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TiO2 is a well investigated material due to its vast array of applications, from the most common white food colouring, to usage as an optical coating due to its high refractive index. When deposited as a thin film for use in solar control coatings using a magnetron sputtering device, TiO2 is found to form in rutile, anatase and amorphous phases, with the rutile (1 1 0) and anatase (1 0 0) crystal surfaces occurring most frequently. While the influence of deposition rate, substrate bias voltage, oxygen partial pressure and temperature have all been investigated experimentally, there are fewer simulated results. This seems to be primarily due to the lack of a suitable empirical potential through which dynamics can be accurately modelled. In this research project, the short-comings of the leading fixed and variable charge TiO2 potentials were revealed through comparison of binding energies and transition barriers for simple ad-clusters and interstitials to DFT. This led to the development of an improved variable charge potential, particularly when modelling the rutile (1 1 0) surface. It has been experimentally demonstrated that rutile growth results in a reduced surface due to the formation of large numbers of Ti interstitials and this was also suggested due to low Ti interstitial formation barriers found using DFT and the variable charge empirical potentials. The high interstitial formation probability was confirmed when performing large numbers of Tix Oy depositions at typical industrial energies. Correlations between impact site and numbers of interstitials and vacancies formed were found along with insight into typical penetration depths and common defect structures. Multilayer growth was successfully modelled using classical MD by accelerating the deposition rate. The large numbers of formed interstitials coupled with a high escape barrier resulted in defective growth and so it was necessary to increase the substrate temperature such that atoms were mobile on the computational time-scale. Multilayer growth was investigated as a function of deposition energy, cluster composition and stoichiometry on the rutile (1 1 0), anatase (1 0 0) and amorphous surfaces. The optimum conditions for forming defect free rutile were found along with more limited insight into the ideal growth conditions when depositing on anatase and amorphous substrates. Finally a long time-scale dynamics technique, the ‘on-fly-kinetic Monte Carlo' method, was developed, and using an efficient bespoke transition search algorithm, rutile TiO2 growth was successfully modelled at 350 K, with some caveats to avoid becoming entrenched in low activation diffusion processes. The final conclusion being that low energy depositions of large clusters with an oxygen excess would produce optimum film growth.

This project mainly concerned the development of novel engineering approaches to optimise the physical properties of the polymer composites with a low loading of carbon nanotubes (CNTs). It was additionally discovered that graphite oxide nanoplatelets (GONPs) can be a strong and affordable substitute for the CNTs in the polymer composites. Colloidal physics and coating methods were applied to fabricate semi-conductive CNT/polymer composites with low percolation threshold. Polyurethane (PU) latex and ultra high molecular weight polyethylene (UHWMPE) powder were used as hosting matrix in the colloidal physics method and coating method, respectively. In the colloidal physics method, the percolation threshold was found to be around O.5wt% MWCNTs and the electrical conductivity of the composites was improved by more than four orders of magnitude with the addition of I wt % multi-walled carbon nanotubes (MWCNTs). The study of rheological behaviour revealed that the addition of the MWCNTs led to the increase in the viscosity of the PU dispersion. In the coating method, the scanning electron microscopy (SEM) images confirmed the strong adhesion of the nanotubes on the surface of the powders. Sheet samples were prepared using compression moulding for electrical test. The percolation threshold for the powders with the size of 60)lm was around I wt% MWCNTs and the percolation threshold for the powders with the size of 100)lm was around 0.5wt% MWCNTs. A novel route was revealed to reduce the interfacial phonon scattering that is considered as the bottleneck for CNTs to highly improve the thermal conductivity of CNT/polymer composites. Semicrystalline PU dispersions were used as latex host to accommodate the MWCNTs following the colloidal physics method. The thermal conductivity increased from 0.15 Wm-'K-' to 0.47 Wm-'K", by -210%, as the addition of the MWCNTs increased to 3wt%. The morphology of the composites suggested that the continuous nanotube-rich phase existing in the interstitial space among the latex particles and the crystaIIites nucleated at the nanotube-polymer interface were the main factors for the effective reduction of interfacial phonon scattering. The optimisation of the crystalline layer around CNTs was studied based on the MWCNT/polycapro!actone (PCL) composites using differential scanning calorimetry (DSC). The study of the non-isothermal crystaIlisation showed that crystaIIisation temperature (Tc) increased with increasing incorporation of the nanotubes, and melting temperature (T m) and heat of fusion (ilHm) was almost unchanged. The incorporation of 2wt% nanotubes resulted in the biggest increase of the T c to be -11 QC. The study of the isothermal crystaIIisation showed the temperature, 14 DC higher than the Tc. was appropriate one to optimise the crystaIIine layer in the composite melts. It was revealed that the incorporation of 0.1 wt% nanotubes significantly affected the rate of crystal growth and crystalline morphology. For more incorporation of the nanotubes, the rate of crystal growth and crystaIIine morphology was less affected. The improvement in the Young's modulus of the composite with the thermal treatment confirmed the contribution of the crystalline layer to the load transfer across the non-covalent interface between the nanotube and polymer matrix. The preparation of the exfoliated GONPs in DMF was revealed. With this method in hand, two kinds of polymers including semi-crystaIline PCL and amorphous PU were selected to be incorporated with the GONPs using the solution method. It was found that the GONPs showed strong nucleating ability in the PCL matrix. The thermal treatment under the "14QC" rule could create an optimised crystalline layer on the surface of the GONPs from the composite melts. The bigger increase in the Young's modulus of the treated GONPIPCL composites confirmed that the crystaIIine layer nucleated on the surface of the GONPs could act as a non-covalent interface between the GONPs and PCL matrix. The significant reinforcement of the PU using GONPs was also disclosed. Morphologic studies showed thai, due to the formation of chemical bonding, strong interaction occurred between the GONPs and the hard segment ofthe PU, which allowed effective load transfer. The GONPs can prevent the formation of crystalline hard segments due to their two-dimensional structure. With the incorporation of 4.4wt% graphite oxide nanoplatelets, the Young's modulus and hardness of the PU were significantly increased by -900% and -327%, respectively. The resultant high anti-scratch property pointed to the promising application of these composite materials in surface coating.

Many problems in solid dynamics involve moving boundaries, finite elastoplastic deformations, and strong non-linear waves. Continuum modelling of such events is difficult on account of these characteristics, and there exist a number of inadequacies in current numerical algorithms. Furthermore, a comprehensive understanding of certain underlying processes is yet to be achieved which places a limit on the derivation of engineering models to simulate these occurrences. Much needed atomistic studies, capable of revealing much about the governing physical processes, remain limited by current computational resources. This thesis is devoted to targeting these difficulties by proposing new continuum numerical schemes and a means of studying both micro- and macro-scale behaviours via a dynamic coupling of continuum mechanics and molecular dynamics theory. Eulerian shock-capturing schemes have advantages for modelling problems involving complex non-linear wave structures and large deformations in solid media. Various numerical methods now exist for solving hyperbolic conservation laws that have yet to be applied to solid dynamics. A three-dimensional finite-volume scheme on fixed grids is proposed for elastoplastic solids. The scheme is based upon the Godunov flux method and thus requires solution of the Riemann problem. Both exact and approximate solutions are proposed for the special case of non-linear elasticity. An implicit algorithm is developed to allow for resolving rate-dependent inelastic deformations. The methods are tested against exact solutions in one-dimension, and symmetrical polar solutions in two- and three-dimensions. To account for multiple immiscible materials it is necessary to include some means of tracking material boundaries within a numerical scheme. A moving grid scheme is a simple means of accommodating transient boundaries. Interface tracking based on the use of level set functions is an attractive alternative for problems with sliding interfaces since it allows discontinuous velocity profiles at the material boundaries whilst employing fixed grids. Both of these methods are explored in the current context. A series of one-dimensional testcases have been carried out that demonstrate the ability of the numerical schemes to accurately resolve complex boundary conditions between interacting free surfaces. Where singularities occur in a system comprising solid materials, atomistic studies are invaluable for achieving a fundamental insight into the governing physical processes. However where non-linear waves are generated, domain size proves to be a limiting factor in achieving solutions free from numerical artifacts. A domain decomposition multi-scale modelling strategy is developed that couples the Eulerian shock capturing scheme with a molecular dynamics solver. The method is demonstrated for one-dimensional testcases involving strong shear waves and multiple components. Attention is devoted to resolving transient wave propagation free from spurious wave reflections through investigation of the numerical parameters.

