Skin wound healing is an urgent problem in clinical treatment, in particular, with a military context. Although significant advances have been made in treating skin wounds, traditional methods face several challenges, e.g., limited donor skin tissue for transplants and inflammation over the period of long term healing. To address these challenges, in this study we present a method to fabricate Poly (ethylene-co-vinyl alcohol) (EVOH) nanofibres encapsulated with the Ag nanoparticle, using the electro-spinning technique. The manufacturing process of nanofibres by electro-spinning is the subject of the present research. Electro-spinning is a process which produces nanofibres through the electrically charged jet of a polymer solution. While the principle has long been understood, the process of forming them still remains difficult to control. In its simplest form, the technique consists of a pipette to hold the polymer solution, two electrodes and a DC voltage supply over a 10 KV range. The polymer dropping from the tip of the pipette is drawn into a jet which is electrically charged and spun into fine fibres by the electronic field. An appropriate combination of the control parameters, such as the charge voltage, density and viscosity of the polymer solution and the travel distance of the jet, etc. will lead to the production of fibres with diameters in the range of 10-7~8 meters. The fibres can then be collected on the surface of a grounded target. regulating three main parameters, namely, a concentrated EVOH solution, the electric voltage and the distance between the injection needle tip (high voltage point) and the fibre collector. Ag was added to the nanofibres to offer long term anti-inflammation properties by the slow release of Ag nanoparticles through the gradual degradation of the EVOH nanofibre. The method developed here could lead to new dressing materials for the treatment of skin wounds. The thin EVOH nanofibre sheets obtained from electro-spinning were tested in uniaxial tension for their mechanical properties, with a view to the possibilities of using them as wound dressings. It was found that the sheets show a mild hardening behaviour with extensive elongation and necking before failure in multiple fractures at random locations. The failure is not simply fibre breakage. Due to the random orientation of the continuing fibres in the sheet, detachment, shear, straightening and twinning. etc., among the fibres all occur at the same time to different extents. The Young’s modulus and the yield stress (at 0.4~0.5% proof strains) are predominately affected by the diameters of the fibres. The latter are largely insensitive to strain rate over the range tested.

The focus of this thesis is to research and develop a uniaxial tensile testing technique and methodology to attain the post-peak softening response for ultra-high performance concrete under confining pressure. This particular multi-axial behavior is valuable in improving current material models in finite element simulations for US Army applications into hardened target structures.

The automotive manufacturing industry is facing an interesting period of trial when a lot of improvement is expected of them in a short period of time to contribute to a cleaner planet by applying technologies that will reduce fossil fuel consumption. Electrification was good, but this must be accompanied by substantial curb weight reduction, which was provided by alloys such as A365, Aural 5 (AlSi8MnMg), Aural 2 (AlSi10MnMg), and Mercalloy 367 (AlSi9MgMnSr) for making structural parts. The use of these Al alloys is accompanied with extensive heat treatment which on its own involves fossil fuel consumption. In this research, test plates were made utilizing high vacuum high pressure die casting (HVHPDC) and a unique Al-Fe based eutectic alloy with Zn and Mg as precipitation strengtheners. Experimental results demonstrated that they age naturally, with their mechanical properties rising to the industry requirement within three days. DSC experiments carried out at various ages gave further experimental evidence to this natural ageing phenomenon. A portion of the samples was then given an experimental "paint bake" treatment at different ages. This is typical on an assembly line where the coated parts are baked at a temperature range of 120 - 200oC for thirty minutes. It was evidently defensible that samples of various ages respond to the treatment in different ways. The mechanical characteristics of the samples decreased after treatment to same value and progressively increased to match the values of the control samples. During the duration of the experiment, some samples rose quickly while others remained "nearly dead" in the state of low mechanical characteristics or climbed sluggishly to catch up with the natural ageing curve. The poorest results were seen in samples handled at the early stage when the initial clusters are forming indicating that it might not be a good idea to interfere with the NA process at those times. / Thesis / Master of Applied Science (MASc) / Fueled by the desire to produce an Al alloy with good mechanical properties arising from natural ageing, high vacuum high pressure die casting (HVHPDC) was used in making castings of this alloy which contains Fe for improvement on its castability and recyclability, contains Zn and Mg which act as the precipitating strengtheners driving the natural ageing phenomenon. Tests and experiments like uniaxial tensile tests, differential scanning calorimetry and electrical conductivity tests were carried out to ascertain its suitability to be used for structural automotive parts without heat treatment. The results showed that the new Nemalloy HE700 met with the minimum industry requirements for mechanical properties of materials for structural automotive applications within 3 days of natural ageing. The alloy was then subjected to experimental paint bake treatment to observe its reaction to paint bake process and the results were able to show when to do paint bake for best outcome.

