Composite structures are commonly joined using adhesive or mechanical joints, withmechanical joints being preferred when components need to be removable for maintenancepurposes. However, the presence of mechanical joints introduces a discontinuity in theload path, which can serve as an initiation point for failure and needs to be taken intoaccount in the design of the joint. Additionally, delaminations may occur around thefastener hole during the manufacturing and assembly processes, further impacting thestrength of the laminate under compressive loading. While some studies have assessedthe residual strength of open-hole specimens, limited information exists regarding theresidual bearing strength in delaminated composite joints. This study aims to assessthe significance of delaminations of varying sizes on the bearing strength of single-bolt,single-lap shear joints under static loading using numerical analysis methods. The effectsof countersinking and bolt size are also examined. Stress and progressive failure analysisare utilized to evaluate different parameters and account for the nonlinear behavior of thematerials. The study reveals that the presence of delamination leads to degradation ofthe bearing strength of approximately five percent when bolt pretension is applied and15 percent in the absence of pretension. Countersinking increases maximum and averagestresses on the cylindrical section of the hole, while a larger bolt size enhances bearingstrength by reducing bolt bending in single-lap shear joints. / Kompositstrukturer sammanfogas vanligtvis med hjälp av lim eller mekaniska fogar,där mekaniska fogar är att föredra när komponenter måste kunna demonteras förunderhållsändamål. Mekaniska fogar introducerar dock en diskontinuitet i lastvägen, somkan fungera som en startpunkt för strukturella fel och måste beaktas vid utformningenav fogen. Dessutom kan delaminering uppstå runt fästelementhålet under tillverkningsochmonteringsprocesserna, vilket ytterligare påverkar laminatets tryckhållfasthet. Någrastudier har utvärderat resthållfastheten hos prov med öppna hål, men det finns begränsadinformation om den resterande tryckhållfastheten vid hålkanten hos delamineradekompositfogar. Denna studie syftar till att bedöma påverkan av delamineringar avvarierande storlek på tryckhållfastheten vid hålkanten hos enskärsförband med ettfästelement under statisk belastning med hjälp av numeriska analysmetoder. Ävenpåverkan av försänkning och bultstorlek undersöks. Analyser av spänning och progressivskada används för att utvärdera olika parametrar och ta materialens olinjära beteendetill hänsyn. Studien ställer fast att förekomsten av delaminering leder till en försämringav tryckhållfastheten vid hålkanten med cirka fem procent när fästelementet är underförspänning och 15 procent utan förspänning. Försänkning av fästelementets huvud ökarmaximala och genomsnittliga spänningar på den cylindriska delen av hålet, medan enstörre bultstorlek höjer tryckhållfastheten vid hålkanten genom att minska bultböjningen ienskärsförband.

