The geotechnical properties of municipal solid waste (MSW) such as compressibility, shear strength and stiffness are of prime importance in design and construction of landfills. However, it is not well clear how the stress-strain and strength characteristics vary with time as the biodegradation of waste continues in the landfill. There is also a need to address the variability of MSW properties and their role in landfill design. The present thesis proposes models for the analyses of stress-strain response of MSW in undrained and drained conditions. The proposed models are based on critical state soil mechanics concept and the modified cam clay model is extended to consider the effects of creep and biodegradation. The models are examined with reference to experimental data and published results of MSW in the form of stress strain response. In addition, the experimental results and the data from published literature are also compared with predictions from hyperbolic model. The proposed models are able to capture the stress strain response of MSW in undrained and drained condition adequately. The applicability of proposed model is presented in terms of shear strength ratio, stiffness ratio and settlement for typical landfill cases. In order to examine the influence of model parameters on shear strength, stiffness ratio and settlement, multilinear regression equations are developed based on response surface method (RSM) for different coefficients of variation (COVs). The effect of variability associated with model parameters is examined using reliability analysis. For better understanding, the present thesis is divided into following seven chapters. Chapter 1 is an introductory chapter, in which the need for use of the constitutive models and its use in engineering response analysis of MSW is presented. Further, the organization of thesis is also presented. Chapter 2 presents various studies with regard to the engineering properties of MSW available in the literature. Different models and approaches proposed by various researchers for the prediction of stress-strain response, time dependent behavior and settlement analysis of the MSW are presented. The uncertainty associated with engineering properties and available methods for reliability analysis and the use of response surface method are presented. Finally, based on the literature review, the scope of the thesis and summary of chapter are presented at the end. Chapter 3 presents composition of MSW, detailed description of the sample preparation, methods adopted in the experimental program and test results of one dimensional compression and consolidated undrained tests. Based on the experimental observations, a constitutive model for municipal solid waste for undrained condition in the framework of modified cam clay model considering mechanical creep and biodegradation mechanisms is proposed. It also provides detailed description of the selection of the input parameters required for the proposed model. Further, the detailed derivation of proposed model and the discussion on evaluation of the input model parameters from triaxial and consolidation tests are presented. The model is examined with reference to the experimental data and published results. The stress strain behavior of MSW is compared with the prediction of stress strain response from hyperbolic model. The comparison of stress strain response is well captured using proposed model for all levels of strain. The major conclusions from the study are presented at the end. Chapter 4 presents experimental results of consolidated drained tests. A constitutive model for MSW for drained condition in the framework of modified cam clay model considering mechanical creep and biodegradation mechanisms is proposed. The model is examined with reference to the experimental data and data from published literature. In addition, stress strain behavior of MSW is compared with the predictions from hyperbolic model. The comparison of stress strain response is well captured using proposed model for all levels of strain. The major conclusions from the study are presented at the end. Chapter 5 presents the applicability of proposed models in terms of shear strength ratio and stiffness ratio for a typical landfill condition. Based on response surface method (RSM), multilinear response surface equations are developed for different variables ( M, λ.b.c.d.Edg ) for different percentages of strain for 10 and 20% COVs of the model parameters. The effect of variability of model parameters is presented in terms of results of reliability analysis for specified performance functions. The major conclusions from the study are presented at the end. Chapter 6 presents an approach for the settlement evaluation of MSW for a typical landfill case of 30 m high. Based on RSM, multilinear response surface equations are developed for the calculation of MSW settlement for 30 years for 10 and 20% COVs. The effect of variability of model parameters is evaluated in term of reliability index for performance function specified in terms of landfill capacity. The major conclusions from the study are presented at the end. Chapter 7 presents a brief summary and conclusions from the various studies reported in the present thesis.

