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Thiolated ligands are known to form self-assembled monolayers on gold nanoparticles, and the self-organisation of these ligands provides a route towards nanoparticles with programmable and complex molecular structures. This body of work investigates the structures and chemical properties of ligand monolayers based on peptides and alkanethiol derivatives. We evaluate a series of published articles reporting the peculiar self-organisation of ligands into striated domains on the surface of nanoparticles, which was shown by scanning tunnelling microscopy (STM). Image analysis of the STM micrographs shows the stripe-like domains to be scanning artefacts, and our attempts to reproduce data on nanoparticle stability and cell entry give results conflicting with those published. Self-assembled monolayers made from peptides allow the use of peptide motifs to drive self-organisation. We investigate the effects of using an amyloidogenic sequence, CFGAILSS, in a monolayer. FTIR, 2DIR and solid state NMR reveal the presence of inter-peptide hydrogen bonding consistent with a parallel β-sheet structure, which is not seen in a monolayer made from the CALNN peptide. Fluorescently labelled peptide-capped gold nanoparticles were irradiated by a femtosecond laser pulse. The timings of the reaction dynamics of this ligand release were measured by splitting the laser beam and introducing a variable delay. These measurements show that this process is a hot electron mediated process. We suggest that such laser induced release measurements can provide some insights into the intermolecular interactions within the monolayer

In the last decade, natural-fibre composites based on thermoplastics and thermosets have been embraced by car producers for use in the manufacture of door panels, seat backs and dashboards. Natural fibres have benefited from the perception that they are "green" or eco-friendly. What is proving more important is their ability to provide stiffness enhancement and sound damping at lower cost and density than glass fibres and mineral fillers. At the same time, interest has been growing rapidly in the potential offered by self-reinforced composites, such as polypropylene fibre reinforced polypropylene and polyethylene fibre reinforced polyethylene. Each of these composite systems offers its own advantages and a number of disadvantages. One way to reduce or remove many of these deficiencies would be to combine these two systems to develop a novel hybrid system that is fully recyclable. Hoo Tien N Kuan ABSTRACT Abstract The work outlined in this research project aims to develop, manufacture and fully characterise the properties of environmentally-friendly composites based on natural fibre and polymer fibre reinforcements, and their fibre metal laminates. The composites are based on natural fibres (e.g. hemp, basalt or flax) and polymer fibres (polypropylene). The composites are manufactured via a compression moulding procedure and their properties are investigated both statically and dynamically through a series of tension, flexure and low velocity impact tests. The fracture region of the laminates is also investigated using optical microscopy techniques. The mechanical response of the laminates is modelled using laminate theory and the impact response is predicted using simple impact models. A range of green composites and hybrid materials has been developed and investigated. The experimental data have shown that the composites based on basalt fibres offer an excellent all-round mechanical performance exceeding those associated with other natural fibre composites. Combining natural fibre composites with SRPP (Self- Reinforced Polypropylene) and aluminium alloy can enhance the mechanical behaviour of the composite. These environmentally-friendly composite systems offer significant potential in engineering design and could potentially help to reduce waste and pollution.

A literature review has been carried out relating to the damage and fracture behaviour of composite laminates based on woven fabric reinforcement containing a stress raiser in the form of either a circular hole or of a mechanically fastened joint - the tensile failure modes in these two types of problem are very similar. Closed form and finite element based approaches that enable the stress distributions in these two classes of problem are presented prior to a review of some of the existing failure models. The failure models considered are based on strength and fracture mechanics approaches, which are applied in some cases at the laminate level and in others on a ply-by-ply basis. A number of these approaches invoke the use of a characteristic distance, which is a material property, but may also be specimen geometry dependent. The aim of the present work is to develop a more unified model for damage and fracture at tensile stress concentrations within a finite element analysis. To this end a traction-separation law (based on physically meaningful material parameters) is implemented within ABAQUS CAE and used to predict the strength of woven composite plates containing open holes and mechanically fastened joints. This approach is applied first to the open hole problem within a two-dimensional framework, with reference to several data sets from the literature. Agreement is good, both with prior experimental data and other modelling approaches. The bolted joint problem is then considered and a two dimensional approach is applied to model net-tension failure data for woven GFRP bolted joints from the literature, using the same traction-separation law as applied to the open hole problem. Agreement is reasonable, but a need for a model that incorporates bolt clamp-up is apparent. Subsequently an extensive experimental data set is obtained for the failure strength of a range of woven CFRP bolted joints, both double-lap and single-lap construction with various lay-ups, plate geometries, hole sizes and bolt clamp-up. These test configurations are then modelled using a 3-D finite element framework. Good agreement between the predicted and measured bearing stress at failure was obtained for double-lap joints that failed in the net tension failure mode. Less good agreement was obtained for the single-lap joints, where the tensile fracture mechanisms were more complex and not captured fully in the model.

