The effect of different fibre volume fractions of hemp and nanoclay reinforcement on the mechanical, thermal and environmental properties of unsaturated polyester composites has been investigated experimentally. Due to the incorporation of different fibre volume fractions of hemp into polyester resin an improvement in tensile strength and tangent modulus was realised. Likewise, the flexural strength and modulus of unsaturated polyester (UPE) matrix increased with the introduction of hemp fibre. The mechanical tests results suggest that the tensile and flexural properties of composites are related to the fibre volume fractions and interfacial bond strengths between the fibre and matrix. Flexural properties of the composites were found to be comparable to those of chopped strand mat (CSM) glass fibre reinforced UPE composites. Low velocity instrumented falling weight impact tests were conducted to evaluate impact and damage characteristics of hemp and nanoclay reinforced composites. A significant improvement in load bearing capability and impact energy absorption was found by introducing hemp fibre and nanoclay as reinforcement. The impact test results in this study show that the total energy absorbed by the 0.21 fibre volume fraction of hemp reinforced specimen is comparable to the energy absorbed by the composites specimen equivalent in fibre weight percentage of CSM E-glass fibre. All nanoclay reinforced nanocomposite specimens have shown a significant improvement in their impact strength and energy absorption properties compared to unreinforced UPE matrix. The effects of various loading levels of nanoclay reinforcement on the nanomechanical properties of UPE/layered silicate nanocomposites were investigated by a nanoindentation test method. It has shown that the nanoindentation behaviour is strongly influenced by nanoclay reinforcement and the extent of clay dispersion in the polymer matrix. The creep behaviour of hemp fibre reinforced unsaturated polyester (LIFRUPE) composites was investigated using a three-point bending clamp system. Creep strain decreased as the hemp fibre reinforcement increased. The creep deflection value was significantly higher for unreinforced samples compared to hemp fibre reinforced samples. Thermal properties were evaluated using Thermogravimetric Analysis (TGA), Thermo Mechanical Analyser (TMA), Differential Scanning Calorimetry (DSC) and thermal conductivity analysis. TGA results suggest that various concentrations of nanoclay and hemp reinforcement increases the thermal stability of UPE/layered silicate nanocomposites and IIFRUPE composites. Glass transition temperatures (Tg) were also increased with the introduction of clay and hemp fibre reinforcement. Hemp reinforced specimens also showed increased thermal stability indicated by an increased Tg value and decreased decomposition rate. Thermal conductivity values were found to be higher for both clay and hemp reinforced specimens compared to unreinforced polyester. Different fibre volume fraction of HFRUPE composites were subjected to water immersion tests in order to study the effects of water absorption on a range of properties. Water absorption tests were conducted by immersing specimens in a de-ionised water bath at room temperature and 100 °C for different time durations. The tensile, flexural and nanohardness properties of water immersed specimens subjected to both aging conditions were evaluated and compared alongside dry composite specimens. The percentage of moisture uptake increased as the fibre volume fraction increased. The tensile, flexural and nanohardness properties of HFRUPE specimens were found to decrease with increase in percentage moisture uptake. However, the impact properties of HFRUPE composites were found increased after water immersion. Moisture induced degradation of composite samples was significant at elevated temperature. The water absorption pattern of these composites at room temperature was found to follow Fickian behaviour, whereas at elevated temperatures it exhibited non- Fickian. Keywords: Polymer matrix composites (PMCs); Layered silicate nanocomposites; Natural fibre reinforced composites (NFRC); Mechanical properties; Mechanical testing; Moisture absorption; Thermal stability

