This thesis describes the steps taken to develop normal strength (30-80 MPa) selfcompacting concrete mixes with 20mm maximum size aggregate. For the selfcompacting concrete mixes with 20mm maximum size of aggregate fulfilment of the flow and cohesiveness criteria are found insufficient for the mix design. It is found that they must additionally meet the passing ability criterion. A Lagrangian particle based method, the smooth particle hydrodynamics (SPH), is used to simulate the flow of SCC mixes. An incompressible SPH method is employed to simulate the flow of such non-Newtonian fluids whose behaviour is described by a Bingham-type model, in which the kink in the shear stress versus shear strain rate diagram is first appropriately smoothed out. The basic equations solved in the SPH are the incompressible mass conservation and Navier-Stokes equations. The yield stress of SCC mixes is predicted in an inverse manner using the SPH simulation methodology and matching the measured and simulated t500, tstop and the final spread of the cone flow test. It is found that the yield stress of SCC mixes varies only slightly with an increase in the characteristic compressive strength of the mix. The plastic viscosity on the other hand shows a marked increase. The latter was estimated by a micromechanical procedure proposed by Ghanbari & Karihaloo (2009) based on the measured viscosity of the cement paste alone and on the volume fractions of the mix constituents. The SPH simulation methodology was also used for predicting the distribution of large coarse aggregates in the cone spread. This distribution was found to be indeed very similar to that revealed in the cut sections of the hardened test cone spread. These large coarse aggregates had been painted with non-toxic non-water soluble paints prior to being used in the test mix. The simulation of SCC mixes revealed that the cone lift rate in the slump flow test has a significant effect on the flow pattern and the measured t500. The latter decreases as the cone lift rate increases from 0.1 to 1 m/s. The effect on the spread (i.e. tstop) is, however, insignificant.

An understanding of the physical mechanisms by which non-wetting fluids become entrapped is important to oil recovery techniques from reservoir rocks, and the structural characterization of porous media. The mechanisms of entrapment and the spatial distribution of non-wetting fluid (mercury) within model materials with similar chemical and geometrical properties to oil reservoir rocks have been investigated using mercury porosimetry and computed X-ray tomography. The combination of both techniques has allowed the direct observation of entrapped mercury within the model materials. In this thesis, a novel experimental technique involving combined mercury porosimetry and mercury thermoporosimetry techniques has been used to determine pore size distributions for disordered porous solids. Mercury porosimetry was conducted, and the mercury entrapped following porosimetry was used as the probe fluid for thermoporosimetry. The fully integrated combination of techniques described here permits the validation of assumptions used in one technique by another. Mercury porosimetry scanning curves were used to establish the correct correspondence between the appropriate Gibbs-Thomson parameter, and the nature of the meniscus geometry in melting, for thermoporosimetry measurements on entrapped mercury. Mercury thermoporosimetry has been used to validate the pore sizes, for a series of sol-gel silica materials, obtained from mercury porosimetry data using the independently-calibrated Kloubek correlations. A Liquid-liquid exchange (LLE) process within mesoporous materials has also been investigated using NMR relaxometry and NMR diffusimetry experiments. In this method, a high affinity liquid (water) displaced a low affinity liquid (cyclohexane) from the sol-gel silica samples. Entrapment of low affinity liquid was observed which was similar to the entrapment of non- wetting fluid observed in mercury porosimetry. In addition, the molecular diffusion of n-pentane has been measured in mesoporous sample using PFG NMR method in a broad temperature range.

The Resin Transfer Moulding (RTM) process is one of the most common manufacturing routes for composites. The challenge in the present work is to be able to predict the flow behaviour in order to manufacture advanced composites truss structures. To that end, there is a lack of an advanced simulation tool capable to predict void formations for the manufacture of three dimensional, multi-layer woven textile composites like the Advanced Composites Truss Structure (ACTS) generic node TSB-funded project that is presented in this thesis. Industrial experience has shown that during mould filling, due to race-tracking and stochastic variability in the material properties, the filling patterns and arising cycle times are rarely the same between a given set of apparently identical mouldings. The objectives of this thesis were 2D, 3D racetrack prediction of textile reinforcements for RTM processes and 3D variability prediction at the component scale. A model that predicts the resin rich zone along a component edge was developed for this purpose. The issue of 2D, 3D racetrack prediction was firstly investigated along a 90° edge for three different geometry, architectures and material preforms, on a generic composite node 3D. Variability was also investigated through the same CAD model with the use of the FE/CV technique. A novel numerical approach for 3D FE CAD modelling was developed in order to predict race-tracking and variability for advanced composites structures. A stochastic analysis technique was developed to account for the effect of node variability during the fabrication process by RTM. The study based on this technique provided important insights into flow filling variations, voidage formation and optimization on a generic advanced composite truss structure. The model developed from this work can be used to account for the effects of race-tracking and variability on any other composite component at the macroscale level. The predicted race-track and variability data can complement experimental data in order to enhance flow simulations at the component scale.

