Viscoelastic materials such as rubbers find ubiquitous use in engineering applications due to their outstanding ability to dampen vibrations and shocks. During a load cycle, the stress-strain curve of a viscoelastic material exhibits energy loss due to hysteresis. The structural response is damped because mechanical energy is dissipated and converted into heat, known as self-heating. The heating of the viscoelastic material results in degraded mechanical properties, and eventually, failure. This study focuses on the application of the viscoelastic material polyurethane in roller coaster wheels. Roller coaster wheels typically consist of a cast aluminium rim with a co-bonded polyurethane rubber bandage. The high forces and high speeds of a roller coaster ride lead to high self-heating in the rubber bandage. The high resulting temperatures in the bandage may cause failure of the bond line and of the rubber bandage itself. Replacement of the rubber bandage (re-treading) is a time-consuming and expensive process and ideally avoided. It is known that the design parameters of the wheel (diameter, width, bandage thickness, rubber hardness, etc.) influence the temperatures in the rubber bandage. At the same time, these design parameters have an influence on the damping capacity of the wheel, which is important for passenger comfort, noise and the longevity of the other mechanical components of the roller coaster vehicle. For example, the wheel with the maximum thermal performance (i.e., minimum temperature) will have minimum damping capacity, and vice-versa. To avoid this complication, this study compares the thermal performance of wheels with similar damping capacities. To evaluate the thermal performance of a wheel, a decoupled thermo-structural finite element analysis methodology is implemented. The method is validated using experimental measurements provided by the polyurethane manufacturer. Subsequently, a novel wheel design is proposed and compared to a regular roller coaster wheel. The 𝛽-ratio was introduced as the ratio of thermal to mechanical power. By comparing the finite element results with the experimental results, it was found that 𝛽 = 0.24 ensures that the numerical temperature matches the experimental temperature 𝑇num = 𝑇exp = 319.4 K. This value for the 𝛽-ratio was subsequently applied to finite element analyses of a regular roller coaster wheel and the novel wheel design. The standard wheel reached a temperature of 351.3 K on the surface and 376.7 K internally. The novel wheel design reached a maximum temperature of only 314.2 K. The maximum temperature of the novel wheel design is much lower than that of the standard wheel, because its structural finite element model is much stiffer, therefore providing less damping. Given the same loading cycle, the maximum temperature of the novel wheel design was found to be significantly lower than that of the standard roller coaster wheel. This indicates that the novel wheel will be more durable and have a longer lifetime. However, the novel wheel was also found to be significantly stiffer than the standard wheel. Toward the end of the report, various design iterations of the novel wheel design are considered which decrease this stiffness and improve damping.

The Netherlands Aerospace Centre (NLR) together with Toray Advanced Composites and 12 other parties take part in the Netherlands liquid hydrogen (LH2) composite tank consortium which is funded by the Netherlands research & development mobility (RDM) Fund. The goal of the RDM project NLR takes part in is to develop a long-life, fully composite LH2 tank for civil aviation. Microcracking and the subsequent hydrogen permeation remain the biggest challenges. This study encompasses three fundamental facets to test and select composite materials: a comprehensive investigation into material behavior, the formulation of a Finite Element Method (FEM) model, and a partial experimental verification of said FEM model. The latter integral component involves an extensive testing system that includes room temperature and cryogenic tensile tests, permeability assessments, and microcrack evaluations facilitated by optical microscopy. During the experiments there is focussed on the critical microcrack density and material selection criteria such as ply thickness.

The accuracy of hot press forming process simulations with unidirectional fiber reinforced thermoplastics is not at the desired level. Fundamental knowledge about the interactions between adjacent plies is needed to enhance predictive quality. Several mechanisms can be distinguished during hot press forming of composites. This thesis focuses on the inter-ply friction behaviour which is the resistance against inter-ply slip. The main variable investigated in this study is temperature.