During the past decade, polymer nanocomposites have emerged as a novel and rapidly developing class of materials and attracted considerable investment in research and development worldwide. Driven by the certainty that by the integration of low nano ller amounts, existing material properties can be improved and moreover new material properties can be developed. Despite the clear bene t and therefore, increasing research, production and utilisation of nanomaterials, little is known about how nanocomposites will perform over their whole life cycle, especially in the usage and end of life phase. Under the in uence of environmental factors such as ultraviolet light, moisture, temperature and mechanical actions, nano-sized particles can be potentially released from nanocomposites and thus may have negative e ects on the human health and the environment. Within the scope of this work an extensive literature review has been conducted in which polymer nanocomposites are brie y introduced and release scenarios of engineered nano-sized particles from nanocomposites during their life cycle are discussed. In the experimental part of this work silica based polypropylene, polyamide and polyurethane composites were manufactured and particle exposure mechanism during mechanical processing and testing were monitored and analysed. A series of comprehensive physical characterisation techniques were utilised to assess particle size distribution, shape, and concentration in di erent mediums, once emitted by the solid composite materials. It was observed that during drilling of PA6 composites, the airborne particle emission rates were 10 times higher than those for the PP based composites. However, the characterisation of deposited particles showed exactly the opposite behaviour, were the total number of particles emitted by the PP based composites was 10-100 times higher than those of the PA6 based composites. To the best of our knowledge, this is the rst time such work has been reported in the literature. Further, the addition of secondary ller into a polymer/glass- bre composites changed the micro-mechanism during crash testing and therefore controlled the energy absorption characteristics of the composites. However, it was shown that once subjected to higher impact energies the geometric particle size of the released particles increased from approx. 25 nm for the 530 J to approx. 60 nm for the 1560 J impact. Additionally, the tensile modulus increased by 0.31 GPa and the speci c energy absorbed during impact test increased from 20.7 kJ to 22.6 kJ by using nano-SiO2 alternative to micro-SiO2 particles in PP/glass- bre matrix. Even though a respective enhancement in mechanical properties were observed by using nano llers over micro llers, no signi cant di erence in particle emission during impact test were measured. Further, it could be shown that during drilling and testing, nano-sized particles were released from all materials studied, regardless of whether they had nanoparticles integrated or not. In one particular case, the neat polymer matrix generated more nano-sized particles during drilling than the exfoliated PA6/nanoclay nanocomposite. Hence, the addition of nanoclay can have bene cial impact in terms of controlled particle release. However, in general the addition of nano llers increased the particle emission rates during drilling and impact testing of the nanocomposites. Further, the emitted nano-sized particles were not all free engineered pristine nanoparticles but also hybrid particles consisting of matrix/nano ller material. A signi cant set of data was obtained during this study and hence the outcomes sets an excellent foundation for risk assessment and life cycle analysis of silica based polypropylene, polyamide and polyurethane nanocomposites.

Over recent years, due to a constant desire for higher efficiency engines and hence increased turbine entry temperatures and a proportional reduction in [Carbon dioxide] emissions, there is a need to understand how molten slags (CMAS: Calcia magnesia alumina-silicate), including volcanic ash, affect engine life. Thermal barrier coatings (TBC) are employed together with cooling technology to protect engine hardware from the high temperature seen within the turbine and combustion zones. At current operating temperatures, CMAS can adhere to the TBC surface resulting in premature degradation of the coating. The columnar, high porosity microstructure of electron beam physical vapour deposited (EB-PVD) TBCs make them particularly susceptible to CMAS/molten deposit attack. CMAS attack of PYSZ is reported in literature to be characterised by penetration of the melt along the columnar structure, chemically attacking the TBC whereupon yttria is leached from PYSZ and into the melt, creating an yttria depleted interaction zone. A new approach for classifying and reporting CMAS attack on TBCs is introduced in this thesis and a degradation map is created to acknowledge that the mechanism and severity of CMAS damage is related to variation in the CMAS compositions. CMAS degradation of EB- PVD has been extensively studied by previous authors, all reporting similar degradation mechanism with varying degree of severity. In this study, this category of CMAS degradation mechanism is termed “classic” CMAS attack. The primary aim of this study has been to investigate the damage caused by volcanic ash and CMAS to materials used within an aerospace gas turbine engine. The thesis investigates two aspects. It is recognised that, debris ingested by the engine will cause erosion damage to components in the cooler section of the engine (compressor), thus the first part examines this issue. A series of erosion tests with Eyjafjallajokull volcanic ash and similar sized MIL spec silica sand have been undertaken with two compressor-typical materials (Ti-6Al-4V and Inconel 718). The results were consistent with volcanic ash behaving like fine silica sand both at room and at compressor operating temperatures. The measured erosion rates are consistent with a ductile erosion mechanism with peak rates of material loss at lower impact angle. The results would appear to fit classical ductile erosion models where the material loss depends on particle velocity and follows a power with an exponent close to 2.4.

