This thesis describes the preparation and continuous printing of zirconia ink under different conditions, as well as the development of silver inks, for the same purpose. The dispersion of sub-micrometer zirconia powder in industrial methylated spirit using other additives such as dispersant and binder was investigated with different mixing methods and at varying powder and binder contents. The use of high shear mixing by triple roll milling followed by ultrasonic disruption as well as adequate sedimentation and filtration produced a homogeneous and stable ink of 2.5 vol. % ZrO2. The ink could be printed directly and continuously on a commercial jet printer without interruption of any kind and the phenomena occurring during printing were investigated. The optimum modulation frequency for printing was determined with the generation of pear-shaped and symmetrical droplets. Printing was made on substrates of surface free energies lower and higher than the surface tension of the Zr02 ink. Powder migration was observed within a relic of the printed dot on the second type of substrate. Layers were also overprinted on the second type of substrate by varying the following: print resolution, printing interval, print area, drying conditions and ink powder loading. These series of prints were accompanied by the appearance of ridges, spattering and non-vertical walls and the effects were investigated. The wettability and shrinkage of droplets of the ceramic ink was also studied in-situ by monitoring the evolution of contact angle, width of ink-substrate interface and droplet height with a video camera. The shape of the droplet experienced different dynamics on different types of substrate. Lastly, the sedimentation behaviour of ethanol-based silver inks dispersed with different types of dispersant was investigated with respect to the sediment volume and half-value time. Deflocculated ink was obtained at a low dispersant level and powder loading.

Early failure of some metal-on-metal (MoM) hip implants are extensively reported but not fully explained. These arthroplasties commonly utilise large-diameter, thin-walled acetabular cups that have the advantage of minimal removal of acetabular bone and a reduced chance of dislocation; however they may deform during insertion which involves impaction. The role of diametrical cup deformation as a factor to unsatisfactory implant performance has not been widely reported. The aim of this thesis was to investigate the extent to which deformations may occur in clinically relevant situations and to assess the significance of a range of variables on the deformation generated. 2D axisymmetric finite element (FE) models established a method of simulating impaction using different momentums. Experimentally validated 3D foam models showed that deformation is clearly influenced by the orientation of the cup, the support of the underlying bone and the geometry of the component itself. CT scans of the pelvis from 8 similarly sized female patients from two discrete age populations were used to develop clinically relevant FE models. Cup deformations were found to occur due to pinching between the iliac and ilial regions and were significant when compared to typical minimum diametrical clearances of 80-120 μm. In young pelvis models deformations of 34–63 μm were found to be significantly greater than in the older pelvis models, p<0.001. Surprisingly, small changes in the cup version increased deformations by up to 40% from the surgeon identified optimal position and were 30% greater when an eccentricity was introduced into the reamed acetabulum. The local deformations estimated in the acetabular cups may cause localised reductions in the fluid-film thickness, resulting in regions where boundary, rather than mixed lubrication takes place. This may help explain why failure and high wear rates are sometimes found in young patients with acetabular components positioned in clinically optimal positions.

Nowadays, the development of externally stimuli responsive vesicles possessing novel functionalities is full of challenging for various potential applications. As a practical matter, ultraviolet (UV) light responsive vesicles are finding intensive interest, as their micro/nano-structures can be tuned remotely by UV lights without involving direct contact or interaction. The development of such highly UV responsive vesicle is of great importance, where sometimes light would be the only available stimulus to drive the systems. The mainly aim of this work was to design polyelectrolyte capsules with unique externally UV responsive properties by using layer-by-layer assembly technique, to develop their applications for cargo encapsulation and release, and to get a better understanding of underlying mechanism based on UV light triggered phenomena. Strategically, three kinds of UV sensitive chemical compounds, benzophenone, azobenzene and diazonium, were introduced into building blocks for capsule preparation. Different functionalities of these capsules were studied, and their potential applications were investigated. To get a better understanding on the topic and contents discussed, an introduction and a literature review were first presented. Then experimental section containing materials, methods and instruments was followed in Chapter 3. In Chapter 4, weak polyelectrolyte microcapsules containing benzophenone groups were prepared. Bezophenone related crosslinking showed a reliable and swift approach to tighten and stabilize the shells without losing their pH-responsive properties. Chapter 5 investigated the microcapsules containing azobenzene groups, which could be activated to form J aggregates and further to destroy the integrity of shells upon exposure to UV light. In Chapter 6, microcapsules were fabricated with diazo-resin containing diazonium groups, which showed the ability to seal the porous shells via photolysis between diazonium and paired nucleophilic groups. Finally, in Chapter 7, Dual-function complex microcapsules containing both azobenzene and diazonium groups were fabricated to achieve both encapsulation and release trigged by same externally UV stimulus.

