Les nids d'abeille d’aluminium combinent légèreté et grande capacité d’absorption d'énergie. Ils sont alors de plus en plus utilisés dans les secteurs du transport (automobile, aéronautique …) pour contribuer conjointement à l’allègement structural et à la sécurité. Dans cette thèse, le comportement à l’écrasement des nids d'abeille est étudié en tenant compte de l'effet combiné de l'angle d'orientation dans le plan des cellules, de l’angle de chargement et de la vitesse de sollicitation, que la littérature ne relate pas. Un dispositif de chargement mixte compression/cisaillement est conçu pour mener l’étude expérimentale. L’analyse des résultats porte sur le pic initial d’effort, le plateau d’effort, ainsi que sur les modes de déformation. Les résultats montrent une augmentation de la résistance sous sollicitation dynamique dépendante de l’angle de chargement Ψ. Elle devient moins significative quand l’angle de chargement augmente jusqu’à atteindre un angle critique. Pour Ψ > Ψcritique, les réponses quasi-statiques sont même plus élevées que les réponses dynamiques. Une étude numérique est alors entreprise. Elle permet de comprendre ce phénomène qui est imputé aux mécanismes de déformation locaux des cellules. Les résultats numériques montrent également que l’effet de l’angle d’orientation □ dans le plan est plus prononcé sur la force tangentielle que sur la force normale, que cela influence également les modes d’effondrement et donc la réponse mécanique. Ces simulations numériques, couplées aux résultats expérimentaux, permettent alors de dissocier les composantes normale et tangentielle de la réponse des nids d’abeille et d’identifier les paramètres d'un critère macroscopique de résistance exprimé en fonction de la vitesse d'impact, de l'angle de chargement et de l'angle d'orientation dans le plan. Finalement, dans le but de réduire le coût des simulations numériques, un modèle élément fini (EF) réduit basé sur un critère de périodicité tenant compte de l'angle d'orientation dans le plan est proposé et son domaine de validité est évalué. / Aluminium honeycombs combine lightweight with an efficient energy absorption capability (specific energy). They are widely used as crash energy absorbing and protective structures in a wide range of transport applications (automotive, aircraft …) to reduce energy consumption and greenhouse gas emission. Reducing vehicle mass has however to be done while at least maintaining the same safety levels. In this thesis, the honeycomb behaviour is investigated under mixed shear-compression loadings taking into account the combined effect of the in-plane orientation angle and the impact velocity, which has not been deeply investigated in the literature. Experimental study based on an improvement of a mixed shear-compression loading device is realised. Experimental analysis focuses on the initial peak and average crushing forces as well as the deforming pattern modes. Comparing quasi-static and dynamic results, a dynamic enhancement depending of the loading angle Ψ is observed under mixed shear-compression loading until a critical loading angle (Ψcritical). Beyond, a negative enhancement is observed. Thus, a numerical study is carried out. The negative enhancement phenomenon is attributed to the collapse mechanisms which are affected by the loading angle Ψ. Numerical results also highlight that the in-plane orientation angle has an effect on the collapse mechanisms and consequently on the mechanical response. This effect is more pronounced on the tangential force than the normal force. The combined effect of the in-plane orientation angle and the loading angle is analysed on the three identified deforming pattern modes. Combining numerical and experimental results, the average crushing normal and shear forces are dissociated. Therefore, the parameters of a macroscopic yield criterion for the mixed shear-compression honeycomb behaviour depending of the impact velocity, the loading angle and the in-plane orientation angle are identified. Finally, in order to optimise the cost in CPU-time of the numerical simulation, a reduced FE model based on the periodicity procedure taking into account the in-plane orientation angle is proposed and its validity range is evaluated.

Wood is a complex organic orthotropic viscoelastic material with acellular structure. When stressed, wood will deform over timethrough a process called creep. Creep affects all wooden structureand can be difficult, time-consuming and expensive to measure. For this thesis, a simple computer model of the woodenmicrostructure was developed. The hypothesis was that the modelledmicrostructure would display similar elastic and viscoelasticproperties as the macroscopic material. The model was designed by finding research with cell geometries ofconiferous trees measured. The model considered late- and earlywoodgeometries as well as growth rings. Rays were ignored as they onlycomposed 5-10% of the material. By applying a finite element method, the heterogeneous late- andearlywood cells could be homogenized by sequentially loading thestrain vector and calculating the average stress. The computer model produced stiff but acceptable values for theelastic properties. Using the standard linear solid method to modelviscoelasticity, the computer model assembled creep curvescomparable to experimental results. With the model sufficiently validated, parametric studies on thecell geometry showed that the elastic and viscoelastic propertieschanged greatly with cell shape. An unconventional RVE was alsotested and shown to give identical result to the standard RVE. Although not perfect, the model can to a certain degree predict theelastic and viscoelastic characteristics for wood given itscellular geometry. Inaccuracies were thought to be caused byassumptions and approximations when building the model.