Additive manufacturing methods has been prevailing for several decades and the recent technological advancements brings in the flexibility and consideration for large-scale production in the industries. The components manufactured with these methods have wide variety of applications and therefore, it is crucial to investigate the mechanical performance of the printed parts. There have been many researches done to investigate the mechanical behaviour of polymer material but the studies are limited when it comes to the fatigue performance of the polymer parts printed using multi-jet fusion technology. The aim of the master thesis is to investigate the fatigue behaviour of polyamide12 (PA12) material with the components manufactured using HP’s multi-jet fusion 3D printing machine. Fatigue life is influenced by several factors such as the loading condition, the topology of the specimen, material properties, print quality and the environmental conditions. It is therefore essential to consider all these factors when developing the experiments for fatigue life prediction. The master thesis work can be divided into three sections. The first section focuses on evaluating the mechanical properties of polyamide12. This includes the quasi-static test for determining the tensile properties of specimens with the geometrical influence, the difference in properties in relation to the print directions, the influence of humidity and porosity over the mechanical performance of the material and finally the effect of internal heat generation and the surrounding temperature. The results show that the temperature and the quality of the specimens are the two major factors affecting the mechanical and fatigue performance of PA12. That being said, the next section focuses on setting up the fatigue experiments based on the data obtained from the static tests. When carrying out the experiment, both the test frequency and the surrounding temperature were foundto have a greater impact over the fatigue results. High test frequency showed a dramatic increase in the temperature of the specimen which caused an early failure. Hence, the experiments were developed in such a way that the influence of the thermal fatigue can be ignored by controlling the temperature of the specimen through a compressed air cooling system. The final section presents the findings, the conclusions about the material behaviour and the development of a finite element model to predict the fatigue life of a topology optimised demonstrator part using the data gathered from the experiments. / Additiva tillverkningsmetoder har använts i flera decennier och de senaste tekniska framstegen möjliggör flexibilitet och storskaliga produktionsprocesser. Komponenter tillverkade med dessa metoder har många olika tillämpningar inom industrin och därför är det avgörande att undersöka de tillverkade materialens mekaniska prestanda. Det har gjorts många undersökningar av det mekaniska beteendet hosmaterial som metaller och polymerer, men studierna är begränsade när det gäller utmattnings prestandan hos detaljer som tillverkats med multi-jet fusionsteknik.  Syftet med examensarbetet är att undersöka utmattnings beteendet hos polyamid-12 (PA12) tillverkat med hjälp av HP multi-jet fusion 3D-utskriftsteknik. Utmattnings livslängden påverkas av flera parametrar såsom belastnings tillståndet, provets topologi, materialegenskaper, utskrifts kvalitet och miljöförhållanden. Det är därför viktigt att ta hänsyn till alla dessa faktorer när man utvecklar experimenten för utmattnings karakterisering. Examensarbetet kan delas in i tre avsnitt. Det första avsnittet fokuserar på att utvärdera de mekaniska egenskaperna hos PA12. Detta inkluderar kvasi statisk provning för att bestämma drag egenskaperna hos prover med olika geometrier, skillnaden i egenskaper i förhållande till utskrifts riktningarna, inverkan av fukt och porositet på materialets mekaniska prestanda och slutligen effekten av yttre temperatur. Resultaten visar att temperaturen och kvaliteten på proverna är de faktorer som har störst inverkan på den mekaniska prestandan hos PA12. Med detta som utgångspunkt fokuserar nästa avsnitt på att sätta upp utmattnings experimenten baserat på data som erhållits från de statiska testerna. Under utformningen av experimenten visade sig test frekvensen och den omgivande temperaturen ha en stor inverkan på utmattnings resultaten. Hög test frekvens bidrog till en dramatisk ökning av temperaturen hos provet vilket resulterade i tidigt brott. Experimenten utformades därför på ett sätt så att termisk inverkan kan undvikas, genom att kontrollera provets yttre temperatur med ett trycklufts kylsystem. Det sista avsnittet presenterar resultaten, slutsatser om materialets beteende och utvecklingen av en finita element modell för att förutsäga utmattnings livslängden för en topologioptimerad demonstratören med hjälp av data som samlats in från experimenten.

The use of continuously reinforced thermoplastics have increased in recent years andoffer some significant advantages over their thermoset counterparts. The utilizationof these materials is however still limited due to the labour intensive processingand manufacturing. In the first part of this thesis, the aim is to investigate howcontinuously reinforced thermoplastics can be used in high volume manufacturingof complex components, specifically when combined with injection moulding. Thesecond part will attempt to develop a conceptual manufacturing process and designof a demonstrator part and perform a structural analysis of the component.To answer the first question, an extensive literature study on continuous fibre materialsand thermoplastics was conducted along with research on established and newlydeveloped manufacturing methods such as automated tape laying and fibre placement,tailored fibre placement and 3D printing combined with injection overmoulding. Theconceptual manufacturing process of the demonstrator part was then based on thisresearch and the design was modeled in using finite element analysis.The results shows that continuously reinforced thermoplastics can be used forhigh volume manufacturing of complex components when combined with injectionmoulding. While some of the processing methods are still in an early developmentstage, the techniques have been tested and implemented. The structural analysis of thedemonstrator part shows that the design can withstand the maximum external loadsthus and provide proof of concept. / Användningen av kontinuerligt fiberarmerade termoplaster har ökat under de senasteåren och erbjuder en del betydande fördelar jämfört med armerade härdplaster.Användningen av dessa material är dock fortfarande begränsad på grund av dearbetsintensiva bearbetnings- och tillverkningsmetoderna. I den första delen av dettaexamensarbete är syftet att undersöka hur kontinuerligt fiberarmerade termoplasterkan användas vid tillverkning med hög volym av komplexa komponenter , speciellti kombination med formsprutning. Den andra delen av arbetet kommer att försökautveckla en konceptuell tillverkningsprocess och design av en exempeldel och utföraen strukturell analys av komponenten.För att besvara den första frågan genomfördes en omfattande litteraturstudie omkontinuerliga fibermaterial och termoplaster samt om etablerade och nyutveckladetillverkningsmetoder som automatiserad tejpläggning och fiberplacering,skräddarsydd fiberplacering och 3D-skrivning kombinerat med formsprutning.Den konceptuella tillverkningsprocessen av exempeldelen baserades sedan pålitteraturstudien och designen modellerades och analyserades med finitaelementmetoden.Resultaten visar att kontinuerligt fiberarmerade termoplaster kan användas förhögvolymtillverkning av komplexa komponenter i kombination med formsprutning.Medan några av bearbetningsmetoderna fortfarande är i ett tidigt utvecklingsskede såhar teknikerna testats och implementerats. Den strukturella analysen av exempeldelenvisar att konstruktionen kan motstå de maximala belastningarna och påvisar på så sättgenomförbarhet.

