The usage of polymeric matrix composites in aerospace applications has been significantly prevalent based on their desired material characteristics, which include higher strength, lower weight and heat resistance. With current advancements in nanotechnology, carbon nanotube reinforced polymeric matrix composites may enhance the operational usage of these advanced materials even further. In this study, a set of novel aerospace material candidates are characterized based on their mechanical properties, resilience to liquid erosion, wettability and ice adhesion. The experimental evaluations presented, allow for a preliminary ranking of the polymeric matrix composites and assessment of the influence of reinforcing carbon nanotubes. The role of erosion in particular is highlighted from both a historical viewpoint and based on empirical results for static and dynamic wettability and ice adhesion. Discussion of different ranking systems and fractography arising as a consequence of liquid impact are further addressed in this study. It is found that the candidate samples exhibit different physical parameters but nominally similar erosion resilience despite the presence of the reinforcing carbon nanotubes. The wettability of the experimental materials and their ice adhesion characteristics are further shown to be influenced by the presence of carbon nanotubes and largely dependent upon degradation of the material surfaces.

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In this study, a new model has been developed for the prediction of thermal profiles for fibre reinforced plastic composites exposed to high heat ux. The model involves expressing the thermal diffusivity of the composite as a function of temperature. Apparent thermal diffusivity (ATD) can take into account the decomposition of the resin, which is endothermic, as well as the consequent changes in specific heat capacity and thermal conductivity of the composite. This offers the possibility of significantly simplifying computational procedures needed for modelling thermal behaviour with decomposition. The possibility of extending thermal analyses to two and three dimensional cases was explored. Techniques for the direct measurement of the apparent thermal diffusivity are presented for different composite systems over a wide range of temperatures: from ambient to ~600°C . Two different techniques were needed for different ranges of temperatures: from ambient to 80°C and from 80-100°C to 600°C. To measure the ATD in the low range, a step temperature change was applied to the surface of a slab-shaped piece of material. Theta, the difference between the middle plane temperature and the outer surface temperature was recorded. The value of the thermal diffusivity at each temperature was calculated from the values of theta. The high range measurement involved the application of a linear temperature rise to the surfaces of a slab of material. The ATD was calculated by means of the Laplace heat transfer equation. The thermal diffusivity function obtained through these measurements was used to model the Fire behaviour of these materials under different heat transfer conditions. Quasi isotropic glass/polyester slab shaped composite specimens were tested under one dimen- sional heat transfer conditions. A one-sided heat flux was applied to the samples and the remaining surfaces were isolated to obtain repeatable boundary conditions. The temperatures were recorded at different depths within the samples during the exposure. The ATD of this material was mea- sured through the techniques mentioned above and implemented in a one-dimensional heat transfer FORTRAN model. I-beam shaped pultruded sections were subjected to two-dimensional heat transfer conditions. The temperatures were recorded at different locations on the cold side. Thermal properties were determined by means of the apparent thermal diffusivity of the material and implemented in a two-dimensional FE thermal model. Carbon fibres reinforced wing box materials were used to perform three dimensional fire tests. To describe analytically the tests, the ATD was measured along the three principal directions by means of the techniques mentioned before. These data were implemented into finite element models. The suitability of the ATD to model complex cases was verified. The failure of polyester and phenolic pultrusions under tensile and compressive load and a one- sided heat flux of 50 kW/m² was studied. A thermal/mechanical model, based on the Henderson equation and laminate theory, was used to model their behaviour. In tension, significant load- bearing capacity was retained over a period of 800 seconds, due to the residual strength of the glass fibres. However, pultruded composites are susceptible to compressive failure in fire, due to the loss of properties when the resin Tg is reached. The fire reaction properties reported here showed the phenolic pultrusions to perform better than polyesters in all fire reaction properties (time-to-ignition, heat release, smoke and toxic product generation). The measurements under load in fire showed that the phenolic system decayed at a slower rate than the polyester, due mainly to the very shallow glass transition of the phenolic, but also the char-forming characteristic of the phenolic. The behaviour described here for phenolic pultrusions is superior to that reported for some phenolic laminates, the main reason probably being their lower water content. In all cases the experimental data and the predicted temperatures were compared. The ATD modelling proved capable of capturing the main features of the temperature curves that relate with the effects of re exposure of composites. This study allowed to determine the characteristics of the ATD curve at different temperatures and relate it to the phenomena occurring to composites exposed to fire.

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The relationship between physical and sensory properties of 40 model skin creams was investigated. Creams were formulated according to an experimental design to ensure that a wide range of textural properties could be produced from a minimal number of ingredients. The core project study comprised of objective sensory profiling of model skin creams (QDA, Quantitative Descriptive Analysis) and the physical characterisation of the textural and flow properties relevant to the use of skin creams (rheology, texture analysis and force plate analysis). Sensory attributes related to initial skin cream application procedures (firmness, thickness, resistance, spreadability, stickiness and slipperiness) were highly correlated to rheological and texture analysis parameters. Attributes related to application procedures involving a time factor and absorption of cream into the skin (drying, dragging, final greasiness and absorption) were found to be correlated to parameters from force plate analysis. A consumer study was also conducted based on a subset of the model skin creams to identify properties of skin creams that are liked by the naïve consumer. Cluster analysis and external preference mapping identified groups of consumers with different types of liking behaviour. The firmness and thickness of the samples were found to be important regarding consumer liking. Models were generated to predict the sensory properties of creams from the physical parameters. Rheological parameters (G′ at 100 % strain and logG′′ at 100 % strain) produced the most robust models that could predict firmness, thickness, resistance, spreadability and slipperiness. Models predicting attributes involving absorption of cream into the skin were less robust, these involved force plate analysis parameters.

