Modern synthetic structural adhesives are finding a place in the drive to improve the fuel efficiencyof automobiles through weight reduction of the structure. One of the most important properties ofthe adhesives used in this type of joining is the fracture energy.A literature study is carried out to gain a broader understanding of the methods used for thedetermination of the fracture energy of adhesives. One of the most common experimental methodsrelies on the use of the Double Cantilever Beam (DCB) test specimen. International standards for theDCB test are studied. Prediction of the fracture energy using Linear Elastic Fracture Mechanics andthe J-integral approach, a closed form solution and finite element methods are also seen. Differencesin these methods are attributed in part to the nonlinear behaviour of the adhesive being studied. It isdecided to use the results of a non-standard DCB test and the 40% error calculated by a theoreticalstandard method as a point of reference.A comprehensive comparison of the American Society for Testing Materials (ASTM) and BritishStandard Institution (BSI) standards for the determination of the fracture energy of adhesives isundertaken. Limitations and overlaps in the standards are identified. A DCB specimen isrecommended and an experimental procedure that satisfies elements one or both standards issuggested along with several small additions such as using a wire to assist in the application of theadhesive and the use of cameras to track the crack growth. In addition, a new fixture to allow testingof the recommended DCB specimen according to the standards is designed and manufactured.Materials for the preparation of tests specimens are ordered and, based on available laboratorytime, a single DCB test specimen is made for the purposes of testing a rubber-based automotivestructural adhesive. The specimen is tested using the recommended experimental procedure usingthe new fixture. The data produced during the test are collected and interpreted using themethodology proposed in the BSI standard for the calculation of the fracture energy of the selectedrubber-based adhesive. Several challenges found during this process are identified. The fractureenergy determined from the standard-based experiment ranges from 140 J/m2 to 1380 J/m2depending on the methodology used.The values of the fracture energy determined from the standard-based DCB experiment are thencompared to the fracture energy seen with the nonstandard-based experiment and to the standardbasednumerical test seen in the literature. It is shown that when simple beam theory method isused the difference in the results found in the standard-based experiment and nonstandard-basedexperiment can be confirmed to lie within the 40% error observed in the literature.Finally, the contributions of the project are summarized and recommendations for future work aremade. In particular, the lack of information given in the BSI standard when calculating the fractureenergy and the need for multiple test specimens are required by the standard, must be addressed inorder to support the obtained results and conclusions.

Cette thèse concerne l'analyse de propagation de dommages dans une structure hybride métal/composite assemblée par collage structural. L'approche choisie est basée sur l'identification expérimentale du taux de restitution d'énergie, G, pour une sollicitation en mode I et II. L'éprouvette de type DCB (Double Cantilever Beam), qui a d’abord été adaptée pour être représentative de la structure hybride, permet de construire la R-Curve (évolution de G en fonction de la longueur de fissure, a) et d'étudier la cinétique de propagation de fissure sous sollicitations dynamiques. La même étude a été portée sur l’éprouvette ENF (End Notched Flexure). Une machine d’essais a été créée afin de réaliser les essais quasi-statiques et dynamiques. Un caisson thermique a été conçu pour faire des essais en température et regarder son impact sur les propriétés de la mécanique de rupture des adhésifs. L'originalité de ce travail est le pilotage des essais dynamiques à ΔG imposé, ce qui permet de s'affranchir de la dépendance de G à la longueur du dommage pour le mode I.Les résultats obtenus mettent en évidence les variations des vitesses de propagation (da/dN) à différentes conditions environnementales en mode I et II sur des assemblages composite/métal collés. / This thesis explains the analysis of damage propagation in a metallic/composite hybrid structure, assembled with structural adhesives. The chosen approach is based on the experimental identification of the energies release rates for a solicitation in mode I and II. The DCB (Double Cantilever Beam) specimen, which design was first adapted in order to adequately represent the hybrid structure, allows the construction of the R-Curve (evolution of G versus the crack length, a) and the study of the crack speed propagation under dynamic solicitations. The same study was carried out on the ENF specimen (End Notched Flexure).A testing machine was created in order to perform quasi-static and dynamic tests. A thermal chamber was designed to carry out temperature tests and observe the impact of the latter on the fracture mechanics properties of the adhesives. Performing dynamic tests with an imposed ΔG, which allows one to overcome the dependence of G to the damage length in mode I, is what makes this work original.The obtained results highlight the variation of the speed propagation in different environmental conditions, for mode I and II, on composite/metal bonded assemblies.