This thesis deals with the scheduling problem for a constellation of Earth observation satellites, focusing on modelling the attitude dynamics to assess the tasking capabilities. A target selection algorithm is developed considering the time dependent manoeuvres between targets and the time-dependent value of the observed targets. Further, a closed-loop dynamics simulation is carried out to assess the agility of the 6U platform and verify the results of the algorithm. The work does not intend to present definitive numerical results, rather the goal is to develop a holistic framework that allows appraising the performance of a platform and the fulfilment of the mission objectives, aiming to maximise the collective value of the observed targets. Given the inputs in terms of platform, sensor, orbit and list of targets, this work serves to simulate the target selection and imaging at an arbitrary day and time for a chosen observation window. / Denna studie behandlar problemet med schemaläggning för en konstellation av jordobservationssatelliter och fokuserar på att modellera attityddynamiken för autonomt utförda uppgifter med beaktande av satellitens kapacitet. En målvalsalgoritm utvecklades med hänsyn till både tidsberoende manövrar mellan målen och tidsberoende värden för de observerade målen. Dessutom utfördes en simulering av styrdynamik i ett slutet system för en 6U-plattform för att bedöma och verifiera målvalsalgoritmen. Arbetet avser inte att presentera definitiva numeriska resultat, utan syftet var att utveckla ett helhetsramverk för möjlig bedömning av plattformens prestanda och att studera plattformens förmåga att välja mål som maximerar det samlade värdet av de observerade målen. Med givna ingångsvärden i form av plattform, sensor, omloppsbana samt lista over mål, ger detta arbete möjlighet att simulera satellitens val av mål i en avbildning vid en godtycklig dag och tid för ett valt observationsfönster.

The Swedish Institute of Space Physics (IRF) at Kiruna focuses on research activities in the ionosphere, magnetosphere, and upper atmosphere of the planet as well as the development and production of various sensors and detectors for space research. The test facility includes the IRF SpaceLab which is equipped with multiple testing equipment. One of the testing resources available is the Solar Simulator, which consists of a vacuum chamber equipped with four metal halide lamps that produce a spectrum closely resembling that of the Sun. When any spacecraft payload or instrument is exposed to the Sun and its radiations, the most important factors to consider are the type of radiation, flux, and how the exposed material will react. Thermal designing and solar balance tests are important factors in achieving expected conditions for different missions. By testing and verifying these lamps, this solar simulator can be used not only for IRF missions but also for other institutes and private organizations that can access it. The characterization of four lamps is done in terms of temperature distribution, radiation, and power. According to preliminary experimental measured values obtained from the setup, exposed material, and its properties can be varied and the best suitable coating can be selected that includes α (absorptivity) and ϵ (emissivity) valueconsideration. The thesis is divided into four phases: Designing, Manufacturing, Testing, and Analyzing. Before entering into these phases, the basic knowledge of thermal engineering and thermal simulation is acquired. Thermal modeling and simulations are done in Airbus Defence & Space’s Systema Thermica software tool. The design phase includes designing a frame structure and a 350 x 350 mm screen in Autodesk Inventor software. Manufacturing of the frame structure and the screen was done in the IRF workshop. This screen kept hanging with the support of a frame structure which is mounted on the copper table inside the chamber. The screen is kept in the field of view of each lamp and every lamp is illuminated accordingly. The analysis is done by measuring the temperature of the back side of the screen. Temperature sensors were mounted and clamped mechanically instead of kapton tape to avoid direct contact with the screen. The obtained values are analyzed and compared with the thermally simulated values. Pressure and the temperature of the system were monitored with independent systems throughout the test procedure. This thesis report could operate as a foundation for future examination of the solar simulator’s lamps in order to determine precise efficiency.

