Die moderne Architektur ist durch gläserne Fassaden und ausgefallene Konstruktionen aus Glas geprägt. Dabei wird Glas nicht nur als raumabschließendes Element verwendet, sondern auch konstruktiv eingesetzt und zunehmend an der Lastabtragung beteiligt. Die Integration von Glaselementen in die Baukonstruktion erfolgt über linien- oder punktförmige Lagerungen. Dabei können mechanisch ausgeführte Halterungen lokale Beanspruchungen und damit Glasversagen verursachen. Eine Alternative bilden Klebverbindungen, welche ein materialgerechtes Konstruieren im Glasbau ermöglichen. Kommerziell wird hierfür eine Vielzahl von Klebstoffen angeboten. Neben der Auswahl eines geeigneten Klebstoffsystems können dauerhafte adhäsive Verbindungen aber meist nur mit Hilfe von Oberflächenvorbehandlungen der Fügeteile gewährleistet werden. Aufgrund der langen Standzeiten von Bauwerken sind große Beständigkeiten von geklebten Verbindungen notwendig, welche nur durch den Aufbau von möglichst hohen Haftungskräften zwischen Fügeteiloberflächen und Klebstoffpolymer erreichbar sind. Spezielle Vorbehandlungsverfahren sorgen für eine bessere Benetzbarkeit der Oberflächen und schaffen zudem energetisch aktive Zentren, die mit den Klebstoffen in Wechselwirkung treten können. Viele der insbesondere für metallische Materialien industriell etablierten Oberflächenvorbehandlungen sind allerdings wenig zukunftsträchtig, da diese Verfahren häufig den Einsatz ätzender, hochgiftiger und umweltgefährdender Substanzen notwendig machen. Hierin liegt der Ansatzpunkt der vorliegenden Arbeit. In verschiedenen Industriebereichen, wie dem Automobilbau, der Elektrotechnik und der Dentalmedizin werden bereits neu entwickelte Oberflächenvorbehandlungsverfahren auf Basis von Plasma- und Abscheidungstechnologien eingesetzt. Daraus ergibt sich die Fragestellung nach der Anwendbarkeit solcher Verfahren auf Fügeteilmaterialien des Konstruktiven Glasbaus und nach dem Nutzen dieser Oberflächenvorbehandlungen in Bezug auf die Optimierung von strukturellen Klebungen. Für die Ermittlung optimaler Eigenschaften von Oberflächen für den klebtechnischen Prozess werden ausgewählte Fügeteile aus Edelstahl, Aluminium und Messing sowie Einscheibensicherheitglas aus Kalk-Natronsilikatglas physikalischen und chemischen Oberflächenanalysen vor und nach der Anwendung von vier verschiedenen Oberflächenvorbehandlungsverfahren unterzogen. Zudem werden die Haftungseigenschaften nach der Vorbehandlung an geklebten Prüfkörpern vor und nach Alterung untersucht. Aus den daraus erhaltenen Ergebnissen wird der Einfluss der Oberflächenbeschaffenheit auf die Festigkeit der Klebverbindungen bestimmt. Die durchgeführten Untersuchungen ergeben sehr unterschiedliche, stark substrat- und klebstoffabhängige Wirkungsweisen der einzelnen Oberflächenvorbehandlungen. Als geeignetes Verfahren in Bezug auf die Verbesserungen des Adhäsionsvermögens und der Alterungsbeständigkeit, die Integrierbarkeit in maschinelle Herstellungsprozesse und die Vermeidung optischer Veränderung der Oberflächen stellt sich die Flammensilikatisierung heraus. Die mit dieser Oberflächenvorbehandlung aufgebrachte, dichte Silikatschicht und deren chemische Aktivität sowie deren vollständige Benetzbarkeit bieten beste Voraussetzungen für die Verklebung verschiedener Fügeteilmaterialien mit unterschiedlichsten Klebstoffen. / The modern architecture is affected by glass facades and novel glass structures. Therein glass is not only used as space enclosing element, rather it finds more and more constructive application and it is increasingly involved in load transfer. State of the art for the integration of glass elements in buildings are mechanically designed point and linear fixings. But they may cause local stresses followed by glass breakage. An alternative to these fixations are adhesive joints which more respect the specific requirements of the fragile material glass. A wide variety of adhesives is already available for this purpose. For strong adhesive joints not only the selection of a suitable adhesive is essential. The surface quality, which can be enhanced by surface treatments, is just as important for a very good adhesion. Due to the long life expectancy of buildings, a permanently aging resistance of the adhesive joints is necessary. For that, a formation of the highest possible adhesion forces between adhesive polymer and adherend surface is essential. Special surface treatment processes ensure a better wettability of the surfaces and also create energetically active sites that can interact with the adhesive molecules. However, many of the industrially established surface pretreatments, especially those for metallic materials, are not sustainable, since these methods often use corrosive, highly toxic and environmentally hazardous substances. This is the basis of the present dissertation. In various industries, such as automotive, electrical engineering and dentistry, newly developed surface treatment methods based on plasma and deposition technologies are already used. This raises the question of the applicability of such methods on materials for glass constructions and of their benefit to the optimization of