Cell walls are a distinct feature of plants and their chemical constituents, cellulose, hemicelluloses and lignin, are economically valuable. Plant fibres rich in cellulose, which mainly resides in their cell wall, are traditionally used in making paper and textiles. The changing global economic situation and environmental concerns have imparted necessity for renewable, but at the same time value added cellulosic materials. The Department of Wood Biotechnology, KTH together with its collaborators, have established EST libraries and performed transcript profiling during wood development in poplar, a tree considered as a model for wood development. The majority of the genes upregulated during cellulose biosynthesis encode proteins with known or predictable functions, such as carbohydrate active enzymes (CAzymes). However, some of them encode proteins with unknown functions. Characterization of these genes will potentially give additional opportunities to modify fibre properties. This thesis describes the discovery and characterization of a highly upregulated gene with a previously unknown function in poplar xylem, here denoted PttMAP20. Following its early discovery by mRNA profiling, the characterization was initiated with a thorough bioinformatic analysis, and the knowledge obtained was used to devise techniques for further functional analysis. Specific antibodies were raised, affinity purified and characterized. The antibodies were used as a tool for screening recombinant expression in E. coli and for the cellular localization of the protein in plant tissues, visualized with confocal and transmission electron microscopy. A purification protocol was developed for the expressed protein, followed by biochemical characterization. Appropriate model systems were used in both in vivo and in vitro studies. Fluorescently labelled protein transiently expressed in tobacco leaves was used for localization studies and the same system was used to characterize the molecular properties of the protein. Phenotypes arising from overexpressing the PttMAP20 gene were traced in the model plant Arabidopsis. All the results obtained so far indicate that PttMAP20 is a novel microtubule associated protein that binds to a cellulose biosynthesis inhibitor, DCB (2,6-dichlorobenzonitrile) and is required during cellulose biosynthesis in secondary cell walls. / QC 20100906

abstract: This research summarizes the validation testing completed for the material model MAT213, currently implemented in the LS-DYNA finite element program. Testing was carried out using a carbon fiber composite material, T800-F3900. Stacked-ply tension and compression tests were performed for open-hole and full coupons. Comparisons of experimental and simulation results showed a good agreement between the two for metrics including, stress-strain response and displacements. Strains and displacements in the direction of loading were better predicted by the simulations than for that of the transverse direction. Double cantilever beam and end notched flexure tests were performed experimentally and through simulations to determine the delamination properties of the material at the interlaminar layers. Experimental results gave the mode I critical energy release rate as having a range of 2.18 – 3.26 psi-in and the mode II critical energy release rate as 10.50 psi-in, both for the pre-cracked condition. Simulations were performed to calibrate other cohesive zone parameters required for modeling. Samples of tested T800/F3900 coupons were processed and examined with scanning electron microscopy to determine and understand the underlying structure of the material. Tested coupons revealed damage and failure occurring at the micro scale for the composite material. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2018

Le collage structural est une technique d’assemblage de plus en plus demandée aujourd’hui dans beaucoup de domaines comme l’automobile, l’aéronautique, l’aérospatial et dans d’autres domaines comme la construction, le sport et les loisirs. Cette technique très avantageuse, permet l’assemblage de matériaux semblables ou différents à l’aide d’un adhésif, la réduction importante du poids et la répartition uniforme des charges sur l’assemblage. Malgré ses avantages, le collage souffre encore de quelques inconvénients liés à l’existence de défauts dans les joints de colle. Parmi eux, il existe des défauts qui sont situés à l’interface colle/substrat comme un « kissing bond » ou un mauvais état de surface, qui restent indétectables ou difficilement détectables utilisant les techniques de contrôle non destructives. Donc, afin de prendre en compte l’existence des défauts d’adhésion dans les assemblages collés lors de la phase de conception, il est nécessaire de fournir un modèle analytique capable de prédire la propagation de fissure. Dans cette thèse, un modèle analytique qui prédit la propagation de fissure et qui évalue la résistance effective d’un assemblage collé contenant des défauts d’adhésion a été développé. Un défaut a