In this dissertation, four test approaches were developed to characterize the adhesion performance and durability of adhesive bonds for specific applications in areas spanning from structural adhesive joints to popular confectionaries such as chewing gum. In the first chapter, a double cantilever beam (DCB) specimen geometry is proposed for combinatorial fracture studies of structural adhesive bonds. This specimen geometry enabled the characterization of fracture energy vs. bondline thickness trends through fewer tests than those required during a conventional "one at a time" characterization approach, potentially offering a significant reduction in characterization times. The second chapter investigates the adhesive fracture resistance and crack path selection in adhesive joints containing patterns of discreet localized weak interfaces created using physical vapor deposition of copper. In a DCB specimen tested under mode-I conditions, fracture energy within the patterned regions scaled according to a simple rule of mixture, while reverse R-curve and R-curve type trends were observed in the regions surrounding weak interface patterns. Under mixed mode conditions such that bonding surface with patterns is subjected to axial tension, fracture energy did not show R-curve type trends while it was observed that a crack could be made to avoid exceptionally weak interfaces when loaded such that bonding surface with defects is subjected to axial compression. In the third chapter, an adaptation of the probe tack test is proposed to characterize the adhesion behavior of gum cuds. This test method allowed the introduction of substrates with well-defined surface energies and topologies to study their effects on gum cud adhesion. This approach and reported insights could potentially be useful in developing chewing gum formulations that facilitate easy removal of improperly discarded gum cuds from adhering surfaces. In the fourth chapter we highlight a procedure to obtain insights into the long-term performance of silicone sealants designed for load-bearing applications such as solar panel support sealants. Using small strain constitutive tests and time-temperature-superposition principle, thermal shift factors were obtained and successfully used to characterize the creep rupture master curves for specific joint configurations, leading to insights into delayed failures corresponding to three years through experiments carried out in one month. / Ph. D.

Understanding the interactions of polymer interfaces is essential to improve polymer-based designs, as the properties of the interface are often different than those of the bulk material. This thesis explores the interfacial interactions of polymer interfaces for two classes of materials, additive manufacturing materials and fiber-reinforced composites. Additive manufacturing (AM) refers to a number of processes which rely on data generated from computer-aided design (CAD) programs to construct components by adding material in a layer-by-layer fashion. AM continues to generate a substantial amount of interest to produce fully functional products while reducing tooling costs associated with traditional manufacturing techniques such as casting and welding. Recent advancements in the field have led to the production of multi-material printing that has the potential to create products with enhanced mechanical properties and additional functionality. This thesis attempts to characterize the fracture resistance of AM materials produced by the PolyJet process. Test standards established for mode I fracture testing of adhesive joints are adapted to evaluate the fracture resistance and interface between two printed acrylic-based photopolymers. Significant differences in fracture energy and loci of failure between the selected test configurations were observed depending on the print orientation. Failures were nominally seen to occur at the interface, alternating from one adherend interface to another in a random fashion. Results demonstrated a decreasing trend in fracture energy at slower crack propagation rates, indicating that such dependency is associated with the fracture resistance of the interface. T-peel tests conducted on specimens prepared with both constant and graded interlayers revealed enhanced peel resistance with gradient interlayers, suggesting design opportunities of enhanced fracture toughness by implementing intricate material patterns at the interface of the two photopolymers. Fiber reinforced composite (FRCs) materials have become increasingly desirable in a number of industrial applications where weight reduction is critical for increased payloads and higher performance. When manufacturing structures from these materials, the presence of friction in the composite forming process is seen to have a major effect on the finished quality. Friction between the plies, or between the composite laminate and forming tool, can be undesirable as shape distortions such as wrinkles can appear and compromise the structural integrity of the finished product. To evaluate these frictional processes, a standard rheometer is used to evaluate tool-ply friction on dry textile fabrics and graphite/epoxy prepregs over a range of temperatures, pressures, and sliding velocities. The results provide some general insights into the frictional response of composite prepregs as a function of the manufacturing environment. The materials tested are shown to have different mechanisms that govern the frictional processes. In particular, the results of friction testing on the prepreg indicate that friction comes from a contribution of both Coulomb and viscous-related mechanisms, the latter which become especially at higher temperatures. / Master of Science

This thesis is intended to identify the mode I and mode II fracture toughness to characterize the thin laminate interface by using the Double Cantilever Beam test (DCB) and End Notched Flexure test (ENF). This study’s thin laminate was Polyethylene Terephthalate and Low-Density Polyethylene (PET-LDPE), which is mostly used by packaging industries in the manufacturing of packages to store liquid food. As PET-LDPE film is very flexible and difficult to handle, DCB and ENF tests cannot be performed directly so, sheet metal (Aluminium) was used as carrier material. PET-LDPE film is placed between two aluminum plates to reduce the flexibility and perform the tests. Therefore, the Aluminium plate was also studied to find the constitutive parameters (young’s modulus (E) and mixed hardening parameters (Plastic properties)) under the tensile test and three-point bending test. From the test response, energy release rate calculation has been done for different Pre-crack lengths to validate the DCB and ENF experimental setup, study the different Pre-crack lengths, and characterize the laminate interface. Finite Element simulation (FE simulation) for those tests were carried out in AbaqusTM2020. When needed, the force versus displacement response from FE simulation was optimized against experimental response to find the required constitutive parameters (Young’s modulus, Hardening parameters, and PET-LDPE material properties). Implementing of optimization algorithm and automated simulation has been done with the help of MATLAB code. In contrast, MATLAB works as a server, and Abaqus works as a client and connected two interfaces to run the optimization. The results obtained from experiments and FE simulations were compared to the results found in the literature.