In this PhD thesis, we study the interplay between symmetry-breaking order and quantum-disordered phases in the milieu of frustrated quantum magnets, and further show how the excitation process of long-wavelength (semi-)classical modes in spin-orbit coupled antiferromagnets crucially depends on the nature and interactions of the underlying quantum quasiparticles. First, we focus on Kitaev's exactly solvable model for a Z2 spin liquid as a building block for constructing novel phases of matter, utilizing Majorana mean-field theory (MMFT) to map out phase diagrams and study occurring phases. In the Kitaev Kondo lattice, conduction electrons couple via a Kondo interaction to the local moments in the Kitaev model. We find at small Kondo couplings a fractionalized Fermi liquid (FL*) phase, a stable non-Fermi liquid where conventional electronic quasiparticles coexist with the deconfined excitations of the spin liquid. The transition between FL* and a conventional Fermi liquid is masked by an exotic (confining) superconducting phase which exhibits nematic triplet pairing, which we argue to be mediated by the Majorana fermions in the Kitaev spin liquid. We moreover study bilayer Kitaev models, where two Kitaev honeycomb spin liquids are coupled via an antiferromagnetic Heisenberg interaction. Varying interlayer coupling and Kitaev coupling anisotropy, we find both direct transitions from the spin liquid to a trivial dimer paramagnet as well as intermediate 'macrospin' phases, which can be studied by mappings to effective transverse-field Ising models. Further, we find a novel interlayer coherent pi-flux phase. Second, we consider the stuffed honeycomb Heisenberg antiferromagnet, where recent numerical studies suggest the coexistence of collinear Néel order and a correlated paramagnet, dubbed 'partial quantum disorder'. We elucidate the mechanism which drives the disorder in this model by perturbatively integrating out magnons to derive an effective model for the disordered sublattice. This effective model is close to a transition between two competing ground states, and we conjecture that strong fluctuations associated with this transition lead to disorder. Third, we study the generation of coherent low-energy magnons using ultrafast laser pulses in the spin-orbit coupled antiferromagnet Sr2IrO4, inspired by recent pump-probe experiments. While the relaxation dynamics of the system at long time scales can be well described semi-classically, the ultrafast excitation process is inherently non-classical. Using symmetry analysis to write down the most general coupling between electric field and spin operators, we subsequently integrate out high-energy spin fluctuations to derive induced effective fields which act to excite the low-energy magnon, constituting a generalized 'inverse Faraday effect'. Our theory reveals a tight relationship between induced fields and the two-magnon density of states.:1 Introduction 1.1 Frustrated antiferromagnets 1.2 Quantum spin liquids 1.3 Fractionalization and topological order 1.4 Spin-orbit coupling 1.5 Outline I Novel phases by building on Kitaev’s honeycomb model 2 Kitaev honeycomb spin liquid 2.1 Microscopic spin model and constants of motion 2.2 Majorana representation of spin algebra 2.3 Exact solution 2.3.1 Ground state 2.3.2 Correlations and dynamics 2.3.3 Thermodynamic properties 2.4 Z2 gauge structure 2.5 Toric code 2.6 Topological order 2.6.1 Superselection sectors and ground-state degeneracy 2.6.2 Topological entanglement entropy 2.6.3 Symmetry-enriched and symmetry-protected topological phases 3 Mean-field theory 3.1 Generalized spin representations 3.1.1 Parton constructions 3.1.2 SO(4) Majorana representation 3.2 Projective symmetry groups 3.3 Mean-field solution of the Kitaevmodel 3.4 Comparisonwithexactsolution 3.4.1 Spectral properties 3.4.2 Correlation functions 3.4.3 Thermodynamic properties 3.5 Generalized decoupling 3.6 Comparison to previous Abrikosov fermion mean-field theories of the Kitaev model 3.7 Discussion 4 Fractionalized Fermi liquids and exotic superconductivity in the Kitaev Kondo lattice 