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Mildly delignified softwood holocellulose fibers featuring native tracheid fiber cell wall structure and high hemicellulose content are prominent building blocks for wood derived fiber-based materials. However, preserving the natural alignment of long softwood fiber is challenging since top-down structure-retaining delignified softwood is unstable as extensive removal of lignin from intercellular space induces cracking and disintegration of wood structure. Here we report the use of chemical crosslinking pretreatment to improve the intercellular bonding between softwood fibers, therefore preserving the integrity of the naturally aligned softwood fibers after delignification. The crosslinked softwood veneer was delignified with peracetic acid and further densified into transparent and high-density film by thermal compression. The obtained transparent film of naturally aligned softwood holocellulose fibers showed high optical transmittance of 71 %, high haze of 85 %, strong optical anisotropy, as well as high tensile strength of 449 ± 58 MPa and high Young's modulus of 49.9 ± 5.6 GPa. This study provides a facile approach to preserve the natural alignment of softwood fibers for the fabrication of high performance holocellulose fibers-based materials., QC 20240925

Screw-bone construct failures are a true challenge in orthopaedic implant fixation, particularly in poor quality bone. Whilst augmentation with polymeric or ceramic bone cement can improve the primary stability of the screws, the cement may block the flow of blood and nutrients and hamper bone remodelling. In this study, soft, non-setting biomaterials based on Hyalectin gels and hydroxyapatite (HA) particles with different morphological parameters were evaluated as potential augmentation materials, using a lapine ex vivo bone model. The pull-out force, stiffness, and work to fracture were considered in evaluating screw attachment. The pull-out force of constructs reinforced with Hyalectin containing irregularly shaped nano-HA and spherically shaped micro-HA particles were found to be significantly higher than the control group (no augmentation material). The pull-out stiffness increased for the micro-HA particles and the work to fracture increased for the irregular nano-HA particles. However, there were no significant augmentation effect found for the spherical shaped nano-HA particles. In conclusion, injectable Hyalectin gel loaded with hydroxyapatite particles was found to have a potentially positive effect on the primary stability of screws in trabecular bone, depending on the HA particle shape and size.

This study presents the fabrication of LiFePO4 (LFP)-coated carbon fibers (CFs) as a positive electrode component for structural batteries, utilizing a spray coating technique. The successful coating of CFs through this method demonstrated their usefulness as efficient current collectors. The electrodes obtained using this method underwent electrochemical evaluations. Throughout the extended cycling tests at C/7, the maximum specific discharge capacity reached 146 mAh/g, maintaining a 77% capacity retention after 100 cycles. In rate performance assessments at the faster C-rate of 1.5C, the capacity measured 123 mAh/g, with a retention of 96%. The application of spray coating emerges as a promising technique for electrode production in structural batteries, showcasing its potential for optimizing performance in multifunctional energy storage systems., QC 20240219

The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small- and wide-angle X-ray scattering with full-field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research., QC 20240325

As research and development of nanocomposites receive more attention in today's fast-paced world. SiC nanowires (SiC NWs) and their composites exhibit numerous unique and exceptional properties. As a result, they are widely used in various fields such as the chemical industry, optoelectronic devices, electronic products, aerospace, and military applications. In this paper, we present a comprehensive summary of the synthesis technology, distinctive properties, and potential applications of SiC NWs and the composite constructed from them. The introduction begins with an overview of the basic concept and characteristics of SiC. It then provides a detailed list of common synthesis methods, including precursor infiltration pyrolysis, chemical vapor deposition, solvothermal synthesis, carbothermal reduction, template method, other methods of molten salt, controllable chemical etching, and self-assembly synthesis. The advantages and shortcomings of these methods are also discussed in the context of specific applications. Then, the special performance and multidisciplinary applications are displayed after summarizing the previous studies. Eventually, this review concludes with an outlook on future research regarding SiC NWs and their composite materials, highlighting major prospects, challenges to be addressed, and possible solutions in a wide range of areas. A systematic overview of the topic of interest actually helps to reveal patterns in research cognition, plays a potential role in fostering awareness of scientific innovation and cross-thinking, and also serves as a guide for scientific research and interest development., QC 20240208

The properties of organic fibre-based hybrid materials are influenced by a variety of factors and even minor changes in these variables can outcome in substantial discrepancies in strength. In this regard, the current study aims to optimise various influencing parameters such as weight percentage, alkaline treatment concentration, and fabrication parameters (compression moulding pressure, and temperature), with the goal of enhancing the overall strength of the composite. Calotropis gigantea-stem and Prosopis juliflora-bark fibres were used in varying weight percentages to create epoxy-based hybrid composites. After fabrication the mechanical characterisation like tensile, flexural, and impact properties of the composites were tested. Taguchi experimental design was applied, and the results were analysed using a hybrid Taguchi-grey relational investigation method. It was observed that a combination of 20 wt.% Calotropis gigantea/20 wt.% Prosopis juliflora/6 % NaOH pretreatment/100 °C temperature with 14 MPa pressure and had the most desirable mechanical properties in the fabricated composites. Calotropis gigantea ranks first in enhancing the composite strength, followed by Prosopis Juliflora, NaOH pretreatment%, compression moulding temperature and pressure. This work highlights the significant role of Calotropis gigantea and Prosopis Juliflora fibres in enhancing composite strength and provides valuable insights for future research in the field of hybrid composite development., Validerad;2024;Nivå 1;2024-03-22 (joosat);Full text license: CC BY 4.0

Due to the high interest in the use of glass/epoxy laminates in aerospace applications, aviation, and as cryogenic tanks, it is crucial to understand the behavior of composites under challenging environmental conditions. Polymer composites are exposed to low temperatures, including cryogenic temperatures, which can lead to the initiation of microdamage. This paper investigates damage initiation/accumulation and its influence on the properties of cross-ply woven glass fiber epoxy composites at low temperatures compared to room temperature conditions. To evaluate the influence of a low-temperature environment on the mechanical performance of glass fiber reinforced epoxy composite (GFRP) laminates, three types of test campaigns were carried out: quasi-static tensile tests and stepwise increasing loading/unloading cyclic tensile tests at room temperature and in a low-temperature environment (−50 °C). We demonstrated that the initial stiffness of the laminates increased at low temperatures. On the other hand, there were no observed changes in the type or mechanism of developed damage in the two test conditions. However, the reduction in stiffness due to the accumulated damage was more significant for the laminates tested at low temperatures (~17% vs. ~11%). Exceptions were noted in a few formulations where the extent of damage at low temperatures was insignificant (<1%) compared to that at room temperature. Since some of the studied laminates exhibited a relatively minor decrease in stiffness (~2–3%), we can also conclude that the formulation of matrix material plays an important role in delaying the initiation and formation of damage., Validerad;2024;Nivå 2;2024-01-22 (joosat);Funder: Polish Ministry of Education and Science (DWD/5/0435/2021);Full text license: CC BY

Fiber reinforced thermosetting composites are essential materials for present and future technologies. However, their lack of reprocessability puts them far behind in achieving current sustainability targets. The recent development of covalent adaptable networks represents a promising approach to mitigate this. Here, mechanical recycling of short-cut aramid fiber reinforced epoxy composites was evaluated with a special focus on the impact of fiber surface functionality. The introduction of aramid fibers with four different surface chemistries to a covalent adaptable network was shown to influence the mechanical properties before and after reprocessing. Epoxy functionalized fibers enabled 52 % and 36 % retention of the original tensile stress and elongation at break after two recycling cycles. In comparison, the unmodified reference samples could only retain 19 % and 12 % of the original tensile stress and elongation at break. Fiber functionalization was thus proven to be a key piece in the development of more sustainable solutions for short-cut fiber reinforced polymer composites (SCFRPC)., QC 20240215

Most products today have several functions, but these are achieved by integrating different monofunctional devices and/or materials in a system. Having several functions simultaneously in one single material has many potential advantages, such as a structural material that can also store energy, have self-sensing or self-healing capability or any other physical function. This would lead mass and resource savings, being more energy efficient and thus more sustainable. This paper presents a mini review on how carbon fibres can be used for integrating several functions simultaneously in a high-performance load carrying structural material using the electrical and electrochemical properties of carbon fibres. Through this carbon fibre composites can also store energy like a lithium-ion battery, be used as a strain sensor, have electrically controlled actuation and shape-morphing, and be used as an energy harvester., QC 20240404