Assembly work requires high levels of performance and quality but may involve complex cognitive and physical tasks. There is evidence that physical and cognitive workloads are not separate, but may interact. Work in exercise and simple physical tasks suggests that physical load may lead to changes in cognitive performance, and in perceived workload. The aim of this thesis is to examine physical and cognitive interactions that might affect assembly work. First, observation was undertaken in industry to identify the physical and cognitive factors relevant to examples of assembly lines. From this, a task analysis of a simulated assembly task was developed. Three experimental studies were conducted, based upon the simulated assembly task, in order to investigate three main assembly variables; working height, memory load and pacing. The first study showed that the number of completed assemblies was reduced when performed at higher pacing and while working at above shoulder height. The number of components dropped was higher when performed at above shoulder height. When the task was performed at elbow height ‘wait’ time increased as the beep time was found to be higher at elbow height than the above shoulder height, which led to increase wait time when performing the task at elbow height. Subjective measures (NASA TLX) showed that temporal demand and effort were reported as higher during high pacing. Perceived physical and temporal demand increased when working above shoulder height. An interaction on subjective measure was identified between pacing and working height. Performance of NASA TLX was found to be poor when performing the assembly operation at high pacing/Takt and above shoulder height as compared to working at high pacing/ Takt and elbow height. In the second study the experimental design was modified by changing the assembly order to variable assembly and consistent assembly, which represented single model assembly line (where only one type of assembly is being processed) and mixed model assembly line (different types of products being processed). Study 2 was found to be more mentally demanding due to task complexity. However, it was also found that completed assemblies were higher for the consistent assembly task. Subjective measures reported stress as being higher for higher pacing and variable assembly. The final study combined the variables from the first two studies as well as investigating different levels of memory load. Performance times for variable assembly were longer and resulted in less correct code responses. A higher memory load resulted in a higher performance time and lower correct code responses as well as fewer completed assemblies. An interaction between working height and perceived mental workload was found. Results showed that perceived temporal demand and perceived effort of NASA TLX were found to be higher when performing the assembly operation at elbow height and high memory as compared to the assembly operation performed at elbow height and low memory. It was also found that memory load affects perceived physical demand. For industry the findings suggest that in variable (mixed model) assembly different levels of pacing, working height and cognitive demands may affect workers’ performance both physically and mentally. Demands will be higher when working at variable assembly but also performance will vary where variable and consistent assembly are used together. The research also discusses theories that might be most useful for describing these effects.

The small punch creep testing (SPCT) technique has received much attention because it can provide information on the creep behaviour of materials with a very small specimen being tested. However, the nature of the test is complex and several aspects of the behaviour of the specimen, characterised by various non-linear concurrent processes, still need investigation. This thesis reports the findings of experimental investigations and numerical analyses of SPCT carried out with the aim of improving the understanding of various features which characterise the behaviour of the specimen and to develop a novel technique to correlate the SPCT experimental output with the corresponding uniaxial creep test data, which is also presented. The experimental programme consisted of SPCTs and pre-strained uniaxial creep tests, all performed at 600°C on the same batch of P91 steel. The pre-strained uniaxial creep tests have been used to evaluate the effects of large initial plasticity on the subsequent creep behaviour of P91 steel. For different stress levels, the results of the experiments have shown that creep was resisted for low pre-strain levels and enhanced for high pre-strains. The SPCT specimens have been investigated by use of scanning electron microscopy (SEM) to identify the effects of the punch load on the fracture surface of the failed specimens and the evolution of microstructural features in the material during the test. When the punch load was increased, the failure mechanism changed from creep-governed to plasticity-governed, as the presence of fresh dimples in the fracture surface increased. For the low-load tests, a macro crack was found to nucleate on the bottom surface of the specimen at approximately 20% of the failure life, and it subsequently propagated along the circumferential direction and through the thickness of the specimen. A modified creep constitutive model has been developed based on the results of the pre-strained uniaxial creep tests and it has been implemented in a FE model of a SPCT capable to take into account the effects of the large initial plasticity, generated by the load application, on the creep response of the SPCT specimen. A global creep resistance in the SPCT specimen, due to the combination of localised different effects in various regions of the sample, was observed when these effects were included. FE calculations have also been performed to investigate the effects of the eccentricity and the misalignment of the punch loading conditions on the punch minimum displacement rate (MDR) and on the time to failure. A correlation equation for these effects has also been reported. When the punch load was eccentric and misaligned, the MDR decreased and the time to rupture increased. Further numerical analyses have been carried out to evaluate the effects of the friction coefficient modelling procedure on the behaviour of the specimen. The results obtained using the classical Coulomb friction theory are compared with those obtained by a more modern friction formulation, which takes into account the dependency of the friction coefficient on the contact pressure. Finally, a nobel interpretation technique for SPCT data has been developed using the results of experimental tests and numerical analyses. The interpretation technique takes into account the effects of the initial, large plasticity on the behaviour of the SPCT specimen, in order to correlate the SPCT results with the corresponding uniaxial data. A significant improvement in the accuracy of the correlation for rupture SPCT data with the corresponding uniaxial test results has been obtained.

Localised magnetic flux density, magnetising field and power loss are believed to distribute non-uniformly in grain oriented electrical steel. Understanding of the causes of their variation can help reduce the overall power loss of the material. In this investigation, magnetic domain observation was often used in the study of domain configuration and crystal orientation of the test specimens. Methods of domain observation have been studied and compared in order to select the appropriate method for different parts of the investigation and to improve the understanding of the image observed. A less destructive local loss measurement sensor has been built for the measurement of localised flux density, magnetising field and power loss. The sensor was tested and evaluated specifically for the measurement of localised magnetic power loss of the high permeability grain oriented electrical steel. The results obtained from local loss scanning measurements indicated that localised flux density and magnetising field can vary substantially in grain oriented electrical steel under AC magnetisation of 50 Hz. The variation of localised flux density has been found mainly resulted by grain misorientation and local grain arrangement. The transverse component of flux density was detected and has been found increases with increasing grain misorientation. The variation of localised magnetising field has been found mainly influenced by the localised demagnetising field due to formation of free magnetic poles at grain boundaries. It has been proved that both flux density and magnetising field have strong influence on the distribution of localised power loss. The study of the effect of domain refinement on distribution of localised flux density showed that domain refinement by means of ball scribing on one surface of grain oriented electrical steel can improve the uniformity of distribution of flux density. However, results also inferred that excessive scribing in a confined area can cause obvious uneven distribution of flux density in the direction of the specimen’s thickness.

A twin disk rig was used to perform a series of experiments investigating mixed lubrication. The disks used in the experiments were manufactured from case carburising steel, were hardened and had a surface finish ground transverse to the direction of oil entrainment in order to simulate the roughness orientation typically found on involute gear teeth. Roughness profile measurements were taken in-situ between experiments which showed that the initial phase of operation for as-manufactured surfaces is a period of rapid plastic deformation, where asperity features on the surfaces accommodate to one another. It was found that this reduction in roughness improved the state of lubrication by reducing instances of contact between the surfaces. Contact was assessed by measuring the electrical contact resistance between the disks during the experiments and the level of the contact voltage between the disks was used as an indicator of the state of lubrication existing between them. It was found that variations in the dimensionless film thickness strongly influenced the level of the contact voltage. The contact voltage waveform was also found to exhibit similarity between revolutions, indicating repeated contact between groups of interacting asperities. Realigned profile traces demonstrate that prominent asperity features undergo significant plastic deformation during the running-in process. Over extended operation, it was seen that these same roughness features can be subject to a degree of fatigue at the roughness scale, which has been identified as micropitting failure in the experiments. Modifications to an existing numerical model simulating the isothermal non-Newtonian EHL point contact to enable the use of measured 3D roughness shows that high pressures are generated in the region of interacting asperity features. Asperity contact is also seen to occur across the length of prominent ridges in agreement with images obtained from 3D profilometry which demonstrate prominent ridges experiencing fatigue.

