It is an important topic for electronic packages to estimate the interfacial bonding strength between dissimilar materials. If it is not strong enough, delamination would arise easily under high temperature, vibration or collision. Its reliability will be reduced. The study on interfacial fracture behavior between epoxy resin and die based on experimental and numerical analyses is investigated, and it is useful to judge where the delamination happens . In terms of interfacial fracture mechanics, the critical strain energy release rate (G ) of crack tip is related to the phase angle (£r ) . Considering the interface of the epoxy /die existing a tiny crack, the compact mixed mode (CMM) fixture is used to decide the critical load . Finally , we adopt the finite element method to calculate that the critical strain energy release rate (G ) and the phase angle (£r ) in comparison with empirical results .

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Concrete is the most essential construction material due to its high availability, low costs, excellent compressive strength, and high durability nature. However, cement-based composites possess some disadvantageous features, notably brittleness and diminished flexural/tensile strength. To surmount these challenges, the integration of reinforcement into cementitious materials becomes imperative. One of the most promising reinforcement materials is high-strength carbon fiber (CF), which manifests in forms such as dispersed short fibers, rebar, and textile to fabricate the carbon fiber-reinforced cementitious composite (CFRC). As opposed to traditional steel-reinforced structural elements, the chemically inert CF does not demand a thick protective cover, which enables the creation of slender-walled, resource-conserving structural components. However, CFRC materials exhibit poor interfacial adhesion between hydrophobic CF and enveloping cementitious matrices, thereby limiting the efficient force transfer at the interface. The commonly used polymeric impregnation for the CF multifilaments is susceptible to degradation under heightened temperatures, a circumstance adverse to structural integrity, particularly in fire scenarios. As an alternative, thermally stable inorganic binders characterized by exceedingly fine particulates emerge as suitable candidates for impregnation. This finely dispersed suspension penetrates the CF roving housing multitudes of filaments, inducing enhancements in bonding interactions among CF filaments as well as between the roving and the cement matrix. The dissertation at hand suggests an innovative approach that utilizes fine mineral particles as a coating material. Its core objective revolves around the advancement of the electrophoretic deposition (EPD) method for nano-silica (NS) onto CF surfaces, with the intention of enhancing interfacial bonding with cementitious matrices. To achieve this, a comprehensive exploration into the effects of voltage, treatment duration, and pH value during surface modification on bond performance and fiber properties is undertaken. The bond-slip behavior of the modified CFs toward the cement matrix depending on the curing ages is systematically studied from various aspects of the single-fiber pullout curves. In extension to the experimental results, a numerical simulation is used to elucidate the stress distribution during the debonding process, while also serving to approximate and describe the force-displacement pullout curves. Furthermore, amorphous silica fume and micro-sized quartz are harnessed for electrophoretic modification of CF surfaces, allowing for a comparative evaluation with NS coating in terms of enhancing bond behavior. The morphological features of modified CF surfaces are scrutinized using scanning electron microscopy. Single fiber tension experiments and thermogravimetric analysis are performed to study the impact of EPD modification on the mechanical properties and temperature sensibility of CFs. Uniaxial quasi-static single-fiber pullout tests are conducted to provide profound insights into the interfacial interaction between CF and surrounding cement matrices at different stages during the pullout process. Within the EPD system, the kinetics of CF electrode reaction and the zeta potential of suspensions are examined through cyclic voltammetry experiments and zeta potential measurements, respectively. These investigations elucidate alterations in the surface chemistry of CFs and the quality of the coating under diverse treatment conditions.

La performance mécanique des composites à matrice céramique repose en partie sur le contrôle de la liaison interfaciale et le choix des matériaux. Ces travaux s’intéressent au renforcement de la liaison interfaciale en traitant la surface des fibres SiC de dernière génération : les Hi-Nicalon S. L’objectif est d’établir une accroche chimique et/ou mécanique principalement avec l’interphase BN. Des composites modèles, minicomposites élaborés par voie CVI (Chemical Vapor Infiltration) sont utilisés comme base de travail. La quantification de la force de la liaison interfaciale s’effectue en évaluant l’énergie de liaisons interfaciales Gci issues d’essais de traction, et en calculant la contrainte de cisaillement τ par essais de pushout. Dans un premier temps, les fibres HNS dont les surfaces ont été légèrement modifiées, ont été testées avec l’interphase classique PyC. La liaison interfaciale sur minicomposites reste faible. Différentes traitements chimiques ont été effectués à la surface des fibres dans l’optique de renforcer la liaison interfaciale avec le BN, interphase plus résistance à l’oxydation que le PyC. Au préalable, les conditions d’élaborations de l’interphase BN ont été étudiées. / Mechanical properties of ceramic composites can be improved by controlling interfacial bonding and choosing materials. To enhance interfacial bonding, treatment on the last SiC fiber, Hi-Nicalon S surface are proposed in this work. The aim is to allow chemical and/or mechanical bonds mainly with BN interphase. For this, composites models, minicomposites are elaborated by CVI (Chemical Vapor Infiltration). Quantification of the strength of interfacial bonding is based by evaluating interfacial bonding energy Gci with tensile tests, and by calculating interfacial shear stress τ with push-out tests. Firstly, Hi-Nicalon S fibers whose surfaces have been slightly modified have been tested with classic interphase PyC. Interfacial bonding on minicomposites is weak. Different treatments have been performed on surface fibers to enhance interfacial bonding with BN, which have a better resistance oxidation than PyC. Before, elaboration parameters of BN interphase have been studied.

