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Oligomers of soft and hard segments of unsaturated polyesters (UPE) were synthesized in two steps of esterification. For the hard segment, isophthalic acid was first reacted with 1,2-propanediol, then maleic anhydride was added for further esterification. For the soft segment, diethylene glycol was used to replace 1,2-propanediol. Oligomers of soft and hard segments were blended in different ratios, and then cured with various amount of styrene. Dynamic mechanical and the stress-strain properties of these cured UPEs were evaluated. The results indicated that both stress and strain were above the criteria of the inhibitors when the amount of hard segment oligomer was 30, 60 or 70 wt% of UPE, and the added styrene was 35 or 45 phr relative to UPE. The formula of 30 wt% hard segment, 70 wt% soft segment, and 45 phr styrene was selected for the following studies. Tetraethyl orthosilicate (TEOS) and poly(dimethyl siloxane) were incorporated into the uncured UPE resins via sol-gel process. Then fillers and 5, 10, 15, 20 or 30 wt% of magnesium hydroxide were blended with UPE resins and cured. Self-extinguished phenomenon was observed in the erosion tests when the amount of magnesium hydroxide was equal or higher than 15 wt% relative to UPE. After 101 days of nitroglycerin migration experiments, the migration rate and amount were significantly reduced for these filled specimens compared with the current formula of inhibitors. In addition, 2.5 or 5 phr of phenyl triethoxysilane (PhTES) relative to UPE was added together with TEOS to study the physical properties of the organic-inorganic hybrid materials. When the amount of PhTES was 2.5 phr, it was found that the miscibility between inorganic and organic components improved, and their stress- strain properties also satisfied the criteria of the inhibitors.

In this study, billet of a binary Al-10at%Fe alloy was prepared from pure Al and Fe powders by the use of conventional press and sinter route. The sintered billet was then subjected to multiple passages of friction stir processing (FSP). After FSP, the structure of a binary Al-10at%Fe alloy can be refined to sub-micrometer scale. Transmission electron microscopy (TEM) showed that particles of Fe-containing phase were distributed uniformly in the aluminum matrix, and the mean size of these second phase particles was about 100nm. From the results of X-ray diffraction and energy dispersive spectroscopy (EDS), the Al-Fe second phase was identified as Al13Fe4. We also observed obvious reaction zone around iron particles in the friction-stirred zone. Apparently, a rapid in-situ reaction between Al and Fe had occurred in FSP. In order to reduce the reaction time and the heat input, the higher traversing speed was used. In addition, a higher sintering temperature was used to promote Al-Fe reaction. Furthermore, micro-hardness, tensile and compressive tests were performed to evaluate the mechanical properties of the Al-10at%Fe alloy fabricated by FSP.

In this work, EPDM rubber was compounded with increasing amount of filler (FEF N 550 type carbon black), process oil (saturated mineral oil), vulcanizing agent [di (t-butylperoxy) diisopropyl benzene, i.e., BBPIB] and diene [5-ethylidenebicyclo(2.2.1)-hept-2-ene, i.e., ENB] in order to investigate mechanical and rheological properties. Effect of Increasing amount of filler was investigated by using FEF N 550 type carbon black in 35, 70, 87.5, 105 phr. Decrease in scorch times of vulcanization reactions, ts2 (25, 21, 19, and 18 s, respectively) and slight increase in rate constants for vulcanization reactions (0.0270, 0.0274, 0.0301 and 0.0302 s-1, respectively) were explained in terms of nature of semi-active filler. Effect of increasing amount of process oil was investigated by using saturated mineral oil (TUDALEN 3909) in 15, 30, 45 phr. Scorch time for vulcanization reaction and rate constants were measured as 95, 103, 97 s and 0.0277, 0.0274, 0.0291 s-1, respectively. Effect of increasing amount of vulcanizing agent was investigated by using BBPIB (PERKADOX 14/40 MB-gr) in 2.5, 5, 7.5, 10 phr. The compound with 5 phr vulcanizing agent gave optimum rheometer data, crosslink density,, ultimate tensile strength, hardness, deflection and damping. Vulcanization reaction rate constant reached 0.0335 s-1 with 7.5 phr vulcanizing agent. Effect of increasing ENB ratio was investigated by using 4 different EPDM with ENB ratios 5.0, 5.6, 7.5, 8.9%. With two different cure systems, compounds with 5.6 and 7.5% ENB ratio gave optimum results. Vulcanization cure time, reaction rate constant and compression set properties changed in irregular manner.

