• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 130
  • 21
  • 1
  • 1
  • Tagged with
  • 153
  • 139
  • 135
  • 131
  • 129
  • 31
  • 21
  • 17
  • 16
  • 15
  • 13
  • 13
  • 13
  • 12
  • 11
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Design analysis and optimization of the Hyperloop shell and chassis / Designanalys och optimering av Hyperloop-skal och chassi

Shao, Fangzhou January 2019 (has links)
In the past decades of years, huge amounts of people chose to move to big cities for better education and medical service, which also makes many cities are very crowded and noisy. Moreover, the house rent in city center is some kind too expensive for many people, especially for the youth. In this sense, more people are willing to live in suburb instead of city center. Due to the larger distance between home and office, people’s requirement for a faster public transportation method is enormous. Elon Musk first publicly mentioned the concept of Hyperloop in 2012[1], which is a sealed tube or system of tubes with nearly vacuum condition through which a pod can transport people or objects at super high velocity. With the linear induction motor and magnetic levitation technology, the drag force on the pod can be reduced tremendously, thus increasing the peak velocity to 1200 km/h. To gather more ideas for this concept, SpaceX holds the Hyperloop Pod Competition where worldwide teams will design their own Hyperloop pod to demonstrate their technical feasibility of new ideas [2]. A Hyperloop system is currently in development by the Integrated Transport Research Lab (ITRL) at KTH Royal Institute of Technology to participate in the upcoming Hyperloop Pod Competition. KTH Hyperloop group has some primary design of chassis and shell. However, they have no idea how good of their current design is. Furthermore, since the velocity is the only criteria for this competition, they also want to reduce the mass as much as possible. In this sense, some finite element analysis and optimization analysis are necessary. The objective of this master’s thesis is to analyze the current shell and chassis design to assess the quality of the attachments and integrity of the design and to reduce the total mass while keeping the stiffness within the safety range. The used tools are HyperMesh, Optistruct and HyperView which are parts of the software HyperWorks from Altair. / Ett Hyperloop-system utvecklas för närvarande av Integrated Transport Research Lab (ITRL) vid KTH Royal Institute of Technology för att delta i den kommande Hyperloop Pod-tävlingen. Hyperloop-gruppen vid KTH har utvecklat en primärkonstruktion av chassi och skal. De har dock ingen aning om hur bra deras nuvarande design är. Eftersom hastigheten är de enda kriterierna för denna tävling, vill de också minska massan så mycket som möjligt. I detta avseende är det nödvändigt med finita element- och optimeringsanalyser. Syftet med denna masteruppsats är att analysera den aktuella skal- och chassikonstruktionen för att utvärdera kvaliteten på dess fästen och integriteten hos designen, samt att minska den totala massan samtidigt som styvheten uppfyller specificerat krav. De använda verktygen är HyperMesh, Optistruct och HyperView som är delar av programvaran HyperWorks från Altair.
122

End-of-life wind blade recycling through thermal process

Benz, Kerstin January 2023 (has links)
Renewable energy production with wind turbines has been rising in the last 30 years and it is a crucial technology, which is necessary for the energy transition. As sustainable as the energy production of wind turbines is, the waste management of the blade material is not. Most of the blades end up on a landfill or get incinerated. There are different types of recycling methods, but the most commonly used is to shred the fibers into little pieces and reusing them for filler material in the concrete industry. This approach does not actually split up the blade material into its components but it is more of a downcycling. In this thesis, a new type of pyrolysis will be looked into, which splits up the blade material into its components namely glass fibers and plastic using molten salt. This process would make the glass fiber industry more sustainable by introducing a recycled glass fiber with minimal loss in quality. In a first step, the blade material will be examined more closely with a thermogravimetric analysis to find out what kind of plastic it is and what temperature would be necessary to pyrolyze it. This information will be used to conduct an experiment in a molten salt solution and determine the necessary reaction time and temperature. This data will be used to compare the costs of this method with shredding the material and the conventional pyrolysis. From the thermogravimetric analysis, it was possible to determine that the type of plastic used in this turbine was made out of epoxy. The maximum degredation of this material occurred at 380 ◦C. Not many experiments could be conducted in order to find the optimal conditions for the pyrolysis process due to difficulties with the furnace. Nevertheless, one sample was successfully pyrolyzed at a temperature of 400 ◦C with a residence time of 15 minutes. With the current market conditions in the recycled glass fibers industry, this product would be too expensive and the demand would be too little. However, the market is expected to grow in the next couple years due to rising interests in circular economy and governments introducing regulations. Nevertheless, it is necessary to increase the efficiency of the molten salt pyrolysis in order to be applicable to a bigger scale. More experiments should be conducted with cheaper molten salt in order to sink the costs of the process.
123

