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Shape changing or morphing structures enable optimisation of structural configuration to suit current operating conditions. Conventional techniques for achieving shape change often result in weight and complexity penalties, which may outweigh the potential benefits of greater shape changing ability. The research presented in this thesis focuses on the use of shape memory materials to achieve a reversible change in shape of an innovative compliant composite structure, which may enable shape change without the drawbacks of conventional shape changing techniques. An initial concept was evaluated using a glass fibre reinforced shape memory polymer which was heated and deformed locally to fix the actuated shape. It was found that a large change in shape can be achieved. However, due to the high shear strain between the fibres during large deformations, fibre/matrix debonding occurred and propagated with repeated cycling. An alternative topology, consisting of a shape memory polymer reinforced with comparatively large diameter precured CFRP composite rods, was proposed and successfully demonstrated to reduce matrix shear strains, thereby reducing damage during deformation. The increased reinforcement size also improved load carrying ability when the shape memory polymer was in its low stiffness state. Initial testing of a rod reinforced composite beam with a low stiffness elastomer matrix indicated that shape memory alloy actuators wound helically around the composite beam could be effectively used to provide Significant rotational actuation. A constitutive model of the shape memory alloy thermo-mechanical behaviour was compared to the experimental findings for different configurations of shape memory alloy winding around the composite beam. A composite beam with a shape memory polymer matrix was found capable of 'locking' and 'releasing' mechanically introduced rotational shape change. The composite beam topology used initially consisted of circular rods and relied upon an adhesive for torsional rod restraint within the end alignment fittings, often resulting in failure of the adhesive and large non- returnable rotations at the temperatures required for softening of the shape memory polymer matrix. Rectangular cross section rods were used to enable the end fittings to mechanically restrain the rods in torsion. The rectangular rod topology also gave a large increase in bending stiffness compared to circular rods, with both topologies having similar torsional rigidities. A key aspect of the actuator performance was found to be the rate at which the shape memory materials could be activated by heating or cooling. This was found to be a particular problem for the shape memory polymer. To increase the rate of heating for the composite beam with a shape memory polymer matrix, efforts were made to incorporate carbon nanotubes to improve the thermal response of the material. However, only a modest change in thermal properties was achieved, combined with some undesirable detrimental effects on mechanical and therrno- mechanical properties. Further work is needed to optimise this combination. A final composite beam demonstrator combining both helically wound shape memory alloy wires for actuation and a shape memory polymer matrix for shape fixing was constructed. The shape memory polymer matrix was heated using an embedded heating element. By activating the shape memory alloy actuators when the shape memory polymer matrix was in its soft state, a rotation was achieved. Cooling the shape memory polymer matrix before the shape memory alloy actuators fixed the rotated, which was returned upon reheating the shape memory polymer matrix.

TiAlN/VN multilayers, with a layer periodicity of ~3nm, have exhibited superior sliding wear resistance (1.26xlO-17m3N-lm-l) and lower friction coefficient (~=0.4, pin-on-disc test, Ah03 ball counterpart) when compared to other commonly used wear protective coatings, e.g. TiN, TiAlN and TiAlN/CrN. They require excellent oxidation and wear resistance for dry high speed machining operations. This project investigates the microstructure of the as-deposited coatings, their oxidation degradation mechanism and their wear and friction properties at room and elevated temperatures. The microstructure of the starting films was studied in terms of intermixing between the TiAlN and VN individual layers caused by the absence of shutters during the industrial PVD deposition. A FEGTEM coupled with EELS revealed chemical distribution of individual layers at nanometre resolution. Cs corrected STEM allowed the composition of individual atomic columns to be imaged. It was also used to probe across the interface of TiAlN/VN with angstrom beam (1 A) using EELS which showed a 1±0.1 nm thick intermixing between TiAlN and VN. Film growth and elemental distributions were therefore theoretically predicted in association with substrate rotation. The experimental compositional profiles and the prediction showed good agreement. The coatings deposited with -75 V and -85 V substrate bias voltage were multilayer TiAlNNN, 37at%:::;V:::;55at%, 0.81:::;(Ti+Al)/V:::;1.73, which were used for subsequent oxidation and wear studies. The oxidation behaviour of these coatings in air was investigated using thermal gravimetric analysis up to 1000°C and compared to TiN and TiAlN. Static oxidation of TiAlN/VN films was studied in the range 550-700°C, and characterised by high temperature in-situ X-ray diffraction and STEM/EDXlEELS of selected surface cross-sections. The oxidation resistance of TiAlN/VN was found to be controlled by the VN layers and consequently oxidation was initiated at a lower temperature than TiN and TiAlN coatings. The onset for rapid oxidation of the TiAlN/VN coating was found to be 2550°C. At temperatures >600°C, a duplex oxide structure was formed; the inner layer comprised a porous region of Ti-rich and V-rich nanocrystallites, while several phases were observed in the outer region, including V20 5, Ti02 and AlV04. V20 5 was the dominant oxide at the outer layer at 2638°C. An Au marker study suggested roughly equal diffusivity of cations outward and oxygen inward diffusion occurred during oxidation. Further to the oxidation study, dry sliding ball-on-disc wear tests of TiAlN/VN (V 55.2at%, Ti 28.5at% and Al 16.3at%) coatings on flat stainless steel substrates were undertaken against Ah03 at 25°C, 300°C and 635°C in air to investigate the relation between the presence of V 205 and low friction. The friction coefficient was 0.53 at 25°C which increased to 1.03 at 300°C and decreased to 0.46 at 635°C. Detailed investigation of the worn surfaces was undertaken using site-specific TEM via FIB, along with FTIR and Raman spectroscopy. Microstructure and tribo-induced chemical reactions at these temperatures were correlated with the coating's wear and friction behaviour. The friction behaviour at room temperature is attributed to the presence of a thin hydrated tribofilm and the presence of V 205 at high temperature.