généralement une géométrie complexe, et une étude générique est difficilement réalisable ce qui nous amène à considérer des géométries de défauts idéales. Le modèle a été vérifié par des expériences réalisées sur des éprouvettes DCB. Des simulations numériques utilisant la méthode de zone cohésive ont été réalisées également pour décrire plus complètement le processus de décohésion et simuler les essais expérimentaux. La dernière partie de ce travail a été dédiée à l’étude de la fissuration des éprouvettes en alliage de titane. Profitant de la collaboration avec Safran et Alphanov, les substrats ont subi un traitement de surface laser en laissant des zones non traitées. Le but de cette partie était de vérifier le modèle analytique proposé avec des configurations plus complexes. / Structural adhesive bonding has known an increasing use in many fields like aeronautics, aerospace and automotive and other fields like construction and sports. This very advantageous technique allows the assembly of similar or different materials using an adhesive, the significant reduction in weight and a uniform distribution of loads on the assembly. Despite its advantages, the bonding still suffers from some disadvantages related to the existence of defects in the bonded joints. Among them, there are defects that are located at the interface glue / substrate as "kissing bond" or poor surface due to bad surface treatment, which remain undetectable or hardly detectable using non-destructive control techniques. Therefore, in order to take into account the existence of adhesion defects in bonded assemblies during the design phase, it is necessary to provide an analytical model capable of predicting crack propagation and estimate the criticality of a defect. In this thesis, an analytical model that predicts crack propagation and evaluates the effective strength of a bonded assembly containing adhesion defects has been developed. A defect usually has a complex geometry, and a generic study is difficult to achieve, which leads us to consider ideal defect geometries. The model was verified by experiments performed on DCB specimens. Numerical simulations using the cohesive zone method were also performed to more fully describe the decohesion process and to simulate the experimental tests. The last part of this work was devoted to the study of titanium alloy assembly containing patterns. Taking advantage of the collaboration with Safran and Alphanov, the substrates underwent a laser surface treatment leaving untreated areas. The purpose of this part was to check the proposed analytical model with more complex configurations.

Cette thèse porte sur l'étude de la durée de vie de composants et modules de puissance dans des environnements thermiques sévères, lorsque les modules de puissance sont amenés à travailler à haute température ou sous des cycles de température de forte amplitude. Les domaines visés par cette étude concernent plus particulièrement des applications extrêmement contraignantes telles que les applications aéronautiques. Un module de puissance est un assemblage de plusieurs matériaux (semi-conducteurs, brasures, céramiques, conducteurs) présentant des propriétés mécaniques, notamment de coefficient de dilatation thermiques (CTE) différentes. Les pertes dans les puces actives et les variations de température ambiante (profils de mission) sont responsables de contraintes mécaniques liées aux différences de CTE entre les différents matériaux. Les modes de défaillance étant principalement d'origine mécanique, ces travaux ont été effectués entre le SATIE et le LMT (Institut Farman). L'étude mécanique a complété des travaux expérimentaux de caractérisation et de vieillissement accéléré de modules de puissance à semi-conducteur. Ces études ont nécessité la mise en place d'essais de vieillissement spécifiques, passifs (utilisation d'une étuve permettant de contraindre les assemblages de puissance sous des cycles thermiques de grande amplitude) et actifs (utilisation de régimes extrêmes de fonctionnement tels que le court-circuit pour accélérer le vieillissement de certaines parties de l'assemblage).La première partie de ce manuscrit présente les principes physiques mis en jeu. Nous présenterons succinctement les concepts de mécanique de la rupture ainsi que les couplages physiques.La deuxième partie porte sur la rupture de la céramique des substrats DCB. Cette rupture peut provenir de défauts répartis aléatoirement dans le matériau. Nous aborderons le problème par une approche statistique où nous introduirons la "Théorie du maillon faible". L'autre cause de rupture est la présence de défauts géométriques que l'on appelle singularité où il existe une concentration des contraintes nécessitant une approche déterministe. A cette occasion nous introduirons le facteur d'intensité des contraintes qui permet d'étudier les problèmes de rupture liés à des zones singulières.La dernière partie portera sur la dégradation de la métallisation du transistor. La recherche d'indicateurs de vieillissement a demandé la mise au