This investigation concerns the mechanical response of binder coated carbon tow preforms and laminates. The main focus is on evaluating and modelling the robustness of preforms whilst the methodologies developed are also applied to cured laminates produced using the binder coated preforms. Conventional manufacturing techniques were altered to address the differences in behaviour due to the presence of the binder with the development of infusion schedules. These involve lower temperatures, which eliminate the possibility of binder reactivation during processing. Different development versions of the material in the form of an inhomogeneously or homogeneously bindered tow were characterised in terms of their mechanical response in the preform state. It was observed that the inhomogeneously bindered material had higher modulus and strength in both tension in the fibre direction and shear, while the behaviour of the homogeneous preform is significantly more robust in the transverse to the fibre direction. Laminates produced, using the homogeneously bindered material, were compared to a reference unbindered laminate system, using an aerospace epoxy as a matrix. The out-of-plane properties of the material with binder were superior to the reference laminate, whereas in-plane properties were similar or inferior. The development of models of the mechanical response built around continuum damage mechanics models allowed the simulation of the behaviour of preforms under loading. The implementation of these constitutive models necessitated the development of appropriate parameter estimation techniques capable of solving the inverse problem of identifying the values of 27 material constants that minimise the error between experimental and modelling results. Two novel methodologies were developed and compared to a conventional technique following simplified laminate analysis. The first method performed a gradient-based error minimisation and the second uses the Markov Chain Monte Carlo technique. The gradient-based technique results in a close fit, while this method requires proper definition of the constraints to yield an appropriate solution set. Markov Chain Monte Carlo yields satisfactory results with the additional advantages of overcoming the ill-posedness of the inverse problem without regularisation and providing an output in the form of multivariate probability distributions that can be used directly instochastic simulations. The material parameters obtained and the corresponding constitutive models were used in finite element models of the mechanical response of preforms and laminates. The models were based on the concept of a combination of shell elements representing sub-laminates and cohesive elements simulating the delamination behaviour of interfaces between them. The performance of the models was evaluated using the case of impact of a spar section for preforms and three point bending for the laminates. The agreement between experimental and simulation results was satisfactory. The validated model was used in the context of a design case study based on a helicopter pitch horn component. The aim was to use the results of a draping analysis in the finite element model to evaluate the effects of the assumption of nominal fibre orientations on design and to combine the results of drape optimisation in respect to fibre shear angle with finite element analysis incorporating damage. The results showed that the use of nominal fibre orientation predicts a good performance of the component, whereas the influence of optimising draping on the mechanical performance was inferior.

This thesis presents a study of the effects of surface colour, surface finish and dent shape on the visual inspection reliability of 3D surface indentations common in shape to those produced by impact damage to carbon fibre reinforced epoxy laminates. Falling weight (2.5kg) apparatus was used to produce impact damage to non-painted, non-mesh Hexcel AS4/ 8552 carbon fibre reinforced plastic (CFRP) laminates and painted AS4/ 8552 laminates containing bronze mesh and glass fabric lightning strike protection layers. Ø20 mm and Ø87 mm hemispherical tip impacts to painted 17ply and 33ply laminates at varying energy levels typically produced circular shaped, smoothly contoured, rounded sectional profiles with an absence of surface breaking cracks. Sectional profiles through coordinate measuring (CMM) data of the impact dents were described using a set of geometric variables. Identifying relationships between impact energy and the geometric variables allowed the typical sectional profile through impact damage dents from Ø20 mm and Ø87 mm hemispherical tips on 17ply and 33ply painted CFRP laminates to be calculated for energies between 5J to 80J. Calculated sectional profiles typical of impact damage dents to CFRP laminates were reconstructed as simple revolved shapes using 3D computer aided design (CAD) models. The 3D CAD models were computer numerical control (CNC) machined into 3mm Plexiglas panels to produce facsimiles of hemispherical impact damage dents on CFRP laminates. Facsimile specimen sets of sixteen 600 mm x 600 mm panels were produced in gloss and matt grey, white and blue finishes. Each set contained the same 32 different sized machined dents representing Ø20 mm and Ø87 mm hemispherical tip impact damage to 17ply & 33ply painted CFRP laminate. Each facsimile specimen set was combined with similarly finished unflawed (dent free) panels. 64 panels in each colour/ finish were presented for 5 seconds in a randomised order to a minimum of 15 novice participants in a visual inspection task lasting approximately 25 minutes. II A set of corresponding visual inspection experiments were performed in which physical specimens were replaced by digitally projected actual size photorealistic images of the machining CAD data. Comparisons between the results of the physical and virtual specimen trials revealed differences in detectability for similarly sized dents. The detection results obtained from visual inspection of physical specimens demonstrated that the detectability of dents similar to those caused by higher (>40J) energy impacts from a Ø87 mm hemispherical tip was less than that of the dents caused by lower energy (<20J) impacts from Ø20 mm tips. However, larger subsurface delamination area was demonstrated by the higher energy Ø87 mm impacts than lower energy Ø20 mm impacts on 150 mm x 100 mm coupons of the same thickness laminate. The results of these experiments imply that detectability of dents caused by larger diameter objects at higher energies cannot be assumed to be greater than that of lower energy impacts from smaller diameter objects. The detection results demonstrate that detectability by visual inspection cannot be assumed the same for an impact dent on different surface colours and finishes. In general terms, the highest numbers of dents returning >90% detection were observed on grey specimens and the highest number of dents returning 0% detection were observed on matt blue specimens. The difference in detection rates for similarly sized dents on a gloss and matt finish was least on grey coloured specimens and greatest on blue coloured specimens.