4.1 Metals with frustration 4.2 Local-moment formation and Kondo effect 4.2.1 Single Kondo impurity 4.2.2 Kondo lattices and heavy Fermi liquids 4.3 Fractionalized Fermi liquids 4.4 Construction of the Kitaev Kondo lattice 4.4.1 Hamiltonian 4.4.2 Symmetries 4.5 Mean-field decoupling of Kondo interaction 4.5.1 Solution of self-consistency conditions 4.6 Overview of mean-field phases 4.7 Fractionalized Fermi liquid 4.7.1 Results from mean-field theory 4.7.2 Perturbation theory beyond mean-field theory 4.8 Heavy Fermi liquid 4.9 Superconducting phases 4.9.1 Spontaneously broken U(1) phase rotation symmetry 4.9.2 Excitation spectrum and nematicity 4.9.3 Topological triviality 4.9.4 Group-theoretical classification 4.9.5 Pairing glue 4.10 Comparison with a subsequent study 4.11 Discussion and outlook 5 Bilayer Kitaev models 5.1 Model and stacking geometries 5.1.1 Hamiltonian 5.1.2 Symmetries and conserved quantities 5.2 Previous results 5.3 Mean-field decoupling and phase diagrams 5.3.1 AA stacking 5.3.2 AB stacking 5.3.3 σAC stacking 5.3.4 σ ̄AC stacking 5.4 Quantum phase transition in the AA stacking 5.4.1 Perturbative analysis 5.5 Phase transition in the σAC stacking 5.6 Macro-spin phases 5.6.1 KSL-MAC transition: Effective model for Kitaev dimers 5.6.2 DIM-MAC transition: Effective theory for triplon condensation 5.6.3 Macro-spin interactions and series expansion results 5.6.4 Antiferromagnet in the AB stacking 5.7 Stability of KSL and the interlayer-coherent π-flux phase 5.7.1 Perturbative stability of the Kitaev spin liquid 5.7.2 Spontaneous interlayer coherence near the isotropic point 5.8 Summary and discussion II Partial quantum disorder in the stuffed honeycomb lattice 6 Partial quantum disorder in the stuffed honeycomb lattice 6.1 Definition of the stuffed honeycomb Heisenberg antiferromagnet 6.2 Previous numerical results 6.3 Derivation of an effective model 6.3.1 Spin-wave theory for the honeycomb magnons 6.3.2 Magnon-central spin vertices 6.3.3 Perturbation theory 6.3.4 Instantaneous approximation 6.3.5 Truncation of couplings 6.3.6 Single-ion anisotropy 6.3.7 Discussion of most dominant interactions 6.4 Analysis of effective model 6.4.1 Classical ground states 6.4.2 Stability of classical ground states in linear spin-wave theory 6.4.3 Minimal model for incommensurate phase 6.4.4 Discussion of frustration mechanism in the effective model 6.5 Partial quantum disorder beyond the effectivemodel 6.5.1 Competition between PD and the (semi-)classical canted state 6.5.2 Topological aspects 6.5.3 Experimental signatures 6.6 Discussion 6.6.1 Directions for further numerical studies 6.6.2 Experimental prospects III Optical excitation of coherent magnons 7 Ultrafast optical excitation of magnons in Sr2IrO4 7.1 Pump-probe experiments 7.2 Previous approaches to the inverse Faraday effect and theory goals 7.3 Sr2IrO4 as a spin-orbit driven Mott insulator 7.4 Spin model for basal planes in Sr2IrO4 7.4.1 Symmetry analysis 7.4.2 Classical ground state and linear spin-wave theory 7.4.3 Mechanism for in-plane anisotropy 7.5 Pump-induced dynamics 7.5.1 Coupling to the electric field: Symmetry analysis 7.5.2 Keldysh path integral 7.5.3 Low-energy dynamics 7.5.4 Driven low-energy dynamics 7.6 Derivation of the induced fields 7.6.1 Perturbation theory 7.6.2 Evaluation of loop diagram 7.6.3 Analytical momentum integration in the continuum limit 7.6.4 Numerical evaluation of effective fields 7.7 Analysis of induced fields 7.7.1 Polarization and angular dependence 7.7.2 Two-magnon spectral features 7.8 Applications to experiment 7.8.1 Predictions for experiment 7.8.2 Magnetoelectrical couplings 7.9 Discussion and outlook 8 Conclusion and outlook 8.1 Summary 8.2 Outlook IV Appendices A Path integral methods B Spin-wave theory B.1 Holstein-Primakoff bosons B.2 Linear spin-wave theory B.2.1 Diagonalization via Bogoliubov transformation B.2.2 Applicability of linear approximation B.3 Magnon-magnon interactions B.3.1 Dyson's equation and 1/S consistency B.3.2 Self-energy from quartic interactions in collinear states on bipartite lattices C Details on the SO(4) Majorana