structural adhesive joints. The effect of four different surface treatment methods used on the surfaces of stainless steel, aluminum, brass and toughened safety glass made from soda-lime glass is investigated in experimental studies. Physical and chemical surface analyses are performed before and after the applications. In addition, the adhesion properties of bonded specimens with pretreated surfaces are examined before and after aging. The influence of the surface conditions on the strength of the adhesive joints is determined from the obtained results. The results show very different effects of the individual surface treatment methods with high dependences on substrate and adhesive. With regard to an increase of adhesion strength, a good aging resistance, an uncomplicated integration into automated production processes and an avoidance of changing the optical surface properties, the investigated combustion chemical vapour deposition is the most suitable method. With this pretreatment, a dense silicate layer is deposite on the surface. Its high chemical activity and its complete wettability offer the best conditions for bonding a variety of materials with different adhesives.

Damages of metallic aircraft structures that occur during manufacturing, assembly and in service require local repair. Especially with current service-life extensions of ageing aircraft fleets, the importance of such repair methods is increasing. Typically, the repair of smaller damages on aluminium fuselage or wing skins is done by riveting a patch onto the flawed structure. However, the use of rivets reduces the strength of the structure and promotes fatigue. Joining the patch by adhesive bonding would not only offer more homogenous load distribution and weight savings, but even an increase of structural integrity. Metal adhesive bonding is commonly used in aeronautics, but requires elaborated surface treatments of the adherends, employing hazardous chemicals like chromates, due to the high durability demands. Furthermore, these treatments are usually tank processes that are not suitable for local repairs. Hence, there is a strong need for locally applicable surface preparation methods that allow safe and reliable adhesive bonding of primary aircraft structures. The aim of this thesis is to assess the – still emerging – method of atmospheric pressure plasma deposition of silicon (Si) containing compounds concerning its suitability as surface preparation for adhesive bonding of aluminium aerostructures. Atmospheric plasma deposition is not yet used in the aircraft industry, and the knowledge on functionality of this technology concerning bonding of aluminium parts is limited. Moreover, the durability requirements of the aircraft industry greatly exceed the standards in other industries. Hence, special attention is paid to a thorough analysis of the key characteristics of the deposited coupling films and their effectiveness in terms of adhesion promotion as well as joint durability under particularly hostile conditions. In order to do so, the altering mechanisms of the treated joints and the behaviour of the coupling films during accelerated ageing will be investigated in detail for the first time in this thesis. Furthermore, the influence of the aluminium surface pre-treatment (i.e. topography and oxide properties of the substrate) on the overall joint performance after coupling film deposition is thoroughly examined. Based on these findings, the surface preparation is optimised, and a process is developed to achieve maximal joint performance. As alternative local surface treatments prior to adhesive bonding, solution derived deposition of silane and sol-gel films have already been widely investigated and can be considered as reference, even though these techniques are rarely used in civil aeronautics. The knowledge on their effectiveness and capabilities in corrosive atmosphere is still very limited. Therefore, all analyses of degradation mechanisms are conducted for both plasma deposition and wet-chemical reference treatments to reveal the differences and communalities of the two Si-based coupling films. Physical and chemical analysis of the films, the oxides and the interfaces reveal differing, but interdependent failure mechanisms that are inhibited differently by the individual coupling films. Using the optimum deposition parameters, plasma films of only several nanometres in thickness significantly enlarge the corrosion resistance of bonded joints, reaching almost the level of anodising treatments with several micrometres thick oxides and strongly outperforming solution derived silane treatments. However, plasma film performance is found to be largely dependent on the precursor selection. With plasma deposition of 3-glycidoxypropyltrimethoxysilane, which has not been reported before, highest joint stability is achieved. Moreover, it is discovered that the properties of plasma and solution derived silane based films are complementary. It is shown that an optimised combined plasma and wet-chemical treatment process provides even superior resistance to bondline corrosion than state-of-the-art anodising techniques.

