This master thesis summarizes the current knowledge about non-commercial 3D printing FDM technology. The goal of this thesis is to demonstrate the gained knowledge by building a 3D printer which can partially replicate itself, and to evaluate its technological parameters. The experimental part of this work is focused on the impact of the changes in technological parameters of printing on mechanical properties of printed parts.

The master´s thesis is focused on the characterization of degradation process of polypropylene and polypropylene with statistic copolymer into which manganese (II) stearate and cobalt (II) stearates were added at 0.05, 0.10 and 0.20 wt.% loadings. The aim of the thesis was to prepare the controlled life-time polypropylene. The degradation was studied at varying temperatures and prodegradant loadings. The prodegradants were synthetized and characterized using the FTIR and DSC techniques. Thermooxidation of the tested samples induced the changes in crystallinity, melting points and melt-flow indexes. Tensile strength and other mechanical properties were determined by means of the tensile test. The carbonyl index was determined using FTIR, the thermooxidation stability test was used to determine the activation energies of reactions. The changes in morphology of degraded samples were observed by SEM analysis.

Orientador: Paulo José Paupitz Gonçalves / Banca: Marcos Silveira / Banca: Carlos de Marqui Junior / Resumo: Um sistema de tensegrity é composto por dois tipos de elementos, elementos de tração e compressão, os quais promovem a estabilidade estrutural do sistema, neste trabalho as partes de tração são cabos (cabos de aço), e as partes compressivas são barras de aço. Uma característica atrativa de uma estrutura de tensegridade é a capacidade de ser retrátil, por esta razão, é interessante para aplicações espaciais devido ao pequeno volume que ocupa um possível transporte para uma estação espacial. Em geral, essas estruturas podem ser grandes com muitas células repetitivas. Neste trabalho, estuda-se uma estrutura de tensegrity composta por dez células periódicas de barras e cabos. O modelo matemático, obtido pelo método dos elementos finitos, é validado experimentalmente considerando o caso de uma célula estrutural. Para tornar o sistema adaptável à excitação externa, um dos cabos de aço na célula elementar é substituído por um fio de liga de memória de forma (SMA) que permite que as características dinâmicas do sistema sejam alteradas de acordo com uma corrente elétrica aplicada no SMA, para que através do efeito Joule a liga seja aquecida. Diferentes configurações para a colocação do cabo SMA são estudadas com o objetivo de reduzir as amplitudes de vibração para uma excitação de força harmônica. / Abstract: A tensegrity system is composed by two types of elements, tensile and compressive parts, which promotes the structural stability of the system, in this case the tensile parts are cables (steel cables), and the compressive parts are bars, in this work made of steel. An attractive characteristic of a tensegrity structure is the capability to be deployable, for this reason, is interesting for space applications due to the small volume that it occupies in a possible transport to a station outside the Earth. In general, these structures can be large with many repetitive cells. In this work, a tensegrity boom structure consisting of ten periodic cells made of bars and cables is studied. The mathematical model, obtained by finite element method is validated experimentally considering the case of one structural cell. In order to make the system adaptable to external excitation, one of the steel cables in the elementary cell is replaced by a SMA (shape memory alloy) wire (Nitinol) allowing the dynamics characteristics of the system to be changed according to an electrical current applied to the SMA, to heat the alloy through Joule effect. Different configurations for placing the SMA cable are studied with the objective of reducing the vibration amplitudes for harmonic force excitation. / Mestre