mean-field theory C.1 SO(4) Matrix representation of SU(2) subalgebras C.2 Generalized SO(4) Majorana mean-field theory for a Heisenberg dimer (Chapter 3) C.3 Dimerization of SO(4) Majorana mean-field for the Kitaev model (Chapter3) C.4 Mean-field Hamiltonian in the Kitaev Kondo lattice (Chapter 4) C.5 Example solutions in the superconducting phase for symmetry analysis (Chapter4) D Linear spin-wave theory for macrospin phase in the bilayer Kitaev model (Chapter 5) D.1 Spin-wave Hamiltonian and Bogoliubov rotation D.2 Results and discussion E Extrapolation of the effective couplings for the staggered field h -> 0 (Chapter 6) E.1 xy interaction E.1.1 Leadingorder ~ S0 E.1.2 Subleadingorder ~ S^(−1) E.2 z-Ising interaction F Light-induced fields by analytical integration (Chapter 7) F.1 Method F.2 Results Bibliography

Un système SHM par ondes guidées a pour but d'évaluer l'intégrité d'une grande variété de structures fines, telles que les fuselages d'avions, les tuyaux, les réservoirs, etc. Un tel système est basé sur un réseau de capteurs piézoélectriques pour l'excitation et la mesure des ondes guidées. Cette méthode de SHM par ondes guidées est prometteuse pour l'inspection de structures de grande taille, ces ondes se propageant sur de grandes distances avec peu d'atténuation, tout en étant sensibles aux défauts surfaciques et subsurfaciques.Cette thèse présente les travaux menés dans le but de développer un système de SHM par ondes guidées capable de détecter, localiser et dimensionner efficacement les défauts dans des structures aéronautiques assimilables à des plaques, en matériaux composites ou en aluminium. Des simulations et des méthodes d'apprentissage sont utilisées pour déterminer les caractéristiques principales des ondes guidées propagées, notamment les vitesses de phase et de groupe ainsi que la fonction de Green 3D. Celles-ci sont ensuite utilisées pour traiter les signaux des ondes guidées afin de produire des images représentant l'intégrité des structures étudiées. Ce travail comprend également une étude approfondie des algorithmes d'imagerie DAS, MV et Excitelet, les plus prometteurs parmi ceux de la littérature, une évaluation de leurs performances par analyse statistique sur une grande base de données de résultats de simulations d'imagerie par ondes guidées et propose une méthode d'imagerie parcimonieuse.Alors que la détection et la localisation des défauts à partir de l'analyse des images est aisée, le dimensionnement du défaut est un problème plus complexe en raison de sa forte dimensionnalité et de sa non-linéarité. Il est démontré que ce problème peut être résolu par des méthodes d'apprentissage automatique sur une grande base de données de résultats de simulations d'imagerie par ondes guidées. Ces méthodes d'imagerie nécessitent cependant une référence, mesurée sur la structure dans un état supposé sain. Elles sont efficaces dans des conditions opérationnelles stationnaires mais sont sensibles aux variations de l'environnement et notamment aux fluctuations de température.Ce travail présente donc l'étude de la robustesse face aux effets thermiques des méthodes d'imagerie par ondes guidées et propose un modèle de détection de défauts capable d'analyser des résultats d'imagerie détériorés. Plusieurs techniques de compensation des effets thermiques sont étudiées et des améliorations sont proposées. Leur efficacité est validée pour les plaques d'aluminium mais des améliorations supplémentaires sont nécessaires pour les étendre aux plaques de composites. / A guided wave-based structural health monitoring (SHM) system aims at determining the integrity of a wide variety of plate-like structures, including aircraft fuselages, pipes, tanks etc. It relies on a sparse array of piezoelectric transducers for guided waves (GWs) excitation and sensing. With a number of benefits, these waves are standing out among other methods as a promising method for the inspection of large structures. They can propagate on significant distances with small attenuation while being sensitive to surface and subsurface defects.This thesis presents