Die moderne Architektur ist durch gläserne Fassaden und ausgefallene Konstruktionen aus Glas geprägt. Dabei wird Glas nicht nur als raumabschließendes Element verwendet, sondern auch konstruktiv eingesetzt und zunehmend an der Lastabtragung beteiligt. Die Integration von Glaselementen in die Baukonstruktion erfolgt über linien- oder punktförmige Lagerungen. Dabei können mechanisch ausgeführte Halterungen lokale Beanspruchungen und damit Glasversagen verursachen. Eine Alternative bilden Klebverbindungen, welche ein materialgerechtes Konstruieren im Glasbau ermöglichen. Kommerziell wird hierfür eine Vielzahl von Klebstoffen angeboten. Neben der Auswahl eines geeigneten Klebstoffsystems können dauerhafte adhäsive Verbindungen aber meist nur mit Hilfe von Oberflächenvorbehandlungen der Fügeteile gewährleistet werden. Aufgrund der langen Standzeiten von Bauwerken sind große Beständigkeiten von geklebten Verbindungen notwendig, welche nur durch den Aufbau von möglichst hohen Haftungskräften zwischen Fügeteiloberflächen und Klebstoffpolymer erreichbar sind. Spezielle Vorbehandlungsverfahren sorgen für eine bessere Benetzbarkeit der Oberflächen und schaffen zudem energetisch aktive Zentren, die mit den Klebstoffen in Wechselwirkung treten können. Viele der insbesondere für metallische Materialien industriell etablierten Oberflächenvorbehandlungen sind allerdings wenig zukunftsträchtig, da diese Verfahren häufig den Einsatz ätzender, hochgiftiger und umweltgefährdender Substanzen notwendig machen. Hierin liegt der Ansatzpunkt der vorliegenden Arbeit. In verschiedenen Industriebereichen, wie dem Automobilbau, der Elektrotechnik und der Dentalmedizin werden bereits neu entwickelte Oberflächenvorbehandlungsverfahren auf Basis von Plasma- und Abscheidungstechnologien eingesetzt. Daraus ergibt sich die Fragestellung nach der Anwendbarkeit solcher Verfahren auf Fügeteilmaterialien des Konstruktiven Glasbaus und nach dem Nutzen dieser Oberflächenvorbehandlungen in Bezug auf die Optimierung von strukturellen Klebungen. Für die Ermittlung optimaler Eigenschaften von Oberflächen für den klebtechnischen Prozess werden ausgewählte Fügeteile aus Edelstahl, Aluminium und Messing sowie Einscheibensicherheitglas aus Kalk-Natronsilikatglas physikalischen und chemischen Oberflächenanalysen vor und nach der Anwendung von vier verschiedenen Oberflächenvorbehandlungsverfahren unterzogen. Zudem werden die Haftungseigenschaften nach der Vorbehandlung an geklebten Prüfkörpern vor und nach Alterung untersucht. Aus den daraus erhaltenen Ergebnissen wird der Einfluss der Oberflächenbeschaffenheit auf die Festigkeit der Klebverbindungen bestimmt. Die durchgeführten Untersuchungen ergeben sehr unterschiedliche, stark substrat- und klebstoffabhängige Wirkungsweisen der einzelnen Oberflächenvorbehandlungen. Als geeignetes Verfahren in Bezug auf die Verbesserungen des Adhäsionsvermögens und der Alterungsbeständigkeit, die Integrierbarkeit in maschinelle Herstellungsprozesse und die Vermeidung optischer Veränderung der Oberflächen stellt sich die Flammensilikatisierung heraus. Die mit dieser Oberflächenvorbehandlung aufgebrachte, dichte Silikatschicht und deren chemische Aktivität sowie deren vollständige Benetzbarkeit bieten beste Voraussetzungen für die Verklebung verschiedener Fügeteilmaterialien mit unterschiedlichsten Klebstoffen. / The modern architecture is affected by glass facades and novel glass structures. Therein glass is not only used as space enclosing element, rather it finds more and more constructive application and it is increasingly involved in load transfer. State of the art for the integration of glass elements in buildings are mechanically designed point and linear fixings. But they may cause local stresses followed by glass breakage. An alternative to these fixations are adhesive joints which more respect the specific requirements of the fragile material glass. A wide variety of adhesives is already available for this purpose. For strong adhesive joints not only the selection of a suitable adhesive is essential. The surface quality, which can be enhanced by surface treatments, is just as important for a very good adhesion. Due to the long life expectancy of buildings, a permanently aging resistance of the adhesive joints is necessary. For that, a formation of the highest possible adhesion forces between adhesive polymer and adherend surface is essential. Special surface treatment processes ensure a better wettability of the surfaces and also create energetically active sites that can interact with the adhesive molecules. However, many of the industrially established surface pretreatments, especially those for metallic materials, are not sustainable, since these methods often use corrosive, highly toxic and environmentally hazardous substances. This is the basis of the present dissertation. In various industries, such as automotive, electrical engineering and dentistry, newly developed surface treatment methods based on plasma and deposition technologies are already used. This raises the question of the applicability of such methods on materials for glass constructions and of their benefit to the optimization