Syftet med projektet var att undersöka hur homogeniserings förhållanden (tryck antal passager och därmed energiinsatsen) vid framställning av MFC (mikrofibrillär cellulosa), från enzymatiskt förbehandlade pappersmassafibrer påverkar hållfastheten av papper förstärkt med MFC. Arbetsgivaren för projektet var Innventia och det laborativa arbetet har utförts i deras lokaler. Fördelen med att använda MFC som tillsats i papper är att arket blir starkare [1]. Detta medför att en mindre mängd material kan användas till ett material med liknande styrkeegenskaper. Vid Innventia används för närvarande en homogenisator för att delaminera (sönderdela) cellulosafibrer till fibriller och fibrillaggregat och därmed producera MFC. Homogenisatorn kan köras vid olika tryck, samt att cellulosafibrerna/MFC kan låtas passera genom homogenisatorn en eller flera gånger. Beroende på tillvägagångssättet varierar produktionsenergin mycket och egenskaperna på den producerade MFC varierar. För att få en så energieffektiv metod som möjligt är det av stor vikt att finna vilken metod som genererar en MFC lämpad för styrkegivning i pappersark. Beroende på hur mycket MFC som tillsätts till arket kan arkets egenskaper variera. Därför är även detta en mycket viktig aspekt att ta hänsyn till då dubbla mängden tillsatt MFC direkt motsvarar dubbla mängden tillförd energi. För att få en jämn dispergering av massafibrer och inbunden MFC utfördes retentionsförsök för att bestämma vilken koncentration C-PAM 1510 som ansågs lämplig att använda vid arkningen för samtliga MFC prover. C-PAM 1510 är en positiv laddad polymer som binder in MFC till massafibrerna [2]. Maskinen som användes för retentionsförsöken är BDDJ (Britt Dynamic Drainage Jar) och syftar till att se hur mycket MFC som retenderar med massafibrerna. Arkningen utfördes enligt ISO 5269-1 med riktvärde att producera ark om 80g/m2 för vidare fysikaliska tester, bland annat dragprovning, densitet och reell ytvikt. Halten C-PAM 1510 som användes under arkningsförsöken bestämdes till 0,15 %. Det fanns ingen säkerställd skillnad i arkstyrka för de olika MFC proverna som testades, förutom prov ett. Prov ett gav en betydande högre mätvärdesvariation vid dragprovningen (figur 8) jämfört med de övriga proverna och får ses extremt påverkad av något. Detta var inte heller ett prov som påverkade slutsatsen. Därav har prov ett utelämnats i diagram. Prov nummer 5 ansågs bäst lämpad som styrkeadditiv i papper. Resultaten kan dock ha påverkats av föroreningar i kranvattnet. Järnjoner och partiklar i varierande koncentrationer hade en påverkan av dispergeringen av fibrer i pappersark. / The goal with the project was to investigate how homogenization conditions (pressure, number of passes and thereby energy consumption) at production of MFC (microfibrillated cellulose), from enzymatic pretreated paper mass fibers affects the strength of paper enhanced with MFC. The employer of the project is Innventia and the laboratory work was conducted in their facilities. The advantage of using MFC as an enhancer in paper is that the paper becomes stronger and more durable [1]. This leads to a decreasing use of material for a paper with similar strength properties as ordinary paper. At Innventia they presently use a homogenisator to delaminate (break apart) cellulose fibers to fibrils and fibril aggregates and thereby produce MFC. The homogenisator can be operated at different pressures and also the cellulose fibers/MFC can pass through one or several times. Depending on the method the energy consumption will greatly vary and so will also the properties of the produced MFC. To make the process as energy efficient as possible it is of most importance to find the best method of production for a MFC suitable as an enhancer in paper. Depending on how much MFC is added to the paper, the papers properties will vary. Therefore this aspect is also important to consider, because if the added MFC doubles, the energy does too. To make an even dispersion of the pulp fibers and adsorbed MFC, retention experiments were conducted to determine which concentration of C-PAM 1510 was most suitable to use during the sheet forming for every MFC sample. C-PAM 1510 is a positively charge polymer that can bind MFC to cellulose fibers [2]. The machine used for the retention experiments was BDDJ (Britt Dynamic Drainage Jar) aiming to determine how much MFC retain in the paper mass. The sheet forming was conducted accordingly to ISO 5269-1 and 80g/m2 sheets where produced for further physical testing, among other things, tensile test, density and basis weight. The C-PAM 1510 concentration used during the sheeting was determined to 0,15 %. There was no big difference for tensile strength compared to the different MFC samples, except sample one. Sample one had significant higher coefficient of variation compared to the other samples (figure 8) during tensile strength test, probably due to a high influence of some interference. The exclusion of sample one did not affect the overall result. Therefore sample one was excluded from diagrams. Sample number 5 was considered to be the best strength enhancing additive for paper. The results may have been influenced by impurities in the tap water and should be considered. Iron ions and particles in various concentrations did have an effect of the dispersion of fibers in paper.