studies conducted with the purpose of developing such a GWs-based SHM system that is capable of efficient defect detection, localization and sizing aeronautical plate-like structures made of aluminum and composite materials. Simulation and data-driven approaches are presented for determining principal characteristics of propagating GWs, namely modal group and phase velocities, 3D Green's functions etc. in structures of interest. They are then used for GWs signals processing in order to compute images representing the integrity of studied structures. This work also provides a comprehensive overview of DAS, MV and Excitelet defect imaging algorithms, determines their performance using statistical analysis of an extensive dataset of simulated guided waves imaging (GWI) results and proposes a method for sparse defect imaging.While defect detection and localization are straightforward from the image analysis, the defect sizing is a more complex problem due to its high dimensionality and non-linearity. It is demonstrated that this problem can be solved by means of machine learning methods, relying on an extensive database of simulated GWI results. Aforementioned defect imaging methods are baseline demanding. They are efficient under stationary operational conditions but vulnerable to environmental variations, especially to the temperature fluctuation.Finally, this work presents studies on the robustness of GWI methods against thermal effects, and a defect detection model capable of analyzing deteriorated GWI results is proposed. Different techniques for thermal effects compensation are reviewed, and improvements are proposed. Their effectiveness is validated for aluminum plates but further improvements are required to translate these techniques to composite plates.

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Sontech International AB är ett företag som är specialiserade på ljudabsorbenter i metall och skum. De har tagit fram en ljudabsorbent i kartong med slitsar som går längs arket med ett avstånd på max 5 mm mellan dem. Denna produceras idag med en CNC-maskin och det tar 17 minuter per kvadratmeter att producera absorbenten med 5 mm mellan slitsarna. För att produkten ska vara lönsam behöver produktionstiden ned på en minut per kvadratmeter. Det är ett relativt litet företag med stora kunder och har därför inte tid eller resurser att lägga på att utveckla produktionen av den. Därför har författarna fått i ansvar att som examensarbete inom maskinteknik försöka utveckla och till sist presentera en färdig modell på en maskin för lösningen. Efter skisser, prototyper och val mellan tre färdiga modeller på föll valet på maskinen vid namn Krattan. Krattan drivs med två pneumatiska cylindrar som lyfter upp arket och drar vad som kallas krattan som består av 199 knivar tvärs över det. Produktionstiden uppskattas ha sjunkit till ca 20 sekunder per kvadratmeter kartongark. / Sontech International AB is a company that specializes in sound absorbents made of metal and foam. They have a new product that is a sound absorbent made of cardboard with cuts along the sheet of cardboard with a maximum distance between the cuts of 5 mm. This product is made with a CNC-machine and it takes 17 minutes per square meter to produce a sheet with 5 mm between each cut. To make the product viable the production time needs to come down to a minute per square meter. Sontech is are latively small company which is why they have not been able to spare the resources to develop a solution for manufacturing this product. The writers have based their thesis paper in mechanical engineering on developing and presenting a complete model of a machine as a method of production. After many sketches, prototypes and a selection between three different solutions they picked a machine that they refer to as ‘‘The rake’’. ‘’The rake’’ is powered by two pneumatic cylinders. One cylinder lifts the sheet of cardboard and either pushes or pulls ‘’the rake’’ part of the machine that is made of 199 blades. The production time is estimated to be about twenty seconds per square meter of cardboard.