Alkali-activated composites (AACs) have attracted considerable interest as a promising alternative to reduce CO2 emissions from Portland cement production and advance the decarbonisation of concrete construction. This study describes the data-driven predictive modelling to anticipate the compressive strength (CS) of AACs. Four different modelling techniques have been chosen to forecast the CS of AACs using the selected data set. The decision tree (DT), multi-layer perceptron (MLP), bagging regressor (BR), and AdaBoost regressor (AR) were employed to investigate the precision level of each model. When it comes to predicting the CS of AACs, the results show that the AR model performs better than the BR model, the MLP model, and the DT model by providing a higher value for the coefficient of determination, which is equal to 0.91, and a lower MAPE value, which is equal to 13.35%. However, the accuracy level of the BR model was very near to that of the AR model, with the R2 value suggesting a value of 0.90 and the MAPE value indicating a value of 14.43%. Moreover, the graphical user interface has also been developed for the strength prediction of alkali-activated composites, making it easy to get the required output from the selected inputs., Validerad;2024;Nivå 2;2024-04-09 (joosat);Funder: Najran University (NU/NRP/SERC/12/7); King Faisal University (GRANT4500);Full text license: CC BY 4.0

The study presents a two-scale modeling approach allowing for an efficient fatigue strength evaluation on a macro scale considering a micro-mechanical defect characterization of a Carbon Fiber Reinforced Polymer (CFRP) material. The modeling approach integrates a macro model with the effective elastic properties from micro-mechanical simulations considering voids. This enables the analysis of defects’ influence on material fatigue strength using a probabilistic weakest link approach. A CFRP laminate with a cross-ply layup was investigated. Two simulation case studies demonstrate the effect of void content and size on the characteristic fatigue strength. An experimental investigation was conducted testing the laminates in tension–tension fatigue verifying the predicted numerical behavior. The numerical models identify a difference in the characteristic fatigue strength consistent with the fatigue test results. It is numerically concluded that the investigated CFRP material's fatigue strength is affected by the presence of voids and even with only a slight difference in the global void volume fraction a scatter in fatigue strength is identified., QC 20240115

Polyurethane (PU) possesses excellent thermal properties, making it an ideal material for thermal insulation. Incorporating Phase Change Materials (PCMs) capsules into Polyurethane has proven to be an effective strategy for enhancing building envelopes. This innovative design substantially enhances indoor thermal stability and minimizes fluctuations in indoor air temperature. To investigate the thermal conductivity of the Polyurethane-Phase Change Materials foam composite, we propose a hierarchical multi-scale model utilizing Physics-Informed Neural Networks (PINNs). This model allows accurate prediction and analysis of the material’s thermal conductivity at both the meso-scale and macro-scale. By leveraging the integration of physics-based knowledge and data-driven learning offered by Physics-Informed Neural Networks, we effectively tackle inverse problems and address complex multi-scale phenomena. Furthermore, the obtained thermal conductivity data facilitates the optimization of material design. To fully consider the occupants’ thermal comfort within a building envelope, we conduct a case study evaluating the performance of this optimized material in a detached house. Simultaneously, we predict the energy consumption associated with this scenario. All outcomes demonstrate the promising nature of this design, enabling passive building energy design and significantly improving occupants’ comfort. The successful development of this Physics-Informed Neural Networks-based multi-scale model holds immense potential for advancing our understanding of Polyurethane-Phase Change Material’s thermal properties. It can contribute to the design and optimization of materials for various practical applications, including thermal energy storage systems and insulation design in advanced building envelopes.

Mortar beams incorporating carbon nanofibers (CNFs), which were synthesized in situ on Portland cement particles, were used to produce nanomodified Portland cement sensors (SmartCem sensors). SmartCem sensors exhibited an electrical response comparable to a thermistor with a temperature coefficient of resistivity of − 0.0152/ °C. The highest temperature sensing was obtained for the SmartCem sensor, which contained ~ 0.271 wt.% of CNFs. The calculated temperature sensitivity was approximately 11.76% higher in comparison with the mortar beam containing only unmodified Portland cement. SmartCem sensors were used to monitor the cement hydration in large-scale self-compacting concrete beams. The measurements were conducted after casting for 7 days. Additionally, commercially available thermocouple and humidity sensors were used as references. The results showed that changes in electrical resistivity measured by the SmartCem sensor were well aligned with the ongoing hydration processes., Validerad;2023;Nivå 2;2023-12-04 (joosat);Full text license: CC BYThis article has previously appeared as a manuscript in a thesis.

The current demand for composites reinforced with renewable fibers is greater than it has ever been. In comparison to glass fibers, natural fibers yield the advantages of lesser density and cost. Although comparable specific properties exist between glass and natural fibers, the latter shows lower strength. However, with the copper coating and chemical treatment of natural fibers, the strength of the composites can be increased nowadays. The current research investigation focuses on the life cycle assessment of the raw, chemically treated, and copper coated fiber reinforced bagasse and banana composites to compare the emissions on the environment of these samples to prove their applicability. The study includes all the processes, from the extraction of fibers to the formation of composites, i.e., from cradle to gate, and detailed inventory. The ReCiPe H midpoint method has been utilized in SimaPro software to quantify the emissions. The results indicate that the maximum global warming emission is due to the energy consumption used during the manufacturing of these composites. Electricity contribution for chemically treated and copper coated composites in global warming contribution is slightly greater than that of raw composites i.e., 73.275% in C- BG/P, 73.06% in Cu- BG/P, 73.65% in C- BN/P and 74.28 % in Cu- BN/P which is comparatively higher than 63.8 % in R- BG/P and 64.97 % in R- BN/P. The next major contributions come from polylactic acid for all the three samples of bagasse fiber reinforced PLA composite and banana fiber reinforced PLA composite. The raw samples also show improved fiber strength compared to chemical and copper coated samples.

Cemented carbide tools are subjected to high loads and temperatures during use. Long before any significant wear can occur on the tool, the material will experience plastic deformation. The purpose of this master thesis was to investigate how Kernel Average Misorientation (KAM) can be utilised to analyse plastic deformation within the microstructure or grains of cemented carbides. Six different cemented carbides were investigated. The materials were plastically deformed by utilizing cutting tests with a feed rate staircase method to induce the plastic deformation. Each material was characterised by using Scanning Electron Microscopy (SEM) either equipped with a secondary electron detector or an Electron Backscatter Diffraction detector (EBSD). This made it possible to investigate the WC grain size, Co infiltration, step formation, cavities and pores, KAM and the average grain size. It was concluded that KAM showed to be a valuable tool to visualise the plastic deformation in the materials. There were some limitations to KAM regarding materials with similar amounts of plastic deformation. Additionally, the data from KAM could be used to create graphs to more easily display the misorientation. However, KAM cannot showcase the mechanisms that lead to plastic deformation. Other characterisation methods are needed as a compliment to completely understand what is happening in the material on a microstructural level.

Polymers are useful engineering materials and are used extensively in almost all walks of life worldwide because of their outstanding engineering properties such as low densities, good strength-to-weight ratios, toughness, and resistance to corrosion, ease of processing, design freedom, and most importantly low-cost and global availability. These factors lead to the high production of polymers. Despite their engineering significance, single-use plastics are becoming a major concern due to the environmental perils associated with the use-and-discard mindset. This thesis work explores the possibility of utilizing post-consumer recyclates of polypropylene (PP) and polyethylene terephthalate(PET) to develop microfibrillar composites (MFCs) that can be used for high-end applications. This process makes use of discarded, single-use plastic materials and renders them into useful engineering products that no longer provide hazards to the environment furthermore such composite materials are completely recyclable in comparison to their conventional counterparts made by incorporation of inorganic fillers.

In this thesis, the potential of using glass fiber-reinforced polymer (GFRP) as reinforcement material in concrete structures is explored, with a focus on its performance when exposed to high temperatures compared to traditional steel reinforcement. The main objective is to compare and analyze how these materials are affected by high temperatures and to investigate the effect of biochar as an additive aimed at improving fire resistance. This study represents the first investigation in Sweden of concrete beams reinforced with GFRP and containing a 10 weight percent addition of biochar. The study is motivated by the ambition to promote the use of GFRP as a sustainable alternative within the construction sector, a strategy that has already been successfully implemented in countries like Canada and Poland. Glass fiber-reinforced polymers offer several advantages over traditional steel, such as high strength relative to low weight, good corrosion resistance, and minimal maintenance needs. Additionally, the manufacturing process of GFRP is less energy-intensive and results in lower carbon dioxide emissions. These properties make GFRP an interesting alternative in modern construction projects. However, the use of GFRP within the construction industry is largely limited by its high cost, limited experience among designers, and an insufficient understanding of its fire resistance. In the study, experimental tests were conducted to assess and compare the strength of concrete beams reinforced with either GFRP or steel, both before and after exposure to fire. Further tests were performed on corresponding concrete beams that contained an addition of biochar, to investigate its potential to improve fire properties. The results indicated that GFRP-reinforced concrete beams, with the addition of biochar, had a better ability to maintain their strength at 220°C compared to steel-reinforced concrete beams without this addition. However, the addition of biochar resulted in a noticeabl, I detta examensarbete utforskas potentialen för att använda glasfiberförstärkt polymer (GFRP) som armeringsmaterial i betongkonstruktioner, med fokus på dess prestanda vid exponering för höga temperaturer i jämförelse med traditionell stålarmering. Huvudsyftet är att jämföra och analysera hur dessa material påverkas av höga temperaturer, samt att undersöka effekten av biokol som tillsatsmedel i syfte att förbättra brandbeständigheten. Denna studie utgör den första undersökningen i Sverige av betongbalkar armerade med GFRP och innehållande en tillsats av 10 viktprocent biokol. Studien motiveras av ambitionen att främja användandet av GFRP som ett hållbart alternativ inom byggsektorn, en strategi som redan har implementerats framgångsrikt i länder som Kanada och Polen. Glasfiberförstärkta polymerer tillhandahåller flera fördelar jämfört med traditionellt stål, såsom hög hållfasthet i förhållande till låg vikt, god korrosionsbeständighet och minimalt behov av underhåll. Dessutom är tillverkningsprocessen av GFRP mindre energikrävande och resulterar i lägre koldioxidutsläpp. Dessa egenskaper gör GFRP till ett intressant alternativ i moderna konstruktionsprojekt. Emellertid begränsas användningen av GFRP inom byggindustrin till stor del av dess höga kostnad, den begränsade erfarenheten bland konstruktörer, samt en otillräcklig förståelse för dess brandbeständighet. I studien utfördes experimentella tester för att bedöma och jämföra hållfastheten hos betongbalkar armerade med antingen GFRP eller stål, både före och efter exponering för brand. Vidare genomfördes tester på motsvarande betongbalkar som innehöll tillsats av biokol, i syfte att undersöka dess potential att förbättra brandegenskaperna. Resultaten indikerade att GFRP-armerade betongbalkar, med tillsats av biokol, hade en bättre förmåga att bevara sin hållfasthet, vid exponering för 220°C, jämfört med stålarmerade betongbalkar utan denna tillsats. Emellertid resulterade tillsatsen av biokol i en märkbar försämri

I ett samhälle som stävar alltmer mot hållbarhet och minskade utsläpp så är det viktigt att arbeta med nya material som bidrar till detta. Denna studie undersöker om den träfiberbaserade termoplasten Prime från Woodcomposites kan vara ett potentiellt ersättningsmaterial till toppkåpan på Husqvarnas Automower. Prime är en termoplast som innehåller 20% träfiber. Komponenten är idag tillverkad i ASA, vilket är en petroleumbaserad termoplast och nära släkting till ABS. På grund av den ökade tillgängligheten till materialdata för ABS jämfört med ASA och plasternas synnerligen liknande egenskaper så kommer samtliga tester i rapporten att utföras med ABS. Rapporten kommer att ta reda på om det går att minska koldioxidutsläppen vid tillverkning av kåpan, samt om Prime klarar av Husqvarnas hållfasthetskrav och att användas i utomhusmiljö. Förutom att de mekaniska egenskaperna är viktiga så spelar även ett materials utseende stor roll i hur attraktiv en produkt blir. Därför presenterar rapporten två designkoncept som syftar till att ge förslag på hur man kan integrera materialet i Husqvarnas design. Resultaten visar att det går att göra en minskning i CO2-utsläpp vid tillverkning på 34,7% om man byter ut ABS mot Prime. Dessutom, i kontrast till hypotesen så absorberar Prime endast marginellt mer fukt. Det handlar om tiondels procentenheter. Utöver detta så är det mer styvt än ABS och har ett liknande inköpspris vilket tyder på goda möjligheter att kunna använda Prime som alternativ till ASA i denna applikation., In a society where sustainability and reduced carbon emissions is an increasingly important topic, it’s important to work with materials that contributes to this. This study is investigating if the wood-fibre based thermoplastic Prime from Woodcomposites has the potential to replace the material of the top cover for Husqvarna’s Automower. Prime is a thermoplastic containing 20% wood-fibres. Today the component is made from ASA, which is a petroleum-based thermoplastic that is closely related to ABS. Due to the increased availability of material data for ABS compared to ASA and the fact that they have very similar physical properties, all of the tests in this report will be performed with ABS. The study will find out if it’s possible to reduce the carbon emissions from manufacturing of the cover, but also if Prime is up to the material standards of Husqvarna and is fit to be used in an outdoor environment. Besides the importance of the mechanical properties, the look of the material also plays a big role in determining if it’s applicable to the product. It has to match the current design language and brand image of the company. Therefore, there are two design concepts presented in the report to give an idea of how the material can be implemented in Husqvarna’s design. The results show that it’s possible to reduce the carbon emissions from manufacturing by 34,7% if you change the material from ASA to Prime. Furthermore, in contrast to the hypothesis the absorption of moisture in Prime is only a fraction of a percent larger than ABS. Prime is also stiffer and has a similar price which speaks for the possibility to use it as an alternative to ASA in this application.

This thesis investigates the challenges and opportunities of recycling PA6-GF30, a glass-filled polyamide, to address the pressing environmental concerns surrounding polymer waste. Through a collaboration between Thule Group and Jönköping University, it aims to understand how the properties of recycled materials evolve over time and reprocessing cycles, proposing practical methods for their utilization in sustainable manufacturing practices. Thule Group's commitment to reducing emissions entails transitioning to sustainable materials, particularly through increased use of recycled engineering materials like PA6-GF30, to lower the carbon footprint of products, emphasizing the importance of maintaining product quality and safety while exploring the effects of recycled materials on mechanical properties. Through producing and testing post-industrial and post-consumer samples added to virgin PA6-GF30 with varying ratios, comparison with the commercially available polymers was conducted. In total, 15 different mixtures of pellets of different quantity and quality of recycled composites were investigated with tensile test and impact test, moreover the fibers of some batches were filtrated from the matrix and the fiber aspect ratio was examined with the help of an optical microscope. Results illustrated that recycled polymers generally showed more mechanical property degradation as the ratio of recycled polymers were increased. Furthermore, adding the same amount of post-consumer regrinds as opposed to post-industrial was more detrimental to the overall mechanical performance. Post-industrial composite regrinds performed 11,3% worse in UTS, meanwhile post-consumer regrinds dropped by 25,5% in the same characteristic when the samples made of 100% recycled materials were compared to the virgin composite. The reason behind this phenomenon was investigated and supported by microscopy. One of them is the natural aging of the material that operates through chain scission, that

Cellulose laminates represent a remarkable convergence of natural materials and modern engineering, offering a wide range of versatile applications in sustainable packaging, construction, and advanced materials. In this study, novel all-cellulose laminates are developed using an environmentally friendly approach, where freshly regenerated cellulose II films are stacked without the need for solvents (for impregnation and/or partial dissolution), chemical modifications, or resins. The structural and mechanical properties of these all-cellulose laminates were thoroughly investigated. This simple and scalable procedure results in transparent laminates with exceptional mechanical properties comparable to or even superior to common plastics, with E-modulus higher than 9 GPa for a single layer and 7 GPa for the laminates. These laminates are malleable and can be easily patterned. Depending on the number of layers, they can be thin and flexible (with just one layer) or thick and rigid (with three layers). Laminates were also doped with 10 wt% undissolved fibers without compromising their characteristics. These innovative all-cellulose laminates present a robust, eco-friendly alternative to traditional synthetic materials, thus bridging the gap between environmental responsibility and high-performance functionality.