The region of space dominated by the Sun's magnetic field is called the heliosphere. It envelops the entire solar system including Earth. Therefore, a strong coupling exists between the Sun and our planet. The Sun continuously ejects particles, the solar wind, and when these high energy particles hit Earth, the magnetosphere (the region around the Earth governed by the geomagnetic field) is affected. When the solar wind is enhanced this disturbs the magnetosphere and perturbations can be seen also in ground-based observations. The upper atmosphere is subjected to solar radiation that ionise the neutral atoms and molecules, this region is referred to as the ionosphere. In the ionosphere, some of the heavier ion populations, such as O+, are heated and accelerated through several processes and flow upward. In the polar regions these mechanisms are particularly efficient and when the ions have enough energy to escape the Earth's gravity, they move outward along open magnetic field lines and may be lost into interplanetary space. Ion outflow in general has already been well studied, however, ion outflow under extreme magnetospheric conditions has not been investigated in detail. Disturbed magnetospheric conditions correlate with solar active periods, such as coronal holes or the development of solar active regions. From these regions, strong ejections called coronal mass ejections (CMEs) emerge. When these extreme events interact with Earth, they produce a compression of the magnetosphere as well as reconnection between the terrestrial magnetic field lines and the interplanetary magnetic field (IMF) lines, which most of the time leads to geomagnetic storms. The amounts of incoming solar particles and energy increase during geomagnetic storms and we also observe an increase in the O+ outflow. Our observations are made with the Cluster mission, a constellation of 4 satellites flying around Earth in the key magnetospheric regions where ion outflow is usually observed. In this thesis, we estimate O+ outflow under disturbed magnetospheric conditions and for several extreme geomagnetic storms. We find that O+ outflow lost into the solar wind increases exponentially with enhanced geomagnetic activity (Kp index) and increases about 2 orders of magnitude during extreme geomagnetic storms. / Den del av rymden som domineras av solens magnetfält kallas heliosfären. Helios-fären omfattar hela solsystemet inklusive jorden, vilket gör att det finns en starkkoppling mellan solen och jorden. Solen sänder oavbrutet ut laddade partiklar in denså kallade solvinden och när dessa energika partiklar träffar jorden påverkas mag-netosfären (det område kring jorden där det geomagnetiska fältet dominerar). Närsolvinden är starkare än vanligt uppstår störningar. I magnetosfären som ger effektersom kan uppmätas med markbaserade instrument. Den övre atmosfären utsätts för strålning från solen som joniserar atomer ochmolekyler, och formar det område som kallas jonosfären. Några av de tyngre jonpop-ulationerna i jonosfären, som till exempel syrejoner, kan hettas upp och accelererasgenom flera olika möjliga processer. Detta gör att de flödar uppåt i atmosfären. Ipolarområdena är dessa mekanismer särskilt effektiva och om tillräckligt med energitillförs jonerna kan gravitationen övervinnas, vilket gör att jonerna flödar upp längsöppna magnetfältlinjer och kan gå förlorade ut i den interplanetära rymden. Generelltsett har jonutflöde redan studerats väl, men jonutflöde under extrema magnetosfäriskaförhållanden har inte undersökts i detalj. Störda magnetosfäriska förhållanden korrelerar med då solen är aktiv, som tillexempel koronahål eller under utvecklingen av aktiva solområden. Från dessa områ-den härstammar koronamassautkastningar. När dessa extrema händelser når jordenkomprimeras magnetosfären och det geomagnetiska och interplanetära magnetiskafältet omkopplas, vilket ofta leder till geomagnetiska stormar. Under dessa införsstora mängder av partiklar i solvinden och energi till magnetosfären, och ett högresyrejonsutflöde är också observerat. Data från Clustersatelliterna har använts; dessa utgörs av fyra satelliter i for-mation i omloppsbana kring jorden. Plasmaområdena där de befinner sig är därjonutflödet vanligtvis observeras. Denna avhandling behandlar syrejonsutflöde understörda magnetosfäriska förhållanden och flera extrema geomagnetiska stormar. Detvisas att syrejonsutflödet som förloras till solvinden ökar exponentiellt med geomag-netiskt aktivitet (Kp-index) och ökar med upp till 2 storleksordningar under extremageomagnetiska stormar.