Mineral wool : From landfill to a sustaianble polymer composite / Mineralull : Från deponi till en hållbar polymerkomposit

Sjöbeck, Noéll January 2022 (has links)
The focus of the project is recycling of the insulation material mineral wool. The aim is to investigate the potential of using post-consumer wool from landfill as fiber reinforcement in a polymer matrix. Information gathering is conducted by a literature study on previous research, with focus on sustainability, circular economy and waste management. Potential is evaluated by producing test specimens, test mechanical properties with tensile and flexural tests, and conducting a life cycle assessment and economic analysis of the material. Mechanical properties of interest in this study are maximum stress and stiffness. The conclusion is that the manufacturing methods selected in the project do not achieve sufficient quality in the material to determine whether the fibers have the desired effect. Rock wool fibers do blend well with both polypropylene (PP) and high-density polyethylene (HDPE), but polymer composites with short fibers require control of fiber length, dispersion and direction, and the material needs to be free of pores which has not been achieved at this stage. As a result, unreinforced HDPE performs best in tensile tests (19,4 MPa in stress and 1,22 GPa Young’s modulus), in bending reinforced PP of virgin plastic achieves the highest stress and unreinforced PP the highest flexural modulus (74,1 MPa and 0,74 GPa respectively). The life cycle assessment shows that recycled rock wool fibers have potential to produce 60% less CO2 emissions than the equivalent glass fiber composite. In addition, stone wool fibers show the potential to save 30 000 SEK/ton compared to glass fiber, which corresponds to a 75% lower price. / Projektets fokus är återvinning av isoleringsmaterialet mineralull. Målet är att undersöka potentialen i att använda avfallet efter rivning eller renovering som fiberförstärkning i en polymermatris. Insamling av information sker genom att utföra en litteraturstudie på forskning, med fokus på hållbarhet, cirkulär ekonomi och avfallshantering. Materialets potential utvärderas genom att tillverka provstavar, testa mekaniska egenskaper med dragprov och böjprov, samt utföra livscykelanalys och ekonomisk analys av materialet. Mekaniska egenskaper av intresse i denna studie är maximal spänning och styvhet. Slutsatsen är att de valda tillverkningsmetoderna i projektet inte åstadkommer tillräcklig kvalitet i materialet för att kunna avgöra om fibrerna har önskad effekt. Fiber och matris blandar sig bra både i fallet med polypropen (PP) och hög-densitet polyeten (HDPE), men polymerkompositer med korta fibrer kräver kontroll av fiberlängd, spridning och riktning, och materialet behöver vara fritt från porer, vilket inte uppnåtts i detta stadie. Resultatet är att oförstärkt HDPE presterar bäst i dragprov (19,4 MPa i spänning och 1,22 GPa i E-modul), i böjning uppnår förstärkt PP av nyproducerad plast högst spänning och oförstärkt PP högst E-modul (74,1 MPa respektive 0,74 GPa). Livscykelanalysen visar att fibrer av återvunnen stenull har potential att bidra med 60% CO2-utsläpp än motsvarande komposit med glasfiber. Stenullsfibrer visar dessutom potential att spara 30 000 kr/ton jämfört med glasfiber, vilket motsvarar 75% lägre pris.
124