It has been shown that alloys with submicron-grained structure can be produced by severe plastic deformation (SPD). However, our understanding about the characteristics of mechanical behaviors of these materials is still limited. According to the literature, many alloys exhibit quite different mechanical properties as the grain size decreasing to submicrometer range. In this study, commercial purity aluminum (AA1050) of grain size ranging from 0.35 to ~ 45 mm was obtained by the proper combination of equal-channel angular extrusion (ECAE) and annealing treatment. The influences of grain size, testing temperature and boundary character on the mechanical properties were studied in this work. Generally speaking, the materials of grain sizes below 1mm have quite different mechanical properties than those of coarser grain sizes. In tensile tests, they exhibited yield drop immediately followed by work softening at RT, while they showed Lüders extension followed by work hardening at 77K. In addition, their yield strength at RT was about 20% higher in compression than in tension. The submicron-grained aluminum has much higher strength but lower tensile ductility than large grained aluminum at room temperature, while it exhibits both high strength and good ductility at 77K. This finding suggests that the poor tensile ductility of submicron-grained alloys at room temperature may be improved by reducing the dynamic recovery rate. The Hall-Petch slope in the submicrometer grain size range showed positive deviation from that extended from coarser grains at both room temperature and 77K. This might be arisen from the phenomenon of inhomogeneous yielding as grain size below 1 mm. In addition, the grain boundary character distribution was found to have influence on the tensile properties of matrials of submicrometer grain sizes. As the grain size increases to the range between 1 mm and 4 mm, the tensile deformation at RT proceeds by the propagation of Lüders band initially, and followed by strain hardening. For materials of grain sizes greater than 4 mm, a normal strain hardening behavior of coarse-grained aluminum resumes.

<p>In this Thesis Ti-Al-C thin films deposited by cathodic arc at 700, 800 and 900 °C were investigated with respect to composition, structure and mechanical properties. The highest growth temperature resulted in close to single crystalline Ti₂AlC MAX phase.</p><p> </p><p>A high oxygen incorporation of 7-12 at.% was detected in all the films, likely originating from residual gas and the Al₂O₃ substrate. It was evident that the characteristic nanolaminated MAX phase structure was retained upon deflection from the ideal MAX phase stoichiometry.</p><p> </p><p>Hardness and elastic modulus of the sample grown at 900 °C were 16 and 259 GPa, respectively, as determined by nanoindentation using a Berkovich tip. Nanoindentation measurements with a cube corner tip were also performed on all three samples in order to extract elastic moduli.</p><p> </p><p>Analysis of loading-unloading curves and SPM images revealed no relation between pop-in events and pile-ups around the residual imprints, indicating that other mechanisms than formation of kink bands may be responsible for formation of pile-ups. This was also confirmed by cross-sectional TEM investigation of an indent: Ti₂AlC MAX phase deformed without kinking and delamination, as opposed to the observations in single crystalline Ti₃SiC₂ films. Several possible reasons for the different deformation mechanism observed are discussed. </p><p> </p><p>These results are of importance for the fundamental understanding of the origin of material characteristics, and serve as an initial study initiating further investigations of the influence of defects on MAX phase properties.</p>

The effect of various inorganic and organic additives as possible nucleating agents on the crystallisation behaviour of P. E. T. and the suosequent influence on the morphological and mechanical properties has been examined. Various methods of mixing(: the polymer and additive were investigated and a method involving the screw-Extrusion of the polymer and the additive was ultimately adopted. Crystallisation studies were carried out using differential scanning calorimetry under dynamic and isothermal modes. The results produced under conditions of isothermal crystallisation were analysed by means of a computer. Despite differences between batches of polymer all the additives with the exception of indigo produced a nucleating effect in the polymer as indicated by an increase in the rate of crystallisation compared with that of the base polymer. Two organo-metallic substances (sodium benzoate and sodium stearate) proved to be the most effective in this respect by decreasing the degree of supercooling of the polymer by 20 [degrees]. Morphological studies were carried out on isothermally crystallised samples, after etching and replication using a transmission electron microscope. A nodular structure whose dimensions were sensitive to both the nucleating agent and the temperature of crystallisation was observed. Mechanical testing of samples direct from the D. S. C. was carried out using a compression method. The breaking loads were found to vary with both the type of nucleating agent used and the crystallisation temperature chosen. A separate study involving the exanination of the resulting fracture surfaces by scanning electron microscopy revealed that a, high breaking load was associated with a fine discontinuous structure whereas lower breaking loads were characterised by a more continuous linear appearance. This implies a higher energy of fracture due to the increased surface area of the fracture surface of the former.

M. Tech. Mechanical Engineering / The increased use of composite materials in different industries has led to the realization of some of its benefits and disadvantages. One of the major problems, however, is the availability of biaxial test data for different composite materials. This is because structures during application face multi-axial stress states examples of such stress state scenarios include wind turbine blades and pressure vessels. This has also led to diverse range of test methods and material compositions such as combining different fibbers. The material used in this work is polymer matrix honeycomb sandwich panels. Sandwich panels are fabricated by attaching two thin stiff skins of fiber glass or carbon fiber reinforced laminates to a lightweight core. This work addresses some of the major advantages and disadvantages of this testing method. The main objective of this study is to develop a repeatable, cost effective and time efficient method for multi-axial testing of sandwich panels using existing resources.

M. Tech. Civil Engineering / Composites of synthetic polymers and natural organic materials, used as fillers, find a wide application due to biodegradability, renewability, low-cost recyclability, low specific gravity, low weight, and non-abrasiveness to processing equipment. These composites find application in various areas such as automotive interior, households, ornaments, building, and packaging. In spite of these advantages, use of these materials as reinforcement or filler in thermoplastics in general and in polyolefin in particular, is not as extensive as expected. This is due to their limited thermal stability during processing, poor dispersion in the thermoplastic melt and limited compatibility with the matrix as well as poor toughness and stress transfer efficiency. The main objective of this research was to determine the suitability and performance of natural fibre reinforced polyolefin foam composite material as a possible construction material.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences