Laser Doppler Blood Flowmetry (LDBF) has for several decades been applied to measure the flow of red blood cells in living tissue. Laser Doppler Perfusion Imaging (LDPI), a recent advancement which enables full-field blood flow visualisation, is gaining clinical acceptance in fields such as burn diagnostics. However, video-rate full-field imagers with appropriate sensor and processing capability require large financial and physical resources and this has prompted the development of under-specified systems. These systems may reduce the bandwidth and processing complexity but the question of how they perform compared to their fully specified counterparts remains. The advantages of these cheaper and often highly reconfigurable systems are recognised and so it is beneficial to ask whether any novel processing schemes can reduce the resultant error. Here a reduced bandwidth LDBF signal processing system has been modelled. Bayesian Inference has been used to show that the Pareto distribution is a likely model for the LDBF power spectrum, despite often being cited as exponential. Methods of evaluating microvascular blood flow have been described and compared. Additionally, one fast algorithm's effectiveness has been explained, and a novel and accurate method using the Hilbert transform has been presented. By understanding how aliasing modifies the frequency distribution, Bayesian Inference has been used to correct the blood flow output towards gold-standard values. The technique has been shown to correct the output of a low bandwidth CMOS camera imaging a rotating diffuser. Low bandwidth LDPI systems may be suitable for certain clinical applications where sensitivity to high flow is not required. However, where sensitivity to higher flow than baseline is required, e.g. in burn diagnostics, low bandwidth systems may underestimate the true blood flow leading to misdiagnosis. Nevertheless, low bandwidth systems could be used in this scenario if reliable post-processing is employed, such as that suggested by this thesis.

Three topics are considered in this thesis. The first is evaluation of the effective elastic moduli of porous materials and considers materials such as porous glass, sandstone, sintered bronze and iron materials, porous ceramics. Models with spherical pores were first considered showing good agreement for some materials but not for materials prepared by powder sintering. A number of modifications of increasing complexity were introduced accounting for non-spherical pores and their interaction. The models then compare well with experimental data for sintered materials. The other topics of the thesis can be used to model mixed lubrication in plain bearings where part of the load is carried by contacting asperities and part by the lubricant film. The roughness features affect the ability of the lubricant to flow in the gap between the surfaces and surface deflection is caused by asperity contact pressures only. A method is presented to solve dry contact problems for nominally plane surfaces using a simple elastic-plastic model at asperity contacts and a differential formulation for the elastic deflection. Periodic roughness defined over a representative area is incorporated using Fourier transforms to calculate the convolutions. The method is validated by comparison with the results of an elastic-plastic rough surface contact analysis obtained using a finite element method. A method is then developed to model the mixed lubrication problem based on the homogenised Reynolds equation where the effect of the roughness features is isolated from that of the global geometry of the bearing. Local rough problems are solved and the average effect of the roughness on lubricant flow expressed in terms of flow factors, which are functions of global film thickness. When direct asperity contact occurs the deflected shape is obtained from dry contact analysis of the representative roughness area. The global problem is then solved using the Reynolds equation modified with appropriate flow factors taking the mean contact pressure obtained from the local problem into account in load determination. The homogenised method is validated against the series of deterministic solutions and cases of surfaces with measured roughness are presented.

This thesis describes the use of cellulose nanocrystals for the fabrication of porous nanocomposites with electronic conducting polymers for electrochemical supercapacitor applications. The exceptional strength and negatively charged surface functionalities on cellulose nanocrystals are utilised in these nanocomposites. The negatively charged surface functionalities on cellulose nanocrystals allow their simultaneous incorporation into electropolymerised, positively charged conducting polymer for charge balancing, i.e. co-electrodeposition occurs. The exception is the case of polyaniline-cellulose nanocomposites which formed with uncharged cellulose nanocrystals. As a result, the cellulose nanocrystals form the structural backbone of the nanocomposites in which the mechanical integrity of the nanocomposites becomes significantly improved. In Chapter 1, supercapacitors and the electrode materials are introduced. The equations relating to the characterisation of supercapacitor materials and devices are also introduced in Chapter 1. In the first half of Chapter 2, the basics of electrochemistry and electrochemical methods used in this work are discussed. In the second half, the preparation of the cellulose nanocrystals is reported. Chapters 3 and 4 report the fabrication and characterisation of polypyrrole-cellulose nanocrystal composites with respect to their capacitance, stability and charging characteristics. Chapter 5 discusses the making of the polypyrrole-cellulose nanocomposites at a practical scale for supercapacitors, and consequently reports the making and testing of a laboratory prototype supercapacitor. Chapter 6 extends the PPy work to other ECPs by the fabrication and characterisation of polyaniline and poly(3,4-ethylenedioxythiophene) nanocomposites with cellulose nanocrystals. Finally, Chapter 7 contains the closing conclusions that I have made for this thesis, and in Chapter 8, I have made some suggestions for future work in this area. In this project, the materials were characterised using mainly scanning electron microscopy and a range of electrochemical techniques. Specifically, the performance of the polypyrrole-cellulose nanocomposites was compared against that of polypyrrole-carbon nanotube nanocomposites, current state-of-the-art materials for supercapacitor. The performance of all the nanocomposites described in this thesis was also critically compared against that of the best available similar materials in literature, to assess the viability of these materials for applications in supercapacitor devices. Significantly, to the best of my knowledge, this is the first time that the nanocomposites of electronic conducting polymers with non-conducting rod-like nanoparticles fabricated using the co-electrodeposition method were described. The performance of conducting polymer composites was significantly enhanced by the presence of the cellulose nanocrystals as the backbone. This work also proves, for the first time, that conducting polymer composite containing non-conducting nanofillers can also achieve high performance. This is a very interesting finding, compared to previous work reported in the literature for similar materials, such as those developed using carbon nanotubes as the composite filler.

The need to provide mechanical connection from one side for the Hollow section connection has arisen in a number of fields and has resulted in the development of several types of so-called blind fasteners. An experimental blind bolt called the Extended Hollobolt is giving a good behaviour performance in terms of stiffness, strength and ductility. The strength performance of this system has been investigated under both monotonic and cyclic loading. However, the performance of such connections under fatigue loading is still unknown. The aim of this study was to investigate the behaviour of blind bolt connection to concrete filled hollow section under repeated load. Further aim was to determine the reliability of the Extended Hollobolt to concrete filled hollow section. The study involved conducting an experimental programme and carrying out fatigue life and reliability analysis. The experiment programme tested 52 specimens of bolts connected to concrete filled hollow sections where 36 tests involved Extended Hollobolt, 10 standard Hollobolt and 6 standard bolts (M16). The test specimens were subjected to tensile fatigue load characteristics with varying stress ranges. Mathematical methods are used to analyse the fatigue test data using the normal, lognormal and Weibull distributions. Normal and lognormal distributions are more suitable. Therefore, statistical analysis procedure proposed by Eurocode for the statistical analysis is valid for fatigue test data. Statistical analysis was conducted to establish S-N curves and to predict the fatigue life of the proposed blind bolt. This was then compared to the normative regulation in Eurocode 3. The failure mode of the Extended Hollobolt under repeated loading was found to be similar with standard bolt, which is a very positive outcome. Statistical analysis of fatigue test data showed that the fatigue life of Extended Hollobolt is higher than the theoretical design S-N curve which is recommended by Eurocode 3 part 1-9 for the standard bolt. However, the actual fatigue life for the standard bolt appears to be higher than the proposed blind bolt. A design model for predicting the fatigue life using S-N curve for the Extended Hollobolt is proposed. A reliability analysis using FORM (First Order Reliability Method) analysis shows that Extended Hollobolt is reliable in connections to concrete filled hollow sections where the safety index is 4.2.

In recent years the use of composites in engineering has greatly increased due to the advantages which may be obtained. These are weight savings, increased strength, the ability to construct complex geometries and the use of mixed materials. Of particular interest in this work are carbon fibre reinforced plastics (CFRP) which are increasingly used in the aerospace industry. Historically, NDE methods for CFRPs have concentrated on through thickness measurements of ultrasonic attenuation or velocity to determine the presence of defects. Whilst this method is relatively fast and easy to employ there are significant disadvantages in terms of defect characterisation and the location of defects in three dimensions. The advent of full waveform capture and increased computing power allowing processing of large volumes of data, has made 3-D characterisation possible for the first time. The overall aim of this work is to develop new signal processing techniques with which to interpret ultrasonic signals from composite materials. The primary consideration is the propagation of normal incidence compression waves through the multi-layered composite structure, and the interaction of the waves with the various types of defect which may be present. The principal interest is the detection and classification of porosity. A multi-layered model of ultrasonic propagation in a composite is combined with a model which calculates the scattering response due to porosity. The model is used to simulate the ultrasonic signals that are obtained from NDE procedures applied to composite. The simulations are then used as the basis on which to develop novel signal processing schemes for the detection, location and characterisation of porosity and other types of defect. The response obtained from differing defect conditions is isolated and investigated using both time domain and frequency domain techniques. Comparisons are drawn between the responses obtained from modelling and from experimental samples. Consideration of the various methods which are sensitive to porosity leads to a system which can be applied to full waveform data to provide 3-D profiles of porosity and other defects. The work described in this thesis is covered by UK Patent Application Number 0818383.2.

Bone repair devices made from degradable polymers, such as poly lactic acid (PLA) have limitation in terms of matching the mechanical property requirements for bone repair, both initially and for the duration of repair. For this reason the use of totally degradable phosphate glass fibre (PGF) reinforced PLA composite has proved attractive. A crucial part of the success of such implants is maintenance of interfacial integrity between the polymer matrix and reinforcement phases of the composite. It is well known that most fibre reinforced composites loose 50% or more of their strength due to interfacial integrity loss. In this study candidate chemical treatments for PGF reinforced PLA composite are being investigated in terms of their reactability, biocompatibility, effect on interfacial mechanical properties and degradation behaviour of these composites. As a crucial part of this project, phosphate based glass (PBG) formulations were devised and assessed for structural, thermal, degradation and cytocompatibility variations with varying P2O5 or Fe2O3 content. Selected formulations were drawn into fibres and tested for single fibre tensile strength. Finally, a glass formulation (P45Ca16Mg24Na11Fe4, number indicates percentage molar concentration of oxides) was selected for surface modification and composite production. Chemical surface treatments were selected on the basis of potential to react with PBG and PLA. Mode of chemical interaction between PBG and surface treatments chemicals were analysed using surface analyses techniques (FTIR and XPS). It was found that aminopropyltriethoxy silane (APS), etidronic acid (EA) and hexamethylene diisocyanate (HDI) were linked through covalent bonds, other agents making hydrogen bonds with PBG. Chemical treatments were optimised and investigated for their effect on interfacial shear strength (IFSS) between polymer/glass, wettability and degradation behaviour. Chemically treated PBG was also assessed for cytocompatibility of elution products, short–term direct contact with MG63 osteosarcoma and long term direct contact with primary human osteoblasts. All selected surface treatment chemicals except amino phosphonic acid (APA) improved the interfacial bond between PBG and PLA. However, the covalently linked agents (HDI, APS and EA) saw up to 4–fold improvement in IFSS. SPLA also improved the IFSS significantly, which was attributed to the presence of several –OH groups. There was no significant effect on degradation rate of PBG. All agents demonstrated acceptable cytocompatibility for their elution products and in direct contact. Selected chemicals (APS, EA, SPLA and HDI) were investigated further in PGF reinforced PLA composite. PGF mats (UD or non–woven), treated with surface treatment chemical were sandwich–pressed between PLA sheets. Flexural mechanical properties with degradation, water–uptake, degradation rate and cytocompatibility were tested. It was found that surface chemical treatment improved the initial flexural properties (APS, SPLA) and/or delayed the mechanical integrity loss (HDI, APS), latter was attributed to the reduced water–uptake and maintenance of relatively strong interface. Human osteoblasts were found to perform normal functions when cultured on prepared composites.