Architecture has a dualistic social responsibility. To provide relevant buildings with appropriate function and planning that will accommodate user needs, as well as providing habitable environments and spaces that will have positive influence on peoples daily routines. This will allow users to freely dwell within their environments and create a positive community atmosphere. It is the aim of this dissertation to investigate the social responsibility of architecture and how ordinary spaces and buildings that call for pragmatic design solutions can also enter into the realm of the metaphysical spatial experience and to find cohesion between the two. The selected project is a glasshouse complex and plant containment research facility within the Botanical gardens at the University of Pretoria, South Africa. GERMAN: Die Architektur trägt gesellschaftlich dualistische Verantwortung: es ist eine Schaffung von Gebäuden, die räumliche Bedürfnisse von Benutzern erfüllen, sowie auch einer qualitätsvollen Umgebung, die tägliche Routine von einer Gemeinde positiv beeinflussen wird. Es handelt sich um eine freundliche, gemeinde Atmosphäre zu schaffen. Dieses Projekt hat zum Ziel die Gesellschaftsverantwortung von der Architektur überprüfen. Es wird untersucht, wie vernünftige Räume, die eine Antwort für die funktionelle Bedürfnisse sind, gleichzeitig eine metaphysische Erfahrung kreieren können. Die Idee ist ein Zusammenhang zwischen diesen zwei Ansätze zu identifizieren. Das ausgewählte Projekt ist eine gegenwärtige Gewächshäuseranlage, Forschungsanstalt und botanischer Garten auf dem Gelände der Universität Pretoria, Südafrika. / Dissertation (MArch(Prof))--University of Pretoria, 2008. / Architecture / MArch (Prof) / unrestricted

Carbon fiber reinforced polymer (CFRP) is widely used in the industrial world due to its high strength-to-weight ratio. Aerospace manufacturers incorporate CFRP into the main structure of their flight vehicles. The extensive use of CFRP sparks the interest in efficient methods for manufacturing and repair. One of the most used repair methods is the bonded joint method, which includes different types of joints, e.g. scarf joint, step joint and single-lap joint. Scarf joint is generally selected for repair method due to its derived outcome. To improve strength of the bonded joint, the mating adherend surfaces are usually treated before being bonded. This treatment aims to enhance the mechanical interlocking and absorption properties between adhesive and adherend. Manual or electrical sanding is a standard method currently used in the industry. Recently, laser treatment is of high interest due to its potential for an automated process and consistent results. Laser treatment is usually preformed uniformly across the CFRP, regardless of the stacking sequence. This process may introduce local enhancement in some ply orientations, but also damage in other plies. This work investigates the effect of local (ply-specific) treatment on the scarf joint strength of CFRP. Effects of laser fluence (energy density) on treated ply were evaluated using surface characterization methods, viz. optical microscopy, profilometry and sessile drop technique. Finally, tensile test was performed on CFRP scarf joint. Results show that ply-specific laser treatment improves the tensile strength of CFRP scarf joint. The treatment offers localized enhancement to the surface properties and bonding strength, which results in overall tensile strength improvement.

Indiana University-Purdue University Indianapolis (IUPUI) / Microabrasion with PREMA Compound (Premier Dental Product Co., King of Prussia, Penn.) has been advocated for the removal of superficial enamel stains. This procedure eliminates stains by removing a microscopic layer of enamel. The objective of this study was to determine whether the use of PREMA microabrasion prior to orthodontic bonding affects the tensile bond strength of an adhesive precoated stainless steel orthodontic bracket. Sixty noncarious extracted human premolar teeth were randomly divided into three groups of 20 and stored in 3-percent buffered formalin solution. Group I was a control group that was etched and bonded in the usual manner. Group II received PREMA Compound microabrasion immediately prior to bonding. Group III received PREMA microabrasion followed by a six-week storage period prior to bonding. After bonding, specimens were thermocycled and stored in distilled water at 37 °C for 14 days. The specimens were then loaded to failure in the tensile mode of an Instron testing machine (Instron Corp., Canton, Mass.). A stress-breaking apparatus was utilized to minimize all forces other than tensile. The data was statistically analyzed using one-way analysis of variance at the 0.05 level. No statistically significant differences were found among the three groups. From these results it was concluded that microabrasion with PREMA did not affect bond strength. Enamel microabrasion can be provided prior to orthodontic treatment without any detriment to bracket bond strength.

