<p> To reduce cost of structural composites the development of more efficient manufacturing methods is of great interest. Sheet forming of thermoset prepreg, also known as hot drape forming, has been a promising manufacturing method for decades. An automatic tape layer (ATL) can be used to perform the lay-up in an efficient way. The flatly stacked unidirectional prepreg forms a sheet to be formed over a given mould. Knowledge about the materials forming behaviour is important to reach the required shape without flaws, such as wrinkles.</p><p>An experimental approach is developed to investigate the intra- (within the layer) and interply deformation. The intraply deformation properties are registered by the use of a bias-extension test and a digital image correlation (DIC) equipment. To measure the interlaminar (between the layers) friction in the prepreg/prepreg interface a specialized rig is designed and built.</p><p>The two tested materials are Cycom^® HTA/977-2 from Cytec and HexPly® T700/M21 from Hexel, which are examples of the second and third generation of carbon fibre/epoxy prepreg. Where M21 includes craze stoppers in form of thermoplastic particles, the 977-2 has the same function but in melted stage. These particles seem to influence both the intraply deformation modes and increase the level of friction between layers.</p><p>The results from the bias-extension test was compared with the theory of pin-jointed net (PJN) and it was found that M21 behaves accordingly. The measured rotation for 977-2 is less than the theoretical, this due to slippage. The rate of deformation seems to have an influence not only on the load level, but also in the mode of deformation. Both for the interlaminar and intraply deformation the resistance to motion were much larger for M21 than 977-2.</p> / KEKS (kostnadseffektiva kompositer)

To reduce cost of structural composites the development of more efficient manufacturing methods is of great interest. Sheet forming of thermoset prepreg, also known as hot drape forming, has been a promising manufacturing method for decades. An automatic tape layer (ATL) can be used to perform the lay-up in an efficient way. The flatly stacked unidirectional prepreg forms a sheet to be formed over a given mould. Knowledge about the materials forming behaviour is important to reach the required shape without flaws, such as wrinkles. An experimental approach is developed to investigate the intra- (within the layer) and interply deformation. The intraply deformation properties are registered by the use of a bias-extension test and a digital image correlation (DIC) equipment. To measure the interlaminar (between the layers) friction in the prepreg/prepreg interface a specialized rig is designed and built. The two tested materials are Cycom® HTA/977-2 from Cytec and HexPly® T700/M21 from Hexel, which are examples of the second and third generation of carbon fibre/epoxy prepreg. Where M21 includes craze stoppers in form of thermoplastic particles, the 977-2 has the same function but in melted stage. These particles seem to influence both the intraply deformation modes and increase the level of friction between layers. The results from the bias-extension test was compared with the theory of pin-jointed net (PJN) and it was found that M21 behaves accordingly. The measured rotation for 977-2 is less than the theoretical, this due to slippage. The rate of deformation seems to have an influence not only on the load level, but also in the mode of deformation. Both for the interlaminar and intraply deformation the resistance to motion were much larger for M21 than 977-2. / KEKS (kostnadseffektiva kompositer)

Carbon-carbon composite brakes are one third the weight of typical steel brakes, and they attain strength and frictional properties at temperatures up to 1600°C. C/C composite brakes can endure high temperatures, but in the presence of oxygen they will begin to oxidize at 400°C. Anti-oxidant systems must be applied to the non-rubbing surfaces of the C/C composite stators and rotors to prevent oxidation. Currently, commercial phosphorus based coating materials are made of crystalline metal phosphates that are derived from heat treated phosphoric acid-based liquid precursors painted on the non-rubbing surface of C/C composites. These crystalline metal phosphate coatings are very porous and tend to move to the friction surface when exposed to increased levels of relative humidity. This anti-oxidant migration towards the rubbing surface causes a drop in frictional properties. Migration reduction and oxidation inhibition was improved upon with advanced anti-oxidant systems. The advanced antioxidants analyzed protected the C/C composite from thermal and catalytic oxidation six to ten times better at 650°C than commercial materials. At 871°C, the antioxidants protected the C/C composite from thermal oxidation ten times better than commercial materials. Migration of the antioxidant to the rubbing surfaces was eliminated through the use of advanced antioxidant compositions. The predicted life of the antioxidants was modeled using Avrami's equation. Characterization of the antioxidants was further analyzed through the use of SEM, EDS, and XRD systems.