All-cellulose composites (ACCs) have been fabricated by using a variety of cellulosic sources, versatile technologies, and are sustainable alternatives for traditional composites. In this study, nonwoven-woven ACC laminates were created from wood-based Spinnova short fibers and Lyocell fabrics via partial dissolution and an NaOH-urea solvent system. The less-known wood-based Spinnova fiber is created for the textile industry, but it also has great potential for the composite industry. To identify the mechanical properties of ACCs—which greatly influence the range of material application—tensile, impact, and flexural tests were conducted. The mechanical properties indicated only moderate properties, which are influenced by high porosity and weak fiber bonding. Despite this, valuable information on the nonwoven-woven structured ACCs was obtained. To improve the ACC laminate’s ability to resist moisture, biobased coatings (e.g., commercially available birch bark betulin and suberin acid mixture) were applied on the surface of ACCs and it successfully improved the wetting resistance. The results of contact angle analyses demonstrated that the highest contact angle of 128° was measured for betulin-coated laminates and the best stable hydrophobicity calculated a minute after the beginning of the experiment were observed at 109° for the uncommercial pressurized hot ethanol (PHE) extract of birch bark.

Thermo-hydrolytic disintegration of medium-density fibreboard (MDF) is a promising method for recovering fibres. This process, however, may affect the geometry and size distribution of the applied fibres initially obtained by thermomechanical pulping (TMP), and thus, the properties of MDF produced thereof. Optical methods based on image acquisition are increasingly common for geometrical characterisation to assess fibre quality. In this study, we analysed the size distribution of recovered fibres (RF) obtained by thermo-hydrolytic disintegration of urea–formaldehyde-bonded waste MDF and subsequent hammer-milling by using three optical fibre analysers, FibreShape Pro, QICPIC and Valmet FS5, while comparing them to virgin fibres (VF). The analysers use different evaluation methods and therefore gave different absolute values. Thus, size distributions could not be directly compared. Nevertheless, the results provided an indication of the changes that occurred during the manufacturing and recycling process. The RF displayed a similar fibre geometry to the VF, in spite of process-related shortening. Mean fibre length and length-based distribution of the VF were always greater than those of the RF, while fibre width of the hammer-milled RF was slightly greater than that of the VF. The analysers, however, provided substantially different results, especially between FibreShape Pro and QICPIC, although the general tendencies observed for the process-related changes were consistent. It can be concluded that the thermo-hydrolytic disintegration applied to the UF-bonded MDF did not cause any substantial changes in fibre geometry (i.e. fibre shortening). All fibre analysers are capable of detecting these changes, but the absolute values provided can vary widely between the instruments., Bibliografiskt granskad

Wood–polymer composites (WPCs) with polypropylene (PP) matrix suffer from low toughness, and fossil-based impact modifiers are used to improve their performance. Material substitution of virgin fossil-based materials and material recycling are key aspects of sustainable development and therefore recycled denim fabric, and elastomer were evaluated to replace the virgin elastomer modifier commonly used in commercial WPCs. Microtomography images showed that the extrusion process fibrillated the denim fabric into long, thin fibers that were well dispersed within the WPC, while the recycled elastomer was found close to the wood fibers, acting as a soft interphase between the wood fibers and PP. The fracture toughness (KIC) of the WPC with recycled denim fabric matched the commercial WPC which was 1.4 MPa m1/2 and improved the composite tensile strength by 18% and E-modulus by 54%. Recycled elastomer resulted in slightly lower KIC, 1.1 MPa m1/2, as well as strength and modulus while increasing elongation and contributing to toughness. The results of this study showed that recycled materials can potentially be used to replace virgin fossil-based elastomeric modifiers in commercial WPCs, thereby reducing the CO2 footprint by 23% and contributing to more efficient use of resources., Validerad;2024;Nivå 2;2024-09-19 (joosat);Full text license: CC BY;Funder: Stora Enso (KAW 2018.0451)

Polyoxymethylene (POM), an engineering polymer commonly used in tribological applications, is often reinforced with fossil-based fibers such as carbon and/or glass fibers to improve its properties. To find more sustainable solutions, in this study, the tribological performance of POM/short cellulose fiber composites at different sliding conditions is investigated. An improvement in the wear coefficient of roughly 69% is observed at the harshest conditions of 5 MPa and 1 m · s−1 with only 10 wt.% cellulose fibers. The friction behavior is furthermore stabilized through fiber addition, as the unfilled polymer did not show a steady state. No signs of thermo-oxidative degradation are found after tribological testing. This study presents promising results for sustainable wear-resistant polymer materials in tribological applications., Full text license: CC BY 4.0;Funder: Horizon 2020 (860246)

Green composites, renowned for their biodegradable and recyclable attributes, have recently gained substantial prominence. Their sustainability, eco-friendliness, and lightweight characteristics position them as a compelling alternative to conventional plastic-based materials. This study delves into the mechanical performance, encompassing tensile, flexural, and Charpy impact test properties, of jute and flax thermoplastic composite laminates. Additionally, it explores the flexural behavior of sandwich composites reinforced with jute and flax fabrics individually. To accomplish this, we manufactured various composite laminates, including jute/PP, flax/PP (64.2 % fiber mass fraction), flax/PP (45.0 % fiber mass fraction), and plasma-treated flax/PP (PTF/PP) composite laminates using compression molding techniques. We also crafted sandwich composites by integrating flax and jute natural fabrics as reinforcements into a polypropylene (PP) matrix for the sandwich surface layer, along with recycled polyethylene terephthalate (PET) foam as the core material. This allowed for a comprehensive comparative analysis of their functional properties. In addition to mechanical testing, the differential scanning calorimetry (DSC) analysis was conducted on various composite laminates to evaluate the crystallinity levels and melting behavior of PP within these diverse formulations. Further characterizations included Fourier transform infrared (FTIR) spectroscopy and digital imaging analysis. Our experimental results unequivocally demonstrated the superior performance of Flax/PP composite laminates over Jute/PP composite laminates in terms of flexural, tensile, and impact properties. In the context of sandwich composites, Flax/PP/PET foam exhibited the highest force resistance, along with superior bending strength and modulus when compared to Jute/PP/PET foam. Notably, Jute/PP/PET foam displayed a higher incidence of delamination and breakage. Interestingly, both sandwich composites d

Mortar sensors were fabricated as beams incorporating different amounts of carbon nanofibers (CNFs) synthesized in-situ on cement particles. Changes in electrical resistivity were measured and compared to recorded changes in compressive stress, temperature, and humidity. Sensing mechanisms and corresponding models were developed. The findings of the study indicate that the piezoresistive effect is influenced by the critical concentration of CNFs inside the composite matrix and the tunneling effect. In addition, water absorption and desorption, as well as the amount of chemically bound water played an important role in humidity sensing. Thermal fluctuation-induced tunneling conduction was dominant for the temperature sensitivity., Validerad;2024;Nivå 2;2024-06-03 (joosat);Funder: Skanska Sverige;Full text license: CC BY

Premature failure of polymeric self-lubricating bearings is a limiting factor in the sustainable and continued operation of hydropower plants. In this work, the tribological performance of two novel polymer composites was studied with respect to commercially available materials. The materials were evaluated under dry and lubricated conditions, using water and an environmentally adaptive lubricant (EAL). The two tested commercial materials yielded a low dry sliding friction and wear. Under water lubricated conditions, the in-house developed polyphenylene sulphide (PPS) based composite provided an exceptionally low friction and a wear rate of a factor of 3 lower than the best performing commercial material. Using the EAL wear was reduced for most materials by up to 85%., Validerad;2024;Nivå 2;2024-08-06 (hanlid);Full text license: CC BY;This article has previously appeared as a manuscript in a thesis.

Revolutionizing construction, the concrete blend seamlessly integrates human hair (HH) fibers and millet husk ash (MHA) as a sustainable alternative. By repurposing human hair for enhanced tensile strength and utilizing millet husk ash to replace sand, these materials not only reduce waste but also create a durable, eco-friendly solution. This groundbreaking methodology not only adheres to established structural criteria but also advances the concepts of the circular economy, representing a significant advancement towards environmentally sustainable and resilient building practices. The main purpose of the research is to investigate the fresh and mechanical characteristics of concrete blended with 10–40% MHA as a sand substitute and 0.5–2% HH fibers by applying response surface methodology modeling and optimization. A comprehensive study involved preparing 225 concrete specimens using a mix ratio of 1:1.5:3 with a water-to-cement ratio of 0.52, followed by a 28 day curing period. It was found that a blend of 30% MHA and 1% HH fibers gave the best compressive and splitting tensile strengths at 28 days, which were 33.88 MPa and 3.47 MPa, respectively. Additionally, the incorporation of increased proportions of MHA and HH fibers led to reductions in both the dry density and workability of the concrete. In addition, utilizing analysis of variance (ANOVA), response prediction models were created and verified with a significance level of 95%. The models' R2 values ranged from 72 to 99%. The study validated multi-objective optimization, showing 1% HH fiber and 30% MHA in concrete enhances strength, reduces waste, and promotes environmental sustainability, making it recommended for construction., Validerad;2024;Nivå 2;2024-07-08 (joosat);Funder: Prince Sattam bin Abdulaziz University (PSAU/2024/R/1445);Full text license: CC BY