In this research, an extensive friction characterization with UD C/LM-PAEK is conducted at temperatures ranging from 300 to 365 ◦C. The neat matrix material has been studied with DSC and rheometry experiments. In general, a peak response can be seen during start-up in a friction characterization experiment. This peak, or overshoot, progresses towards a steady state friction response after a slip distance of several mm. Reducing the temperature showed similar effects to increasing the sliding velocity in a ply-ply slip system. The peak during start-up increases in magnitude while the steady state response remains approximately constant. Indications of flow induced crystallisation have been observed during friction characterization around the melting point of the material. The timetemperature-superposition principle has been applied to experimental friction data. This enabled to predict the duration of the transition of peak friction response towards a steady state. Several modelling efforts have been compared to the experimental data. The accuracy of the model predictions is similar between 315 and 365 ◦C. Influences of flow induced crystallisation impede the reliability of the specific models around and below the melting point.

The research lead to useful insights in the friction behaviour at relatively low temperatures. Further research is required on the field of flow induced crystallisation for a better understanding of its role in the friction response. Further study with other materials is needed to validate the application of the time-temperature-superposition principle to predict the speed of the transition of peak friction response towards steady state.

Technological advancements are conducted at accelerating rates in all areas of human activity, with air travel being no exception. In order to design aircraft that are faster, safer and very importantly more efficient, multiple solutions can be investigated. This thesis looked in particular at the structural side of aircraft innovation, and more specifically at the use of composite materials (both thermoset and thermoplastic) in comparison to aluminium, in an attempt to build lighter structures. The aim was to generate a comparative study using a wing rib as a case study and investigate the environmental sustainability of these structures using a life cycle assessment. The project was conducted in collaboration with GKN Fokker Hoogeveen, and the case study used was that of rib 14 within the Wing of Tomorrow project, initiated by Airbus.
The investigated material flows included a sheet formed aluminium rib, a machined aluminium rib, prepreg manufactured epoxy CFRP thermoset rib, RTM manufactured epoxy CFRP thermoset rib, and lastly an out of autoclave consolidated (hot press consolidated) PEKK CFRP thermoplastic rib. The results indicated that the machined aluminium in this application consumes the highest amount of energy and as a result has the highest carbon dioxide equivalent emissions as well, whereas the lowest values are seen for the sheet formed aluminium rib. The composites fall in between these two, with the thermoplastic having the third highest energy consumption and emissions from all materials considered. Lastly, a discussion was conducted on the potential of thermoplastic composites and their recyclability for the aircraft of the future, as well as future steps in the movement towards more sustainable aviation.

The objective of the thesis was to evaluate the cost reductions and tower design when production costs are included in the design process of an offshore wind turbine tower. First, a tower cost model had to be developed. Then, based on the findings, a cost optimization model was built with the tower design software from Siemens Gamesa Renewable Energy (SGRE). Three scenarios were developed
to mimic different supply chains. The results show that the production costs can be reduced by [0.2, 2%]. Moreover, in each scenario, a different optimum tower design was found. Another study into the optimum number of shells per section showed wind turbine manufacturers could reduce production costs up to 20%.

The purpose of this research study was to experimentally investigate transpiration cooling through additively manufactured porous structures, using Thermochromic Liquid Crystals (TLC). This was done by calculating two cooling parameters: heat transfer coefficient and film cooling effectiveness. Different materials, thicknesses of the porous structure, porosities and blowing ratios (M) were tested. Additionally, the distributions uniformity of the through-pores for each samples were also studied. The experiments showed that the materials tested had similar cooling performances. For all the samples the heat transfer coefficient was increasing with the increasing blowing ratio. Whereas, the film cooling effectiveness was the highest for the blowing ratio M=1. The thickness of the porous structure had no effect on the laterally averaged parameters studied. However, with the thicker samples, the distributions of the through-pores were non-uniform, with some areas having no through-pores.