point de différents bancs de caractérisation électrique pour la mesure fine de différentes grandeurs électriques (courants de fuite, tensions de seuil, chute de tension à l'état passant...) dans un environnement thermique contrôlé. De plus ces caractérisations électriques sont corrélées à des observations de la métallisation effectuées par un microscope électronique à balayage de manière régulière. Nous chercherons à montrer comment la modification de la morphologie de la métallisation peut modifier les caractéristiques électriques des transistors de puissance testés. / This PhD focuses on the study of the lifetime of components and power semiconductor modules under thermal constraints, when power devices are used at high temperature or under high temperature cycles. The areas covered by this study relate more particularly to extremely harsh applications such as aerospace constraints. A power device is an assembly of different materials (semiconductors, solders, ceramics, conductors) with mechanical properties, including coefficient of thermal expansion (CTE). Losses in the die and ambient temperature variations (mission pro les) are responsible for strain constraints at material interfaces due to CTE mismatch between the different materials. Failure modes result for mechanical constraints so study was done in collaboration between LMT and SATIE laboratories (Farman Institute). The mechanical study completed experimental characterizations and accelerated aging of power semiconductor modules. These studies involved the development of specific aging tests allowing thermal cycles (thermal air streamer to force the power assemblies under thermal cycles of high amplitude) and active power cycles (use of hard working conditions such as short circuit for accelerating the aging of parts of the assembly).The first part of this manuscript presents the physical principles set in. We briefly introduce the concepts of fracture mechanics and the physical couplings.The second part focuses on the fractured DCB ceramic substrates. This failure can arise from defects randomly distributed in the material. We consider the problem using a statistical approach where we introduce the "weak link theory". The other cause of failure is the presence of geometrical defects called singularity where there is stress concentration requiring a deterministic approach. On this occasion we introduce the stress intensity factor which allows to study the failure problems associated with singular zone.The last part will focus on the aging of the transistor metallization. The search for indicators of aging has requested the development of several electrical characterization test benches for the precise measurement of different electrical parameters (leakage currents, threshold voltages, voltage drop in the on state ...) in a controlled thermal environment. Moreover, these electrical characterizations are correlated with observations at different aging states of the metallization degradation using a scanning electron microscope. We seek to show how the change in the morphology of the metallization can change the electrical characteristics of tested power transistors.

The effect of the element length is examined in modelling crack growth in fatigue loading of an adhesive joint. This is done for a cohesive element using an expression for the damage evolution developed at the University of Skövde which is implemented using the UMAT subroutine in the FE-solver Abaqus. These analyses are done for pure mode I loading by analysing a DCB-specimen loaded by a pure moment. An expression is developed in which the critical element length is dependent on the geometry of the specimen (in the form of the wave number of the adhesive joint), the element length, the material properties of the adhesive (in form of the material parameters , , ), the load applied (in form of the stress in the crack tip), the time step used in the analysis and the crack growth rate. It is shown that the results converge by decreasing the element length and the time step used. Therefore an expression for the crack growth rate as a function of the remaining parameters can be determined. Another expression is thereafter developed for the element length needed in order to get a crack growth rate within a certain range of the critical element length. The results show a regular pattern but are not monotone. Therefor two different definitions of the critical element length are tested, either by defining the critical element length as the point where the error is greater than an arbitrary boundary of 1 % of a converged result or where a least square approximation of the error is within 1 % of the converged results. The first method shows a highly irregular result which makes it difficult to develop an expression out of these results. The second method on the other hand gives results that are predictable enough to develop a function out of them. This is done using a regression analysis with all parameters of a third order expression in order to get an expression.