Investigation of the mechanical effects of recycling post-industrial and post-consumer glass-filled Polyamide-6

Zoltán Kristóf, Molnár January 2024 (has links)
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 slowly makes that polymer stiffer and weaker. The other and more dominant reason is the damage taken by the fibers, that create numerous stress concentration sites at fiber ends, within the structure, ultimately damaging the fiber-matrix interface.
125

Strong and Flexible TEMPO-CNF/Boron Nitride Nanocomposite Films / Starka och flexibla nanokompositfilmer av TEMPO-CNF/boronnitrid

Sadatifard, Sara January 2023 (has links)
Nanokompositfilmer med fem olika sammansättningar av hexagonala bornitrid nanosheet och TEMPO-CNF tillverkades med hjälp av vakuumassisterad filtreringsteknik. sond-ultraljudsteknik användes som en grön väg för exfoliering av bornitridpulver i vattenhaltigt medium. TEMPO-CNF spelade nyckelroller som både matris och dispergeringsmedel för stabilisering av bornitrid nanosheets i kompositen. Nanokompositfilmerna var flexibla och formbara och de visade höga mekaniska egenskaper inklusive hög draghållfasthet och god brottöjning. / Nanocomposite films with five different compositions of hexagonal boron nitride nanosheets and TEMPO-CNF were fabricated using vacuum-assisted filtration technique. probe-ultrasonication technique was applied as a green route for exfoliation of boron nitride powder in aqueous medium. TEMPO-CNF played key roles as both matrix and dispersant agent for stabilization of the boron nitride nanosheets in the composite. The nanocomposite films were flexible and ductile, and they showed high mechanical properties including high tensile strength and good elongation at break.
126

Investigation of the usage of composite materials for bus frames / Fallstudie för tillämpning av kompositmaterial i bussramar

Bozdog, Maria Mira January 2024 (has links)
The primary contributor to greenhouse gases emissions in the European Union is the road transport sector, accounting for over 70% of total emissions. In response to this environmental concern, the EU is working on implementing strict regulations aimed at reducing emissions by 45% by the year 2030, compelling manufacturers of heavy-duty vehicles to produce emission free alternatives. While vehicle electrification is a promising solution,it introduces a new challenge: the need for lighter vehicles becomes more increasing with the incorporation of powerful yet heavy battery systems. This work aims to study the possibility of substituting the steel bus frames with composite material frames with the dual objectives of reducing the overall weight of the bus and minimising its environmental footprint throughout the life cycle of the part. The most suitable composite materials, manufacturing processes and joining methods for the studied frames were investigated based on literature review and a list of requirements. Composite finite element analysis was performed to study the behaviour of the composite assembly when it is inserted into the steel bus model to simulate the real-life environment.  The analysis performed showed that composite frames can facilitate a mass reduction of over half of the steel frames weight. An unfailing structural behaviour of the laminate can be achieved using adhesive bonding as the joining method between the two distinct materials. At the same time, two significant needs were highlighted: the importance of laminate optimisation (in terms of different material properties, number of layers and orientations) both to reduce costs and to maximise the structural strength through effective and efficient material distribution and the importance of partitioning the composite structure in a cost beneficial way (when it comes to scrap levels and moulds complexity). / Den huvudsakliga bidragande faktorn för utsläpp av växthusgaser inom den Europeiska Unionen är vägtransportsektorn som står för över 70% av alla utsläpp. Som gensvar på detta bekymmer för klimatet jobbar EU på att implementera stränga regler som syftar till att minska utsläppen med 45% till år 2030, vilket tvingar tillverkare av tunga fordon att producera utsläppsfria alternativ. Fastän fordonselektrifieringen är en lovande lösning, introducerar den en ny utmaning: behovet av lättare fordon ökar i takt med införandet av kraftfulla men tunga batterisystem.  Syftet med detta arbete är att studera möjligheten att ersätta bussars stålramar med kompositmaterialramar med det dubbla målet att minska bussarnas totala vikt samt minimera deras klimatvtryck under ramarnas livscykel. Tillverkningsprocessen och sammanfogningsmetoderna för de studerade ramarna undersöktes baserat på litteraturgenomgång och en kravlista för att ta fram de mest lämpliga kompositmaterialen. Kompositfinit elementanalys genomfördes för att studera beteendet hos ihopsättningen av kompositen när det sattes in i stålbussmodellen för att simulera den verkliga miljön. Den genomförda analysen visade att kompositramar kan leda till en massreduktion på över hälften av stålramarnas vikt. Ett osvikligt strukturellt beteende hos laminatet kan uppnås genom att använda adhesiv bindning som sammanfogningsmetod mellan de två distinkta materialen. Samtidigt lyftes två betydande behov: vikten av att optimera laminatet (vad gäller olika materialegenskaper, antal lager och orienteringar) både för att minskakostnader och för att maximera den strukturella styrkan genom effektiv materialfördelning och vikten av att dela upp kompositens struktur på ett kostnadseffektivt sätt (när det kommer till avfallsniv ̊aer och gjutningskomplexitet).
127