The concept of reinforcement was developed in late 20th century and since then till the recent past there are many works carried out on the effect of fibers in imparting strength and stiffness to the soil. Experimental investigations on fiber reinforced soils showed an increase in shear strength and reduction in post peak loss of strength due to the reinforcement. Analytical/mechanistic models are developed to predict the stress-strain response of fiber reinforced soil (under discrete framework, energy dissipation methods, force equilibrium methods etc). Numerical investigations are also carried out, and it was observed that the presence of random reinforcing material in soils make the stress concentration diffuse more and restrict the shear band formation. Soil properties vary from point to point at micro level and influence stress mobilization. Hence, there is a need to carry out probabilistic analysis to capture the effects of uncertainties and variability in soil and their influence on stress-strain evolution. In the present thesis an attempt has been made to propose a mechanistic model that predicts the stress-strain response of fiber reinforced soil and also considers the effect of anisotropy of fibers. A stochastic/probabilistic model is developed that predicts the stochastic stress-strain response of fiber reinforced soil. In addition, probabilistic analysis is carried out to observe the effect of number of fibers across the shear plane in imparting shear resistance to soil. The mechanistic model and stochastic models are validated with reference to the experimental results of consolidated undrained (CU) triaxial tests on coir fiber reinforced red soil for different fiber contents. The entire thesis is divided into six chapters. Chapter-wise description is given below. Chapter one presents a general introduction to the works carried out on fiber reinforced soils and also the investigations carried out on probabilistic methodologies that takes into account the soil variability. Thus, the chapter gives an outline of the models developed under mechanistic and probabilistic frameworks in the thesis. The objectives and organization of the thesis are also presented. Chapter two presents a detailed review of literature on the role of fibers in fiber reinforced soil. The details of experimental investigations carried out and models developed are explained briefly. Also, the literature pertaining to the role of variability in soil on its engineering behavior is presented. Based on the literature presented in this chapter, concluding remarks are made. Chapter three presents the details of a new mechanistic model developed based on modified Cam-clay model. This model considers the effect of fiber content and also the effect of anisotropy due to fibers. The predictions from the mechanistic model are compared with the experimental results. Under anisotropic condition, as angles of inclination of fiber vary from 0° to 90° with the bedding plane, it is observed that the strength increment in the reinforced soil is not as significant as that observed in isotropic case. Horizontal fibers turn out to be most effective since they are subjected to maximum extension thereby inducing tensile resistance which in turn contributes for strength increase in fiber reinforced soil. Chapter four presents a new approach to predict the stochastic stress-strain response of soil. Non-homogeneous Markov chain (multi-level homogeneous Markov chain) modeling is used in the prediction of stochastic response of soil. The statistical variations in the basic variables are taken into account by considering the response quantities (viz. stress at a given strain or settlement at a given load level) as random. A bi-level Homogeneous Markov chain predicts the stochastic stress-strain response efficiently. The predicted results are in good agreement with the experimental results. An illustration of this model is done to predict the stochastic load-settlement response of cohesionless soil. A simple tri-level homogeneous Markov chain model is proposed to predict settlements of soil at a given load for an isolated square footing subjected to axial compression. A parametric study on the effect of correlation coefficient on the prediction of settlements is performed. Chapter five presents the results of probabilistic analysis carried out to determine the effect of number of fibers across the shear plane in improving the shear strength of soil. It is observed that as the percentage of fibers in the specimen increases, the probability of failure of specimen under the same stress condition reduces and thus the reliability of the fiber reinforced soil system increases. In Chapter six, a summary of the important conclusions from the various studies reported in the dissertation are presented.

La Chine est actuellement confrontée à de sérieux problèmes environnementaux et est listée parmi les pays qui contribuent le plus à la pollution et à la destruction de l'environnement mondial. En particulier, la Chine du Sud est une zone naturellement sujette aux glissements de terrain à cause de conditions tectoniques, climatiques et anthropiques particulièrement défavorables. Depuis la fin des années 1990, l'Etat chinois a mis en place des politiques de reforestation de grande envergure. mais il existe des lacunes de connaissances qu'il convient de combler. En particulier, le choix des espèces les plus adaptées n'est pas aisé parce que les processus par lesquels les plantes stabilisent les pentes ont besoin d'être mieux compris.En introduction, afin de mieux préciser les périmètres qui cadrent cette thèse, sont présentées la situation de la Chine du Sud au regard des glissements de terrain, la discipline d'éco-ingénierie et les solutions qu'elle peut apporter. Ainsi, ce travail (i) se concentre sur des espèces végétales locales, (ii) se limite aux glissements de terrain superficiels, et (iii) concerne à la fois les processus mécaniques et hydriques entre le sol et les racines. A l’intérieur de ces cadres, la thèse a pour objectif de répondre à la question scientifique : quels sont les propriétés racinaires qui influencent la stabilisation des pentes ? La réflexion est ensuite appliquée aux plantes de Chine du Sud afin d’identifier les meilleures espèces-outils. Pour répondre à cette question, à la fois les données de terrain (en Chine du Sud), les expériences de laboratoire (en France) et la formulation de concepts sont mobilisées. Les résultats sont organisés en deux chapitres. Le premier pose la question de l’efficacité de la présence de racines pour stabiliser les pentes, tous d’abord sous l’angle des processus mécaniques, puis sous l’angle des processus hydriques. Le deuxième chapitre permet