of structural adhesive joints. The effect of four different surface treatment methods used on the surfaces of stainless steel, aluminum, brass and toughened safety glass made from soda-lime glass is investigated in experimental studies. Physical and chemical surface analyses are performed before and after the applications. In addition, the adhesion properties of bonded specimens with pretreated surfaces are examined before and after aging. The influence of the surface conditions on the strength of the adhesive joints is determined from the obtained results. The results show very different effects of the individual surface treatment methods with high dependences on substrate and adhesive. With regard to an increase of adhesion strength, a good aging resistance, an uncomplicated integration into automated production processes and an avoidance of changing the optical surface properties, the investigated combustion chemical vapour deposition is the most suitable method. With this pretreatment, a dense silicate layer is deposite on the surface. Its high chemical activity and its complete wettability offer the best conditions for bonding a variety of materials with different adhesives.

Damages of metallic aircraft structures that occur during manufacturing, assembly and in service require local repair. Especially with current service-life extensions of ageing aircraft fleets, the importance of such repair methods is increasing. Typically, the repair of smaller damages on aluminium fuselage or wing skins is done by riveting a patch onto the flawed structure. However, the use of rivets reduces the strength of the structure and promotes fatigue. Joining the patch by adhesive bonding would not only offer more homogenous load distribution and weight savings, but even an increase of structural integrity. Metal adhesive bonding is commonly used in aeronautics, but requires elaborated surface treatments of the adherends, employing hazardous chemicals like chromates, due to the high durability demands. Furthermore, these treatments are usually tank processes that are not suitable for local repairs. Hence, there is a strong need for locally applicable surface preparation methods that allow safe and reliable adhesive bonding of primary aircraft structures. The aim of this thesis is to assess the – still emerging – method of atmospheric pressure plasma deposition of silicon (Si) containing compounds concerning its suitability as surface preparation for adhesive bonding of aluminium aerostructures. Atmospheric plasma deposition is not yet used in the aircraft industry, and the knowledge on functionality of this technology concerning bonding of aluminium parts is limited. Moreover, the durability requirements of the aircraft industry greatly exceed the standards in other industries. Hence, special attention is paid to a thorough analysis of the key characteristics of the deposited coupling films and their effectiveness in terms of adhesion promotion as well as joint durability under particularly hostile conditions. In order to do so, the altering mechanisms of the treated joints and the behaviour of the coupling films during accelerated ageing will be investigated in detail for the first time in this thesis. Furthermore, the influence of the aluminium surface pre-treatment (i.e. topography and oxide properties of the substrate) on the overall joint performance after coupling film deposition is thoroughly examined. Based on these findings, the surface preparation is optimised, and a process is developed to achieve maximal joint performance. As alternative local surface treatments prior to adhesive bonding, solution derived deposition of silane and sol-gel films have already been widely investigated and can be considered as reference, even though these techniques are rarely used in civil aeronautics. The knowledge on their effectiveness and capabilities in corrosive atmosphere is still very limited. Therefore, all analyses of degradation mechanisms are conducted for both plasma deposition and wet-chemical reference treatments to reveal the differences and communalities of the two Si-based coupling films. Physical and chemical analysis of the films, the oxides and the interfaces reveal differing, but interdependent failure mechanisms that are inhibited differently by the individual coupling films. Using the optimum deposition parameters, plasma films of only several nanometres in thickness significantly enlarge the corrosion resistance of bonded joints, reaching almost the level of anodising treatments with several micrometres thick oxides and strongly outperforming solution derived silane treatments. However, plasma film performance is found to be largely dependent on the precursor selection. With plasma deposition of 3-glycidoxypropyltrimethoxysilane, which has not been reported before, highest joint stability is achieved. Moreover, it is discovered that the properties of plasma and solution derived silane based films are complementary. It is shown that an optimised combined plasma and wet-chemical treatment process provides even superior resistance to bondline corrosion than state-of-the-art anodising techniques.