The concept of smart structures with integrated optical fibre sensors capable of performing real-time structural health-monitoring has attracted much attention in recent years due to the potential safety and economic benefits they offer. In addition, optical fibres have also been employed as in-situ sensors to monitor the fabrication cycle of polymer composites. The aim of the present research study is to explore the concept of smart composite structures for damage detection and strain monitoring using optical fibre technology. The first part of this thesis summarises a study of the use of two types of optical fibre systems for realtime health-monitoring of advanced composite structures based on a conventional multi-mode optical fibre and a Bragg grating sensor. These sensors have either been embedded or surface-bonded to the host material for health assessment of the structure. The second part of the thesis outlines an investigation which has been carried out to assess the potential of an intensity-based optical fibre sensing system to monitor the chemo-rheological changes which take place during the processing of a thermoplastic composite. The study has demonstrated the potential of the system and has shown that this technique offers a cost-effective means of monitoring the processing cycle of a polymer composite material. Regarding the health-monitoring aspect of the research, intensity-based optical fibre sensors have been embedded in a thermoplastic composite and a fibre-metal laminate system based on the same composite constituent. Impact tests and quasi-static three-point bend tests have been conducted to investigate the ability of these optical fibres to detect damage induced by these loading types. The embedded UAT-type optical fibre was found to be sensitive to impact energies as low as 1 Joule. The hard-clad EMT-type optical fibre on the other hand was shown to be capable of surviving extensive sub-perforation-type impact damage and could be used for detecting ballistic damage in aircraft combat situations. In the three-point bend tests, embedded UAT-type optical fibres were observed to be sensitive to flexural failure and were shown to be capable of detecting damage in the host material. Fibre Bragg grating sensors were embedded in a number of thermosetting composites and a thermoplastic fibre-metal laminate to examine their potential for strain monitoring and damage detection. Uniaxial tests have demonstrated that specimens exhibiting a single peak spectrum show excellent linearity. In contrast, specimens with multiple-peak spectra were shown to exhibit strain anomalies. In impact tests, the specimens were impacted repeatedly and, although in each case the spectrum underwent a significant change in shape, the sensor showed excellent survivability. Postimpact fatigue tests have demonstrated that the linearity of the FBG was maintained. The results also highlighted the potential of the sensor to detect impact event and damage propagation. In addition, the study has demonstrated the ability of fibre Bragg gratings to measure post-processing residual strains within a multi-material structure. Multi-mode optical fibres were used as sensors in an intensity-based optical fibre system to obtain real-time information during the processing of thermoplastic-based glass fibre-reinforced polypropylene (GFPP). The technique used to monitor the melting and solidification process in this study is based on monitoring the modulation of the refractive index of the polymer matrix. The intensity modulation of the signal was monitored during the composite processing cycle. Differential scanning calorimetry (DSC) was performed to provide a reference to evaluate the validity of the optical fibre data. The results have demonstrated the potential of this method in achieving a repeatable and accurate indication of the melting and recrystallisation temperatures within the semicrystalline matrix.