Bioactive glasses exhibit unique characteristics as a material for bone tissue engineering. Unfortunately, their extensive application for the repair of load-bearing bone defects is still limited by low mechanical strength and fracture toughness. The main aim of this work was two-fold: the reinforcement of brittle Bioglass®-based porous scaffolds and the production of bulk Bioglass® samples exhibiting enhanced mechanical properties. For the first task, scaffolds were coated by composite coating constituted by polyvinyl alcohol (PVA) and microfibrillated cellulose (MFC). The addition of PVA/MFC coating led to a 10 fold increase of compressive strength and a 20 fold increase of tensile strength in comparison with non-coated scaffolds. SEM observations of broken struts surfaces proved the reinforcing and toughening mechanism of the composite coating which was ascribed to crack bridging and fracture of cellulose fibrils. The mechanical properties of the coating material were investigated by tensile testing of PVA/MFC stand–alone specimens. The stirring time of the PVA/MFC solution came out as a crucial parameter in order to achieve a more homogeneous dispersion of the fibres and consequently enhanced strength and stiffness. Numerical simulation of a PVA coated Bioglass® strut revealed the infiltration depth of the coating until the crack tip as the most effective criterion for the struts strengthening. Contact angle and linear viscosity measurements of PVA/MFC solutions showed that MFC causes a reduction in contact angle and a drastic increase in viscosity, indicating that a balance between these opposing effects must be achieved. Concerning the production of bulk samples, conventional furnace and spark plasma sintering technique was used. Spark plasma sintering performed without the assistance of mechanical pressure and at heating rates ranging from 100 to 300°C /min led to a material having density close to theoretical one and fracture toughness nearly 4 times higher in comparison with conventional sintering. Fractographic analysis revealed the crack deflection as the main toughening mechanisms acting in the bulk Bioglass®. Time–dependent crack healing process was also observed. The further investigation on the non-equilibrium phases crystallized is required. All obtained results are discussed in detail and general recommendations for scaffolds with enhanced mechanical resistance are served.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21462号 / 工博第4537号 / 新制||工||1707(附属図書館) / 京都大学大学院工学研究科マイクロエンジニアリング専攻 / (主査)教授 田畑 修, 教授 鈴木 基史, 准教授 土屋 智由, 教授 平方 寛之 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Dovetail joints are commonly seen in a furniture frame construction because of their unique configuration and strength. The tensile strength of dovetail joints was experimentally and analytically investigated using fracture mechanics method in this study. Experimental results of the investigation of effects of geometry factors on the tensile strength of dovetail joints in southern yellow pine and red oak indicated that the tensile strength of red oak joints was about 2 times higher than the one of southern yellow pine joints. Statistical analysis results indicated that the tail angle and tenon length of dovetail joints had significant influences on their tensile strength, and the tenon width was not a significant factor on the joint tensile strength. The fracture behaviors of southern yellow pine and red oak materials were investigated in the radial-longitudinal crack propagation system using a compact tension test method. Effects of wood specific gravity on fracture toughness for two wood species were studied in terms of their three growth ring combinations; earlywood, earlywood and latewood interface, and latewood. Regression analysis results indicated that the fracture toughness of two evaluated wood species can be predicted based on their specific gravity values. Statistical analyses indicated that the latewood yielded the significantly higher fracture toughness value, followed by earlywood and latewood interface, then earlywood for both wood species. Proposed prediction equations for tensile strengths of dovetail joints based on fracture toughness values of wooden materials used for frame construction were validated experimentally.