Topological insulators are electronic materials that behave like an ordinary insulator in their bulk but have robust conducting states on their edge. Besides, in some materials the band structure presents completely flat bands, a special feature leading to strong interactions effects. In this thesis we present a study of the edge states of three particular two-dimensional models presenting flat bands: the honeycomb-Kagome, the $\alpha$--graphyne and a ligand decorated honeycomb-Kagome lattice models. We extend earlier work done on these lattice models by focusing on the topological nature of the edge states involving flat bands. We start by giving a review of the band structure theory and the tight-binding approximation. We then present several main topics in two-dimensional topological insulators such as the notion of topological invariants, the Kane-Mele model and the bulk-edge correspondence. Using these theoretical concepts we study the band structure of these lattices firstly without taking into account the spin and spin-orbit interations. We finally add these interactions to get their bulk band structures as well as the edge states. We observe how these spin-orbit interactions relieve degeneracies and allow for the emergence of edge states of topological nature. Since the lattices studied have an arrangement based on the honeycomb-Kagome lattice, two-dimensional materials having the structures of these lattices can be designed assembling metal ions and organic ligands. Therefore the results obtained could be used as a first hint to create new two-dimensional materials presenting topological properties. / Topologiska isolatorer är elektroniska material som uppför sig som en vanlig isolator i sin bulk men har robusta ledande stater på kanten. Dessutom presenterar bandstrukturen i vissa material helt platta band, en speciell egenskap som leder till starka interaktionseffekter. I denna avhandling presenterar vi en studie av kanttillstånden för tre speciella tvådimensionella modeller som presenterar platta band: bikakan-Kagome, $\alpha$-grafynen och en liganddekorerad honungskaka-Kagome modeller. Vi utökar tidigare arbete med dessa gittermodeller genom att fokusera på den topologiska karaktären hos kanttillstånd som innefattar platta band. Vi börjar med att ge en genomgång av bandstruktursteorin och den tätt bindande approximationen. Vi presenterar sedan flera huvudämnen i tvådimensionella topologiska isolatorer såsom begreppet topologiska invarianter, Kane-Mele modellen och bulk-kant korrespondensen. Med hjälp av dessa teoretiska begrepp studerar vi bandstrukturen för dessa gitter först utan att ta hänsyn till spinnen och spinnsorbital interaktioner. Vi lägger sedan till dessa interaktioner för att få sina bulkbandstrukturer såväl som kanttillstånden. Vi observerar hur dessa spinnsorbital interaktioner lindrar degenerationer och möjliggör uppkomsten av kanttillstånd av topologisk naturen. Eftersom de undersökta gitterna har ett arrangemang baserat på honungskaka-Kagome gitteren, kan tvådimensionella material med strukturerna hos dessa gitter utformas genom att montera metalljoner och organiska ligander. Därför kan de erhållna resultaten användas som en första ledtråd för att skapa nya tvådimensionella material med topologiska egenskaper.

Mobility is a symbol of dignity. A platform lift enables everyone of different physical abilities to move vertically with ease. Currently, the platform lift by Aritco Lift is made of steel sheet metal. It is heavy, thus difficult to handle. Sandwich design is researched to see whether and, if possible,how much dead load reduction. A simulation model is produced in SolidWorks to facilitate the material selection and the sandwich design. Sandwiches of aluminium face sheets are investigated, although steel face sheet works as well. No recommendation on core material can be made. Connection methods are investigated in SolidWorks to join the 35mm-thick sandwich-based floor to the lift body without creating a large deflection. Several general directions are investigated. None yielded results sufficiently satisfactory, although two directions have provided results that are very close to the requirements. Simulations are conducted on a 40mm-thick sandwich using one of the optimal joint options, yielding better weight savings and deflection results. Certain honeycomb properties are approximated using formulae rather than measured or simulated directly. To quantify how significant is the deviation of the approximated model, simulations are conducted by changing the length, width, and height of the sandwiches modelled using both the approximation and exact geometry. Fatigue life analyses are conducted on two of the candidate floors. Both are comfortably within the limit imposed by the standards. The success of a design in this thesis hinged on the validity of the honeycomb model. The test results reject the honeycomb model as the deflection is significantly higher than simulated. Plastic deformation has also occurred, though more probably due to the deformation local at the weld. Even though honeycomb is demonstrated not to be able to meet the requirements on its own, sandwich as a category of structure should not be