The objective of this study was to evaluate and gain a better understanding of the short-term impact performance and the long-term durability of electrically conductive adhesives for electronic interconnection applications. Three model conductive adhesives, designated as ECA1, ECA2 and ECA3, supplied by Emerson & Cuming, were investigated, in conjunction with printed circuit board (PCB) substrates with metallizations of Au/Ni/Cu and Cu, manufactured by Triad Circuit Inc. Effects of environmental aging on the durability of conductive adhesives and their joints were evaluated. All the samples for both mechanical tests and thermal tests were aged at 85%, 100%RH for periods of up to 50 days. Studies of bulk conductive adhesives suggested that both plasticization, which is reversible and further crosslinking and thermal degradation, which are irreversible, might have occurred upon exposure of ECAs to the hot/wet environment. The durability of electrically conductive adhesive joints was then investigated utilizing the double cantilever beam (DCB) test. It was observed that the conductive adhesive joint was significantly weakened following hydrothermal aging, and there was a transition from cohesive failure to interfacial failure as aging continued. A comparative study of the durability of different conductive adhesive and substrate metallization combinations suggested that the resistance of the adhesive joints to moisture attack is related to the adhesive properties, as well as the substrate metallizations. It was noted that the gold/adhesive interface had better resistance to moisture attack than the copper/adhesive interface. A reasonable explanation of this phenomenon was given based upon the concept of surface free energy and interfacial free energy. XPS analysis was performed on the fractured surfaces of DCB samples. For adhesive joints with copper metallization, copper oxide was detected on the failed surfaces upon exposure of the conductive adhesive joints following aging. XPS analysis on the fractured surfaces of adhesive joints with Au metallization suggested that diffusion of Cu to the Au surface might have happened on the Au/Ni/Cu plated PCB substrates during aging. The impact performance of conductive adhesives was quantitatively determined using a falling wedge test. This unique impact resistance testing method could serve as a useful tool to screen conductive adhesives at the materials level for bonding purpose. Moreover, this test could also provide some useful information for conductive adhesive development. This study revealed that the viscoelastic energy, which is a result of the internal friction created by chain motions within the adhesive material, played an important role in the impact fracture behavior of the conductive adhesives. This study also demonstrated that the loss factor, evaluated at the impact environment conditions, is a good indicator of a conductive adhesive's ability to withstand impact loading. / Ph. D.