Both GKN Aerospace Fokker Aerostructures B.V. (Fokker) and Delft University of Technology (DUT) are partaking in a Clean Sky 2 program called MANTA. MANTA stands for: MovAbles in the Next generaTion Aircraft, and is a program created by the European Union in order to meet the ’ACARE Flightpath 2050 objectives’ by achieving cleaner air travel. The MANTA program aims to reduce the fuel consumption by 3% to 5% using the knock on effects of smart usage of movables.   The contribution of Fokker in the MANTA program is the Morphing Tab concept. This is a newly introduced tab which will be located in the wingtip and must allow load alleviation during manoeuvres. By deflecting the tab in a smart manner, it will be able to generate an internal moment in the wing structure opposite to the internal moment generated by the lift. These internal moments counteract one another, reducing the peak stresses which can result in a lighter wing structure. This will have multiple aerodynamic beneficial knock on effects such as the potential for a more slender wing.  The solution of Fokker. to keep the drag introduced by the tab to a minimum, is to use a morphing tab rather than a conventional tab. The morphing tab has a continuous inboard skin surface which morphs in the section between the Rigid winglet structure and the rigid tab. The continuous skin will add to the aerodynamic efficiency as airflow along the surface stays attached further along the wing chord and airflow leakage is largely avoided.  The morphing part of the winglet exists of multiple components. the component studied in this thesis is the flexible skin. More precisely, it is the attachment of the morphing skin to the non-morphing parts of the concept, the winglet and the tab. As the morphing skin is very thin, and the condition of use is an out-of-plain movement, a complex and rarely studied combination is formed. This has led to the following research question: What is the best method to connect a thin flexible skin element undergoing a peel-like motion to a rigid structure without disturbing the aerodynamic surface at the outside of the skin? Answering this question must lead to a solution for this specific situation as well as contribute to the body of knowledge to fill the current literature gap. Based on the findings of the literature study, the analysis started with selecting a joining method. This process was performed by a trade-off in which six groups of joining methods (Integral Structure, Bonding, Welding, Mechanical Fastening, a Piano Hinge and a Flexible Hinge Element) have been compared. This resulted in the selection of Mechanical Fastening as the best joining method. Within this category, Rivets have been selected as the best suited solution for the Morphing Tab Connection. Along with design guidelines, a comparison between the failure limits of the rivets and the loading conditions of the tab, led to the design of the riveted connection. A test had to be created in order to investigate whether the design is able to meet the requirements of the joint under the relevant loading conditions. No standardised test could be used as they did not create representative loading conditions. During the test, the stress and strain of the skin at the connection are measured via the machine output, Digital Image Correlation software and strain gauges. Additionally, video recordings are made of the test from the side in order to validate results. Three main test conclusions can be made: • The Aerodynamic Profile does not experience a significant effect of the Riveted connection. The required rotation angle and accuracy are achieved and the contour deformation is within the tolerance. • The Static Failure is caused by skin bending without interference of the fasteners. The Static Failure Level is higher than the required minimum stress. Therefore, the Static Load Requirements are met. • The rivets do not interfere on the skin behaviour during fatigue tests. The stiffness reduction due to the fatigue tests shows similar results with and without fasteners. Overall this means that the Riveted connection meets all Aerodynamic and Structural Requirements. Besides this, no indication was apparent during the tests that another joining method would lead to better performance. Also, the riveted connection outperformed the other joining methods in the other Trade-off categories. The combination of these two facts warrant the overall conclusion of this thesis: A riveted connection is the best method to connect a thin flexible skin element undergoing a peel-like motion to a rigid structure without disturbing the aerodynamic surface at the outside of the skin. The connection design created during in this thesis can be applied in further investigations in the Morphing Tab Concept.