Melding is a novel process which offers a promising route to creating seamless bonds, by partially curing two laminates in a controlled manner using a Quickstep chamber and subsequently co-curing them. Previous research has focused on melding lap joints in the x-y plane of a composite, whereas this study investigates through-thickness melding, or melding in the z-plane of a composite. In this process, two composite stacks were exposed to heat from one side and actively cooled on the other through the z-axis. The two semi-cured parts were then co-cured creating a monolithic part with a seamless bond.The initial stage of the project developed the semi-curing process. After unsuccessful attempts to produce a semi-cured part in a general purpose Quickstep chamber, due to excessive heat transfer, the process was moved to a hot press with independently controlled platens. The hot press succeeded because the platens were separated from each other by the composite plate, unlike the Quickstep bladders which, as they are designed to conform to the part, came into contact allowing for heat transfer. Thermocouples were embedded every 15 plies to quantify the temperature profiles generated through the laminate stack.The next stage of the project developed a process of joining the semi-cured panels to form a through-thickness melded part. The final process involved constraining the sides of the panel with cork edge dams and inserting woven glass fabric at the corners to allow for gasses to escape. However, the outer parts of the fully melded panel exhibited excessive porosity which had an adverse effect on mechanical properties. For example, whereas tensile and flexural moduli measured for material from the edges of the panels were comparable to values reported in literature, the properties of samples from the middle of the panels deteriorated significantly due to the porosity. Mode I interlaminar fracture energy was approximately 10% lower than values measured for panels fabricated in an autoclave.The entire curing process, from semi-curing to a fully melded panel, was characterized extensively. Differential scanning calorimetry was used to determine the degree of cure and values of glass transition temperature (Tg). The degree of cure of the material exposed to the hot side was approximately 50%, the middle 25%, whereas the cold side was only 15% cured. A corresponding Tg profile through the curing process was developed in which the Tg varied from 0 degrees C for the uncured resin to 245 degrees C in highly cured samples. After melding the sample, the degree of cure was found to be in excess of 99%. Rheological studies were carried out to determine the effects of the semi-curing process on resin flow during the melding cycle.Results showed that there was a large transition zone between uncured plies and solid (cured) plies.This thesis demonstrated the broad feasibility of through-thickness melding as a process to create thick composite laminates. However, the complexity of the process gives rise to thermal and rheological phenomena which affect the structural and chemical properties of the fully melded part. The process must therefore be engineered with these factors in mind in order to create a high quality part.

The following master thesis is conducted on behalf of The Royal Institute of Technology and Manetos AB with the purpose of investigating potential business markets for the new innovation, the Digital Circuit Breaker (DCB). The DCB is a mean for digitalising the distribution board, which is the middleman between households’ electrical appliances and the electrical grid. Through this digitalisation, a two-way communication between households and the grid can emerge, creating possibilities for demand side flexibility and energy management. The technology also provides more transparency for homeowners and real estate owners into households’ and buildings’ energy consumption, through monitoring and disaggregation. The study found that the energy landscape is facing significant challenges for the future. The integration of more intermittent energy, unpredictable energy consumption, new power consuming technologies and an aging grid were examples of challenges which potentially could jeopardize the security of electric supply. Many of these challenges however were also found to be issues which the DCB could potentially solve. It was also found that power-based tariffs spoke in favour of the DCB. Based on the overall empirical results, the study found that there is a need amongst utilities for demand side flexibility solutions and that there is a need amongst homeowners for electricity