Adhesive joints are widely used as a structural element in automotive and in aerospace applications because of their main advantage of more uniform stress distributions within lap joints relative to conventional bonding for example riveting or bolting. Adhesives can produce a stronger joint and potentially lengthen its service life. However, the stress distribution in the joint is not uniform and stresses are concentrated at the edges of the overlap. This can cause fatigue and reduce the service life of the joint. Therefore, a large number of analytical and numerical studies have been carried out to study this effect. Comparatively speaking, there is lack of experimental data to prove or cast doubt on the theoretical results. One of the main disadvantages of adhesive joints is that they have low durability when exposed to hostile environments. Moisture is the most commonly encountered service environment among various environmental conditions, to be considered a critical factor to affect the service life of adhesive joints. In this thesis, strain gauge, neutron diffraction, and X-ray diffraction methods have been used to directly investigate residual strains and stresses and also strains and stresses under tensile load in the adherends within adhesive joints. The residual strains and stresses have also been studied indirectly by means of a bimaterial method. In addition, the effect of moisture on the joints has been investigated by means of bimaterial and bulk adhesive samples. Neutron diffraction and bimaterial experiment results have been compared to FE predictions and good agreement achieved. The diffraction studies show that residual stress in joints due to manufacture are small and that water diffusion into the joint is a main critical factor affecting the performance of adhesive and adhesive joints.

The target of this work is to study the effect of the stylus tip geometry on the surface roughness measurements by the stylus methods. A computer simulation of the measuring process in 3D using arbitrary tip shapes has been undertaken. A novel feature of this simulation is that it determines and reports the contact distribution of the contact points on the stylus when scanning each surface. Following analysis of fully simulated data to establish the fidelity of the simulation process, it was applied to data set from real surfaces. First these were examined using ideal (sometimes truncated) pyramid, conical and spherical tips. Then tip shapes determined from the measurement of real styli were used. Relatively large tips (of the order of 10 μm) were used in order to ease the need for measurement resolution. The simulation results were evaluated against real measurements of the surfaces. A bespoke measuring system was developed for this, adding X-Y scanning and a means of interchanging styli while maintaining micrometer lateral positioning between measurements. The shape of each stylus tip has been determined using a technique based on the replication by indentation into a soft substrate (typically lead). The roughness values of the real surfaces when scanned (theoretically) by the real tips have been compared to the roughness values of the same surfaces when measured by the measuring system with different tips. This comparison has shown a good compliance of both the theoretical and the practical results. This provides a degree of confidence for interpreting details of the simulation as having practical relevance. Both computer simulation and real measurements confirm the trends that would be expected from earlier studies. For example, amplitude parameters tend to drop in value as stylus size increases. The distribution of stylus contacts in simulation suggests that it is rarely to be found near the nominal centre of the tip. It is also clearly demonstrated that real worn tips do not necessary act as if blunt, contacts concentration in small regions when local features dominate. These results have significant implementations for the uncertainty in topographic measurements.

This study investigates a novel approach to the problem of shock isolation. The questions considered are whether friction produces a better performance in terms of reduced response during a shock compared to viscous damping and a lower residual response after the shock. To gain physical insight, a single degree of freedom model with friction applied to the isolated mass is analysed. It serves as a benchmark to the performance of a two degree of freedom model where friction is applied to a secondary mass. The isolation system performance is then quantified. For the two degree of freedom system with an intermediate secondary spring which connects the primary and secondary mass, it is possible to obtain the reduction in the displacement response as good as the single degree of freedom system and at the same time smoother acceleration response compared to the single degree of freedom system. For the purpose of further improvement, a control strategy is introduced to switch on and off friction in both models depending on some response parameters and this is compared to the passive systems. This is the semi active control strategy where friction is changed within a cycle of vibration (discontinuous). The control strategy provides more displacement reduction to ensure the maximum displacement response is much smaller than the base input which cannot be obtained with the passive systems. The practical implementation and experimental validation is presented only for the first stage of the response during the shock. For the practical implementation of the switchable friction, an electromagnet is applied to separate the friction surfaces. Good agreement with the simple theoretical models for both passive and switchable systems is obtained. The reduced displacement and smooth acceleration response were obtained from the experiments with the system used to represent the two degree of freedom model. The issues and limitations in the practical implementation are identified and discussed.