The aim of this study is the assessment of the mechanical performance reduction due to manufacturing-induced gaps and voids (delaminations) in thermoplastic composite pipes. The effects of gaps are assessed based on the finite element modeling of an internal pressure load case and is validated by experimental tensile coupon testing. Results show a stress increase through-the-thickness in the layers having the same orientation, which depends linearly on the gap width. The assessment of voids is based on the modeling of external pressure and lateral crushing, in which the latter is also experimentally tested for validation purposes. No reduction in performance is observed for external pressure and an onset of delamination growth is observed for lateral crushing. A tool is proposed for a fast and computational inexpensive assessment of manufacturing-induced gaps in thermoplastic composite pipes to improve the design and manufacturing process and contribute to an improved integrity management system.

Assembly, Integration and Verification (AIV) in space makes launching geosynchronous satellites faster and significantly cheaper in the long term. A space-tug is launched into space to perform AIV there. It assembles a standardised satellite consisting of several modules. The modules are designed in such a way that the required subsystems for a communication satellite are incorporated in the modules. Examples of these modules are a propulsion module, a solar array module and a computer module. Due to the standardised modules, testing time and costs can be reduced significantly. This ensures a delivery time of maximum one year, which is the time from order until operations in space. The modules are efficiently packed and connected to external beams in the launch vehicle, to make sure that two satellites can be launched simultaneously. The external beams take up the extreme loads that occur during launch. This decreases the dry mass of the satellite, as the modules do not need as much structural mass. The subsystem design and structural analysis result in a drymass of 1847 kg per satellite. Next to the two satellites, a refuelling tank is added in the launch vehicle to refuel the tug. The tug requires 2921 kg of fuel to transfer the two satellites and go back to its initial state. Due to the modularity of the satellites, the lifetime of the satellites can be increased. Regarding the economic feasibility of the mission, a full return on investment is expected after 15 years of operations in base case scenario.

A Solar Electric Vehicle is a vehicle that receives a significant amount of its total energy consumption through sunlight gathered using solar arrays. The main objective of this thesis was to determine how the design of the rear low-speed crash structures should be different for a Solar Electric Vehicle, compared to conventional cars. This is done by creating a general optimization tool that can be used for the conceptual design of the rear low-speed crash structures of passenger cars. Next to the structural performance during three low-speed load cases, the manufacturing cost and intrusion distance are also taken into account. It was found that for a Solar Electric Vehicle the intrusion distance should be reduced in order to increase the size of the solar arrays (and therefore their yield) without damaging them during low-speed rear impact, even though this comes with a weight penalty.

In this comparative eco-design study, the environmental impact of LM’s 58.7 blade was assessed for multiple material composition and waste management scenarios. Material variations were largely focusses on the resin fraction of the blade. This is since the matrix has the biggest impact of all materials and has a big impact on the available waste management options that are available. Material and waste management scenarios were largely selected based on a literature review. This knowledge was combined with the knowledge and current direction of LM to determine the investigated scenarios. Life Cycle Assessment (LCA) methodology was applied to calculate the potential emissions and resulting environmental impacts. To calculate the impacts, the Ecoinvent 3.5 database was used in combination with the ReCiPe 2016 Life Cycle Impact Assessment (LCIA) methodology. Analysis showed that Sub Critical Water (SubCW) hydrolysis likely is the waste management method with the lowest impact for the current used glass fibre - polyester design. However, two design changes can potentially lead to big reductions in total single score impact scores. These two are: designing for reuse of blade sections and interchanging thermoplastic resin for the currently used thermoset polyester resin. Both are beneficial because of the relatively direct reuse/recycling of material. This research can be extended to more resin types and waste management methods of these resin types. This will shed a broader light on the matter. When waste management methods reuse methods should be prioritized over recycling methods and ’clean’ recycling methods (i.e. methods that do not lean on heavily polluting processes) over dirty recycling methods.