This review systematically examines the multitude of factors influencing bonding strength in bamboo-based composite materials, given the rising prominence of bamboo as a green building material. With bamboo's inherent variability in mechanical properties and structure, engineered bamboo products have emerged to address challenges related to connections and joints. Such advancements have necessitated a detailed exploration of adhesive systems, a significant cost determinant in bamboo production. The adhesive bonding mechanism in bamboo, akin to wood, involves intricate processes including adhesive spreading, penetration, and solidification, influenced by the unique chemical composition of bamboo. The interfacial bond quality plays a pivotal role in determining the durability and performance of the final products, with numerous factors such as bamboo species, layered structure, adhesive type, and treatment types impacting the mechanical properties. Particular attention is given to the disparities in physical and mechanical properties between the bamboo culm's core and shell layers, attributing complexities to the gluing process. Examining shear failure strength reveals its criticality in mechanical investigations, with variations in bonding strength affecting the outcome. The review underscores the need for consistent quality control and adept manipulation of these influential factors for the successful manufacture of bamboo-based products. A comprehensive discussion ensues on the variables controlling the bonding properties of the developed bamboo products, aiming to evaluate and highlight the optimal parameters and procedures essential for enhancing the quality and reliability of bamboo-based composite materials for sustainable construction applications., Validerad;2024;Nivå 2;2024-07-03 (hanlid);Funder: Prince Sattam bin Abdulaziz University (PSAU/2024/R/1445);Full text license: CC BY

Presented test results on transverse cracking in cross-ply laminates upon tension–tension cyclic loading show that the increase of crack density depends not only on the maximum transverse stress in the cycle but also on the local cyclic stress ratio RTloc in the analyzed layer. To include the effect of the RTloc in the model with statistical failure stress distribution for crack initiation (based on Weibull distribution) adapted for fatigue, an equivalent stress is introduced in a similar manner as the equivalent strain energy release rate has been used for delamination crack propagation. The equivalent stress in the layer is defined as a power function of the maximum stress and the stress ratio in the layer. It was found, testing laminates with two different fiber contents that higher the local stress ratio in 90-layer, higher the transverse cracking resistance. Transverse crack density simulation using the developed equivalent stress model has been validated against test results., Validerad;2024;Nivå 2;2024-07-31 (signyg);Funder: Swedish Aeronautical Research Program NFFP 7 (2019-02777); Swedish Aeronautical Research Program NFFP 8 (2023-01199); GKN Aerospace, Sweden;Full text license: CC BY

The combination of different materials enables to achieve highly efficient structures in terms of lightweight and mechanical performance, as well as in terms of manufacturing costs. However, the weakest points of these structures use to be the joints. For this reason, in the last years, many studies have dealt with joining technologies for dissimilar materials. The Reinforce3D’s Continuous Fibre Injection Process (CFIP) technology delivers a unique method to join dissimilar materials. CFIP is based on injecting continuous fibers, such as carbon fibers, simultaneously with liquid resin into tubular cavities within the part. Then the resin is cured and the final composite part is obtained. This work focuses on the characterization of the mechanical properties of CFIP-made specimens and describes the potential lightweight benefits of the technology. Mechanical tests were performed under tensile and bending conditions following standardized methods. The lightweight potential is addressed by developing a representative case study by implementing finite element and topology optimization methods. The results of this case study were finally compared with a monomaterial equivalent component (aluminium) demonstrating the improvement that CFIP provides in terms of lightweight while keeping the strength., Full text license: CC BY;ISBN for host publication: 9781644903131; Funder: Catalan Government (TRAÇA-M3DTALL)

Lightweight and mechanically robust hybrid foams based on cellulose nanocrystals (CNC) and multi-walled carbon nanotubes (MWCNT) with an anisotropic structure are prepared by directional ice-templating. The anisotropic hybrid CNC-MWCNT foams displayed a combination of highly anisotropic thermal conductivity and an orientation-dependent electromagnetic interference (EMI) shielding with a maximum EMI shielding efficiency (EMI-SE) of 41–48 dB between 8 and 12 GHz for the hybrid foam with 22 wt% MWCNT. The EMI-SE is dominated by absorption (SEA) which is important for microwave absorber applications. Modelling of the low radial thermal conductivity highlighted the importance of phonon scattering at the heterogeneous CNC-MWCNT interfaces while the axial thermal conductivity is dominated by the solid conduction along the aligned rod-like particles. The lightweight CNC-MWCNT foams combination of an anisotropic thermal conductivity and EMI shielding efficiency is unusual and can be useful for directional heat transport and EMI shielding.

Accumulation of transverse cracks in carbon fiber heat resistant polymer (with bismaleimide formulation) cross-ply laminates during tensile loading at elevated temperatures and after long heat treatment is analysed. Data shows that both the iso-thermal heat treatment and testing at elevated temperatures reduce the transverse cracking resistance. A two-parameter Weibull failure stress distribution model with scale parameter degrading with heat treatment and elevated temperature is used for crack initiation analysis. The degradation is described by polynomial expansion including interaction terms. Data shows that the scale parameter dependence on the heat treatment time and the test temperature is rather linear. The same expansion parameters have been successfully used for laminates with the same constituents but with a different layup and fiber content., Validerad;2024;Nivå 2;2024-04-12 (signyg);Funder: Swedish Aeronautical Research Program NFFP 7 [project number 2019-02777]; Swedish Aeronautical Research Program NFFP 8 [project 2023-01199]; GKN Aerospace Sweden AB;Full text license: CC BY

The main purpose of the article is to present the potential use of hemp fibers as reinforcement in composites, but from a design perspective. The authors ask whether sustainable nonwovens, produced based on natural fibers, have the potential as a material for designers and artists and not only as a technical textile. Technical production of nonwovens like carding, punching and laser cutting was used to achieve not just functional, but also aesthetic quality of the samples. The possibilities of utilizing natural materials for design endeavors were presented. The production process of these items was described, along with the main design concept. Research was carried out through a series of interdisciplinary activities, using the knowledge and tools typical for textile and materials engineering, as well as the methodology and strategies derived from the fields of visual art and design. It has been shown that during the development of a new sustainable material significant attention should be paid to design aspects, so it shows its full potential, as not just being eco-friendly, but also functional and aesthetic. While technical hemp and PLA composites have been produced and studied before, the design aspect is unique in the current study.

In this study, tension-tension fatigue tests were conducted to investigate the residual stiffness degradation of carbon fiber-reinforced polymer (CFRP) tendons. Different stress levels were used in the tests, and measurements of residual stiffness and the number of loading cycles were taken. Based on experimental data for CFRP tendons, a quantitative residual stiffness model was developed by modifying Yao's model. This model is applicable to various stress levels. To assess its accuracy and applicability, the predicted results of this model were compared with those of cited models from other researchers. The findings revealed a three-stage degradation of residual stiffness in CFRP tendons under different stress levels. Furthermore, it was observed that the proportion of fatigue life accounted for by Stage III decreased with smaller stress ranges, while the proportion accounted for by Stage II increased. The proposed quantitative residual stiffness model was verified using both experimental and cited data. Tension-tension fatigue tests of CFRP tendons were conducted at various stress levels. A quantitative model was proposed based on the residual stiffness of the CFRP tendon. Stress level influence on stiffness degradation of composite material was discussed. Model accuracy was verified against experimental and cited data., Validerad;2024;Nivå 2;2024-05-21 (joosat);Funder: National Key Research and Development Program of China (2017YFC0703006-01);Full text license: CC BY

The present study delivers a methodology for investigating the gradual damage development in a carbon fibre-reinforced cross-ply polymer composite during a sequence of thermo-mechanical loadings with the help of X-ray computed tomography. The procedure allows an in-depth analysis of the occurrence and nature of the multiple cracks that form within layers oriented perpendicular, or transverse, to the loading direction. This is achieved by using Attention U-Net architecture for semantic segmentation of the transverse cracks. The model shows promising results, through an ability to identify all the transverse cracks and reflect the damage progression. The described method provides a robust routine for analysing challenging polymer composite tomographic datasets., Godkänd;2024;Nivå 0;2024-04-08 (marisr);Funder: KN Aerospace,Trollhättan, Sweden;Full text license: CC BY, INTDEMO MOTOR