No description available.

The primary aim of this research was to develop a method for determining the true uniaxial tensile strength of concrete by conducting a series of cylinder splitting, modulus of rupture (MOR) and cylinder/cube compression tests. The main objectives were: • Critically reviewing previous published research in order to identify gaps in current knowledge and understanding, including theoretical and methodological contributions to the true uniaxial tensile strength of concrete. In order to maintain consistency and increase the reliability of the proposed methods, it is essential to review the literature to provide additional data points in order to add additional depth, breathe and rigor to Senussi's investigation (2004). • The design of self compacting concrete (SCC), normal strength concrete (NSC) and high strength concrete (HSC) mixes and undertaking lab-based experimental works for mixing, casting, curing and testing of specimens in order to establish new empirical evidence and data. • Analysing the data, presenting the results, and investigating the application of validity methods as stated by Lin and Raoof (1999) and Senussi (2004). • To draw conclusions including comparison with previous research and literature, including the proposal of new correction factors and recommendations for future research. 29 batches of NSC, 137 batches of HSC, 44 batches of fly ash SCC and 47 batches of GGBS SCC were cast and their hardened and fresh properties were measured. Hardened properties measured included: cylinder splitting strength, MOR, cylinder compressive strength and cube compressive strength. A variety of rheological tests were also applied to characterise the fresh properties of the SCC mixes, including: slump flow, T50, L-box, V-funnel, J-ring and sieve stability. Cylinders were also visually checked after splitting for segregation. The tensile strength of concrete has traditionally been expressed in terms of its compressive strength (e.g. ft = c x c f ). Based on this premise, extensive laboratory testing was conducted to evaluate the tensile strength of the concretes, including the direct tension test and the indirect cylinder splitting and MOR tests. These tests however, do not provide sufficiently accurate results for the true uniaxial tensile strength, due to the results being based upon different test methods. This shortcoming has been overcome by recently developed methods reported by Lin and Raoof (1999) and Senussi (2004) who proposed simple correction factors for the application to the cylinder splitting and MOR test results, with the final outcome providing practically reasonable estimates of the true uniaxial tensile strength of concrete, covering a wide range of concrete compressive strengths 12.57 ≤ fc ≤ 93.82 MPa, as well as a wide range of aggregate types. The current investigation has covered a wide range of ages at testing, from 3 to 91 days. Test data from other sources has also been applied for ages up to 365 days, with the test results reported relating to a variety of mix designs. NSC, SCC and HSC data from the current investigation has shown an encouraging correlation with the previously reported results, hence providing additional wider and deeper empirical evidence for the validity of the recommended correction factors. The results have also demonstrated that the type (size, texture and strength) of aggregate has a negligible effect on the recommended correction factors. The concrete age at testing was demonstrated to have a potentially significant effect on the recommended correction factors. Altering the cement type can also have a significant effect on the hardened properties measured and demonstrated practically noticeable variations on the recommended correction factors. The correction factors proved to be valid regarding the effects of incorporating various blended cements in the HSC and SCC. The NSC, HSC and SCC showed an encouraging correlation with previously reported results, providing additional support, depth, breadth and rigor for the validity of the correction factors recommended.

No description available.