The standard agar plate technique was found to be a good method for screening the presence of leachable antimicrobial additives in rubber compounds. However, this technique restricts the growth of microorganisms to the perimeter of the samples and is less satisfactory as a long term test. In a liquid medium, there should not be any problem for the microorganisms to gain access to the inorganic and organic nutrients as well as oxygen. Many experimental trials were carried out in liquid media under dynamic and static conditions with Streptomyces lipmanii NCIMB 9841 as test organism. This led to the development of the modified batch processes. The modified tests allowed experiments to be performed over a long period of time without concern of accumulation of toxins from the leachable antimicrobial additives in the rubber samples and the metabolites from the utilisation of carbon sources by the microorganisms. The test procedure developed proved to be very reproducible and repeatable. The use of neutral chemically defined media with no added carbon source, the absence of strong oxidation catalysts coupled with the use of proper control samples defined the least vigorous conditions for biodeterioration of rubber compounds. On the other hand, the degradation of the rubber compounds under field and semi-field tests is likely to be a combined effect of biodeterioration, hydrolytic degradation, leaching and oxidation of samples. Five strains of fungi and four strains of actinomycetes were tested against five carbon black-filled seal compounds. The types of rubbers used were based on natural, styrene/butadiene, peroxide-cured EPDM, sulphur-cured EPDM and acrylonitrile /butadiene rubbers. Among all the species tested, Nocardia was found to be the most aggressive group of microorganisms in affecting the rubber samples. The strains NCIMB 12811 and 12814 had activity towards vulcanised gum NR samples, whilst Nocardia asteriodes NCIMB 12082 was very capable of utilizing rubber additives. It was found that besides the physical dimensions, types and formulations of rubber compounds; test conditions such as temperature, agitation speed, pH; amount of rubber sample used per unit volume of test medium, and renewal or non-renewal of test media also played an important role in affecting the activities of microorganisms towards rubber compounds.

The aim of this research project was to gam a complete, quantified, understanding of microstructural changes in high Cr ferritic-martensitic power plant steels, as a function of preservice heat treatment, stress, time and temperature. The creep strength, which is the main design criteria for this class of alloys, depends on the stability of the microstructure, which consists of tempered martensite and a fine dispersion of carbide precipitates. An understanding of the changes of these two features forms an essential process towards the creation of a physically or microstructural-based model, which may improve the current approaches towards the prediction of remanent operational lifetime of these materials in service in conventional fossil-fired power plant.

Thermoset and thermoplastic polyurethanes have been prepared which are transparent and flexible. A synthesis technique and reaction and curing conditions were investigated to establish a reproducible method of obtaining these transparent urethanes: this is based on a polycaprolactone diol/4,4 1 -methylene biscyclohexyl diisocyanate (H12MDI) prepolymer system. Only certain chain extenders will give transparent polyurethanes and these are aliphatic diols, cycloaliphatic diols and triols. Their relative reactivities with diisocyanates were studied. The way in which the various chemical constituents control light transmission characteristics in polyurethane elastomers has been investigated by studying the morphology using differential scanning calorimetry (DSC), infrared spectroscopy and dynamic mechanical thermal analysis techniques. Physical and mechanical properties of the prepared materials were used as the criteria of their quality and measurementswere made of modulus, ultimate tensile strength, elongation at break, hardness, tear strength, tension set and compression set. The stability of these materials toward thermooxidative degradation, UV exposure, hydrolysis and gamma radiation have been quantfied. In Northern Australia outdoor weathering trials for retention of transparency in these polyurethanes have been organised and these are still progressing, but no firm conclusions can be drawn at this date.