Rubber components under cyclic loading conditions often are considered to have failed as a result of the stiffness changing to an amount that makes the part no longer useful. This thesis considers three distinctive but related aspect of the fatigue failure exhibited by rubber components. The first considers the reduction in stiffness that can result from a phenomenon known as cyclic stress relaxation. The second considers fatigue crack growth encountered resulting in potentially catastrophic failure. The final issue relates to the complex topography of the resulting fatigue fracture surfaces. Previous work has shown that the amount of relaxation observed from cycle to cycle is significantly greater than that expected from static relaxation tests alone. In this thesis the reduction in the stress attained on the second and successive loading cycles as compared with the stress attained on the first cycle in a stress strain cyclic test of fixed strain amplitude has been measured for elastomer test pieces and engineering components. Adopting the approach of Davies et al. (1996) the peak force, under cyclic testing to a specific maximum displacement, plotted against the number of cycles on logarithmic scales produces a straight line graph, whose slope correlates to the rate of cyclic stress relaxation per decade. Plotting the rate of stress relaxation per decade against the maximum average strain energy density attained in the cycle reduces the data measured in different deformation modes for both simple test pieces and components to a single curve. This approach allows the cyclic stress relaxation in a real component under any deformation to be predicted from simple laboratory tests (Asare et al., 2009). Earlier work (Busfield et al., 2005) has shown that a fracture mechanics approach can predict fatigue failure in rubber or elastomer components using a finite element analysis technique that calculates the strain energy release rate for cracks introduced into bonded rubber components. This thesis extends this previous work to examine real fatigue measurements made at both room temperature and 70±1ºC in both tension and shear using cylindrical rubber to metal bonded components. Dynamic testing of these components generated fatigue failures not only in the bulk of the component but also at the rubber to metal bond interface. The fatigue crack growth characteristics were measured independently using a pure shear test piece. Using this independent crack growth data and an accurate estimate for the initial flaw size allowed 3 the fatigue life to be calculated. The fracture mechanics approach predicted the crack growth rates accurately at both room temperature and 70±1ºC (Asare et al., 2011). Fatigue crack growth often results in rough fatigue crack surfaces. The rough fatigue crack surface is, in part, thought to result from anisotropy being developed at the front of a crack tip. This anisotropy in strength whereby the material is less strong in the direction that the material is stretched might allow the fatigue crack to grow in an unanticipated direction. It might also allow the crack front to split. Therefore the final part of this thesis examines how, once split, the strain energy release rate associated with growth of each split fatigue crack develops as the cracks extend in a pure shear crack growth test specimen. The aim being to understand how the extent of out of plane crack growth that results might allow a better understanding of the generation of particular crack tip roughness profiles. Using a method of extending one split crack at a time, whilst keeping a second split crack at a constant length, it has been possible to evaluate the initial strain energy release rates of split cracks of different configurations in a pure shear specimen. It was observed that, for a split crack in a pure shear specimen, the initial strain energy release rate available for crack growth depends on the precise location of the split crack. It is also clear that the tearing energy is shared evenly when the crack tip is split into two paths of equal length, but as one crack accelerates ahead it quickly increases in tearing energy and leaves the slower crack behind. It is thought that this phenomenon is responsible for a lot of the roughness observed on the resulting fracture surfaces.

This research provides a comprehensive investigation into the effects of carbon nanotubes (CNTs) on the sintering behaviour, grain growth and properties of ceramics. Contradictory results reported in the literature on the effect of CNTs on sintering behaviour indicated the need for a systematic investigation under reproducible, controllable conditions. The sintering studies were performed using instrumented spark plasma sintering (SPS). It is a rapid sintering process that allows sintering to be studied in real time under isothermal conditions, enabling accurate calculation of time exponents and activation energies. A study into the effects of CNTs on the sintering behaviour of PSZ and B4C has shown that the presence of CNT content above the percolation threshold significantly reduces the sintering activation energies by 62 and 38% respectively. In both systems, the CNTS were also found to enhance the grain boundary diffusion mechanism of consolidation. Below the percolation threshold there was no significant effect on the activation energy. As well as the sintering behaviour, the grain growth of the PSZ and PSZ CNT composites was investigated. This research found that the CNTs acted as a grain growth inhibitor through a solute drag like mechanism both below and above the percolation threshold although with a high CNT content the solute drag effect was enhanced further with no significant change to the activation energy. The degradation of the CNTs was examined to determine whether they maintain their structural integrity during sintering. It was found that in both matrices with increasing temperature the CNTs were degraded to a greater extent. In the case of the PSZ-CNT composite the degradation was measured with respect to time at a series of temperatures to investigate the mechanism of degradation. Abstract ii The thermal properties of the ceramic CNT composites and porous ceramics were examined to determine the effect of CNTs on the transport properties of the matrix. It was found that the inclusion of CNTs in a PSZ matrix could enhance the thermal diffusivity and the residual porosity caused by burning them out causes a reduction.