In many industrial applications, nonwoven fibre networks are facilitated to operate under partly saturated conditions, allowing for filtration, liquid absorption and liquid transport. Resolving the governing liquid distribution in loaded polyamide-6 (PA6) fibre networks using X-ray computed micro-tomography is a challenge due to the similar X-ray attenuation coefficients of water and PA6 and limitations in using background subtraction techniques if the network is deformed, which will be the case if subjected to compression. In this work, we developed a method using a potassium iodide solution in water to enhance the liquid’s attenuation coefficient without modifying the water’s rheological properties. Therefore, we studied the evolving liquid distribution in loaded and partly saturated PA6 fibre networks on the microscale. Increasing the external load applied to the network, we observed an exponential decrease in air content while the liquid content was constant, increasing the overall saturation with increasing network strain. Furthermore, the microstructural properties created by the punch-needle process in the manufacturing of the network significantly influenced the out-of-plane liquid distribution. The method has been proven helpful in understanding the results of adaptions in both the fibre network design and manufacturing process, allowing for investigating the resulting liquid distribution on a microscale., QC 20240925

Composite materials with 3-dimensional (3D) reinforcement were manufactured and corresponding simulation models were created in parallel. The used simulation approach has earlier been shown to produce close to authentic geometrical representation of the yarn architecture in 3D reinforcement. It is shown that although the as-woven reinforcement pattern can be modelled quite reliably, significant distortion from the nominal fibre arrangement might take place later in manufacturing, primarily related to compression during moulding. Such effects have earlier received significant attention for composites with 2-dimensional reinforcement but not as much for their 3D counterparts. The yarns in the real and the simulated materials are studied and compared, and some of the discrepancies and the mechanisms behind are discussed. The distortions are partly attributed to the relatively sparse weave that allows yarns oriented in the through-thickness direction, in particular, to deviate from their original positions., QC 20240902

Nanocellulose, originated from cellulose, the primary structural component of the cell walls of plants, has garnered significant attention for its excellent mechanical, optical, and barrier properties, as well as its renewable and sustainable nature. Various forms of nanocellulose, including cellulose nanocrystals and cellulose nanofibers (CNFs), are produced by breaking down lignocellulosic fibers into nanoscale dimensions, typically through mechanical or chemical processes. The large surface area and rich hydroxyl groups of CNFs are ideal for surface modifications, offering great versatility in the development of functional biocomposite materials. This thesis aims to design CNF-based composites with integrated multifunctionalities, including redispersibility, biocompatibility, mechanical robustness, wet integrity, as well as optical transparency, through surface engineering of cellulose nanofibers. The methodology involves strategically selecting CNFs, integrating CNFs with biopolymers, applying surface modifications, and implementing facile processing techniques. In Paper I, inspiration from plant cell wall was drawn to customize the interaction between water and CNFs. By Incorporating mixed-linkage beta-glucan from barley, superior rehydration, redispersion, and recycling of dried CNFs have been achieved. This advancement holds the potential to enhance the transportation and processability of CNF-based materials. In Paper II, by leveraging the interaction between CNF and water, a facile material processing technique was introduced to fabricate CNF/regenerated silk fibroin (RSF) composites. This involved rehydration and swelling of TEMPO-oxidized CNF nanopaper structures with both random-oriented CNF and nematic-ordered CNF in the RSF solutions. Remarkably, the CNF/RSF composite films thus prepared exhibited exceptional mechanical properties in both dry conditions and in PBS, and demonstrated excellent biocompatibility when cultured with L929 fibroblast cell. In, Nanocellulosa, som ursprungligen kommer från cellulosa, den primära strukturella komponenten i växters cellväggar, har fått betydande uppmärksamhet för sina unika egenskaper, inklusive utmärkta mekaniska, optiska och barriäregenskaper, samt dess förnybara och hållbara natur. Nanocellulosa, inklusive cellulosa nanokristaller och cellulosa nanofibrer (CNF), produceras genom att bryta ned lignocellulosa fibrer till nanoskala dimensioner, vanligtvis genom mekaniska eller kemiska processer. Den stora ytan och de rika hydroxylgrupperna hos CNF är idealiska för ytmodifieringar, vilket avsevärt ökar dess mångsidighet i utvecklingen av funktionella biokompositmaterial. Denna avhandling syftar till att designa CNF-baserade kompositer med integrerade multifunktionaliteter inklusive redispergerbarhet, biokompatibilitet, mekanisk robusthet, våtintegritet, samt optisk transparens genom ytmodifiering av cellulosananofibrer. Metodiken innefattar strategiskt val av CNF, integrering av CNF med biopolymerer, tillämpning av ytmodifieringar och implementering av enkla bearbetningstekniker. I Paper I inspirerades man av växtcellväggen för att anpassa interaktionen mellan vatten och CNF. Genom att tillsätta betaglukan från korn, har bättre rehydrering, redispersion, och återvinning av torkade CNF uppnåtts. Denna framsteg möjliggör förbättring av transporten och bearbetningen av CNF-baserade material. I Paper II, utnyttjades interaktionen mellan CNF och vatten, vilket introducerade en enkel materialbearbetningsteknik för att tillverka CNF/regenererad silkfibroin (RSF) kompositer. Detta involverade rehydrering och svullnad av TEMPO-oxiderade CNF nanopapperstrukturer med både slumpmässigt orienterade CNF och nematiskt ordnade CNF i RSF-lösningarna. De förberedda CNF/RSF kompositfilmerna uppvisade exceptionella mekaniska egenskaper både i torra förhållanden och i PBS, och visade utmärkt biokompatibilitet när de odlades med L929 fibroblastcell. I Paper III, förbereddes CNF/alginate dubbelnätve, QC 20240404Embargo godkänt av skolchef Amelie Eriksson Karlström via e-post 2024-04-04

Metals plates and screws are the gold standard in metacarpal and phalangeal fracture fixation as they provide high stability to complex fractures. However, incidence rates of complications ranging from 42 to 92 % have been reported. Bone bioadhesive fixation based on light-cured thiol-ene technology and reinforced with hydroxyapatite (HA) is a promising solution for customizable devices with tailored mechanical properties and reduced soft tissue adhesion. The reinforcement of these thiol-ene composites with 2D textiles or meshes has been proposed; however, their role in the mechanical performance has not been explored. In this study, structural and mechanical behavior properties of a light-cured resin composite with thiol-ene precursors and HA in the presence and absence of one and three-layer of poly(ethylene terephthalate) (PET) meshes were assessed. The lack of effect of the meshes on the light-cure efficiency and the structural homogeneity of the cured composite is shown using Raman spectroscopy, water uptake measurements, and micro-computed tomography. The insertion of meshes increased the strength and energy to fracture of resin-based composite. The woven geometry of the PET meshes enables frictional sliding behavior, and reduced crack propagation ensuring integrity after matrix failure. This effect increases with the number of meshes and was significantly higher in bending than in tensile stress conditions. Related to hand and wrist fractures, the design of composite fixation devices, based on HA and meshes fillers can significantly increase the strength and toughening of those medical devices with a potential impact on post-operation by reducing mechanical mismatch of stress shielding and prevent complications due to material disintegration, resulting from the compliant and personalized bone bioadhesive fixation application., QC 20240405

Pyramidal lattice structures have frequently been employed as the core material in the design of sandwich panels due to their impressive weight-specific strength. However, the struts in pyramidal lattice structures bend when subjected to axial, shear, or bending loads, leading to non-uniform stress distributions, especially at low relative densities. The current work introduces a geometrical tailoring scheme that provides the designer with additional parameters that can be adjusted to tune the cross-sectional properties of the lattice struts with the goal of obtaining more uniform stress distributions across their thickness. Specifically, the conventional square and circular pyramidal lattice struts are reshaped into I-beam-like cross-sections, forming a tailored pyramidal lattice. These geometrically tailored pyramidal lattices are 3D printed via the Digital Light Processing (DLP) technique. The quasi-static compressive responses of the lattices are experimentally evaluated in terms of elastic modulus, collapse strength, and energy absorption capacity. Additionally, the collapse mechanisms of the geometrically tailored structures were assessed via a non-linear finite element analysis which was validated against the experimental evidence. The results substantiate the validity of the geometrical tailoring strategy as the reported energy absorption capacity of the tailored pyramidal lattice structure exhibits a significant enhancement up to 64% and 15% respectively. The latter enhancements were attributed to the lateral buckling of struts, prompting the tailored struts to bend sideways during the collapse phase., Part of ISBN 978-0-7918-8774-5QC 20240716