d’identifier un panel de traits pertinents et non redondants évaluant l’efficacité d’une espèce pour la stabilisation des pentes puis s’appuie sur ce panel afin de sélectionner les espèces chinoises les plus efficaces. Enfin, la discussion aborde les limites de ce travail et propose de nouvelles pistes de recherche.Du point de vue mécanique comme du point de vue hydrique, c’est la conjonction des effets des racines de structure et des racines fines qui importe. Les racines de structure sanas racines fines ne sont pas optimales et peuvent même faire apparaître des lignes de fragilité. Plus précisément, les racines de structure sont particulièrement bienvenues vers l’aval de la pente pour des raisons à la fois mécaniques et hydriques. Les racines fines seules ne sont pas optimales non plus, elles peuvent faire apparaître localement des zones de faiblesse qui, si elles sont proches, participeront au déclenchement d’un glissement de terrain. Des ramifications racinaires denses améliorent la stabilité mécanique. Orientées vers l’aval de la pente, elles améliorent la stabilité hydrique. Les autres traits racinaires pertinents pour évaluer l’efficacité des racines à stabiliser le sol sont la contrainte et la déformation maximale en tension, la concentration en azote et la concentration en sucres solubles. / China is currently facing serious environmental issues and is listed among the countries that contribute most to pollution and destruction of the global environment. Particularly, Southern China is naturally prone to landslides because of unfavourable tectonic, climatic and anthropogenic conditions. Since the late 1990s, the Chinese government has implemented policies of large-scale reforestation, but the question of the most suitable species is still pending. The introduction of this thesis presents the different types of landslides, the context in Southern China and what eco-engineering means, in order to clarify the boundaries within which this work is situated. Thus, this study (i) limits itself to the study of superficial landslides, (ii) fits into the requirement scheme of low-cost solutions using local plant species, and (iii) focuses on the root, plant and hotspot degradation scales. Within those geographical, sociological, political and scientific frameworks, this thesis aims to answer the following scientific question: which species and root architectures are the most efficient to stabilize the steep slopes in Southern China? To answer this question, field data (in Southern China), laboratory experiments (in France) and the formulation of concepts are mobilized. The results are organized into two chapters. The first chapter identifies a panel of relevant and nonredundant traits assessing a given species effectiveness in slope stabilization, and then draws on that panel to select the most efficient Chinese species. The second chapter raises the question of the effectiveness of the presence of roots to stabilize slopes, first in terms of mechanical processes, then in terms of hydraulic processes. Finally, the discussion addresses the limitations of that work and suggests new avenues of research. Root traits relevant to assessing the root effectiveness to soil stabilization are maximum tensile stress and strain, nitrogen concentration as well as concentration in water-soluble sugars. The most efficient species among nine pioneer species measured on the Chinese slopes are Pueraria stricta, a legume native from Southeast Asia which plantation happened from reforestation programs, and Artemisia codonocephala, a spontaneous Asteraceae native from Southern China. Recommendations regarding the nine species are presented for the use of their characteristics in eco-engineering. From the mechanical as well as the hydraulic viewpoint, the conjunction of structural roots and fine roots is determinant. Structural roots alone are not optimal and may even bring up lines of weakness. Specifically, for both mechanical and hydric reasons, structural roots are particularly efficient when they grow downslope. Fine roots alone are not optimal either, as they can produce local areas of weakness which, if they are close, can participate in the triggering of a landslide. The branching organization is also particularly important: dense throughout the root profile, branches improve the mechanical stability. Oriented downslope, branching forks improve underground water flow and thus hydraulic stability. The limits of this thesis point out the difficulty to choose indicators and to follow their evolution over time. Another limitation lies in the difficulty to assess the relationship between roots and soil, as the only root resistance is not sufficient to prevent soil from sliding. Finally, the spatial integration of root properties remains challenging. In conclusion, this thesis contributes to improve the knowledge of the plant material available in the mountains of Southern China. Its results will optimize eco-engineering actions related to slope stability. It also upgrades the knowledge about processes at stake between roots and their environment during a landslide

The Vertically Oriented Interlocking Timber (VOIT) panel is a new solid wood panel similar to Interlocking Cross Laminated Timber (ICLT) and the more commonly known Cross Laminated Timber (CLT). Like ICLT, VOIT panels use timber connections instead of the adhesives or metal fasteners common to CLT. The difference of VOIT is the orientation of the layers. Where CLT and ICLT panels alternate the orientation of each layer, VOIT panels orient all the layers in the same direction. The vertically oriented layers are then attached to one another by smaller horizontal dovetail members.Two types of VOIT panels were provided to be tested for in-plane lateral loading. Type I had three rows of horizontal dovetail members connecting the layers and Type II had four rows of dovetail members as well as two diagonal members to provide stiffness. Two panels of each type were provided, measuring 8 ft. wide, 8 ft. tall, and 13.75 in. thick. Each panel was disassembled after monotonic lateral in-plane loading to determine possible failure modes. Testing results suggest the VOIT panels to be comparable in shear strength to other wood shear walls, including light frame, CLT, and ICLT walls. A two-part analytical model was created to determine the deflection of the wall when loaded as well as the shear strength of the wall. The model predicted deflection and wall strength reasonably well. Due to the small sample size, additional testing is necessary to confirm the results of the Type I and Type II VOIT panels. Additional testing with more variations of the panel and member geometries is also needed to validate the scope of the model.