The electric car is a technically efficient driveline, although it is demanding in terms of the primary energy source. Most trips are below 50 km and the mean power required for maintaining speed is quite low, but the system has to be able to both provide long range and high maximum power for acceleration. By separating power and energy handling in a hybrid driveline, the primary energy source, e.g. a battery can be optimised for specific energy (decreasing costs and material usage). Kinetic energy storage in the form of flywheels can handle the short, high power bursts of acceleration and decceleration with high efficiency. This thesis focuses on the design and construction of flywheels in which an electric machine and a low-loss magnetic suspension are considered an integral part of the composite shell, in an effort to increase specific energy. A method of numerically optimising shrink-fitted composite shells was developed and implemented in software, based on a plane stress assumption, with a grid search optimiser. A composite shell was designed, analysed numerically and constructed, with an integrated permanent magnet synchronous machine. Passive axial lift bearings were optimised, analysed numerically for losses and lift force, and verified with experiments. Active radial electromagnets optimised for high stiffness per ohmic loss were built and analysed in terms of force and stiffness, both numerically and experimentally. Electronics and a high-speed measurement system were designed to drive the magnetic bearings and the electric machine. The control of these systems were implemented in an FPGA, and a notch-filter was designed to suppress eigenfrequencies to achieve levitation of the rotor. The spin-down losses of the flywheel in vacuum were found to be 1.7 W/Wh, evaluated at 1000 rpm. A novel switched reluctance machine concept was developed for hollow cylinder flywheels. This class of flywheels are shaft-less, in an effort to avoid the shaft-to-rim connection. A small-scale prototype was built and verified to correspond well to analytical and numerical models, by indirect measurement of the inductance through a system identification method.

The price of crude glycerol has significantly decreased worldwide because of its oversupply. Many chemical and biological processes have been proposed to transform glycerol into numerous value-added products, such as glycolic acid, 1,3-propanediol (1,3-PDO), 1,2-propanediol (1,2-PDO), glyceric acid, and lactic acid. However, these processes suffer from several drawbacks, including high production cost. Therefore, in this study, a simple and robust electrochemical synthesiswas developed to convert glycerol into various value-added compounds. This study reports for the first time the use of Amberlyst-15 as a reaction mediumand redox catalyst for electrochemical conversion of glycerol. In the first part, the electrochemical performance of Amberlyst-15 over platinum (Pt)electrode was compared with that of conventional acidic (H2SO4) and alkaline (NaOH) media. Other parameters such as reaction temperature [room temperature (27°C) to 80 °C] and applied current (1.0 A to 3.0 A) were also examined. Under the optimized experimental condition, this novel electrocatalytic method successfully converted glycerol into glycolic acid after 8 h of electrolysis, with a yield of 45% and selectivity of 65%, as well as to glyceric acid after 3 h of electrolysis, with a yield of 27% and selectivity of 38%. In the second part of this study, two types of cathode electrodes, namely, activated carbon composite(ACC) and carbon black diamond (CBD) electrodes, were used in electrochemical conversion of glycerol. To the best of our knowledge, electrochemical studies of glycerol conversion using these electrodes have not been reported yet. Glycerol was also successfully reduced to lactic acid, 1,2-PDO, and 1,3-PDO, in addition to oxidation compounds (e.g. glycolic acid). Three operating parameters, namely, catalyst amount (6.4% to 12.8% w/v), reaction temperature [room temperature (27 °C) to 80 °C], and applied current (1.0 A to 3.0 A), were tested. In the presence of 9.6% w/v Amberlyst-15 at 2.0 A and 80 °C, the selectivity of glycolic acid can reach 72% and 68% (with yield of 66% and 58%) for ACC and CBD electrodes, respectively. Lactic acid was obtained as the second largest compound, withselectivity of 16% and yield of 15% for the ACC electrode and 27% selectivity and 21% yield for the CBD electrode. Finally, electro-oxidation and electroreduction of glycerol were performed in a two-compartment cell separated by a cation exchange membrane (Nafion 117). This study only focused on the electroreduction region. Three cathode electrodes (Pt, ACC, and CBD) were evaluated under the following conditions: 2.0 A, 80 °C, and 9.6% w/v Amberlyst-15. ACC demonstrated excellent performance in the electroreduction study and successfully reduced glycerol to 1,2-PDO, with a high selectivity of 85%. The selectivity of 1,2-PDO on Pt and CBD was 61% and 68%, respectively. Acetol and diethylene glycol were also obtained. The reaction mechanisms underlying the formation of these products are then proposed.