Thermo-stabilized lignin fibers from pH-fractionated softwood kraft lignin were carbonized to various temperatures during thermomechanical analysis (TMA) under static and increasing load and different rates of heating. The aim was to optimize the carbonization process to obtain suitable carbon fiber material with good mechanical strength potential (high tensile strength and high E-modulus). The carbon fibers were therefore mainly evaluated of mechanical strength in Dia-Stron uniaxial tensile testing. In addition, chemical composition, in terms of functional groups, and elemental (atomic) composition was studied in Fourier transform infrared spectroscopy (FTIR) and in energy-dispersive X-ray spectroscopy (EDS), respectively. The structure of carbon fibers was imaged in scanning electron microscope (SEM) and light microscopy. Thermogravimetrical analysis was performed on thermo-stabilized lignin fibers to evaluate the loss of mass and to calculate the stress-changes and diameter-changes that occur during carbonization. The TMA-analysis of the deformation showed, for thermo-stabilized lignin fibers, a characteristic behavior of contraction during carbonization. Carbonization temperatures above 1000°C seemed most efficient in terms of E-modulus and tensile strength whereas rate of heating did not matter considerably. The E-modulus for the fibers was improved significantly by slowly increasing the load during the carbonization. The tensile strength remained however unchanged. The FTIR-analysis indicated that many functional groups, mainly oxygen containing, dissociate from the lignin polymers during carbonization. The EDS supported this by showing that the oxygen content decreased. Accordingly, the relative carbon content increased passively to around 90% at 1000°C. Aromatic structures in the carbon fibers are thought to contribute to the mechanical strength and are likely formed during the carbonization. However, the FTIR result showed no evident signs that aromatic structures had been formed, possible due to some difficulties with the KBr-method. In the SEM and light microscopy imaging one could observe that porous formations on the surface of the fibers increased as the temperature increased in the carbonization. These formations may have affected the mechanical strength of the carbon fibers, mainly tensile strength. The carbonization process was optimized in the sense that any heating rate can be used. No restriction in production speed exists. The carbonization should be run to at least 1000°C to achieve maximum mechanical strength, both in E-modulus and tensile strength. To improve the E-modulus further, a slowly increasing load can be applied to the lignin fibers during carbonization. The earlier the force is applied, to counteract the lignin fiber contraction that occurs (namely around 300°C), the better. However, in terms of mechanical performance, the lignin carbon fibers are still far from practical use in the industry.

H αύξηση των περιβαλλοντικών, αισθητικών και λειτουργικών απαιτήσεων που πρέπει να πληρούν οι σύγχρονες κατασκευές Πολιτικού Μηχανικού, σε συνδυασμό με την απαίτηση για συμπίεση του κόστους του κύκλου ζωής τους, οδηγούν στην ανάγκη για τη διερεύνηση της εφαρμογής νέων υλικών και μεθόδων που θα εφαρμοσθούν στη κατασκευή των δομικών έργων. Στην κατεύθυνση αυτή κινούνται οι μέθοδοι κατασκευής δομικών στοιχείων με τη χρήση παραμενόντων τύπων. Η παρούσα Διατριβή πραγματεύεται, τόσο σε αναλυτικό όσο και σε πειραματικό επίπεδο, το σχεδιασμό επίπεδων στοιχείων Ο/Σ που παρασκευάζονται έναντι παραμενόντων τύπων παρασκευασμένων από σύνθετα υλικά τσιμεντοειδούς μήτρας και οπλισμένων με πλέγματα μη μεταλλικών ινών (Ινοπλέγματα σε Ανόργανη Μήτρα-ΙΑΜ). Η Διατριβή αναπτύσσει την διαδικασία σχεδιασμού που προορισμός της είναι να ενσωματωθεί σε έναν αλγόριθμο βέλτιστου σχεδιασμού για την επίτευξη σχεδιαστικών λύσεων που θα αντιστοιχούν στο ελάχιστο κόστος κατασκευής για το σύμμεικτο στοιχείο. Η διαδικασία σχεδιασμού τροφοδοτείται από ένα εκτενές πρόγραμμα πειραματικών δοκιμών. / The continuously raising demands for cost effective and environmental friendly concrete structures which should fulfill also high aesthetic design criteria, lead the Engineers to explore new construction methods and materials. The application of semi-prefabrication techniques, involving the use of participating Stay-in-Place formwork elements seems to be an attractive solution. The present dissertation deals with the experimental and analytical investigation of one-way concrete slabs cast over Stay-In-Place formwork elements produced from cementitious composite materials reinforced with textile structures from non-metallic continuous fibers (Textile Reinforced Concrete). In this dissertation a design procedure for Composite Reinforced Concrete (RC)/TRC one-way slabs is developed. For the development of the design procedure the results from an extensive experimental investigation campaign were exploited. The campaign focused on the mechanical behavior of RC/TRC composite slabs under four point bending. Also tests on the formwork elements under four point bending tests were carried out. Ahead of the bending tests, uniaxial tension tests on dumbbell TRC specimens were conducted in order to characterize this composite material. Finally, the design procedure was integrated on a Genetic Algorithm in order to achieve minimum-cost design solutions.