Accurate Acoustic Emission (AE) source location is crucial for monitoring the thermal fatigue crack in nuclear piping systems. Conventional Time of Arrival (TOA) location techniques can provide estimated location of fatigue cracks but are not accurate enough to allow crack size estimation. This thesis examines the role of AE as a Non-destructive Testing (NDT) tool for thermal fatigue damage monitoring in nuclear piping system. The work focuses on developing an accurate AE source location technique. The works is divided into three main areas of research: 1. Development of Wavelet Transform analysis and Modal Location (WTML) method A novel location method was successfully developed using modal location theory and wavelet transform analysis. Source location was performed on a steel plate of 790 x 300 mm with nominal thickness of 5 mm under a planar location setup using H-N sources. The accuracy of the new technique was compared with the major location methods (the time of arrival (TOA) technique, triple point filtering and DeltaT location methods). The result of the study shows that the WTML method produces more accurate location result compared with other AE location methods. 2. Validation of WTML method for accurate location of fatigue crack growth in steel plate Laboratory fatigue tests were conducted on steel plate in order to monitor and locate fatigue crack growth, and validate the workability of WTML method. WTML was successful in locating the AE signal released from fatigue crack growth. The accuracy of WTML is much better than TOA, DeltaT and triple point filtering location methods. 3. Crack size measurement using WTML method The capability of the WTML location method to measure crack length due to fatigue crack growth under tensile-tensile loading is investigated. The WTML method successfully used to determine the crack length in the steel pipe with the maximum measurement error of 5 mm. Key Words: Acoustic Emission, Damage detection, Fatigue Crack Growth, Source location, Modal Analysis, Wavelet Transform Analysis, Crack-length measurement

The structural members of steel frames are jointed by connections. These connections are neither rigid nor pinned but semi-rigid. The performance of steel structures is highly influenced by the behaviour of connections which is characterized by the moment-rotation curve. This thesis studies the effects of semi-rigid connections on steel and composite steel-concrete frames, in particular the behaviour and influence of end plate connections. The first part of the thesis concerns the performance of unbraced planar steel frames with semi-rigid joints. Several aspects are investigated, concerned mainly with the serviceability limit state. Using the definition given in Eurocode 3 for a rigid connection, it is suggested that the conventional limit for the sway angle should be relaxed by 10% when the rotational behaviour of the joints is included in the analysis. For frames designed by the wind-moment method, it is proposed that deflections based on the assumption of rigid joints should be increased by 50% to allow for the connection flexibility. An approximate method, in which the stiffness of beams are reduced to account for joint flexibility, was found to be sufficiently accurate if deflections based on semi-rigid behaviour were to be calculated. Finally, studies on the ultimate limit state show that the resistance of a joint has significant effect on the collapse load of a frame, compared to the more modest influence of joint flexibility. The second part of the thesis concerns the behaviour of composite connections in braced frames. This part consists of a concise collection of the available experimental data, a description of the test programme conducted by the author, a proposed method for prediction of connection stiffness and studies on redistribution of moments in composite beams. Eleven tests have been carried out on bare steel and composite end plate joints. Their moment-rotation behaviour is recorded and the influence of variables on the joint stiffness is pointed out. These variables are the amount of reinforcement in the concrete slab, the type of steelwork connection and the beam depth. Increase in the amount of reinforcement increases significantly the moment resistance of the composite joint but does not influence its initial stiffness. I % reinforcement with respect to the area of concrete slab is proposed to be used for an efficient design. The increase in the depth of steel section increases the moment resistance and stiffness of composite connection but reduces its rotation,capacity. The effect of semi-rigid composite connections on column stability is also studied and a value of 0.75 is proposed as the effective length factor for columns. The proposed method for prediction of connection behaviour is shown to be in satisfactory agreement with the test results. From the final studies in Part Two formulae are proposed for calculation of the required rotation capacity of composite connections.

