunctional performance 2021 Ingår i: Advanced Energy and Sustainability Research. - : Wiley. - 2699-9412. ; 2:3 Tidskriftsartikel (refereegranskat)abstract Engineering materials that can store electrical energy in structural load paths can revolutionize lightweight design across transport modes. Stiff and strong batteries that use solid-state electrolytes and resilient electrodes and separators are generally lacking. Herein, a structural battery composite with unprecedented multifunctional performance is demonstrated, featuring an energy density of 24 Wh kg-1 and an elastic modulus of 25 GPa and tensile strength exceeding 300 MPa. The structural battery is made from multifunctional constituents, where reinforcing carbon fibers (CFs) act as electrode and current collector. A structural electrolyte is used for load transfer and ion transport and a glass fiber fabric separates the CF electrode from an aluminum foil-supported lithium–iron–phosphate positive electrode. Equipped with these materials, lighter electrical cars, aircraft, and consumer goods can be pursued.
42.	Frihart, Charles R., et al. (författare) Joining and Reassembling of Wood 2023 Ingår i: Springer Handbooks. - 2522-8692 .- 2522-8706. ; , s. 707-791 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract Commonly the raw material round timber is reduced into smaller parts such as solid wood boards, sheets of veneer, strands, particles, and fibers for further manufacturing and processing. In following steps, the single wooden pieces are joined together by adhesive bonding to achieve the final structures such as various types of wood laminations or wood-based panels. This chapter describes the various mechanical connecting and adhesive bonding solutions. Different mechanical connector systems are introduced in theory and practice. A major part of the chapter is dedicated to wood adhesion and the basic aspects of the wood-adhesive interactions. Various adhesive types, their chemistries, morphologies, and their processes of solidification and curing are introduced, and additionally their utility in wood bonding is emphasized. Different methods of assessing and testing bond strength are also presented. Linear-friction wood welding, as an innovative approach for bonding, which is not yet fully established in practice, is also described. Pressing processes are indispensable in the various adhesive bonding processes of wood in order to produce wood-based materials from veneers, particles, and fibers. Different basic pressing types and press processes are given and are discussed with respect to their application.
43.	Fernström, Vilma, et al. (författare) VARIATION ANALYSIS OF CARBON FIBRE REINFORCED POLYMERS LIGHT WEIGHT AERO ENGINE PARTS 2022 Ingår i: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE). ; 2-B Konferensbidrag (refereegranskat)abstract In this paper the focus is on variation analysis for composite CFRP (carbon fibre reinforced polymers) parts. A detailed study of possible sources of variation in manufacturing of CFRP parts is presented. Based on the variables identified a simulation chain on how to manage and simulate this variation is described. This paper also presents a logical approach to how a digital twin for a fully automated production line of compression molded CFRP parts can be built, and to investigate and quantify how much each individual variable contributes to the final variation in the component.
44.	Siam Siraj, Mohammad, 1993, et al. (författare) Advancing Structural Battery Composites: Robust Manufacturing for Enhanced and Consistent Multifunctional Performance 2023 Ingår i: Advanced Energy and Sustainability Research. - 2699-9412. ; 4:11 Tidskriftsartikel (refereegranskat)abstract Multifunctional materials offer a possibility to create lighter and more resource-efficient products and thereby improve energy efficiency. Structural battery composites are one type of such a multifunctional material with potential to offer massless energy storage for electric vehicles and aircraft. Although such materials have been demonstrated, their performance level and consistency must be improved. Also, the cell dimensions need to be increased. Here, we develop a robust manufacturing procedure and repeatedly manufacture structural battery composite cells with double the multifunctional performance and size compared to state-of-the-art structural battery cells. Furthermore, six structural battery cells are selected and laminated into a structural battery composite multicell demonstrator to showcase the technology. The multicell demonstrator performance is characterised for two different electrical configurations. The low variability in the multifunctional properties of the cells verifies the potential for upscaling offered by the proposed manufacture technique.
45.	Jungstedt, Erik, et al. (författare) Fracture toughness of wood and transparent wood biocomposites in the toughest LT-direction 2023 Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 231 Tidskriftsartikel (refereegranskat)abstract Fracture toughness and mechanisms of crack growth are characterized for transparent wood polymer biocomposites and compared to native wood, with the crack normal to the fiber direction (LT fracture plane). Side-grooved specimen geometries generated pure mode I crack growth, whereas previous investigations commonly report 90° crack path deflection. Crack growth micromechanisms were analyzed by experimental fracture tests and in-situ microscopy observations. Large damage zones around the crack tip with fiber bundle bridging and pull-out were observed in the crack wake, justifying more advanced cohesive zone modeling suitable for composite materials design. The polymer matrix resulted in much higher fracture energy of the biocomposites compared to native wood due to increased local cohesive strength. This strength increased from the polymer contribution and more homogeneous stress distribution in the wood fibers.