Graphene is the first 2D material consisting of carbon atoms densely packed into planar structures. Graphene oxide (GO) is the intermediate derivative of chemically-produced graphene, which retains 2D basal plane structures but is also decorated with functional groups along the basal plane and edges. This functionality allows self-assembly of planar sheets into a paper-like material. However, formations of both intrinsic defects within the sheet structures as well as larger scale extrinsic defects in the paper are expected to significantly degrade mechanical performance. Strength provides the most direct evidence of defect related mechanical behaviour and is therefore targeted for understanding defect effects in GO paper. Such evaluations are crucial both from a technological perspective of realizing designed functions and from a fundamental interest in understanding structure-mechanics in 2D nanomaterials. A complete strategy of performing mechanical testing at different length scales is thus reported to provide a comprehensive description of GO strength. Both conventional larger scale mechanical testing as well as novel smaller length scale evaluations, using in situ atomic force microscopy (AFM) combined with scanning electron microscopy (SEM) and optical microscopy as well as structural probing using synchrotron FT-IR microspectroscopy, were applied to GO materials. Results showed that large structural defects determined mechanical properties of GO papers due to stress concentration effects whereas smaller scale intrinsic effects were defined by interfacial defects and stress concentrations within sheets. Synchrotron FT-IR microspectroscopy provided molecular deformation mechanisms in GO paper, which highlighted the interaction between in-plane C=C and cross-linking C=O bonds. A comprehensive description of macroscopic GO paper using evaluations of strength at the range of length scales studied was attempted, with a good correlation between predictions and experimental observations. This thesis therefore provides a hierarchical understanding of the defects impact on the strength of graphene-based materials from the macroscale to the nanoscale.

In Europe, the rapidly growing thermosetting foam insulation products industry comprises over 11,500 companies employing over a third of a million people and is worth about 6 billion Euros in trade. It is currently estimated 4-7 % of total new UK production is scrapped and goes to landfill. Estimated costs of disposing of this waste foam are of the order of £20 million/annum to the producers of foam panels and insulation blocks. A new strategic direction for rigid polymeric foams waste management has been developed converting the scrapped thermosetting foams into high added value material that can be used in various applications such as fire resistant insulating applications. Thus by this new innovative recycling process the waste is not only eliminated but benefits can be gained from the new material that comes out of it as a structural composite panel. The project involves a new concept that mixes fragmented scrap thermosetting foams materials with a proprietary liquid that cures at ambient temperature to form an incombustible material capable of withstanding high temperatures >1000 C. In this research different kind of polymeric foams used for manufacturing of reconstituted recycled samples. Sodium silicate solution has been chosen as the binder to binds shredded foams together. Due to fastening of sodium silicate curing different kind of acidic powders have been tested. For increasing of post properties after curing variety of fillers as an additive have been tried through out this research. Different foam cutting methods have been tested to find the suitable shredding routine. Rationale for selection of generic binder and its hardeners/fillers has been discussed in this project. Also as post properties evaluation compressive strength, thermal resistance, fire resistance and acoustic properties of recycled structural composite panels have been measured. At last a model for thermal conductivity of composite panels is developed.

