The aim of this research was to develop predictive models for residual stresses and environmental degradation in adhesively bonded joints exposed to hot/wet environments. Different single lap joint configurations and a hybrid double lap joint with dissimilar adherends (CFRP/AIIFM73 double lap joint), were exposed to different ageing environments in order to determine the durability of the joints and the effects of ageing on the failure load. Thermal residual stresses in bonded joints were investigated with analytical solutions and finite element modelling, first with a bimaterial curved beam to validate the modelling process and determine the most suitable method for calculating thermal stresses in bonded joints. It was found that none of the analytical solutions and 2D geometric approximations was fully able to describe the 3D stress state in the strip. The incorporation of geometric and material non-linearity into the models was necessary to obtain accurate results. The validated methods were then used predict the thermal residual stresses in bonded lap joints. The thermal stresses were found to be highest in joints with dissimilar adherends. Moisture uptake in bonded joints was investigated using Fickian diffusion modelling. Gravimetric experiments were used to determine the Fickian diffusion parameters for the bulk adhesive and composite adherends. Transient diffusion modelling was used to predict the uptake in bonded joints. It was seen that moisture diffusion is a fully three dimensional process, and the effects of moisture absorption can only be adequately studied using 3D FEA. The effects of swelling from moisture absorption in bonded joints were investigated using coupled stress-diffusion FEA models. Coupled stress-diffusion 3D FEA was used to predict the transient and residual hygroscopic stresses that develop in bonded lap joints as a function of exposure time in accelerated ageing environments, taking into account the effects of moisture on the expansion and mechanical properties of the adhesive and CFRP substrate. It was seen that moisture absorption induces significant stresses in the joints and markedly different behaviour was seen in the cases of absorbent and non-absorbent adherends. Hygro-thermo-mechanical stresses arising from the exposure of single and double lap joints with thermal residual stresses to hot/wet environments were investigated. In the single lap joints, a reduction in the stresses present in the adhesive was predicted, owing to swelling of the adhesive from moisture absorption. In the double lap joint with dissimilar adherends, exposure to hot/wet environments initially reduced the stresses in the joint when dry, followed by an increase in the magnitude of some stress components and reductions in others with increasing levels of moisture absorption. This led to a higher equivalent stress state in the adhesive than when dry. Thermal residual and mechanical strains predictions were validated with internal strains measured by neutron diffraction and surface strains measured by moire interferometry. Comparisons of predicted and measured thermal residual strains showed low levels of strain in joints with similar adherends. The magnitude of strains in the CFRP/AI double lap joint was significant, with the same spatial distribution and magnitude in both measured and predicted strains. The comparison of mechanical strains predicted by FEA and measured strains by moire interferometry showed good agreement. High magnification moire interferometry also confirmed the location of strain concentrations predicted by FEA. A path independent cohesive zone model (CZM) and a coupled continuum damage model were used to predict and characterise damage and failure initiation in bonded joints. Progressive failure prediction was calibrated in the cohesive zone model using the moisture dependent cohesive fracture energy of FM73. There was a reasonably good agreement with the experimental failure loads. This implementation of the cohesive zone model is limited by the ability of the interface elements used, thereby creating mesh dependency. The Gurson-Tvergaard-Needleman (GTN) coupled damage model was used to predict the effects of residual stresses on failure loads. However, this method is difficult to implement, given the numerous parameters required. The failure loads predicted by the GTN model were comparable with the experimental data when the joints were dry or wet. The damage models were capable of predicting the sudden crack growth and propagation seen experimentally.

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This work developed various two-phase colloidal nanomaterials from aqueous dispersions and applied them as pressure-sensitive adhesives. A fundamental understanding of the nano-scale interfacial friction and the macro-scale viscoelasticity and adhesive properties of these nanomaterials was developed via various existing models.

The behaviour of damage parameters in adhesive bonding has been investigated in order to predict the location of the initial crack in the adhesive region. Research started using bulk adhesive in which the loading is uniaxial, In this case the triaxiality, a variable that defines the stress state will have a value around unity.