The objective of this study was to evaluate and develop an understanding of durability of an adhesive bonded system, for application in a future high speed civil transport (HSCT) aircraft structure. The system under study was comprised of Ti-6Al-4V metal adherends and a thermosetting polyimide adhesive, designated as FM-5, supplied by Cytec Engineered Materials, Inc. An approach based on fracture mechanics was employed to assess Ti-6Al-4V/FM-5 bond durability. Initially, wedge tests were utilized to find a durable surface pretreatment for the titanium adherends. Based on an extensive screening study, chromic acid anodization (CAA) was chosen as the standard pretreament for this research project. Double cantilever beam specimens (DCB) were then made and aged at 150° C, 177° C, and 204° C in three different environments; ambient atmospheric air (14.7 psia), and reduced air pressures of 2 psi air (13.8 KPa) and 0.2 psi air (1.38 KPa). Joints were aged for up to 18 months (including several intermediate aging times) in the above environments. The strain energy release rate (G) of the adhesive joints was monitored as a function of exposure time in the different environments. A 40% drop in fracture toughness was noted over the 18 month period, with the greatest degradation observed in samples aged at 204° C in ambient atmospheric air pressure. The loss in adhesive bond performance with time was attibutable to a combination of physical and chemical aging phenomena in the FM-5 resin, and possible degradation of the metal-adhesive interface(s). Several mechanical and material tests, performed on the bonded joints and neat FM-5 resin specimens, confirmed the above statement. It was also noted that physical aging could be "erased" by thermal rejuvenation, partially restoring the toughness of the FM-5 adhesive material. The FM-5 adhesive material displayed good chemical resistance towards organic solvents and other aircraft fluids such as jet fuel and hydraulic fluid. The results from the FM-5 adhesive and its bonded joints were compared and contrasted with VT Ultem and REGULUS polyimide adhesives. The FM-5 adhesive showed the best performance among the three adhesive systems. The effect of mode-mixity on the fracture toughness of the Ti-6Al-4V/FM-5 adhesive bonded system was also evaluated. DCB tests in conjunction with end-notched flexure (ENF) and mixed-mode flexure (MMF) tests, were used to fracture the bonded joints under pure mode I, pure mode II, and a combination of mode I and II loadings. The results showed that the mode I fracture toughness was twice as large as the mode II toughness. This was a rather surprising find, in sharp contrast to what several researchers have observed in the past. Our current understanding is that the crack path selection during the failure process plays a significant role in explaining this anomalous behavior. Finally, failure envelopes were generated for the titanium/FM-5 bonded system, both prior to and following thermal aging. These envelopes could serve as useful tools for engineers designing with Ti-6Al-4V/FM-5 bonds. / Ph. D.

Le dimensionnement des joints collés est une préoccupation majeure du CNES pour lesapplications spatiales des futurs lanceurs. Pour dimensionner une structure collée, il est nécessaire depouvoir apprécier les caractéristiques mécaniques du joint collé.Dans cette étude, trois adhésifs structuraux ont été sélectionnés (Hysol®EA 9321, Hysol®EA9394 et Hysol EA® 9395). Après leur caractérisation massique, une étude statistique pour mettre enévidence les effets des différents paramètres (vitesse d’essai, géométrie éprouvette, le degré depolymérisation…) a été entreprise.La deuxième étape a pour objectif de fiabiliser l’analyse des essais de fissuration etd’améliorer la compréhension des mécanismes d’endommagement et de propagation de fissure dansles liaisons collées. Trois types d’essai ont été utilisés, à savoir, l’essai Double Cantilever Beam(DCB), pour l’étude du mode I, l’essai End Notched Flexure (ENF), pour le mode II, et l’essai MixedMode Bending (MMB), pour les chargements en mode mixte I/II. Nous avons développé de nouvellesinstrumentations et méthodologies d’analyse. Pour affiner le protocole de test standard, la techniquedite de « backface strain monitoring » a été utilisée. Elle consiste à positionnées des jauges dedéformation sur les surfaces de l’éprouvette de façon à enregistrer l’évolution du signalextensométrique durant la propagation de la fissure. Cette méthode permet une meilleure estimation dela position front de fissure ainsi que l'étude de la répartition des contraintes le long du joint de colle.La corrélation d'images numériques (DIC) a également été utilisée afin de proposer un nouveauprotocole de calibrage de la longueur de fissure et pour comparer un modèle analytique (poutre deTimoshenko sur fondation élastique) avec les résultats expérimentaux. / Adhesive bonding is being strongly considered in space applications CNES as anadvantageous assembly technique for future launchers. Correct design of adhesive joints is of majorconcern. Aerospace adhesives are tough viscoelastic matrices (special epoxy resins) reinforced withnano-, or microparticles. Extended use of adhesive joints in structural applications is limited due to thedifficulties in predicting in-service performance, frequently leading to over-conservative design.Three structural adhesives (Hysol®EA 9321, Hysol®EA 9394 and Hysol®EA 9395) wereselected. After their bulk characterization, statistical studies to highlight effects of different parameterse.g. speed, test piece geometry, degree of polymerization were undertaken.In the second stage, fracture mechanics tests were effected employing: the double cantileverbeam (DCB) configuration (mode I characterisation), the three point bending end-notched flexure(ENF) (mode II) and the mixed-mode bending (MMB) (combined mode I/II loading). Crack growth inbonded joints was investigated in a novel way. To refine standard test protocol, the backface strainmonitoring technique was used. Strain gauges were used to measure the strain on the exposed skin ofthe adherends during crack onset and propagation. This method allows better estimation of the crackfront position as well as fine investigation of the stress distribution along the bondline and in the crackfront vicinity. Digital image correlation (DIC) was also used to compare analytical models, e.g.Timoshenko beam on elastic foundation model with experimental results.