Replacing a building’s façade offers the prospect of improving the whole life performance of the building, in some instances as a favourable alternative to replacing the entire structure. This presents the opportunity to exploit the properties of advanced composite materials for maximum benefit. ‘Upwards and outwards’ retrofit, where extending floor slabs yields extra floor area, is permitted by a lightweight replacement façade, without the need to underpin foundations. For typical medium or high-rise office buildings, the extra let-able space obtained, and reduced heating and maintenance costs, can work to offset the expense of implementation. The specific materials, manufacturing processes, and façade type, most appropriate for such a scheme have been investigated. A unitised façade of sandwich panels with foam cores and pultruded GFRP skins has formed the ‘design platform’ for research conducted. It is paramount to resolve how the connections in such a façade system can meet the many requirements of an integrated building envelope. Structural integrity, enhanced environmental control, sustainability attributes, fire provisions, acoustic control, ease of manufacture, tolerance control, durability, lightness in weight, cost effectiveness and aesthetics must all be addressed simultaneously by any proposed design methodology. Investigating suitable connections through prototype development and review reveals key issues requiring targeted research. The permanent action acting on light, selfsupporting GFRP panels is small, however wind and occupancy loading impart significant imposed actions. Therefore, whilst creep deflection is often a significant consideration for structural GFRP design, quantifying fatigue performance is a higher priority for validating the ideology of polymeric facades. The unidirectional nature of pultrusion reinforcement yields a scenario of principle stresses at the panel interfaces, occurring in the weaker, secondary fibre, direction. As a consequence a fatigue-testing programme is aimed at understanding the performance and characteristics of pultruded angles compatible with ‘long-edge’ panel connections. The long-term performance of fibre-reinforced polymer (FRP) structures must be assessed if FRP is to win acceptance as a mainstream material for use in the construction industry. The environmental durability of wholly polymeric structures is often called in to question. In response, accelerated testing is usually undertaken on artificially aged FRP specimens; lack of genuine naturally aged material has previously hindered research and validation of material related design life. Case study investigation has permitted a full durability appraisal of naturally aged GFRP through laboratory testing campaign. Retrofit of existing buildings as an activity makes up 50% of all building construction in the UK. This project aims to address the shortfall in industry-required design knowledge. The tensile strength of pultruded naturally aged GFRP has been shown to reduce by only 0.65% over 17 years where natural exposure does not include UV irradiation, and by 13.1% where UV irradiation does occur as one element of exposure. The findings expose the degree of inaccuracy and fundamental flaws in existing predictive ageing models. The physical mechanisms of degradation do not match. A procedure to quantify the extent of polymer brittle hardening has been developed and applied as an analytical tool. Mechanical testing campaign has pioneered the use of the RMS (Route Mean Square) procedure to present the performance of connection specimens as a continuous function throughout programmes of fatigue testing. Testing has shown that though a threshold strain for damage accumulation does exist in complex fatigue loading of connections, and for direct tension fatigue loading.

The performance of components, structures and vehicles are always in some way limited by the materials they are made from , often leading to compromises. This drives development to invent and discover new materials or processes to improve upon the current state of the art. In this respect the research contained in this thesis has investigated the use of plasma treatment~ as a method for modifying the properties of carbon nanotubes and carbon fibres to improve upon current composite materials technology. The initial study focused on functionalising relatively large quantities of carbon nanotubes using a unique and scalable technique suitable for industrialisation. The research began with a standard oxygen and ammonia treatment, which led to the development of an oxygen plasma treatment for increased carboxyl functionality. The important discoveries were that processing time and gas pressure had a large impact upon the agglomerate size, bulk density, surface energy, solvent stability and the quantity of carboxyl functionalisation. The treated carbon nanotube~ developed in the initial study were investigated for their use within an epoxy system. The treated carbon nanotubes were shown to disperse better, reduced resin viscosity, increase resistivity, but had little effect upon mechanical properties, degree of cure or glass transition temperature compared to the untreated carbon nanotubes. The development of the oxygen treated carbon nanotubes led the research to investigate if these treated carbon nanotubes could be used to improve the fracture toughness of a pre-preg system. The results showed that it was possible to improve initiation and propagation mode I fracture toughness significantly. Mode II results also showed increased initiation but relatively unchanged propagation toughness at lower areal densities, however in both mode I and II at the highest carbon nanotube coating density the fracture propagation resistance was reduced. The final study looked into the use of plasma treating carbon fibres as a method to modify the fibre matrix interface. The interface strength was found to improve for short oxygen and ammonia treatments, while reduce for the tetrafiuoromethane treatment on the unsized fibres . However for the commercially sized fibres each plasma treatment appeared to damage the propriety treatment in terms of interface strength. A further investigation into attaching carbon nanotubes to carbon fibres showed a dramatically reduced interface strength. The research demonstrates a variety of methods which could be used to tailor the interface for improved strength or damage tolerance.