Structural members carrying dominantly compressive forces are present in many types of structure. These members are referred to as columns and are frequently present in for example lifting appliances and offshore structures. Whether or not a column consists of longitudinally welded subsections is relevant for its mechanical performance in compression. Steel columns consisting of longitudinally welded members contain residual stresses caused by the non uniform longitudinal expansion and shrinkage during the welding process. The distribution and magnitude of these residual stresses are dependent on the dimensions of the heat affected zone (HAZ), and varies for instance as function of the welding procedure, and whether or not post weld measures are taken to diminish these residual stresses. In this thesis the width of the region in a column's cross section where tensile residual stress is present is referred to as the HAZ width. Using practical experiments an estimate is made of realistic HAZ widths in column structures using _nite element analyses. These column structures where welded and kept free of restraints during this process, so that a resulting curvature is developed upon cooling down to ambient temperature. The established value of the width of the tension zone is on the order of the thickness of the column's cross section. Based on existing norms a trapezoidal distribution of residual stress having a width of the earlier found value is applied on a _nite element model of a single square column, both for pinned and clamped boundary conditions. Mesh independence of the obtained results are verified by convergence studies. The compressive load capacity of the considered column is accected in the intermediate range of slenderness ratios, and shows a maximum reduction of approximately 21%. The effect of welding residual stresses is also investigated on a scaled model inspired by an existing design of a tower crane. A crane section is modelled by four vertical columns connected by multiple side bars. These side bars reduce the effective slenderness ratio of the columns loaded in compression, and therefore a less severe effect of the residual stresses on the collapse load is found.

The thesisproject concerns the development of a methodology to connect data, from theAirbus department in Stade, with each other and find relationships between themwhich lead to a prioritising tool with which justifiable decisions can bededuced in order to plan which Measurement System Analysis (MSA) to conductnext, focusing on cost effectiveness.  Therefore, the main content will revolvearound studying and analysing relevant literature and connecting this with theactual data, as present at Airbus, to arrive at a functional tool.  As such, the main aim and objectivesconcentrate around developing a thorough understanding of the relevant data anddiscovering how they relate with one another and with costs. Aim would be tofind a causal relationship, which is then subsequently also verified andvalidated.      The main findings areexpected to give the relationships between the data, e.g. that a certainimprovement of X% in MSA leads to Y% better Cpk (Process Capability Index. Adjustmentof Cp for the effect of non-centred distribution) and as such Z% reduction inCost of Non Quality (CNQ) per process.      As Airbus is in a toughcompetition with Boeing and other aircraft manufacturers, finding ways to bemore cost effective is very useful. Especially now with the populationof the earth rapidly growing and the use of aircraft for travel becoming morereadily available/affordable for everyone, the amount of aircraft that need tobe in the worlds fleet is expanding even more. As such, the rate ofconstruction of aircraft is rising tremendously and improvements in recurringcosts are ever more valuable. Even though the work is dedicated to Airbusprocesses, the methodology as developed for the prioritisation tool should begeneralisable to also be applicable for other situations and as such give aworthwhile contribution to the body of knowledge: How these data relate witheach other and how this knowledge/information can be turned into practicalimprovements.

At this moment, industrial robot arms are increasingly used to automate manufacturing processes in the aerospace industry. However, these robot arms lack position accuracy to effectively mill parts or assemble products. In this work, this gap is investigated following two approaches; on one hand existing calibration methods of robot arms are evaluated. On the other hand, two methods to define the impact of the robot arm inaccuracy on final dimensional variance of assembly products are compared. It is concluded that at least three extensions to current calibration models improve the accuracy of industrial robot arms. Moreover, multiple advantages and drawbacks of two tolerance analysis methods are given.