Structural Composite Material with Novel Cellulose Fibre Reinforcement / Strukturellt sammansatt material med nyskapande förstärkning av cellulosafibrer

Murrone, Mauro Antonio January 2024 (has links)
In recent decades, the necessity to find a completely environmentally friendly substitute for synthetic fibres in composite applications has intensified, driven by the objective of reducing emissions in both the production and disposal of composite components. Natural fibres present a potential solution, yet they have some issues such as the inhomogeneous quality of their cross-section and mechanical properties, depending on different aspects, for example, growing conditions and the amount of intake water. Another potential solution is organic man-made fibres, such as fibre made from Cellulose NanoFibrils, which do not present the previously cited drawbacks.This thesis investigates and compares the potentials of organic fibres, either man-made or natural, in composite reinforcement applications. To accomplish this, organic fibres are integrated into composite plates using two distinct thermoset matrices, epoxy and vinyl ester, respectively via methods of hot pressing and vacuum infusion. Subsequently, the produced composite plates undergo tensile testing, with the results being compared with the theoretical values. Furthermore, microscopy is employed to examine the adhesion at the interface between reinforcement and matrix.The findings indicate that man-made fibres from Cellulose NanoFibrils bind more efficiently with thermoset matrices compared to flax fibres, making them more adept as reinforcement materials for thermoset composites. / Under de senaste decennierna har behovet av att hitta en helt miljövänlig ersättning för syntetiska fibrer i kompositapplikationer intensifierats, drivet av målet att minska utsläppen både vid produktion och avfallshantering av kompositkomponenter. Naturliga fibrer presenterar en potentiell lösning, men de har vissa problem som den ojämna kvaliteten på deras tvärsnitt och mekaniska egenskaper, beroende på olika aspekter, till exempel växtförhållanden och mängden intaget vatten. En annan potentiell lösning är organiska konstgjorda fibrer, som fibrer tillverkade av cellulosa nanofibriller, som inte har de tidigare nämnda nackdelarna.Denna avhandling undersöker och jämför potentialen hos organiska fibrer, antingen konstgjorda eller naturliga, i kompositförstärkningsapplikationer. För att uppnå detta integreras organiska fibrer i kompositplattor med hjälp av två olika termohärdande matriser, epoxi och vinyl-ester, via metoder för varmpressning och vakuuminfusion. Därefter genomgår de producerade kompositplattorna dragprovning, med resultaten jämförda med de teoretiska värdena. Dessutom används mikroskopi för att undersöka vidhäftningen vid gränssnittet mellan förstärkning och matris.Resultaten indikerar att konstgjorda fibrer från cellulosa nanofibriller binder effektivare med termohärdande matriser jämfört med linfibrer, vilket gör dem mer lämpliga som förstärkningsmaterial för termohärdande kompositer.
128