Defects in composite materials lead to reductions in the mechanical performance of components. The presence of fibre waviness and through-thickness ply wrinkles has been shown to reduce the Compressive strength of laminates, and are therefore subject to significant scrutiny in the aerospace industry. Whilst a large volume of industrial effort and published research has addressed the reduction of the compressive strength Due to defects, the source of such defects is currently not well understood. The work presented in this thesis aims to elucidate the source of fibre waviness and ply wrinkles. Its ultimate goal is to understand the link between material and manufacturing process variations with the formation of such defects. Once mechanisms for defect generation are understood, measures can be taken by industrial manufacturers to mitigate their formation. As a result, part acceptance rates will increase; the composites industry depends on the reliability of component manufacture. A number of themes have been investigated by proposing specific mechanisms for the formation of fibre waviness and Ply wrinkles. Such themes include fibre-matrix interaction, tool part interaction and consideration. The most significant mechanism Has been shown to be consolidation. In both prepreg and woven preform materials, poor layup has been shown to lead to severe Ply bridging at tooling radii.

Composite parts reinforced with unidirectional or 2D woven reinforcements have been widely used for many years in numerous industries from aerospace to automotive parts. Although their use is widespread, laminated reinforcements have some significant weaknesses that limit their usefulness, including poor interlaminar strength and high cost driven by the need for lengthy hand lay-up to create complex parts. Considerable effort has been put into developing three-dimensional composite reinforcement in order to alleviate these problems. This thesis focuses on materials produced via the weaving method. "3D weaving" can produce fabrics with interlacing yams that provide genuine through thickness reinforcement. The weaving process can also produce multi-layer fabrics, reducing the amount of lay-up required to produce thick parts. A review of current literature showed that 3D woven composites have good interlaminar properties but can have poor in-plane mechanical properties, the main cause being architectural distortions such as local yam crimp and resin rich regions. It was evident that there has been relatively little study into the detail of 3D woven architecture and how it is affected by forming forces and in turn how this affects mechanical properties. In addition, [mite element modelling of 3D woven fabrics has been limited by idealised mesh generation, hampering predictive fabric analysis. The work presented here addresses the issue by developing a fundamental understanding of 3D woven composite architecture via a detailed characterisation of yam crimp and resin channels for a selection of angle-interlock weaves. The effect of compaction on these architectural features was also investigated and coupled with an innovative use of kinematic modelling that could help predict the final internal state of a compacted 3D woven fabric. Finally, compression testing of specimens reinforced using 3D woven fabrics at a range of compaction levels was used to ascertain the influence of fabric architecture on mechanical properties.

The recent resurgence and growing interest in high temperature structures to maximise design space and performance in motorsport applications, led to the need for greater understanding of high temperature composite materials. This study aimed to investigate suitable materials for high temperature structures with application to the motorsport environment. Composite materials were quickly identified as the most appropriate materials given the needs of motorsport, with polysialate composites championed after a thorough review of available materials. A commercially available composite reinforced with silicon carbide fibres was selected to meet the study requirements. This led to the need for thermal and mechanical characterisation in order to provide temperature dependant data suitable for accurate design of high temperature structures. The result of .this was a full engineering dataset for the most widely used polysialate composites, filling In significant gaps in the literature, whilst simultaneously producing a novel and unique high temperature tensile testing rig for this composite laminates. In turn, this new data was exploited with application to a polysialate composite case study structure; an exhaust liner used on current Formula One vehicles. This required full understanding of the thermal and mechanical load cases experienced by the liner, in order to accurately simulate the liner and environment using finite element analysis. Not only did this provide an application of the newly acquired temperature dependant material properties, but it also highlighted the need for temperature dependant properties in the design of high temperature structures. The study, its aims and approach, were validated through comparison of simulation failure predictions against component failed in service.

The automotive and construction industries are actively involved in substituting natural fibre composites (NFCs) for other engineering materials in motor vehicles and buildings. In this work, emphasis has been placed on evaluating agave fibre composites containing well aligned, closely packed straight fibre bundles and focussing on the development of different types of practical joints for NFCs in composite structures. Two novel co-cured joints were proposed and evaluated, based on laminated and intermingled configurations.