The use of adhesively-bonded joints instead of the traditional types of joining can give reduced weight and increased stiffness in a structure. However, most industries have concerns about the use of adhesive joints in anything other than secondary structures, due to uncertainties over the long-term service life. This thesis discusses the prediction of the lifetime of adhesively-bonded composite structures. A fracture mechanics approach was used to characterise the fracture behaviour of an epoxy film adhesive, Cytec FM-300M, mainly using composite substrates prepared using wet peel ply, removing the need for any additional surface treatment. Aluminium alloy substrates were also used for some tests. Tapered double cantilever beam and double cantilever beam specimens were used to determine the mode I critical strain energy release rate, GIC, and end loaded split specimens were tested to obtain the mode II critical strain energy release rate, GIIC. Lastly, fixed ratio mixed mode specimens were used to obtain the relationship between GIC and GIIC when a joint undergoes mixed mode failure. For validation purposes, single lap joint and double scarf joint specimens were also tested. These data were then applied in finite element models using Abaqus. Two different modelling techniques were used, the virtual crack closure technique and cohesive zone modelling, CZM. Simulations of the tests performed were executed, in the process obtaining the CZM fitting parameters. Good agreement with the experimental data was verified for each of the models tested. Fatigue tests were also performed in order to obtain the mode I and mode II threshold values of the fracture energy below which crack growth did not occur, by executing double cantilever beam and end loaded split tests, respectively. For validation purposes, single lap joint fatigue tests were also performed to determine the threshold maximum load the joint could withstand without failure. Finally, using the CZM fitting parameters obtained in the quasi-static tests and the experimentally obtained threshold values of the fracture energy, modelling of single lap and double scarf joints was performed in order to predict the maximum load value for which no failure would occur when subject to cyclic loading. These predictions showed excellent agreement with the experimental results, showing that this simpler model can obtain good results.

Au cours d’un traitement de surface de type dépôt assisté par plasma, les caractéristiques et propriétés de l’interface entre le dépôt et le substrat sont déterminées par la première couche atomique du dépôt, voire les premiers atomes qui commencent à recouvrir la surface du substrat. Aussi, la parfaite connaissance du comportement des particules incidentes et du réarrangement des atomes suite à l’impact d’une particule du plasma est-elle un élément essentiel à la description du comportement de la surface en cours de traitement et donc de ses propriétés ultérieures. Au cours de cette thèse, nous avons entrepris d’étudier, par une approche combinant expériences et simulation numérique par dynamique moléculaire, l’interaction d’espèces (C, Ti, W) avec une surface de silicium en fonction de paramètres tels que l’énergie, la fluence ou encore l’incidence des particules arrivant sur la surface. Une part importante de ce travail a consisté à adapter les codes de dynamique moléculaire (utilisation des champs de force réactifs) aux systèmes étudiés. La partie expérimentale a nécessité la mise en place de procédures spécifiques pour l’utilisation de l’équipement Storing Matter. Les résultats montrent que, quelles que soient l’espèce incidente, parmi celles étudiées, le coefficient de collage (SC) est dans la gamme [0.7 – 1] ; dans le cas de W, quasiment tous les atomes incidents restent sur la surface (SC~~1). Outre la détermination du coefficient de collage, pour différentes conditions initiales des espèces incidentes (énergie, incidence, fluence) les modifications apportées à la surface ont également été déterminées en termes d’implantation et de trajectoire dans le matériau des espèces incidentes, et de pulvérisation de la surface du substrat / During plasma assisted deposition, properties of the coating substrate interface depend on the first atomic layer of the deposit, or the atoms that first start to cover the surface. Therefore the good knowledge of the sticking coefficient and the reorganization of the surface following particle impact is an essential issue to achieve the description of the behavior of the processed surface and, therefore, its expected properties. Consequently, we investigated the interaction between incoming particles (C, Ti, W) and a silicon surface by using an approach combining molecular dynamic simulations and experiments. Various initial conditions were studied, energy, fluence and incidence angle of the incoming particles. An important part of this work has consisted in adapting the molecular dynamic codes (using reactive force fields) to the investigated systems. Meanwhile, experimental procedure specifically devoted to the use of the Storing Matter facility was also developed. Results show that the sticking coefficient (SC) value is in the range [0.7 – 1] irrespectively of the incoming species; in the case of W, almost all atoms stick on the surface (SC~~1). Besides the determination of sticking coefficient, the surface modification resulting from the particles impingement were determined for various initial conditions (energy, fluence, angle) in terms of implantation and displacement of the incoming species, and surface sputtering as well