No description available.

L'utilisation de matériaux polymères a su s'imposer au cours du 20ième siècle, en remplaçant ou se combinant aux matériaux métalliques, pour des applications mécaniques toujours plus techniques. La grande diversité des propriétés physiques des polymères est intimement lié à leur forte complexité microstructurale, qui malgré leur utilisation massive reste, au demeurant, encore très incomprise. Afin de mieux comprendre les évolutions microstructurales aux échelles nano et micrométrique dont résultent le comportement macroscopique il est nécessaire de développer de nouvelles techniques de caractérisation in situ. Ce travail fait état de l'utilisation de la spectroscopie Raman couplée au système VidéoTractionTM afin d'obtenir des informations microstructurales de la déformation de polymère semi-cristallins. Pour cela, des polypropylènes de formulations diverses ont été étudiés, permettant de souligner le rôle joué par la matrice et les charges organiques et minérales dans le processus de déformation plastique. Des mesures in situ de l'orientation des chaînes macromoléculaires déterminées in situ par Raman ont été confirmées, au synchrotron Petra III d'Hambourg, par une expérience couplant le système VidéoTractionTM-Raman à un dispositif de diffusion des rayons X aux grands angles. L'endommagent volumique des matériaux a été étudié post mortem par Tomographie X et radiographie X. Les améliorations apportées au système VidéoTractionTM-Raman ainsi qu'une étude de la diffusion de la lumière incohérente de nos matériaux au cours de leurs déformations ont permis l'établissement d'un critère de mesure de l'endommagement volumique in situ par Raman / The use of polymer materials - replacing or combining with metallic materials - has successfully established itself in the 20th century for increasingly technical mechanical applications. The great diversity of polymers physical properties is closely related to their high microstructural complexity, which is still very misunderstood despite their massive use. The development of new techniques for in situ characterization allows to better understand the microstructural evolutions on nanoscale and micrometer scale which affect the macroscopic behavior. This work report the use of Raman spectroscopy coupled with the VideoTractionTM system in order to obtain information about the microstructural deformation of polymer. Various formulations of polypropylene were studied to highlight the role played by the polypropylene matrix and the organic and mineral fillers in the plastic deformation process. The in situ measures of the macromolecular chains' orientation determined by Raman were confirmed by the performing of an experimental setup coupling the Raman-VideoTractionTM system with a device of Wide angle X-ray scattering. The volume damage of material was studied post mortem using X-ray tomography. The improvements made to VideoTractionTM-Raman system and a study of the incoherent light scattering of our materials enabled the setting of a Raman criterion for measuring in situ the volume damage. The studies carried out to evaluate in situ macromolecular orientation and volume damage highlight the existence of competition between these two processes. The degree of influence of organic and mineral fillers in this competition within the polypropylene matrix was determined