Träfiberbaserade termoplaster för trädgårdsbruk : En studie om framtida design och material för Husqvarnas Automower® / Wood fiber-based thermoplastics for horticultural use

Persson, Emelie, Svensson, Erik January 2024 (has links)
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.
129

Optimerad design av drönare : Projekt i samarbete med Vattenfall

Johansson, Oliver, Svantesson, Tim January 2024 (has links)
The use of drones is becoming increasingly common in the industry due to their efficiency and safety in environments that are difficult to access. The development of industrial drones has created a new need for specialized drones with unique functions. This has led to a growing interest in additive manufacturing as a production method. Additive manufacturing, previously primarily used for prototyping, is now emerging as a viable manufacturing method. This evolution has in turn opened new design methods intended for additive manufacturing, such as topology optimization. The purpose of this project was to redesign a drone to increase its strength, reduce its weight and improve water resistance and appearance. This was achieved using a classic product development process where a concept was developed and refined using simulation tools and a product requirement specification derived from interviews and observations of the existing drone. The product was developed using SolidWorks tools such as Topology Optimization, The Finite Element (FEM) and Computer Aided Design (CAD). The result of the work is a detailed design and a prototype developed using Topology simulations based on the product requirement specification. This project lays the foundation for continued production and development of the drone. The conclusion drawn from the work is that the new product is an improved version in several aspects compared to the previous product.
130

Enhancement of Phenol Formaldehyde Adhesive with Crystalline Nano Cellulose

Ekstrand, Johan January 2019 (has links)
Abstract The wood industries to this day use almost exclusively petroleum derived adhesives that are based mainly on the reaction of formaldehyde with urea, melamine or phenol. These adhesives have low cost and good adjustable properties which makes it hard for bio-based alternatives to compete. Phenol formaldehyde (PF), as an example of a synthetic adhesive, has been in use for over 100 years. In some parts of the world, legislation around formaldehyde is changing, and there is an increasingly voluntary awareness about the toxicity and unsustainability of formaldehyde. Industries realize that raw materials from oil is unstainable. The latter is currently a driving factor behind research on alternatives to amino based adhesives. Also, consumer interest in healthy and sustainable products, such as emitting less formaldehyde indoors, increases the need for bio based adhesives. Cellulose contained in plant cell walls is a renewable, abundant and nontoxic resource. During the last decades, many innovations have been achieved around cellulose and this trend does not seem to be slowing down. Cellulose shows excellent mechanical properties, high strength, high elastic modulus as well as having a low density. Research about cellulose reinforced adhesives has been increased the last years. This thesis studied the enhancement of phenol formaldehyde adhesive with Crystalline Nano Cellulose (CNC) at 5wt% and 10wt% loading levels for producing plywood boards. Indecisive results when using CNC higher than 3wt%, especially with PF resin, have been reported by other authors. In this thesis, European standards were applied. EN 314 was applied to test the panels shear strength. Three (3) treatment classes were selected, indoor room condition as well as pre-treatments 5.1.1 and 5.1.3. Other properties measured were modulus of elasticity, thickness swelling, formaldehyde emissions. Results showed a shear strength increase for all pre-treatment classes. 10wt% CNC mixture with phenol formaldehyde in water bath, pre-treatment (5.1.1) for 24h showed the highest increase in shear strength (+73,9%). The 10 wt% CNC mixture panels also showed the highest wood fibre failure of all panel types produced. A decrease in MOE has been observed with 10 wt% CNC compared to the 5 wt% CNC panels. Formaldehyde emissions tests were inconclusive, but since less PF was used, there was a general reduction in emissions. The 5 wt% CNC panels were superior in terms of modulus of elasticity and swelling and also showed improved shear strength.

Page generated in 0.087 seconds