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This thesis examines the surfaces of polyacrylonitrile (PAN) based high strength (HT) carbon fibres modified by electrochemical and ultra-violet ozone (UV/O3) treatment methods. The surface and bulk study was conducted by x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. In addition, immersion calorimetry in polar and non-polar liquids, as well as dilute resins, is used to investigate fibre surface energies while temperature programmed desorption (TPD) is used to investigate adsorption of linear alcohols (C1 to C4) on the fibres. One of the main aims of the work is to understand the reaction mechanisms that take place between the surface oxygen functionalities on treated carbon fibres and the resin molecules that are used in forming composites. UV/O3 treatments were shown to produce significant levels of oxygen on the fibre surface. Anodic treatments did not alter the surface morphology, while UV/O3 treatments were seen to increase surface areas six fold. Immersion calorimetry measurements showed similar trends to carbon black materials but, due to the small surface areas of the fibre (typically 1 m2/g), the rush-in effect and heat of ampoule breakage was found to overshadow the signal from the fibre. TPD measurements showed that alcohol adsorption was considerably enhanced by the presence of surface oxygen. In addition a relationship between the acidity scale of the alcohols in the gas phase and the extent of their dissociative adsorption at room temperature was established. Overall this work has shown UV/O3 to be a successful surface treatment method, superior to electrochemical treatments and TPD to be a promising method for investigating bonding.

In this work, the behaviour of nano-structured materials that is controlled by the interface is studied using Molecular Dynamics (MD). Four different types of nano-structured materials were investigated: (1) the sintering behaviour of nanoparticle; (2) the evolution of bamboo-like nanowires; (3) the mechanical property of the interlamellar phase of semicrystalline polymers; and (4) the mechanical property of the interlamellar phase of biodegradable polymers. In the MD simulation of nanoparticle sintering, it is observed that the particles can reorient themselves to match their crystalline orientations at the beginning of the sintering and thereby form different types of necks between different particles. This leads to different mechanisms of matter redistribution at the different necks. It has also been observed that the particles switch the mechanism of matter transportation halfway through the sintering process. None of these can be handled by the continuum model. However, assuming the right scenario, the continuum theory does agree with the MD simulation for particles consisting of just a few thousand atoms. In the multi-scale MD simulation of the evolution of bamboo-like nanowires, the microstructure evolution behaviour of the bamboo nanowire is observed very different to the conventional bamboo structure polycrystals. When the materials reduce to the nano-size, different evolution behaviour occurs: the low angle tilt grain boundary (GB) tends to be eliminated by forming a bending crystal form and dislocation slip might occur when raise the temperature; the large tilt GB is found stable at low temperature but the GB diffusion is very sensitive to the temperature; An interesting microstructure evolution behaviour of the nanowire with the small radius starting with the large angle GB is observed. A new hcp grain is nucleated from the triple point of the bamboo structure. In the multi-scale MD study of the mechanical property of the interlamellar phase of semicrystalline biodegradable polymers, it is found that the mechanical stiffness of interlamellar phase below Tg is mainly governed by the LJ interaction along the polymer backbone. Therefore, good polymer chain entanglement enhances the LJ interaction and increases the mechanical strength. Although the amorphous interlamellar phase is not the idea elastomer when temperature is above the glass transition temperature, it also shows the elastomer behaviour above Tg when we examine the number of long chains inside the amorphous interlamellar phase. The results of this study further support Pan's entropy spring theory by showing the Young's modulus drop lags behind the biodegradation process at temperatures above the glass transition temperature. For the amorphous interlamellar phase below the glass transition temperature, the Young's modulus drops quickly as the chain scissions quickly reduce the polymer chain entanglement.

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Work is reported on composites comprising either epoxy resin or crosslinked polyethylene (XLPE) filled with silica nanoparticles (surface functionalisated and unfunctionalisated). Measurements were made of the dielectric spectra, charging and discharging currents under high electric fields, and space charge dynamics using the pulsed electroacoustic (PEA) technique. Considerable studies were made of the effect of humidity on epoxy nanocomposites. It was found that the epoxy composites filled with nanoparticles could absorb up to 60% more water by weight than the unfilled epoxy. For composites filled with microparticles, nearly all the water was absorbed by the resin. The glass transition temperature (Tg) for all epoxy samples, measured by both differential scanning calorimetry (DSC) and dielectric spectroscopy, showed a monotonic reduction with increase of hydration resulting in a 20K decrease for fully hydrated samples. This led to the conclusion that the extra hydration found in the nanocomposites was not in the bulk resin but was likely to be located on the surface of the nanoparticles. This is further supported by measurement of the hydration isotherms at room temperature and the resultant swelling as a function of humidity. A "water shell" model is developed in which there is an inner layer of approximately 5 – 10 bound water molecules on the surface of the nanoparticles, a further layer, approximately 25nm thick, in which water is in sufficient concentration to allow conduction, and an outer layer, approximately 50nm thick, which cannot support true conduction (i.e. the continuous movement of charge carriers.) This model is used to explain the sub-hertz dielectric results (in terms of percolation limited conduction) as well as those at around 1 – 10Hz that indicate the presence of bound or free water.