This thesis focuses on the topic of preventive maintenance for electric aircraft and aims to examine its significance and implementation within the aviation industry. Electric aircraft have become increasingly popular as a sustainable alternative to conventional aircraft, making it crucial to develop effective maintenance strategies to ensure their reliability and performance. To achieve this objective, a comprehensive literature review of existing research and practices in the field of preventive maintenance for electric aircraft is conducted. The study identifies the key components and systems in an electric aircraft that require regular monitoring and maintenance, such as electric motors, batteries, power converters, and control systems. By analyzing the benefits of preventive maintenance, such as reduced downtime, increased component lifespan, and decreased maintenance costs, various methods, and techniques for implementing preventive maintenance for electric aircraft are presented. This includes the use of condition monitoring systems, sensors, and data-driven analysis to monitor and predict the health of components and anticipate any faults or deviations in advance. To explore the challenges of preventive maintenance for electric aircraft, aspects such as data management, cooling, and electromagnetic compatibility are also discussed. Furthermore, the need for training and skill development for maintenance personnel to effectively carry out preventive maintenance activities for electric aircraft is explored. By compiling and analyzing the available information, this thesis provides a comprehensive overview of preventive maintenance for electric aircraft and its significance in ensuring reliability, performance, and sustainability within the aviation industry. The findings can be valuable to airlines, maintenance organizations, and researchers interested in implementing effective maintenance strategies for electric aircraft and contributing to the continued development of sustainable aviation. The literature review showed that the use of preventive maintenance strategy for electric aircraft is well-founded and supported by research and experiences from various industries. The implementation of IoT and fault diagnostic techniques can enhance the maintenance process and increase the reliability of electric aircraft by identifying and addressing potential faults at an early stage. These findings provide valuable insights and guidelines for the aviation industry in developing and optimizing their maintenance strategies for electric aircraft.

The tendency of recent years towards electrification of aircraft components and subsys-tems has opened the door for a wider usability of electro-mechanical actuators (EMAs) inthat context. EMAs are already in use in aircraft industries but mainly in civil aviation forsecondary control systems and non-critical applications. Therefore it is evident that thereexists a need for further research in the sector of utilization of EMAs for other areas withinthe aircraft manufacturing industry before they can be effectively applied. In this thesisan analysis of the power and thermal behaviour of EMAs has been done to evaluate theirapplicability in primary control systems for fighter aircrafts as compared to conventionallyused hydraulic systems. Furthermore, a method for scaling of such actuators in an initialdesign stage where few parameters are known has been developed and validated. One ofthe most substantial drawbacks against choosing EMAs for these purposes is the disadvan-tageous thermal transfer capability of electrical machines in high power applications. Aninvestigation has therefore also been made on calculation of power losses of electrical mo-tors and inverters. The results have been compared against a servo hydraulic actuator. Ascalable simulation model derived from motor data statistics has been developed in orderto simulate power losses and the thermal behaviour of these actuators. The model takesvery few parameters as input as an aircraft designer working in the preliminary stages ofthe design process often have limited knowledge of the final product, but at the same timeneed a fairly accurate view of how the actuators ought to be scaled with regard to weight,power and thermal transfer. The model shows promising results when verified against anactual electro-mechanical actuator on Iron Bird test rig. Finally, this work aims to furtherthe development of an Iron Bird situated on Linköping University, through an integrationbetween three thesis projects where the final product shall be an Hardware In The Loop(HWIL) simulation with several actuators involved.

This thesis presents a simulation study on the thermal performance of the fuel systemin a fighter aircraft. The main objective is to investigate the potential utilization of thefuel system as a heat sink and explore various operational aspects that can enhance itsperformance. To achieve this, the study focuses on analyzing the impact of tank emptyingsequences, fuel types, and the implementation of bypass recirculation under low thrustconditions.The fuel system is modeled using the Modelica language-based tool, Modelon Impact,which enables a thorough and detailed examination of its thermal behavior. A functionalmodel of the fuel system has been successfully built in this modeling tool. The investiga-tion of the three operational aspects has been divided into two heat sink studies. Heat sinkstudy 1 examines the tank emptying sequences, with three different sequences being inves-tigated. The simulation results did not demonstrate any clear and significant benefits fromusing different emptying sequences. However, emptying the fuselage tank first showedslightly better behavior compared to the sequence that involved emptying the wing tanksfirst. Heat sink study 2 focuses on the implementation of bypass recirculation of the fuelback to the tanks. The primary objective of heat sink study 2 is to maintain the feed linetemperature close to the threshold determined by the fuel type in order to . The simulationresults revealed significant improvements in the heat sink capacity of the system, reachingup to 168%.

As the commercialization of space continues on a global scale, it is increasingly common to see companies, as well as space agencies, become more and more interested in developing constellations of satellites, mainly for telecommunication and remote sensing missions. While there are multiple issues that arise when operating constellations of medium to large scales, one of the most challenging issue is the distribution of commands and control among satellites. The present thesis introduces a system that solves this issue through blockchain technology which provides multiple advantages. There are not many studies that have addressed the potential uses of blockchain in the space industry. The rest of this thesis illustrates the  benefits of using blockchains in a number of scenarios and does not address the usage of this technology in the financial industry. This thesis considers a number of scenarios corresponding to different operational modes of a constellation of satellites. Towards the end of the thesis, a recommended architecture and settings will be proposed for a real-world use case of a blockchain-based network for the command and control of a constellation of satellites.