Tow-based discontinuous composites are an attractive alternative material to conventional continuous composites as they offer in-plane isotropy, enhanced manufacturability allowing to achieve complex 3D shapes with high curvatures and local reinforcement in critical areas, while also maintaining high strength and stiffness, therefore expanding the design space significantly. In addition, the use of ultra-thin tapes and optimised manufacturing methods can increase the mechanical properties even further and change the damage mechanisms. Fatigue, however, could be a limiting design factor, as the fatigue behaviour of these materials has not been fully characterised. This work presents a complete study on the fatigue response of ultra-thin tow-based discontinuous composites: fatigue S–N curves are measured, and the damage and failure mechanisms are characterised utilising optical and scanning electron microscopy. Finally, a critical interpretation of the results is also presented by comparing the performance of ultra-thin tow-based discontinuous composites against other similar fibre reinforced composites and metals. It is shown that the optimised manufacturing methods combined with low tape thickness leads to enhanced quasi-isotropic fatigue performance. In addition, the fatigue limit was raised significantly compared to other discontinuous composites, and the tow-based discontinuous composites outperformed their metal counterparts when the results were normalised with density., QC 20240527

Polyamide 11 (PA11) and copolyester (TPC-E) were compounded through melt extrusion with low levels (below 10%) of expanded graphite (EG), aiming at the manufacturing of a thermally and electrically conductive composite resistant to friction and with acceptable mechanical properties. Thermal characterisation showed that the EG presence had no influence on the onset degradation temperature or melting temperature. While the specific density of the produced composite materials increased linearly with increasing levels of EG, the tensile modulus and flexural modulus showed a significant increase already at the introduction of 1 wt% EG. However, the elongation at break decreased significantly for higher loadings, which is typical for composite materials. We observed the increase in the dielectric and thermal conductivity, and the dissipated power displayed a much larger increase where high frequencies (e.g., 10 GHz) were taken into account. The tribological results showed significant changes at 4 wt% for the PA11 composite and 6 wt% for the TPC-E composite. Morphological analysis of the wear surfaces indicated that the main wear mechanism changed from abrasive wear to adhesive wear, which contributes to the enhanced wear resistance of the developed materials. Overall, we manufactured new composite materials with enhanced dielectric properties and superior wear resistance while maintaining good processability, specifically upon using 4–6 wt% of EG., QC 20240425

Stretchable electronics allows for direct integration into deforming systems like clothing, skin, and tissue, thereby enabling novel applications in soft robotics, wearable electronics, health monitoring, therapeutics, and human-machine interfaces. However, achieving seamless integration with the human body poses significant challenges, necessitating the development of functional materials with a low Young’s modulus matching biological tissues to avoid any discomfort or immune response. Additionally, as electronic devices are becoming increasingly used in different settings, accumulation of electronic waste, and the utilization of unsustainable raw materials are emerging as pressing environmental challenges. Therefore, it is important that the design and fabrication of these devices consider not only high performance, but also its environmental sustainability. Therefore the focus of this thesis is on enhancing the performance and sustainability aspects of stretchable electronics through using renewable wood-based functional wood-based materials in 4 papers. Paper I focuses on the development of versatile soft electromagnetic actuators for soft robotic applications. These stretchable electromagnetic actuators were capable of contraction, expansion, hopping, and locomotion without the need for external magnetic fields. By embedding strain sensors made of conductive cellulose nanofibril (CNF)-based foam, the actuators could internally monitor their states, enhancing their controllability and autonomy. In Paper II, a soft haptic system was designed to stimulate the sense of touch. The haptic system was based on a soft electromagnetic actuator concept that included a soft magnet and stretchable conducting composite consisting of silver flakes and a styrene elastomer. The system demonstrated an improved tactile response enabled by vibration amplitude sensing through conductive CNF-based foams. This novel design offers potential applications in human–machine interface, Töjbar elektronik möjliggör direkt integrering av elektronik i system som ändrar form, så som kläder, hud och vävnad, vilket möjliggör nya tillämpningar inom mjuk robotik, bärbar elektronik, hälsoövervakning, terapi och gränssnitt mellan människa och maskin. Att uppnå sömlös integration med människokroppen innebär betydande utmaningar, vilket kräver utveckling av mjuka funktionella material som matchar mjukheten i biologiska vävnader för att undvika obehag eller immunsvar. Vidare, eftersom elektroniska enheter blir alltmer använda i olika miljöer, uppstår miljöproblem med ansamling av elektroniskt avfall samt utnyttjande av icke hållbara naturresurser. Därför är det viktigt att designen och tillverkningen av elektronik inte bara tar hänsyn till hög prestanda, utan även dess miljömässiga hållbarhet. Denna avhandling utforskar töjbar elektronik innehållande förnybara träbaserade funktionella material för detta ändamål. Artikel I fokuserar på utvecklingen av mångsidiga mjuka elektromagnetiska ställdon för mjuk robotik. Dessa töjbara elektromagnetiska ställdon var kapabla till mångsidig rörelse utan behov av externa magnetfält. Genom att bädda in sensorer gjorda av ledande cellulosa nanofibril (CNF)-baserat skum, kunde ställdonen internt känna av deras tillstånd, vilket förbättrade deras kontrollerbarhet och autonomi. I artikel II designades ett mjukt haptiskt system för att stimulera känseln. Det haptiska systemet bygger vidare på det utvecklade mjuka elektromagnetiska manöverdonskonceptet som beskrivs i papper I genom att inkludera en mjuk magnet och en utvecklad mjuk töjbar ledande komposit. Systemet visade en förbättrad taktil respons som möjliggjordes av en vibrationsamplitudsensor baserad på ledande CNF-baserade skum. Denna nya design erbjuder potentiella tillämpningar i gränssnitt mellan människa och maskin och för virtuella verklighet. Artikel III presenterar ett skalbart tillvägagångssätt för tillverkning av ultramjuka högupplösta flerlagers sträckbara kr, Funding: Knut and Alice Wallenberg (KAW) Foundation.2024-04-12: The thesis was first published online. The online published version reflects the printed version.2024-05-08: The thesis was updated with an errata list which is also downloadable from the DOI landing page. Before this date the PDF has been downloaded 88 times.

This thesis examines the manufacturing process of a novel flax fibre polypropylene composite material, focusing on understanding the process and its influencing factors. The composite was manufactured using pre-impregnated twill-woven flax fibre sheets (AmpliTex 5040 – PP) as outer layers and two core layers of pre-impregnated polypropylene sheets reinforced with short, randomly oriented natural fibres (NfPP). The manufacturing process involved preheating the material to core temperatures of 180°C, 190°C, or 200°C, followed by compression moulding with tool gaps of 3.0 mm, 3.2 mm, and 3.4 mm. The study found that the core temperature after preheating did not significantly affect the composite's thickness or layer compaction. However, the tool gap exhibited a significant effect, with an increase in thickness with larger tool gaps. The lowest deviation from the tool gap size was observed at 3.2 mm. The compaction of the AmpliTex 5040 – PP layers demonstrated no dependency on the tool gap, while the NfPP layers exhibited the highest compaction at a gap size of 3.0 mm. Thermal degradation analysis indicated that flax fibre is the most critical component, with higher core temperatures reducing the ultimate tensile strength and fracture strain of the composite material. The maximum tensile properties were observed for materials preheated to 180°C during manufacturing. The manufacturing process demonstrated an improvement in reproducibility compared to previous methods, although substantial variance in thickness remained.

Natural biopolymers have extensively applications in intelligent food packaging due to their renewable nature, easy availability, environmental-friendly, low-cost and excellent processibility. Recently, the integration or embedding of nanocomposites on polymer substrates to improve the multi-faceted performance of packaging materials has attracted widespread attention. Herein, the irregular spherical Co-based metal-organic framework (Co-MOF) loaded with phenol red (PR) and bromothymol blue (BTB) were fabricated, resulting in absorbed nanocomposites Co-MOF/PR and Co-MOF/BTB. Afterward, the nanocomposites were integrated into a sodium carboxymethyl cellulose (CMC-Na) substrate to prepare a CO2-responsive packaging material (CMC-Na/PR/CoMOF and CMC-Na/BTB/Co-MOF) for real-time and in-situ monitoring apple freshness. The synthesis of Co-MOF and the hydrogen-bonding interactions between MOF and pigments adsorption were confirmed. The advantages exhibited by the film with adding Co-MOF, including excellent hydrophobicity and water resistance, improved time-temperature stability and mechanical properties, were explored. Notably, the Co-MOF-based composite film exhibited enhanced UV-visible barrier, anti-migration performance of pigment, and thermal stability. Finally, a significant linear response (R2 = 0.9923 and 0.9781) between the total color difference values (Delta E) of Co-MOFbased film and hardness and total soluble solids (TSS) of fresh-cut Fuji apples at 4 degrees C was demonstrated, respectively. These findings indicate the significant potential of CMC-Na-based composite film containing multifunctional MOF nano-filler as a visual monitoring system, which will pave the way for fresh-cut fruit intelligent packaging.

