Energy harvesting has become a popular topic for battery substitution in recent years. In particular, mechanical vibrational energy, one of the most common energy sources, has been intensely studied. Piezoelectric materials play a crucial role in vibrational energy harvesting as they can directly convert the mechanical energy to the desired electric energy. In particular these are attractive when they are made into a cantilever form allowing the harvester to harness larger energy. This project aimed at optimizing the performance of single-layered piezoelectric cantilevers, also known as the unimorphs, from the point of view of output power and operation lifetime with the use of a stroke limit stopper. \ In this study, a cantilever beam consisting of PZT (PZT5A4) bonded to an elastic substrate (Pernifer 45) with a tip mass attached to the free end is used as the harvester. To reduce the cracks generated in the piezoelectric material and subsequently increase the lifetime, a limit stopper is introduced to constrain the deflection of the unimorph.The influence of the stroke on the lifetime and power output is shown by a series of vibration tests under different operation conditions with varied unimorph lengths, configurations, attached tip masses and stroke distances. The result confirms the possibility of the limit stopper to improve output energy of longer unimorphs in certain distance ranges. It also points out that current designs do not allow performance optimization in both output and lifetime simultaneously. One ought to choose one of the two, as the methods which increased the instant power output also resulted in a sharp reduction in lifetime as well as total power capacity.

The aerospace engineering industry is continuously striving for faster methods to solve and optimize engineering and research problems with a higher degree of accuracy. It is therefore relevant to investigate possibilities that are expected to accelerate computational speed, such as quantum computing. For this reason, the objective of this thesis is to investigate the feasibility of optimizing 2D determinate truss structures with a quantum algorithm run on a Gate-Based Quantum Computer (GBQC). The Quantum Approximate Optimization Algorithm (QAOA) is currently expected to be the most suitable quantum algorithm candidate for optimization problems, because of its simplicity and robustness. The most important take-away from this thesis is that it is possible to map a truss structure to QAOA format to optimize it on a GBQC. The program proves to be working on quantum virtual machines. However, it is currently not possible to obtain correct results when running on real quantum hardware due to noise.

Alumina (Al2O3) is an attractive ceramic for engineering applications operating at elevated or high temperatures because of its good thermal and chemical resistance. It also maintains high strength and hardness at high temperatures. These desirable properties are due to the strong covalent and ionic bonds existing between its atoms. However, these same strong and directional bonds are the origins of its inherent brittleness. Over the last decade, material scientists have adopted self-healing as a means of restoring the load bearing capability of such materials after damage from micro-sized surface cracks. In this methodology, the material is restored to a status comparable to the original one by the ‘healing’ of such surface cracks at high temperatures. Healing is achieved by the addition of ‘healing agents’ to the base ceramic material which upon the occurrence of a crack oxidise into a healing oxide which fills and seals of the crack. There are some gaps in the build-up of the knowledge ladder of self-healing ceramics to an application ready level. This thesis addresses some design questions and tests the capability of newly identified healing particles under laboratory and application conditions.@en

When high-temperature steels are loaded under under industrially relevant conditions not only creep (i.e. a time dependent strain increase even under nominally constant loading conditions) occurs, but also local damage is formed. At relatively short exposure times quasi-spherical micron-sized cavities form preferentially at the grain boundaries oriented perpendicular to the principal loading direction. These cavities subsequently grow and coalesce into micro and macro cracks, which ultimately lead to failure of the structure. The concept of self healing, in which such damage is healed in-situ and under the applied loading conditions rather than is being prevented by a special microstructure, provides a new principle to extend the creep lifetime. Well-selected supersaturated solute atoms can selectively segregate at the free internal surface of the grain boundary cavities and fill them, thereby preventing the coalescence of cavities. This reduction in coalescence rate leads to an extended lifetime. The potential of the concept has been demonstrated in previous studies for binary Fe-based model alloys in which only one healing reaction can take place. The current work aims to take the validation one step further and to demonstrate it for a Fe-3Au-4W (in weight percent) model system in which two healing reactions can take place simultaneously, but without any intention to achieve decent mechanical properties. This work also aims to apply the selfhealing concept for two multi-component steels designed to have both decent mechanical properties and to demonstrate self-healing behaviour when exposed to the right conditions.@en