discounted as a whole. Environmental factor is a drawback for using large quantities of aluminium even considering the weight difference between the design and the original steel structure. / Rörlighet är en symbol för värdighet. En plattformslyft gör att alla med olika fysiska förmågor kan röra sig vertikalt med lätthet. För närvarande är plattformslyften av Aritco Lift gjord av stålplåt. Den är tung och därför svår att hantera. Sandwichdesign undersöks för att se om och, om möjligt, hur mycket egenlastreduktion kan åstadkommas. En simuleringsmodell tas fram i SolidWorks för att underlätta materialvalet och sandwichdesignen. Sandwichkonstruktioner av aluminiumplåtar undersöks, även om stålplåt fungerar också. Ingen rekommendation om kärnmaterial kan ges. Fogningsmetoder undersöks i SolidWorks för att sammanfoga det 35 mm tjocka sandwichbaserade golvet till lyftkroppen utan att skapa en stor nedböjning. Flera allmänna riktningar utreds. Ingen av dessa gav tillräckligt tillfredsställande resultat, trots att två riktningar har gett resultatsom ligger mycket nära kraven. Simuleringar utförs på en 40 mm tjock sandwich med ett av de optimala fogalternativen, vilket ger bättre viktbesparingar och nedböjningsresultat än förväntat. Vissa bikakeegenskaper uppskattas med formler snarare än att mätas eller simuleras direkt. För att kvantifiera hur betydande avvikelsen av den approximerade modellen är, genomförs simuleringar där längden, bredden och höjden ändras på de modellerade sandwicharna med användning av både approximationer och data från den exakta geometrin. Utmattningsanalyser genomförs på två av designförslagen. Båda är bekvämt inom de gränser som ställs av standarderna. Framgången för en design i denna avhandling hängde på giltigheten av honeycomb-modellen. Testresultaten förkastar modellen eftersom nedböjningen är betydligt högre än simulerad. Plastiskdeformation har också förekommit, men troligen på grund av den lokala deformationen vid svetsen. Även om honeycomb har visat sig inte kunna uppfylla kraven på egen hand, bör sandwich som strukturkategori inte bortses från som helhet. Miljöfaktorn är en nackdel för att använda stora mängder aluminium även med tanke på viktskillnaden mellan konstruktionen och den ursprungliga stålkonstruktionen.

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Nous évaluons des films polymères poreux structurés en tant que nouveaux supports pour des photosensibilisateurs de l’oxygène singulet. L’objectif de cette association est l’obtention de matériaux photo-actifs à grande surface d’échange. Ces surfaces polymères, structurées ici en nid d’abeille, sont obtenues par la technique « breath figure » (trad. figure de souffle), à partir de polymères bien définis synthétisés par polymérisation radicalaire contrôlée par des nitroxydes (NMP), par transfert d’atome (ATRP) et par transfert réversible par addition/fragmentation (RAFT). Le photosensibilisateur rose Bengale a été greffé de manière covalente au polymère, soit par post-greffage sur un polymère précurseur, soit par modification d’un monomère fonctionnel puis copolymérisation de ce dernier avec du styrène. Ces différentes synthèses conduisent à des films contenant différents taux de rose Bengale. Les films ont été examinés en microscopie (fluorescence, confocale et champ large, électronique à balayage) afin d’établir la structuration des films et la localisation des espèces fluorescentes. L’efficacité des films polymères pour la photo-oxydation a été testée à l’interface liquide/solide en suivant par spectroscopie UV-visible la dégradation du dihydroxynaphtalène (DHN) ou de l’α-terpinène par l’oxygène singulet produit sous irradiation visible. Les films structurés sont environ cinq fois plus efficaces que les films non-poreux de même composition utilisés dans les mêmes conditions, ce qui s’explique par leur surface spécifique et par la localisation préférentielle du rose Bengale à la surface du matériau. / We evaluate structured porous polymer films as new substrates for photosensitizers of singlet oxygen, with a view to obtaining photo-active materials with high specific exchange areas. Here, honeycomb polymer films are obtained by the breath figure process, using well defined polymers synthesized by nitroxide-controlled radical polymerization (NMP), atom transfer polymerization (ATRP) and reversible addition/fragmentation transfer (RAFT). The photosensitizer, rose Bengal, is either post-grafted covalently to the polymer precursor, or pre-grafted to a monomer functional unit which is copolymerized with polystyrene. These syntheses lead to films with different rose Bengal concentrations. We determine the structure of the films and the location of the fluorescent dye by scanning electron microscopy and widefield and confocal microscopy. Efficiency of production of singlet oxygen was tested at a solid/liquid interface by monitoring the oxidation of dihydroxynaphthalene and α-terpinene, using UV-visible absorption spectroscopy. Honeycomb films are about five times more efficient than non-porous films of the same composition used in the same, as may be explained by their higher specific surface area and the preferential location of the photosensitizer at the film surface.