Presented in this thesis is an investigation on the response of hot-finished and cold formed, hollow and concrete-filled circular hollow section braces in earthquakeresisting concentrically braced frames. The role of these braces is to act as structural ‘fuses’ in the frame, dissipating the seismic energy by undergoing plastic deformations. Circular hollow sections offer aesthetic and structural advantages over conventional rectangular hollow sections owing to the uniformity of the section geometry. Distinct behaviour is observed between cold formed and hot-finished tubes, since the cold formed sections retain a higher degree of residual stresses from manufacturing. Braces subjected to cyclic loading fail after the occurrences of global and local buckling, but the performance can be enhanced by employing concrete infill. The concrete-filled steel tube is an optimum combination of the two materials, resulting in an efficient, economic and practical structural member. Experiments were performed in which cyclic axial loading was applied to hollow and composite braces of each section type. Hot-finished specimens exhibited superior ductility to cold formed members. Concrete infill enhanced the tensile resistance for members of all lengths, the compressive resistance of shorter members and the number of cycles to failure. Finite element models were subsequently developed with ABAQUS® software, using the inbuilt nonlinear isotropic/kinematic hardening model and the damaged plasticity model to define the steel and concrete characteristics. Reliable simulations were achieved for the hollow braces but further work is required for the composite braces. Both local and global slenderness values influenced the specimen response. Expressions were proposed to predict the displacement ductility and energy dissipation capability of hollow braces in terms of these parameters. The findings suggest that distinct guidelines could be developed for introduction into Eurocode 8 for each steel section type, and that the benefits of concrete infill could be taken into account in dissipative design.

The research presented in this thesis examines various aspects on connections and joints in Pultruded Fibre Reinforced Polymeric (PFRP) structures. The work is divided into two experimental investigations on the determination of pin-bearing strength and the characterisation of dowel connections and joint for the Startlink Lightweight Building System (SLBS). To support the development of a strength formula for bearing resistance in bolted connections two pin-bearing strength test series were conducted to study the effects of load orientation and hot-wet conditioning. The limitations of existing standard test methods are exposed from a critical review to show that they do not specify the need for a clearance hole, the range of bolt diameters and PFRP thicknesses found in practice. Because the size of tension coupons is found to be too big to be cut from standard structural profiles an alternative test method, having a smaller coupon size, is needed for every pin-bearing strength to be quantified by testing. Reported in this thesis are test results using an in-house test method that requires a maximum blank coupon of 100 mm × 125 mm. Characteristic strength are determined using Annex D7 of Eurocode 0. Pin-bearing strengths for load orientations of 0, 5, 10, 20, 45 and 90o, to the direction of pultrusion are obtained for a web material taken from a standard wide flange section of 9.53 mm thick. In the test matrix there were four sizes of pin diameter from 9.7 mm to 25.4 mm and a minimum clearance hole of 1.6 mm. The in-house test method is shown to satisfactorily determine pin-bearing strength. Another finding from this study is that the Hankinson formula cannot be applied to establish pin-bearing strength at any orientation on knowing the two characteristic strengths at 0o and 90o. To characterise the effect of hot-wet conditioning 0, 45 and 90o specimens were immersed under water for 3000 hours at 40° C. It is found that the average reduction in characteristic strength is in the range of 18 to 31%. The extent of strength reduction is found to be independent of pin size, except when the diameter is 25.4 mm. The second experimental investigation is for fact finding strength tests towards the application of PFRP dowelling as a method of connection in SLBS. This innovative building system has been engineering for the execution of a FRP house that meets the requirements for code level 6. A series of static coupon-sized tests were conducted to determine the minimum resistance of dowel connections similar to those used in the Startlink house. These results were used to verify the structural engineering design calculations. Another sub-assembly test configuration was used to determine the moment-rotation characteristics of joint details for the portal frame in the SLBS house. Four different beam-to-column joints with dowel connections, and with and without adhesively bonded connections, were statically loaded so that their rotational stiffnesses and modes of failure could be determined. The main conclusions from this study are that: -- all joints had adequate strength against the design ULS moment; -- only when the joint had adhesive bonding between the overlapping beam and column members does the rotational stiffness approach the design rigid condition; -- when clearance holes are present the rotational stiffness is low and applying adhesive bonding around the dowels cannot remove this structural limitation.