Les opérations de dragage génèrent d’importants volumes de sédiments à teneur en eau élevée qui sont difficilement transportables. Toute opération de valorisation ou stockage des sédiments implique de réduire la teneur en eau. Le séchage naturel et la déshydratation mécanisée des sédiments répondent à cette attente. Le séchage naturel des sédiments est la technique de déshydratation la plus économique et la meilleure du point de vue environnemental. Le temps de séchage peut être réduit par des moyens techniques adaptés (retournement, scarification) mis en action par l'application de critères d’aptitude au séchage naturel. Pour ce faire, le processus de séchage naturel a été reproduit à l’échelle du laboratoire à l’aide d’essais d’Égouttage et de Séchage et d’essais de Séchage et de Retrait couplés à des essais scissométriques. Ils ont porté sur neuf sédiments : sept sédiments de barrage, deux sédiments marins et une kaolinite. Une relation Su=f(IP) a été établie. Cette relation permet d’obtenir la cohésion non drainée Su à partir d’une mesure de teneur en eau. Elle permet aussi de définir ou cerner le moment le plus propice au retournement des sédiments à l’aide d’engins spécifiques sur site. Une autre méthode mécanique pour réduire le temps de séchage est suggérée. Il s'agit de pratiquer une scarification des sédiments à l’aide d’outils mobiles, voire robotisés, comme un rouleau scarificateur ou d'une rangée d'outils transportés par un treillis mobile adapté. En ce qui concerne la déshydratation mécanisée des sédiments, une nouvelle méthode de déshydratation en continu a été proposée à partir d'une presse à boues KDS®. Pour des raisons de conception et d'application, la presse à boues KDS® n’a jamais été utilisée pour déshydrater des sédiments. Un plan expérimental a été développé. Il est démontré que la presse KDS® est capable de déshydrater un sédiment fin sableux sans une maintenance démesurée. Des adaptations de la presse KDS® à la déshydratation de sédiments et des améliorations sont finalement proposées. / Dredging operations produce large amounts of sediments with high water content, that are difficult to handle. Storage management and future reuses need to reduce the water content of sediments. Natural and mechanical dewatering of sediments meet this need. The most economic and eco-friendly method of dewatering is natural dewatering. Dewatering period can be reduced with suitable technical means such as adapted plough or scarifier for sediments, operating under defined dewatering criteria. The natural dewatering process was investigated and reproduced at the laboratory scale by performing Natural dewatering test and Shrinkage test coupled with shear measurements (vane shear testing). Nine sediments have been considered: seven dam sediments, two marine sediments and a kaolinite clay. A relationship Su = f(IP) has been established. It allows to deduce the undrained shear strength Su from only a measurement of water content. It allows to state on the right moment to put in operation the specific tools for ploughing and returning over or scarifying sediments stored. These tools can move in the sediments (adapted plough) or roll on the sediments (scarifiying roller) or roll on banks of sediment storage basin. Another way to dewater high water content sediments concerns a mechanical device. Thus a new method of continuous dewatering has been investigated using a prototype machine patented and referenced as KDS® sludge press. This type of press was not adapted for dewater sediments. Full of dewatering tests have been undertaken and performed with this prototype concerning some of sediments (see natural dewatering testing) and sandy clayey mixtures. It has been shown that KDS® press is able to dehydrate sediments including fine sandy sediments without excessive maintenance. Some adaptations and improvements of KDS® press to dewatering sediments are finally suggested.