Composite materials are known to have superior stiffness and strength properties per unit weight compared to metallic materials. These properties and the ability to tailor the mechanical properties of composites is the main motivation for choosing composite materials for structural components. Design of composite structures requires consideration of many material, design and manufacturing factors to generate designs with desired behaviour. A promising approach to handle this is to use structural optimization (SO) in the design process to obtain composite structures with optimal performance. However, optimality often comes at the cost of robustness unless consideration is taken to uncertainty in the input data to the optimization problem. It is for example well-known that composite materials can exhibit significant variation of mechanical properties and it is thus important that this is accounted for in the optimization. In this thesis, SO methods for design of composite structures are developed, including continuous and discrete parametrization methods, a method for reducing the impact of cure-induced distortion of composite parts in manufacturing; and methods for handling uncertainty to ensure robustness of optimized designs. The focus has been to extend the SO methodology to handle material uncertainty associated with the mechanical properties of composite materials. An uncertainty parametrization was developed for the stiffness properties of a composite material based on a worst-case, or deterministic, approach. Using this parametrization, an uncertainty quantification was performed to investigate the influence of material uncertainty on the performance of optimized composite structures, indicating that the effect can be significant. Combining a discrete parametrization method with the uncertainty quantification, a deterministic method for handling material uncertainty in SO of composite structures was then proposed. This method consists of a min-max optimizat, Kompositmaterial har väldigt goda styvhets- och hållfasthetsegenskaper samt låg vikt jämfört med exempelvis metaller. Dessa egenskaper tillsammans med möjligheten att skräddarsy de mekaniska egenskaperna hos kompositstrukturer har varit de främsta skälen till att välja kompositmaterial vid tillverkning av strukturella komponenter. Utveckling av kompositstrukturer styrs av ett stort antal faktorer kopplat till materialval, design och tillverkning som är viktiga att ta hänsyn till. Ett sätt att hantera detta är att använda strukturoptimering (SO) för att generera kompositstrukturer med önskade mekaniska egenskaper. Vid tillämpning av SO tas oftast ingen hänsyn till osäkerhet i indata till optimeringsproblemet, vilket medför att prestandan hos den optimerade strukturen kan vara känslig för variation i indata. Då kompositmaterial kan uppvisa en betydande variation i de mekaniska egenskaperna är det viktigt att denna osäkerhet tas med i formuleringen av optimeringsproblemet för att säkerställa robustheten hos strukturen. Denna avhandling behandlar utveckling av SO-metoder för design av komposit-strukturer. Tonvikten i arbetet har varit att utveckla metoder som tar hänsyn till materialosäkerhet i kompositmaterial, och därmed förbättra robustheten hos optimerade designer. Första steget i detta arbete är utvecklingen av en ny teknik för diskret designparametrisering, kallad Hyperbolic Function Parametrization (HFP), vilken möjliggör simultan optimering av topologi och materialval för kompositstrukturer. Tekniken använder filter baserade på hyperboliska funktioner för att generera diskreta designvariabler som behandlar kompositdesignen. Vidare utvecklas en teknik för osäkerhetsparametrisering som inkluderar variation av styvhetsegenskaperna hos kompositmaterial. Denna teknik baseras på en deterministisk, värsta-fallsformulering. Tekniken tillämpas för osäkerhets-kvantifiering genom att undersöka inverkan av materialosäkerhet på prestandan hos optimerade kompositstrukturer. D, Funding: The research papers included in the dissertation have been funded as follows: Papers I and II received funding from the Swedish Foundation for Strategic Research (SSF) through grant agreement PV08.000.02. Papers III and V-VI received funding from the Swedish Energy Agency (Energimyndigheten) through grant agreement P48175-1. Paper IV received funding from the Clean Sky 2 Joint Undertaking under the EUs Horizon 2020 program through grant agreement 716864. Paper VII received funding from the Swedish Agency for Innovation Systems (Vinnova) through grant agreements 2022-01200 and 2022-20565.

Waste management in the northern latitudes is often more challenging than in the more central regions. Under the Arctic climate conditions with large distances between settlements and to the recycling facilities, and relatively smaller markets and volume of produced waste, there are special needs for developing new innovative solutions for waste management. WANO focuses on cross-border business and innovation cooperation in the field of waste management, including municipal and industrial waste, in the regions of Troms, Finnmark and Nordland (Norway), Lapland and North Ostrobothnia (Finland) and Norrbotten (Sweden). The project identifies key actors, technologies, innovation trends, and cross-border collaboration possibilities in the Arctic waste sector. Among the lessons learned so far which are highlighted in this policy brief are that waste management in Norway has already taken important steps to promote innovation and cooperation but that there is a demand for additional knowledge-based expertise among the waste management actors in north Norway. Cross-border initiatives are welcomed in north Norway by the actors. The big hindrance seems to be “know-who”: the Norwegian actors need more information about the actors across the border in north Finland and north Sweden.

Producing cross-laminated timber (CLT) has opened a new market for the lumber industry in North America, while few hardwood species have been studied in the U.S. for CLT production. Combining hardwood species in mixed hardwood CLT or in hybrid CLT can be a solution to boost the market of the undervalued hardwoods. However, the knowledge gap on bonding hardwoods needs to be filled to provide evidence of feasibility. This study focused on the face bonding properties of the cross laminations made of seven hardwood species and two softwood species from the Great Lakes region using two commercial structural adhesives, the phenol resorcinol adhesive (the Resorcinol) and the melamine urea formaldehyde adhesive (the Melamine). A total of 45 combinations of the selected species were studied for the bonding strength (shear under compression) and the percentage of wood failure. For single species samples, the bond strength was positively related to the specific gravity of wood and the bond strength of hardwoods was 33% and 82% stronger than that of softwoods bonded with the Resorcinol and the Melamine respectively. The mixed hardwoods showed higher bonding strength (the Melamine: 5.45 MPa, the Resorcinol: 5.28 MPa) than mixed softwoods (the Melamine: 2.8 MPa and the Resorcinol: 2.7 MPa). Among the Resorcinol bonded mixed combinations, 54% had a percentage of wood failure less than 80%, while the Melamine bonded had only 4 out of 22 which had a percentage of wood failure less than 80%. The overall bonding strength of the hybrid combinations was 5% weaker than that of the mixed hardwoods. All hybrid combinations bonded with the Melamine met the 80% wood failure criterium, but some bonded with the Resorcinol had a percentage of wood failure less than 80%. Anatomical features, especially pore distribution, played a key role in the bonding performance. However, the Melamine adhesive consistently achieved over 80% wood failure across all pore distribution types.

Polymer composite laminates are preferred in many load bearing applications for its tailorable mechanical properties while offering light-weight solution, corrosive resistance etc. Hence, polymer composites are attractive material choice for aircraft manufacturers to reduce weight and emissions. However, one of the challenges existing in composite laminates is accumulation of damage before final failure, that reduces mechanical properties of the composite laminates during service life. Hence it is crucial to develop a reliable model to predict damage and consequently mechanical properties degradation. The thesis focuses on transverse/intralaminar cracks, that are the first form of damage to appear in off-axis layers of composite laminates when subjected to tensile load and they increase in number with increase in load. Transverse crack growth in numbers was analyzed in terms of transverse crack density (= number of cracks / observed length) growth. Appended papers present methodologies developed using statistical transverse failure stress distribution approach to predict the transverse crack density growth when composite laminates subjected to quasi-static tensile and tension-tension fatigue loading at different temperatures. For that purpose, continuous fibers reinforced polymer composite cross-ply laminates containing different material systems were manufactured, and damage growth was studied in 90-layer in coupon scale specimens. In static tests, the crack density growth in specimens were analyzed against the thermo-mechanical transverse stress in the 90-layer. Distribution of transverse failure stress to initiate a crack along the transverse direction of the layer has been defined using 2 parameter Weibull distribution model. Paper 1 presents, methodology to predict crack density growth, using probability of failure stress distribution (based on Weibull model) in Monte Carlo simulation along with the developed stress distribution model between cracks, in specime