The friction between a rubber surface in contact with a rigid surface is still not fully understood. Unlike other materials, friction behaviour in rubber is significantly dependent upon a variety of parameters due to its viscoelastic nature. The aim of this work is to understand frictional phenomena occurring on different length scales of intrest. In the first part of this work the influence of an entirely geometric factor on friction is confirmed by FEA and is validated by experiments for the first time. Under certain conditions, it can increase the frictional force significantly above that expected from a consideration of the interfacial coefficient of friction alone. This term is thought likely to make a considerable contribution to frictional sliding applications such as a tyre on a road surface. In the second part of this work an instability, observed at the rubber surface during sliding, is investigated. Despite experimental research in the past, virtually no information has been published on the modelling of the so-called Schallamach waves using FEA techniques. This work models successive Schallamach waves, giving the opportunity to investigate the transition of individual waves throughout the area of contact, for the first time. The use of FEA allows for a detailed stress and strain analysis at the interface and thus gives new insights into the onset of buckling instabilities. So far, Schallamach waves have only been observed experimentally for optically smooth rubber surfaces, however, during this work, surface waves have been also noticed for rough rubber surfaces. Furthermore, the examination of the frequency dependence of Schallamach waves allows for the consideration of a relationship to stick-slip behaviour. The third part of this work investigates the influence of the rubber surface topography as well as the rigid slider geometry on rubber friction under a wide range of experimental conditions. It was noted that subtle changes of surface finish significantly change the resulting frictional force. The knowledge gained from this can help in the design and understanding of more complex frictional interfaces.

This thesis examines the possibility of reinforcing thermoplastic matrices, notably polypropylene (PP) and polyhydroxyalkanoates (PHAs), by (a vegetable fibre) flax. An effort is made to enhance/optimise the mechanical properties of flax, PP composites through a micromechanical and macromechanical study. The fibrc'matrix interface is modified via chemical modifications as well as modifications in processing parameters (transcrystallinity). Effects of parameters like fibre length, fibre volume fraction and fibre-matrix interface modification on the mechanical properties of long flax fibre reinforced PP composites (compression moulded) as well as short flax fibre based composites (injection moulded) are studied. In order to get a better insight in the importance of these different parameters for the optimisation of composite performance, the experimental results are compared with model predictions using micromechanical models for random short-fibre-reinforced composites. For the injection moulded composites, different compounding routes are used and compared. The moisture resistance (pick-up and diffusivity) as well as dimensional stability (swelling) of natural fibre mat reinforced thermoplastics (NMTs), based on different kinds of flax fibres and PPs, are studied. The effects of a novel fibre upgrading method for flax fibres (DuralinTM) on the moisture pick-up and residual tensile properties of NMT composites are explored. Biodegradable composites based on flax fibre and PHAs are analysed. It is observed that addition of (cheap) flax fibre to polyhydroxybutyrate (PHB) could be advantageous as far as cost-performance of biopolymer composites is concerned. especially for stiffness critical applications. Mechanical properties of `biocomposites' manufactured through different routes (i. e. injection moulding and compression moulding) are compared. Addition of cheap flax fibres to an expensive and brittle PI IA composite leads to enhanced toughness of the composites. Abstract A life cycle assessment (LCA) study on glass-fibre-mat-reinforced-thermoplastic (GMT) and NMT manufactured by a current production method for thermoplastic prepregs followed by compression moulding into an automotive and non-automotive part is carried out.

An aspirating and dispensing printer established inside a robot gantry equipped with furnace and measurement table is used to prepare thick-film combinatorial libraries. Implementation of series of screening tests for ceramic inks that address stability against sedimentation, evaporation and particle segregation during drying, has provided a series of calibration inks can be used for calibration of this printer. The instrument can assemble ceramic mixtures with compositional accuracy of 1-3 wt %. By changing the amount of dispersant used in the inks or by printing onto a porous substrate, the geometry of residues from dried ceramic ink droplets can be modified to facilitate property measurements and uniform composition, as planned, can be achieved. The same material prepared in three ways, in the form of dried ink, ink-jet printed as for a combinatorial sample and by conventional compaction gave similar dielectric measurements. A combinatorial system has been developed so that combinatorial libraries can be printed, fired and screened automatically. A ternary A1203-TiO2-ZrO2 system was first studied using the developed combinatorial method. The particle segregation during drying of multi-component ceramic ink drops is not due to preferential sedimentation unless dispersant addition is restricted. The segregation is due to the partitioning of particles between the growing peripheral 'foot' that develops during drying and the diminishing liquid pool which contains vigorous recirculation flows. Better dispersed particles remain in the pool and hence are found in excess on the upper surface of residues. Less well dispersed particles join the 'foot' earlier in the drying process. The contact angle and height of droplets containing large amounts of dispersant, steadily reduced during drying until a minimum value was reached; the contact diameter being almost unchanged during drying. These droplet residues retained a dome shape. Droplets of suspensions containing small additions of dispersant terminated in a 'doughnut' shaped residue.