A number of investigators have reported enhancement in oxidation and wear resistant of carbon-carbon composites (CCC) in the presence of protective coating layers. However, application of a surface and subsurface coating system that can preserve its oxidation and wear resistance along with maintaining lubricity at high temperature remains unsolved. To this end, thermodynamically stable protective oxides (ZnO/Al2O3/ZrO2) have been deposited by atomic layer deposition (ALD) to infiltrate porous CCC and graphite foams in order to improve the thermal stability and wear resistance in low and high speed sliding contacts. Characterization of microstructural evolution was achieved by using energy dispersive x-ray spectroscopy (EDS) mapping in scanning electron microscope (SEM) coupled with focused ion beam (FIB), x-ray tomography, high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD). Evaluation of the tribological properties of CCC coated with abovementioned ALD thin films were performed by employing low speed pure sliding tribometer and a high speed/frequency reciprocating rig to simulate the fretting wear behavior at ambient temperature and elevated temperatures of 400°C.It was determined with x-ray tomography imaging and EDS mapping that ALD ZnO/Al2O3/ZrO2 nanolaminates and baseline ZrO2 coatings exhibited excellent conformality and pore-filling capabilities down to ~100 μm and 1.5 mm in the porous CCC and graphite foam, respectively, which were dependent on the exposure time of the ALD precursors. XRD and HRTEM determined the crystalline phases of {0002} textured ZnO (wurtzite), amorphous Al2O3, and {101}-tetragonal ZrO2. Significant improvements up to ~65% in the sliding and fretting wear factors were determined for the nanolaminates in comparison to the uncoated CCC. A tribochemical sliding-induced mechanically mixed layer (MML) was found to be responsible for these improvements. HRTEM confirmed the presence of a high density of ZnO shear-induced basal stacking faults inside the wear tracks responsible for intrafilm shear velocity accommodation that mitigated friction and wear.

This work is focused on optimalisation of coposite materials for civil engineering. In the theoretical part of the project is introduction of the composite materials and materials which are used for their production. There are also concerned their properties and possible application areas. In conclusion of theoretical part this project is a summary of the possible use of composite materials. The practical part compares the characteristics of the different types of composites made in terms of conductivity and the rate of corrosion.

L’utilisation d’un composite Carbone/Carbone 2D est envisagée pour des pièces de structure, travaillant entre 150 et 400°C, dans l’aéronautique civile. Dans ce domaine de température, la durabilité de ces matériaux n’est pas connue car ils n’ont jamais été développés pour de telles applications. Une première approche a permis de corréler la réactivité chimique des constituants élémentaires (fibres et matrices) à leur état d’organisation structurale. Les vieillissements réalisés sur matériau composite ont ensuite mis en évidence qu’un faible taux d’oxydation pouvait conduire à un abaissement significatif des propriétés mécaniques résiduelles. Les fissures et les décohésions consécutives au procédé d’élaboration conduisent à une oxydation préférentielle du composé le plus réactif et à la ruine prématurée du composite par délaminage. L'évolution des propriétés de ce matériau sur de longues durées est finalement discutée afin d’évaluer sa capacité à remplacer les matériaux métalliques dans des pièces aéronautiques. / A 2D Carbon/Carbon composite is envisaged for structural parts, operating between 150 and 400°C, in civil aircraft. In this temperature range, the durability of these materials remains unknown because they have never been developed for this kind of applications. A first approach allowed us to correlate the chemical reactivity of the elemental constituents (fiber and matrix) to their structural organization. Then, thermal ageing tests performed on the composite material have demonstrated that a low rate of oxidation could be responsible to a significant reduction of residual mechanical properties. Cracks and fiber/matrix debonding resulting to the elaboration process create an extended pathway to a preferential oxidation of the most reactive compound. This latter is followed by a premature failure by delamination. The reduction of the material properties over long periods is finally discussed in order to evaluate its ability to replace metallic materials in aircraft structural parts.