The work reported in this thesis demonstrates the potential of the squeeze casting process for the production of castings using magnesium aIloys and its composites. In particular, the studies involving composites are focused on fabrication through squeeze infiltration. These show the ability of the squeeze casting process to produce castings of high metallurgical integrity. The work offers a clear understanding of a number of key parameters for the squeeze casting process which are prerequisites for the production of high strength castings of magnesium aIloys and composites. A better understanding of the behaviour of the squeeze cast material tested at both ambient and elevated temperature has been achieved. A methodology, which aIlows the identification of optimum squeeze casting conditions, has been developed. This has been successfully used in the identification of casting conditions which produce the best tensile properties at both test temperatures. Two casting programmes, namely: primary and secondary programmes, were designed to evaluate the controlling parameters for squeeze cast magnesium alloys and composites. The investigation was conducted with two magnesium alloys: ternary RZ5DF (Mg-4.2o/oZn-RE) alloy and commercial RZ5 (MgZn- RE-Zr) alloy. Different preform systems were investigated during the primary casting programme and the results showed that 14% volume fraction alumina fibres with 5 % silica binder provided the most satisfactory results in terms of ease of fabrication, improvement in strength and cost. Applied pressures of 0.1 to 120 MPa were studied with and without the addition of fibre reinforcement. Pressures of 60 MPa and 80 MPa were found to yield optimum tensile properties in the RZ5DF alloy and its composite respectively. It was also found that a preform temperature of 600°C or above was necessary to achieve minimum resistance to magnesium infiltration at the preform surface. Other process settings, such as applied pressure duration, were also investigated. The influence of pouring and die temperature on the tensile properties was studied during the secondary casting programme. It was found that a higher pouring and intermediate die temperature provided the highest tensile properties. The mechanical properties of castings were tested at both ambient and elevated temperatures. It was found that fibre reinforcement improved the mechanical properties of the materials at ambient temperature but the most significant improvement was observed at 250°C. The effect of grain refinement (zirconium) addition on the squeeze cast magnesium alloys and composites was also investigated. The results indicated that the tensile properties in the zirconium-free RZ5DF alloy were comparable to those of the RZ5 alloy grain refined with zirconium. The influence of zirconium addition on the tensile properties of RZ5DF and RZ5 MMC was similarly reported. Heat treatment improved the properties of the alloys by a small margin and adversely affected the properties of the composite. The overall results showed that there is an opportunity to achieve a significant saving in material and process cost when producing Mg-Zn-RE alloys and composites by the squeeze casting process.

This thesis presents the results of some investigative fieldwork carried out on the Great Ouse Estuary in May and September 1979 under a joint collaborative study between the Hydraulics Research Station (HRS) and the Tidal Waters Research Group, (TWRG) of the Civil Engineering Department, University of Birmingham. The Growing use of mathematical models to solve engineering problems in stratified flows has highlighted the need to understand the basic mechanisms behind the exchange of momentum and solutes through turbulent fluctuations. In this study direct readings of turbulent fluctuations have been obtained in a partially stratified tidal flow. These measurements along with data for the turbulent mean velocity and density fields, have been used. to characterize turbulence, by turbulent parameters, spectral analysis, to evaluate the vertical exchange of momentum and solute, and in particular to examine the mixing length functions of Rossby and Montgomery, and Kent and Pritchard relating to Richardson numbers (Ri) less than 1, when the mixing length is most sensitive to change in the vertical density gradient. The turbulent parameters obtained from the data are in reasonable agreement with appropriate results from atmospheric and laboratory data. The mixing length results based upon direct measurements of turbulence have been used to evaluate the coefficients in the Kent and Pritchard and Rossby and Montgomery equations. These coefficients are applicable up to a gradient Richardson number of 0.6 and clearly show the sensitivity of the turbulent transport mechanisms in the vertical direction to even small values of Ri (^-'0.05). Estimates have been made of some of the coefficients associated with the second order solution to the turbulence closure problem for stratified flows.