In 2007 there was an important change in the architecture of nanotransistors - the building blocks of modern logic and memory devices. This change was from utilising thermally grown silicon dioxide as a dielectric to so-called high-κ hafnium oxide dielectrics grown by atomic layer deposition. The first production logic devices of this era used a hafnium oxide dielectric layer deposited by thermal atomic layer deposition; using HfCl₄ and H₂O as the precursors. Present day fabrication makes use of hafnium oxide-based atomic-layer-deposited dielectric films. The latest nanotransistor devices utilise a third generation hafnium oxide-based dielectric material. This thesis examines hafnium oxide-based thin film dielectric materials prepared by thermal atomic layer deposition on silicon substrates. Specifically the enhancement of the dielectric response of hafnium oxide by the addition of other elements is examined. Two ternary materials systems were deposited by thermal atomic layer deposition and analysed: titanium-hafnium oxide and cerium-hafnium oxide. Hafnium oxide films were deposited to be used as measurement benchmarks. Cerium oxide films were also deposited and analysed in their own right as potential dielectric layers. The hafnium oxide and both ternary deposition experiments used (MeCp)₂Hf(OMe)(Me) as the hafnium precursor. The titanium-hafnium oxide growth used Ti(ⁱOPr)₄ as a titanium source and the cerium oxide and cerium-hafnium oxide work utilised Ce(mmp)₄ as a cerium source. Post-deposition specimen sets consisted of an as-deposited sample, a sample spike-annealed in N₂ at 850°C and a sample annealed for 30 minutes at 500°C. These annealing regimes were performed to mimic typical gate-first and gate-last transistor processing steps. The compositions and thicknesses of the films were measured using medium energy ion scattering. The structure of the films was analysed by X-ray diffraction and Raman spectroscopy. Capacitance-voltage and current density-field measurements were taken from fabricated MOS capacitor specimens to assess the dielectric response of the films. X-ray diffraction and Raman measurements showed that un-doped HfO₂ had monoclinic crystallinity as-deposited and after the two annealing regimes. The dielectric constant and leakage current density, 17 and 1.7x10⁻⁷ A/cm² at -1 MV/cm respectively, are consistent with values reported in the literature for HfO₂ films. The addition of titanium suppressed the crystallinity of the material resulting in amorphous films in compositions with Ti₀_.₃Hf₀_.₇O₂ titanium and above. The optimum electrical results were recorded for the titanium-hafnium oxide material in the composition Ti₀_.₅Hf₀_.₅O₂ which had a dielectric constant of 35 as-deposited and a leakage current density of 1.0x10⁻⁷ A/cm² at -1 MV/cm. This composition of film demonstrated similar values after the 500°C/30 min anneal but both dielectric constant and leakage current density suffered after the 850°C/spike anneal; 22 and 1.8x10⁻⁶ A/cm² at -1 MV/cm respectively. Films with compositions of Ti₀_.₁Hf₀_.₉O₂ demonstrated much lower dielectric constant and higher leakage current density, especially after heat treatment. The addition of cerium in a Ce₀_.₁₁Hf⁰_.₈₉O₂ composition was found to suppress crystallinity as-deposited and then provoke a lattice-substitutional phase change to the metastable tetragonal/cubic phase after both types of heat treatment. This ceriumactivated phase change resulted in a molar volume modulation compared to un-doped HfO₂. An increased dielectric constant compared to un-doped HfO₂ of 31 was recorded for the 500 °C/30 min anneal with the 850°C/spike anneal resulting in a lower value of 21. Leakage current density was 1.3x10⁻⁷ A/cm² and 3.2x10⁻⁷ A/cm² at -1 MV/cm respectively for the same anneals. Deposition with Ce(mmp)₄ and water was found to result in cubic crystalline films across a growth temperature range 150-350 °C. The frequency dependency of the dielectric properties was found to be influenced by the crystallite size which was governed by the deposition temperature. The highest dielectric constant, 42, was measured for the 150 °C growth temperature with C-V measurements performed at 1 MHz. The two doped HfO₂-based materials systems studied have demonstrated potential as dielectric materials for use in future nanoelectronic devices.

The aim of this research work is to investigate the mechanical properties of corrugated-core sandwich structures under quasi-static and dynamic loading conditions and to determine the failure mechanisms and energy-absorbing characteristics of the corrugated-cores with different cell wall thickness and filled with a foam core. Triangular corrugation structures were made from an aluminium alloy (AL), a glass fibre reinforced plastic (GFRP) and a carbon fibre reinforced plastic (CFRP). The composite corrugations were fabricated using a hot press moulding technique and then adhesively bonded to skins based on the same material, to produce a range of lightweight sandwich structures. The role of the number of unit cells, the thickness of the cell walls and the width in determining the mechanical behaviour of the structures was investigated. Buckling of the struts was identified as the initial failure mode in these corrugated systems. Continued loading resulted in plastic deformation in the aluminium system, in contrast, fibre fracture, matrix cracking and localised delamination in the composite systems, as well as debonding between the skins and the core were observed in the composites. The compression strength and modulus were shown to be dependent on the number of unit cells and the cell wall thickness, but independent of specimen width. Subsequent mechanical testing was undertaken using an Arcan rig capable of generating a range of loading conditions between pure shear and pure compression. The failure strength in the aluminium system was accurately represented using a two dimensional quadratic failure criterion. In contrast, due to the initation of delamination within the composite struts, the composite corrugated-cores were accurately predicted using a modified failure criterion. Low velocity compression loading was subsequently performed on the sandwich structures, where the dynamic strength enhancement factor was shown to increase for all the corrugation systems. This was attributed to both a material strain-rate sensitivity and inertial stabilisation effects. The failure mechanisms in the sandwich structures were found to be similar under both quasi-static and dynamic loading conditions, where damage initiated due to buckling of the struts. To simulate the mechanical response of the corrugation systems, FE models have been developed using the Abaqus finite element package. The FE results were compared to measured responses, and good agreement was achieved. The failure modes predicted by the FE models show reasonably good agreement with the experimental observations. Finally, foam filling the composite corrugation systems significantly improved the specific strength as well as specific energy-absorbing characteristics of the structures. The compression properties of the corrugated structures have been compared to those of other core materials, where the evidence suggests that these systems compare favourably with other cellular core materials.