This thesis describes the development, validation and implementation of piezoelectric flow sensors. These sensors are meant to measure flow phenomena such as transition and separation in the boundary layer of an aircraft wing. Such information can be used as input variables to a control loop to push laminar-to-turbulent transition towards the trailing edge of a wing, thereby reducing the overall skin friction drag. The developed sensors are installed in the SmartX wing, which is a morphing wing developed at the Delft University of Technology (TUD).@en

The main objective of the research as described in this thesis was to enhance the piezo- and electrical properties of bismuth ferrite-based (BiFeO3 or BFO) piezoceramics at room and elevated temperatures, using both chemical and physical approaches.@en

In order to establish a sustained extra-terrestrial presence, habitats need to be built on the Moon and Mars using novel materials made from local resources. Several material processing methods can be applied to transform the locally abundant regolith into materials suitable for structural purposes. One promising method is sintering. This process can be used to create strong material using little to no Earth-imported additives. However, sintering still requires a large amount of energy to heat the material. A possible method to lower the energy requirement is by introducing small amounts of sintering aids. However, little is known about the effect of aids on the properties of sintered regolith. This research aims to investigate the effect of sintering aids on the densification and mechanical properties of sintered Martian regolith simulant. In this study, the chosen Martian regolith simulant, Martian Global Simulant - 1 (MGS-1), was first investigated using a variety of powder characterisation techniques to assess the similarity with actual Martian material. Using the Spark Plasma Sintering (SPS) technique, disk shaped samples were sintered at temperatures between 700 °C and 1060 °C and pressures of 30 MPa to 50 MPa. Several powder mixtures were used. Two different additives, aluminium and bismuth oxide, were used in two weight percentages, 2.5wt% and 5wt%, and mixed with baseline material. Samples sintered from this enriched material were compared to those made using baseline MGS-1 material. In order to assess the mechanical properties, the Ball-on-Ring (BoR) compression test was used to determine the biaxial flexure strength of the samples. Since the BoR compression test is a semi-standardised method, an effort was made to validate the testing procedure and obtained results using soda-lime glass samples. Additionally, mortar disks were created and tested to provide a reference for terrestrial material properties. After compression testing, some samples were ground back into a powder and examined using X-ray Diffraction (XRD) to assess any bulk composition changes induced by the additive and/or sintering process. The results from the powder characterisation techniques show that the chemical composition of MGS-1 is close to that of actual Martian material. In order to achieve strengths comparable to terrestrial mortar, a relative density of at least 70 % needs to be achieved. For the baseline material, the sintering temperature needs to exceed 1000 °C in order to obtain these results. This value is 950 °C for 2.5wt% aluminium additive material, and 900 °C for 5wt% aluminium, 2.5wt% and 5wt% bismuth oxide additive material. For equal sintering temperatures, the biaxial strength of enriched powders exceeds that of baseline material. Hence, the sintering temperature can be lowered for enriched materials to achieve similar strengths. Samples made from bismuth oxide enriched material exhibited superior properties compared to aluminium enriched material. For aluminium enriched material, no clear increase in properties is observed with increasing additive fraction. For bismuth oxide enriched material, there appears to be an increase in properties with increasing additive fraction. A material behaviour transition from brittle to tough appears to be linked to biaxial strengths exceeding 12 MPa. Compared to literature on Martian regolith-based materials, the results for sintered enriched MGS-1 perform well in terms of required additive fraction and mechanical properties. Using additives could potentially be a way to lower the energy requirement for regolith sintering on Mars. This work opens up areas of further research into the optimal additive, additive amount and sintering parameters for on-site application.

The main objective of this thesis was to develop new piezoelectric ceramic polymer composites that maintain the ease of manufacturing of random composites and could function as a human touch sensor, while simultaneously exploring their potential as energy harvesters.@en