<p>Bonding techniques intended for assembling space microsystems are studied in this work. One of the largest problems in bonding pre-processed semiconductor wafers are the severe process restrictions imposed by material compatibility issues. Plasma processes have shown to be good for sensitive materials integration why the influence of different plasma parameters on the bondability of wafers is particularly studied. Conventional wet chemical and field-assisted methods are also examined. The resulting bond quality is assessed in terms of mechanical strength, homogeneity, and yield.</p><p>The effect of spaceflight environment on the reliability of wafer bonds is also investigated. Both high and low temperature annealed bonds are found to be very robust. Effects observed are that low temperature bonds are reinforced by thermal cycling in vacuum and that high temperature bonds degrade slightly by low dose γ irradiation.</p><p>Adhesion quantification is important for all bonding. Development of accurate quantification methods is considered necessary since most methods at hand are limited. This work includes the development of the blister test method. Former test structures are improved to be more practical to work with and to yield low experimental scatter. A physical stress model for the improved structure is suggested with which successful predictions of fracture for different test specimen configurations are made. The blister test method is used throughout this work to assess the strength of wafer bonds. The physics background and modelling of other common test methods are also thoroughly analysed. The methods’ practical capabilities and limitations are commented; origin and mitigation of measurement errors are discussed. It is shown that all methods can be significantly improved by small means.</p><p>Weibull statistics is introduced as a tool to characterise wafer bonds. This method is suitable to use in brittle materials design as the inherent variability in strength can be properly accounted for.</p>

Bonding techniques intended for assembling space microsystems are studied in this work. One of the largest problems in bonding pre-processed semiconductor wafers are the severe process restrictions imposed by material compatibility issues. Plasma processes have shown to be good for sensitive materials integration why the influence of different plasma parameters on the bondability of wafers is particularly studied. Conventional wet chemical and field-assisted methods are also examined. The resulting bond quality is assessed in terms of mechanical strength, homogeneity, and yield. The effect of spaceflight environment on the reliability of wafer bonds is also investigated. Both high and low temperature annealed bonds are found to be very robust. Effects observed are that low temperature bonds are reinforced by thermal cycling in vacuum and that high temperature bonds degrade slightly by low dose γ irradiation. Adhesion quantification is important for all bonding. Development of accurate quantification methods is considered necessary since most methods at hand are limited. This work includes the development of the blister test method. Former test structures are improved to be more practical to work with and to yield low experimental scatter. A physical stress model for the improved structure is suggested with which successful predictions of fracture for different test specimen configurations are made. The blister test method is used throughout this work to assess the strength of wafer bonds. The physics background and modelling of other common test methods are also thoroughly analysed. The methods’ practical capabilities and limitations are commented; origin and mitigation of measurement errors are discussed. It is shown that all methods can be significantly improved by small means. Weibull statistics is introduced as a tool to characterise wafer bonds. This method is suitable to use in brittle materials design as the inherent variability in strength can be properly accounted for.