Residual stress analysis within hybrid structures is the focus of this study. The non linear stresses through the thickness are determined using a semi-destructive method known as Incremental Hole Drilling (IHD). Finite element modeling is used to build a mathematical code simulating GLARE laminates with initial residual stresses applied. The code includes the structure, orientation, mechanical and micro-thermal properties of the constituents into account. Matrices of elastic coefficients that represent the stress-strain relation within the laminate are found. In addition, strain responses are measured during incremental hole drilling of the GLARE laminates using tools specifically designed for hole drilling. Using the numerically determined matrices in conjugation with the experimental strain outputs lead to the computation of residual stresses. Verification and validation of the simulation models and the stress results are done through the use of theoretical methods such as the Classical Laminate Theory.

Fibre metal laminates (FML) are manufactured by stacking metal sheets and fibre reinforced prepreg in an alternating fashion, and curing it in an autoclave. The most well-known FML is Glare, which has been successfully applied on Airbus A380 for its fuselage skin. It consists of aluminium sheets and glass fibre prepregs. FMLs have a better impact and fatigue performance compared to the bare metal and are therefore more damage tolerant. The drawback of Glare is the high manufacturing cost because of the use of an autoclave and the expensive prepregs. This study investigates the feasibility of vacuum infusion for the manufacturing of FMLs to reduce costs, while keeping an acceptable fibre volume content of 45% to 60%. An experimental approach is taken to explore the manufacturing process to determine under which conditions an infusion is possible, and to analyse which process parameters influence the duration of the infusion. Three variables: resin viscosity, vacuum infusion pressure and the reinforcement permeability are identified from Darcy’s law, which can influence the infusion process. The experimental data was gathered through multiple infusion process tests by adjusting these variables. Because the resin flow on the composite layers cannot be monitored visually through the metal sheets, glass plates are used to investigate these variables’ effect on the process. Through the analysis of the experimental data, the vacuum infusion process including the material selection, equipment and processing details are determined. Aluminium and dry glass fibre sheets are used to conduct the Vacuum Infusion process. The product is used to verify how the process parameters adhere to actual FML product fabrication. It can be concluded that during the experimental study, the Vacuum Infusion process has successfully been applied on the manufacturing of Fibre Metal Laminates with a satisfying fibre volume content of 54% to 65%, and a void content of 0.5% to 1.5%. By extrapolating the experimental infusion length curves, it was estimated that under the current conditions a maximum infusion length of 1.4 m most likely is possible when infused over the 0º direction, and a maximum infusion length of 1.0 m is expected to be possible when infused over the $90\degree$ direction. The total manufacturing cost of Vacuum Infusion process was found to be reduced 43% compared to the autoclave manufacturing process. These results show that vacuum infusion is a promising technique for the manufacturing of low cost FML, and it opens a door for future research on this topic to reduce the manufacturing cost of Glare.

Clear ice formation on aircraft is a large economic and safety problem. The phenomenon, also known as ‘freezing rain’, usually occurs when subcooled rain droplets impact the aircraft while it descends from high altitude to prepare for landing. It can quickly increase the aerodynamic drag by up to 80% and reduce the lift force by 50%. Inefficient heating methods or toxic or corrosive chemicals are used to keep flying safe. In this thesis, infrared imaging (IRI) and laser speckle imaging (LSI) are used to observe freezing of water on surfaces with different material properties. A freezing front can be seen to travel through a molecular liquid layer of water (MLL) that covers all surfaces. If this freezing front has passed, impacting droplets freeze much sooner and at unusually high temperatures, which could explain the formation of clear ice on aircraft surfaces.

In the past decade, the interest in anti-icing research has spiked. However, no systematic study has been performed to find out the origin of clear ice. Using the new insight of a freezing molecular liquid layer of water, this thesis is able to explain the origin of clear ice and runback icing. It also suggests that the ongoing conflict in literature on the anti-icing performance of superhydrophobic surfaces might be caused by the presence of the molecular layer of water.

With a systematic study, the surface temperature, contact angle and relative humidity were found to be able to delay freezing of the water layer and the contact angle was able to decrease the velocity of the freezing front. Using this insight, coating architectures and scalable production methods were used to produce hydrophilic-hydrophobic patterns for passive anti-icing coatings.