transparency and monitoring tools. This gives rise to a situation where the possibility to commercialize the DCB exists. By making the DCB a demand flexibility solution for utilities and a transparency and monitoring tool for homeowners, the needs for both utilities and homeowners can be fulfilled. The recommendations towards Manetos were to focus on the business markets electric utilities, more specifically municipally owned grid companies, and homeowners. It was found that the municipally owned grid companies focused more on socioeconomics than profit based grid companies. Furthermore, the municipally owned grid companies that had powerbased tariffs in place today showed great interest in the DCB as a tool for better managing electrical load and avoiding power peaks. For homeowners it was found that the people who owned electric vehicles or had direct electric heating showed great interest in an electricity management tool such as the DCB. The study also found real estate companies to be a business market of interest, however, not enough interviews were conducted in order to draw conclusions for the markets viability. Therefore, further investigation of the real estate company market is recommended. / Följande examensarbete har utförts på uppdrag av Kungliga Tekniska Högskolan och Manetos AB med syftet att undersöka potentiella affärsmarknader för en ny innovation kallad den Digitala Brytaren (DCB – Digital Circuit Breaker). DCBn är ett verktyg för att digitalisera elskåpet, vilket fungerar som en mellanhand mellan hushåll och elnätet. Denna digitalisering möjliggör för tvåvägskommunikation mellan hushåll och elnät, vilket öppnar upp möjligheter för efterfrågeflexibilitet och bättre energihushållning. Teknologin ökar även transparensen gällande byggnaders energikonsumtion, både för hushåll och fastighetsägare, genom övervakning och dissaggregering. Studien fann att energilandskapet står inför betydande utmaningar inför framtiden. Integrationen av mer intermittent energi, oförutsägbar energikonsumtion, nya teknologier och ett åldrande elnät är några exempel på utmaningar vilka kan komma att äventyra leveranssäkerheten i systemet. Många av dessa utmaningar visade sig dock vara problem som DCBn skulle kunna lösa. Studien fann även att effektbaserade tariffer, vilka idag används som ett verktyg för att motverka höga effektuttag, fungerar som incitament för DCBn och för en mer hållbar energikonsumtion generellt. Baserat på de övergripande empiriska resultaten fann studien att det finns ett behov för efterfrågeflexibilitets lösningar bland elnätsägare, samt ett behov för transparens- och kontroll-verktyg för villaägare. Detta ger möjlighet för att kommersialisera DCBn. Behoven hos både elnätsägare och villaägare kan uppnås genom att paketera DCBn som ett efterfrågeflexibilitets-, transparens- och övervaknings-verktyg. Rekommendationen till Manetos var att fokusera på kundsegmenten elnätsägare, främst de kommunalt ägda, samt villaägare. Studien fann att kommunalägda elnätsägare fokuserade mer på samhällsekonomi är de vinstdrivande elnätsföretagen. Vidare så fann studien att de kommunala elnätsägarna vilka idag använder effekt tariffer, hade ett stort intresse för DCBn som ett verktyg för att minska effekttoppar och uppnå bättre övervakning. För villaägare kunde det ses att de personer som ägde elbilar eller hade direktverkande el i bostaden visade störst intresse för ett verktyg såsom DCBn. Även kundsegmentet fastighetsägare visade sig vara av intresse, dock genomfördes inte ett tillräckligt stort antal intervjuer inom segmentet för att kunna dra slutsatser om marknadens lönsamhet. Därför föreslås undersökning av detta segment för vidare framtida studier, såväl som att undersöka potentialen för DCBn internationellt samt att inkludera ett större antal villaägare i studien.

In dieser Arbeit werden Postprocessing-Verfahren zum Steigern der Genauigkeit und Verfügbarkeit satellitengestützer Positionierungsverfahren, die ohne Inertialsensorik auskommen, untersucht. Ziel ist es, auch unter schwierigen Empfangsbedingungen, wie sie in urbanen Gebieten herrschen, eine Trajektorie zu erzeugen, deren Genauigkeit sie als Referenz für andere Verfahren qualifiziert. Zwei Ansätze werdenverfolgt: Die Verwendung von IGS-Daten sowie das Smoothing unter Einbeziehung von Sensoren aus der Fahrzeugodometrie. Es wird gezeigt, dass durch die Verwendung von IGS-Daten eine Verringerung des Fehlers um 50% bis 70% erreicht werden kann. Weiterhin demonstrierten die Smoothing-Verfahren, dass sie in der Lage sind, auch unter schlechten Empfangsbedingungen immer eine Genauigkeit im Dezimeterbereich zu erzielen.