L'objectif de ce travail est de développer de nouveaux matériaux carbonés dont la structure poreuse est contrôlée en taille et en morphologie dès l'étape de synthèse. Nous nous sommes tout d'abord intéressés à la technique de nanomoulage. Nous avons, tout d'abord, cherché à optimiser les conditions de synthèse de la réplique carbonée de la zéolithe EMC-2 (EMT) qui a l'avantage de conduire à un diagramme de diffraction bien résolu. Ensuite, différentes zéolithes ont été utilisées comme moule en s'appuyant sur les conditions optimales définies par la première étude. Dans un troisième temps, nous avons étudié la capacité d'adsorption et de séparation de gaz à température ambiante de la réplique carbonée de la zéolithe Y (FAU). L'inconvénient de cette technique est qu'elle est multi-étapes et de grandes quantités ne peuvent être obtenues. Aussi, nous avons cherché à développer d'autres méthodes d'obtention de carbones poreux. Nous nous sommes alors intéressés à la synthèse basée sur l'auto-assemblage entre un tensioactif structurant et un polymère précurseur de carbone. Nous avons cherché à comprendre le mécanisme de formation de ces matériaux et l'influence des différents paramètres de synthèse. Ce type de synthèse permet également l'obtention de composites silice/carbone mésoporeux lorsqu'un précurseur silicique est ajouté au milieu de synthèse. En outre, nous avons étudié la synthèse et la caractérisation de composites obtenus par « tapissage » des pores d'un matériau silicique par une couche de carbone. Les matériaux obtenus présenteraient alors des pores de plus petits diamètres dont la surface aurait des caractéristiques proches de celles de matériaux carbonés. / The aim of this work is to develop new carbon materials with controlled pore structure and to control the size and the morphology of pore structure during the synthesis step. First we interested to the nanocasting technique and to optimise the synthesis conditions in order to obtain the carbon replica of zeolite EMC-2 (EMT). The use of this zeolite allow to obtain well resolved X-ray diffraction pattern. Then carbon replicas have been obtained by using various zeolites as mould and the optimal conditions defined during the first study. The adsorption and separation capacities of carbon replica of zeolite Y (FAU) have been studied. But this technique is multi-step and it is not possible to obtain large quantities. Also other methods in order to obtain porous carbons have been developped. We interested to the synthesis by self-assembly between surfactant as structuring agent and polymer as carbon precursor. We tried to understand the formation mechanism and the inflence of synthesis parameters. Theses types of synthesis allows to obtain mesoporous silica/carbon composite if silicic precursor is added. Moreover, we studied the synthesis and the characterization of carbon-coated porous silica. The obtained materials have pores with smaller diameters but their surfaces have the same characterics than carbon materials.

Afin de comprendre les mécanismes d’usure et de frottement des composites carbone/carbone (C/C) utilisés en freinage aéronautique, un modèle numérique est utilisé pour dissocier les effets mécaniques des effets physico-chimiques et thermiques. Le modèle repose sur l’utilisation d’une approche par éléments finis et de techniques d’homogénéisation appliquées à un volume élémentaire représentatif (VER) du matériau à l’échelle mésoscopique frottant sur une surface rigide ou déformable. A cette échelle, le matériau est décrit par une matrice en carbone et des paquets de fibres de carbone appelés torons, perpendiculaires à la surface frottante. Pour assurer la représentativité de la structure du matériau, plusieurs modèles hétérogènes sont étudiés. Les résultats sont comparés à ceux obtenus avec le modèle homogène équivalent qui découle de l’homogénéisation. L’influence des conditions de contact (la rigidité), ainsi que l’influence de la distribution des torons proches de la surface frottante sur les régimes de vibrations des différents modèles sont mises en évidence. L’extension du modèle numérique à un contact entre deux composites a mis en évidence une forte augmentation des contraintes maximales localisées principales dans les torons présents à la surface frottante. Ces fortes localisations de contraintes peuvent avoir pour conséquence l’endommagement des torons ce qui induit la dégradation de la surface frottante jusqu’aux détachements de particules. / To understand the mechanisms of wear and friction of carbon 1 carbon composites (C/C} used in aeronautical braking, a numerical model is used to separate the mechanical effects of the physico-chemical and thermal effects. The model is based on the use of an approach by finite elements (FE} and techniques of homogenization applied to a representative elementary volume (RVE} of the material in the mesoscopic scale rubbing on a rigid or deformable surface. In this scale, the material is described by a matrix in carbon and packages of carbon fiber called strands, perpendicular on the contact surface. To insure the representativeness of the structure of the material, several heterogeneous models are studied. The results are compared with those obtained with the equivalent homogeneous model which ensues from the homogenization. The influence of the conditions of contact (the rigidity), as well as the influence of the distribution of strands at the contact surface on the regimes of vibrations of the various models are revealing. The extension of the numerical model in a contact between two composites underline a strong increase of maximal constraints mainly localized in the strands present on the contact surface. These strong localizations of constraints can have for consequence the damage of strands what leads the degradation of the contact surface until the detachments of particles.