The present work was undertaken to develop a composite osmotic distillation (OD) membrane consisting of a thin hydrogel coating on a microporous hydrophobic substrate for the concentration of aqueous feeds containing surface-active agents. The range of OD applications using the hydrophobic membrane alone have been severely limited by the propensity for membrane wet-out when contacted by amphiphilic agents such as oils, fats and detergents. Wet-out allows the feed solution to track freely through the membrane pores with a resulting loss of solutes and a decrease in selectivity. The rationale for the approach taken was based on the hypothesis that the high water selectivity of the hydrophilic coating would maintain good water mass transfer to the underlying hydrophobic substrate but exclude other components including surface-active agents. The first stage of this work involved the identification of potential coating materials and the fabrication and structural characterization of films of these materials to determine their suitability. The second stage involved the development of techniques to facilitate adhesion of the hydrophilic coatings to the hydrophobic substrate, and the testing of the resulting composite membranes for OD performance and resistance to wet-out by surface-active agents. Sodium alginate was selected as the major coating component on the basis of its non-toxicity and its potential for stable hydrogel formation. Structural characterization of noncrosslinked films and films crosslinked using a water-soluble carbodiimide (WSC) was carried out using differential scanning calorimetry (DSC), Fourier Transform infrared spectroscopy (FT-IR) and swelling measurements. Maximum crosslinking through esterification of hydroxyl and carboxylic acid groups on adjacent polymer strands using the film immersion method was achieved with a non-solvent (ethanol) concentration of 60 vol % and a WSC concentration of 100 mM at pH 4. These conditions resulted in a hydrogel with an equilibrium water content of 60 wt %. DSC measurements of noncrosslinked and crosslinked alginate films showed an increase in crystallinity and hence rigidity on crosslinking. Therefore, several coatings were prepared as blends of sodium alginate and amorphous highly flexible carrageenan gum in order to meet the flexibility requirements of a membrane subjected to varying operating pressures in an industrial OD plant. Structural characterization with respect to polymer blend ratio was carried out using scanning electron microscopy (SEM), DSC, X-ray diffraction (XRD). The optimisation for crosslinking conditions was undertaken as for sodium alginate alone. Optimum conditions for film preparation were 20 wt % carrageenan content and a crosslinking medium containing 60 vol % non-solvent (ethanol) and 120 mM WSC at pH 4. These conditions produced a hydrogel with an equilibrium water content of 85 wt %. Two different techniques were employed to anchor the coatings on substrate PTFE membranes. For membranes with a nominal diameter of 0.2 µm, the technique involved surface tension adjustment of the coating solution by ethanol addition in order to enhance penetration of the coating solution meniscus into the substrate pores. This was followed by polymer precipitation by the selective removal of water using OD to provide structural interlocking. T-peel strength measurements showed that this technique resulted in a ten-fold increase in adhesion strength when compared with a coating cast without surface tension adjustments. For membranes with a nominal diameter of 0.1µm, an interfacial bonding agent, myristyltrimethylammonium bromide (MTMA), was used. This technique gave a three-fold increase in adhesion strength relative to that of coating cast without the use of MTMA. The composite membranes were tested in extended OD trials using pure water and feeds containing limonene, the major surface-active components of orange oil. The sodium alginate-carrageenan blend membrane, which was the preferred membrane based on flexibility and water sorption considerations, was also tested against full-cream milk and an industrial detergent, sodium dodecylbenzene sulfonate (DBS). The results indicated that the coatings offered little resistance to water transport and were effective in providing protection against membrane wet-out. Durability trials showed that the composite membranes retained their integrity in water for a minimum of 30 days. Overall, this study has expanded the potential applications of OD to include many important industrial concentration steps that are currently being undertaken by conventional processes with unsatisfactory results. These include the concentration of citrus juices, full-cream milk and nuclear power plant liquid waste. These feeds contain limonene, fats and detergents respectively, all of which wet out unprotected hydrophobic membranes.

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