Structural adhesives are widely used with great success, and yet occasional failures can occur, often resulting from improper bonding procedures or joint design, overload or other detrimental service situations, or in response to a variety of environmental challenges. In these situations, cracks can start within the adhesive layer or debonds can initiate near an interface. The paths taken by propagating cracks can affect the resistance to failure and the subsequent service lives of the bonded structures. The behavior of propagating cracks in adhesive joints remains of interest, including when some critical environments, complicated loading modes, or uncertainties in material/interfacial properties are involved. From a mechanics perspective, areas of current interest include understanding the growth of damage and cracks, loading rate dependency of crack propagation, and the effect of mixed mode fracture loading scenarios on crack path selection. This dissertation involves analytical, numerical, and experimental evaluations of crack propagation in several adhesive joint configurations. The main objective is an investigation of crack path selection in adhesively bonded joints, focusing on in-plane fracture behavior (mode I, mode II, and their combination) of bonded joints with uniform bonding, and those with locally weakened interfaces. When removing cured components from molds, interfacial debonds can sometimes initiate and propagate along both mold surfaces, resulting in the molded product partially bridging between the two molds and potentially being damaged or torn. Debonds from both adherends can sometimes occur in weak adhesive bonds as well, potentially altering the apparent fracture behavior. To avoid or control these multiple interfacial debonding, more understanding of these processes is required. An analytical model of 2D parallel bridging was developed and the interactions of interfacial debonds were investigated using Euler-Bernoulli beam theory. The numerical solutions to the analytical results described the propagation processes with multiple debonds, and demonstrated some common phenomena in several different joints corresponding to double cantilever beam configurations. The analytical approach and results obtained could prove useful in extensions to understanding and controlling debonding in such situations and optimization of loading scenarios. Numerical capabilities for predicting crack propagation, confirmed by experimental results, were initially evaluated for crack behavior in monolithic materials, which is also of interest in engineering design. Several test cases were devised for modified forms of monolithic compact tension specimens (CT) were developed. An asymmetric variant of the CT configuration, in which the initial crack was shifted to two thirds of the total height, was tested experimentally and numerically simulated in ABAQUS®, with good agreement. Similar studies of elongated CT specimens with different specimen lengths also revealed good agreement, using the same material properties and cohesive zone model (CZM) parameters. The critical specimen length when the crack propagation pattern abruptly switches was experimentally measured and accurately predicted, building confidence in the subsequent studies where the numerical method was applied to bonded joints. In adhesively bonded joints, crack propagation and joint failure can potentially result from or involve interactions of a growing crack with a partially weakened interface, so numerical simulations were initiated to investigate such scenarios using ABAQUS®. Two different cohesive zone models (CZMs) are applied in these simulations: cohesive elements for strong and weak interfaces, and the extended finite element method (XFEM) for cracks propagating within the adhesive layer. When the main crack approaches a locally weakened interface, interfacial damage can occur, allowing for additional interfacial compliance and inducing shear stresses within the adhesive layer that direct the growing crack toward the weak interface. The maximum traction of the interfacial CZM appears to be the controlling parameter. Fracture energy of the weakened interface is shown to be of secondary importance, though can affect the results when particularly small (e.g. 1% that of the bulk adhesive). The length of the weakened interface also has some influence on the crack path. Under globally mixed mode loadings, the competition between the loading and the weakened interface affects the shear stress distribution and thus changes the crack path. Mixed mode loading in the opposite direction of the weakened interface is able to drive the crack away from the weakened interface, suggesting potential means to avoid failure within these regions or to design joints that fail in a particular manner. In addition to the analytical and numerical studies of crack path selection in adhesively bonded joints, experimental investigations are also performed. A dual actuator load frame (DALF) is used to test beam-like bonded joints in various mode mixity angles. Constant mode mixity angle tracking, as well as other versatile loading functions, are developed in LabVIEW® for use with a new controller system. The DALF is calibrated to minimize errors when calculating the compliance of beam-like bonded joints. After the corrections, the resulting fracture energies ( ) values are considered to be more accurate in representing the energy released in the crack propagation processes. Double cantilever beam (DCB) bonded joints consisting of 6061-T6 aluminum adherends bonded with commercial epoxy adhesives (J-B Weld, or LORD 320/322) are tested on the DALF. Profiles of the values for different constant mode mixity angles, as well as for continuously increasing mode mixity angle, are plotted to illustrate the behavior of the crack in these bonded joints. Finally, crack path selection in DCB specimens with one of the bonding surfaces weakened was studied experimentally, and rate-dependency of the crack path selection was found. Several contamination schemes are attempted, involving of graphite flakes, silicone tapes, or silane treatments on the aluminum oxide interfaces. In all these cases, tests involving more rapid crack propagation resulted in interfacial failures at the weakened areas, while slower tests showed cohesive failure throughout. One possible explanation of this phenomenon is presented using the rate-dependency of the yield stress (commonly considered to be corresponding to the maximum traction) of the epoxy adhesives. These experimental observations may have some potential applications tailoring adhesive joint configurations and interface variability to achieve or avoid particular failure modes. / Ph. D.