Biopolymers with defined recognition pattern were used to generate the first artificial replicating systems. Stripping down these systems to their most fundamental properties allowed to move away from the biological origins to construct replicators consisting of simple organic molecules. These systems have proven highly instructive for the in-depth understanding of the main requirements for the targeted development of efficient replicators. With this knowledge at hand, it is now possible to combine several replicators for the formation of molecular networks, and to use the unique properties of replication to manipulate these networks by external stimuli. In the thesis presented, the investigation of a family of self-replicators culminated in the successful construction of several examples of a multicyclic system in which four building blocks are able to react via two autocatalytic and two reciprocal pathways. Owing to the connectivity in this reaction system, it was demonstrated that its outcome can be influenced in a programmable manner by the addition of informational template. Some of the responses can be deduced directly from the functioning of the individual systems, others however are to be classified as emergent properties of the network. Upon elucidation of the multicyclic systems, it became apparent that working in closed reaction systems puts intrinsic boundaries on the possibility to bias the outcome of the reaction network. This limitation prevented the extinction of the inferior type of replicators even under highly unfavourable conditions and instead always led to coexistence for all species.

Knowledge of the coefficient of thermal expansion (CTE) of a ceramic material is important in many application areas. Whilst the CTE can be measured, it would be useful to be able to predict the expansion behaviour of multiphase materials. There are several models for the CTE, however, most require a knowledge of the elastic properties of the constituent phases and do not take account of the microstructural features ·of the material. If the CTE could be predicted on the basis ofmicrostructural information, this would then lead to the ability to engineer the microstructure of multiphase ceramic materials to produce acceptable thermal expansion behaviour. To investigate this possibility, magnesia-magnesium aluminate spinel (MMAS) composites, consisting of a magnesia matrix and magnesium aluminate spinel (MAS) particles, were studied. Having determined a procedure to produce MAS from alumina and magnesia, via solid state sintering, magnesia-rich compositions with various magnesia contents were prepared to make the MMAS composites. Further, the MMAS composites prepared from different powders (i.e. from an alumina-magnesia mixture and from a magnesia-spinel powder) were compared. Com starch was added into the powder mixtures before sintering to make porous microstructures. Microstructural development and thermal expansion behaviour of the MMAS composites were investigated. Microstructures of the MAS and the MMAS composites as well as their porous bodies were quantified from backscattered electron micrographs in terms of the connectivity of solids i.e. solid contiguity by means of linear intercept counting. Solid contiguity decreased with increasing pore content and varied with pore size, pore shape and pore distribution whereas the phase contiguity depended strongly on the chemical composition and was less influenced by porosity. The thermal expansion behaviour of the MAS and the MMAS composites between 100 and 1000 °C was determined experimentally. Variation in the CTE of the MAS relates to the degree of spinel formation while the thermal expansion of the MMAS composites depends strongly on phase content. However, the MMAS composites with similar phase compositions but made from different manufacturing processes showed differences in microstructural features and thermal expansion behaviour. Predictions of the CTE values for composites based on a simple rule-of-mixtures (ROM) using volume fraction were compared with the measured data. A conventional ROM accurately predicted the effective CTE of a range of dense alumina-silicon carbide particulate composites but was not very accurate for porous multiphase structures. It provided an upper bound prediction as all experimental values were lower. Hence, the conventional ROM was modified to take account of quantitative microstructural parameters obtained from solid contiguity. The modified ROM predicted lower values and gave a good agreement with the experimental data. Thus, it has been shown that quantitative microstructural information can be used to predict the CTE of multiphase ceramic materials with complex microstructures.