46.	Shoja, Siavash, 1982, et al. (författare) Application of low frequency guided waves to delamination detection in large composite structures: a numerical study 2020 Ingår i: ECCM 2018 - 18th European Conference on Composite Materials. ; , s. 1-7 Konferensbidrag (refereegranskat)abstract The aim of the current work is to identify the challenges in computational modelling of ultrasonic guided wave propagation in large structures and developing methods to overcome them. The work includes investigating the application of GW in composite laminates and sandwich materials with the aim of delamination detection. Moreover, phased array systems are introduced as a method of overcoming the negative effect of high damping properties in such structures. Propagation of GW in a wind turbine blade is studied as an example of large structure with the aim of defect detection. Results that show GW can be used as a potential tool for structural health monitoring of wind turbine blades.
47.	Niemz, Peter, et al. (författare) Important Data 2023 Ingår i: Springer Handbook of Wood Science and Technology. - : Springer Science and Business Media Deutschland GmbH. - 9783030813147 - 9783030813154 ; , s. 1977-2003 Bokkapitel (refereegranskat)abstract This chapter is an Appendix that provides information on material and process parameters. The data may constitute a basis for a first approximation in calculations of material characteristics and production capacities, etc. The presentation is in tabular form, sometimes with indications of the variation range. Data are presented for solid wood of different species and from different parts of the world, modified wood, and wood-based materials. Information on natural fibers, adhesives, and coating materials is also provided. For some selected processes, values for material and energy consumption during the production of materials such as sawn timber, wood-based materials, paper pulp, and paper are also presented. The chapter also contains an overview of standardization in different regions of the world, and a compilation of useful books in the field of wood science and technology.
48.	Edgren, Aina, 1995, et al. (författare) High temperature compression of Mo(Si,Al)2-Al2O3 composites 2023 Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 865 Tidskriftsartikel (refereegranskat)abstract The aim of this study was to investigate the effect on high temperature of mechanical properties of adding Al2O3 particles to polycrystalline Mo(Si,Al)2. Mo(Si,Al)2-Al2O3 composites, containing 0–25 wt% Al2O3 particles have been compression tested at 1300 °C, and the microstructure after deformation was studied using electron backscatter diffraction. It was shown that even small amounts (5 wt%) of Al2O3 particles resulted in a grain-refined material through inhibition of grain growth during sintering, which lead to lower flow stresses compared to the coarse-grained Al2O3-free material. The inverse grain size effect and post-test microstructure investigations suggest that creep-like deformation mechanisms dominate in fine grained Mo(Si,Al)2-Al2O3 composites at 1300 °C. In the materials containing 5–15 wt% Al2O3, the maximum stress decreased with increasing Al2O3 content. In materials with higher Al2O3 additions, the maximum stress increased with the Al2O3 addition, but did not reach the strength levels in the Al2O3-free reference material. It is suggested that the deformation behaviour is affected by electroplasticity effects as resistive heating was used. Electroplasticity contributes to the decrease in maximum stress observed in the lower Al2O3 containing materials, while this is outweighed by particle strengthening at higher Al2O3 contents.
49.	Ishfaq, A., et al. (författare) Multifunctional design, feasibility and requirements for structural power composites in future electric air taxis 2023 Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 57:4, s. 817-827 Tidskriftsartikel (refereegranskat)abstract This study investigates the viability of implementing multifunctional structural power composites in a four-seater air taxi, the CityAirbus. For a given specific energy of the power source, the cruise endurance can be approximately doubled by using structural power composites as opposed to conventional batteries. Replacing all the eligible composite mass and batteries with structural power composites can reduce the CityAirbus weight by 25%. To achieve the current design performance, the minimum required elastic modulus, strength, specific energy and power for the structural power composite are 54 GPa, 203 MPa, 74 Wh/kg and 376 W/kg, respectively: current state-of-the-art structural power composites are now approaching this level of performance. Hence, structural power composites are considered feasible for adoption in the urban air mobility sector and have the potential to improve endurance and facilitate commercialization. This paper also discusses several key challenges that must be addressed to realize the adoption of structural power composites in future electric air taxis.
50.	Zhang, Hanzhu, 1991-, et al. (författare) Refractory multicomponent boron-carbide high entropy oxidation-protective coating for carbon-carbon composites 2021 Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 425 Tidskriftsartikel (refereegranskat)abstract A novel refractory multicomponent boron-carbide coating of 300 nm thickness, HfMoTaTi-BC, was deposited on carbon-carbon composites (CCC). The coating showed a face-centred cubic (FCC) structure of lattice parameter of 0.4429 nm with an average crystallite size of 5 nm. The FCC coating transformed from single-phase solid solution into multiple ceramic carbides and boride phases at 900°C during long-term thermal stability test. The exposure of HEC coated CCC to the flame (2000°C) of liquefied petroleum gas (LPG) torch for 5 minutes revealed that the film had excellent resistance to oxidation and protected the CCC material under extreme aerothermal heating.

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