Global-local finite element analyses were used to study the damage tolerance of curvilinearly stiffened panels; fabricated using the modern additive manufacturing process, the so-called unitized structures, and that of adhesive joints. A damage tolerance study of the unitized structures requires cracks to be defined in the vicinity of the critical stress zone. With the damage tolerance study of unitized structures as the focus, responses of curvilinearly stiffened panels to the combined shear and compression loadings were studied for different stiffeners' height. It was observed that the magnitude of the minimum principal stress in the panel was larger than the magnitudes of the maximum principal and von Mises stresses. It was also observed that the critical buckling load factor increased significantly with the increase of stiffeners' height. To study the damage tolerance of curvilinearly stiffened panels, in the first step, buckling analysis of panels was performed to determine whether panels satisfied the buckling constraint. In the second step, stress distributions of the panel were analyzed to determine the location of the critical stress under the combined shear and compression loadings. Then, the fracture analysis of the curvilinearly stiffened panel with a crack of size 1.45 mm defined at the location of the critical stress, which was the common location with the maximum magnitude of the principal stresses and von Mises stress, was performed under combined shear and tensile loadings. This crack size was used because of the requirement of a sufficiently small crack, if the crack is in the vicinity of any stress raiser. A mesh sensitivity analysis was performed to validate the choice of the mesh density near the crack tip. All analyses were performed using global-local finite element method using MSC. Marc, and global finite element methods using MSC. Marc and ABAQUS. Negligible difference in results and 94% saving in the CPU time was achieved using the global-local finite element method over the global finite element method by using a mesh density of 8.4 element/mm ahead of the crack tip. To study the influence of different loads on basic modes of fracture, the shear and normal (tensile) loads were varied differently. It was observed that the case with the fixed shear load but variable normal loads and the case with the fixed normal load but variable shear loads were Mode-I. Under the maximum combined loading condition, the largest effective stress intensity factor was very smaller than the critical stress intensity factor. Therefore, considering the critical stress intensity factor of the panel with the crack of size 1.45 mm, the design of the stiffened panel was an optimum design satisfying damage tolerance constraints. To acquire the trends in stress intensity factors for different crack lengths under different loadings, fracture analyses of curvilinearly stiffened panels with different crack lengths were performed by using a global-local finite element method under three different load cases: a) a shear load, b) a normal load, and c) a combined shear and normal loads. It was observed that 85% data storage space and the same amount in CPU time requirement could be saved using global-local finite element method compared to the standard global finite element analysis. It was also observed that the fracture mode in panels with different crack lengths was essentially Mode-I under the normal load case; Mode-II under the shear load case; and again Mode-I under the combined load case. Under the combined loading condition, the largest effective stress intensity factor of the panel with a crack of recommended size, if the crack is not in the vicinity of any stress raiser, was very smaller than the critical stress intensity factor. This work also includes the performance evaluation of adhesive joints of two different materials. This research was motivated by our experience of an adhesive joint failure on a test-fixture that we used to experimentally validate the design of stiffened panels under a compression-shear load. In the test-fixture, steel tabs were adhesively bonded to an aluminum panel and this adhesive joint debonded before design loads on the test panel were fully applied. Therefore, the requirement of studying behavior of adhesive joints for assembling dissimilar materials was found to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints of the nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. Since the design of the combined load test fixture was for transferring the in-plane shear and compression loads to the panel, in-plane loads might have been responsible for the debonding of the steel tabs, which was similar to the results obtained from the nonlinear finite element analysis of the combined load test fixture. Then, fundamental studies were performed on the three-dimensional finite element models of adhesive lap joints and the Asymmetric Double Cantilever Beam (ADCB) joints for shear and peel deformations subjected to a loading similar to the in-plane loading conditions in the test-fixtures. The analysis was performed using ABAQUS, and the cohesive zone modeling was used to study the debonding growth. It was observed that the stronger adhesive joints could be obtained using the tougher adhesive and thicker adherends. The effect of end constraints on the fracture resistance of the ADCB specimen under compression was also investigated. The numerical observations showed that the delamination for the fixed end ADCB joints was more gradual than for the free end ADCB joints. Finally, both the crack propagation and the characteristics of adhesive joints were studied using a global-local finite element method. Three cases were studied using the proposed global-local finite element method: a) adhesively bonded Double Cantilever Beam (DCB), b) an adhesive lap joint, and c) a three-point bending test specimen. Using global-local methods, in a crack propagation problem of an adhesively bonded DCB, more than 80% data storage space and more than 65% CPU time requirement could be saved. In the adhesive lap joints, around 70% data storage space and 70% CPU time requirement could be saved using the global-local method. For the three-point bending test specimen case, more than 90% for both data storage space and CPU time requirement could be saved using the global-local method. / Ph. D.