Los resultados del estudio que se expone en la presente tesis, tratan sobre las arcillas expansivas en “Talara”, en base a resultados obtenidos en los ensayos de laboratorio como el Análisis Granulométrico por Tamizado, ensayo de Límite Líquido, Límite Plástico e Índice de Plasticidad, ensayo de Proctor modificado y el ensayo Corte Directo. Cabe decir que dichos ensayos se realizaron tomando como punto de partida las características geológicas, geomorfológicas, geotécnicas y la evaluación de daños en las diversas estructuras de la zona como viviendas producto de la expansión y consolidación del terreno. La problemática se origina a raíz del suelo arcilloso, ya que la principal característica que puede tener ese tipo de suelo es que sea un suelo expansivo, por lo tanto, se debe tener en consideración mejorar el suelo para evitar posteriormente daños estructurales. En la investigación se describirán las principales consecuencias y factores que intervienen en el fenómeno de la expansión y el cómo enfrentar a este tipo de suelo. El presente estudio busca la mejora del suelo mediante una técnica innovadora, eco amigable y factible como es la estabilización física usando el vidrio reciclado y las fibras de polipropileno (materiales de desecho en las operaciones de la construcción), ya que en la actualidad estos dos tipos de materiales generan un impacto negativo en el medio ambiente, por lo cual se trata de reutilizar dichos materiales en el mejoramiento del suelo. El estudio se basó en una muestra de suelo medianamente expansivo, debido al registro del Límite Líquido, Límite Plástico e Índice de Plasticidad, extraído de la Urbanización Sudamérica, localizado en Talara, Piura con el fin de mejorarlo, para luego verificar el comportamiento de mejora de las propiedades de resistencia al corte del suelo. Como parte del desarrollo de la investigación se realizaron los diversos ensayos para comprobar con datos numéricos la mejora del suelo, otorgando porcentajes de sustitución con respecto al peso seco (0%, 5%, 6% y 7.5%) a la muestra en estado natural. Finalmente, se obtuvieron las mejoras de las propiedades de resistencia al corte con un porcentaje de sustitución equivalente a 5%, el cual registra las mejoras en cohesión y ángulo de fricción. / The results of the study that is presented in this thesis, deals with the expansive clays in "Talara", based on results obtained in laboratory tests such as the Granulometric Analysis by Screening, Liquid Limit test, Plastic Limit and Plasticity Index, modified Proctor test and the Direct Cut test. It is possible to say that these tests were carried out taking as a starting point the geological, geomorphological, geotechnical characteristics and the evaluation of damages in the different structures of the area as houses product of the expansion and consolidation of the land. The problem originates from the clay soil, since the main characteristic that this type of soil can have is that it is an expansive soil, therefore, it is necessary to consider improving the soil to subsequently avoid structural damage. The research will describe the main consequences and factors involved in the phenomenon of expansion and how to deal with this type of soil. The present study seeks to improve the soil through an innovative, eco-friendly and feasible technique such as physical stabilization using recycled glass and polypropylene fibers (waste materials in construction operations), since these two are currently Types of materials generate a negative impact on the environment, so it is about reusing these materials in soil improvement. The study was based on a sample of moderately expansive soil, due to the registry of the Liquid Limit, Plastic Limit and Plasticity Index, extracted from the South American Urbanization, located in Talara, Piura in order to improve it, and then verify the improvement behavior of the properties of resistance to the cut of the floor. As part of the development of the research, the various tests were carried out to verify the improvement of the soil with numerical data, granting replacement percentages with respect to dry weight (0%, 5%, 6% and 7.5%) to the sample in its natural state . Finally, the improvements of the properties of resistance to the cut with a percentage of substitution equivalent to 5% were obtained, which records the improvements in cohesion and angle of friction. / Tesis

The undrained shear strength and preconsolidation pressure are key parameters in describing the characteristics of soft clays. The two parameters both reflect the clay’s structure and state of stress, and hence empirical correlations for undrained shear strength normalized with respect to preconsolidation pressure are widely used to assess soil behavior. The empirical correlations given in the literature are typically dependent on liquid limit, or plasticity index, but some studies have questioned the dependency and proposed correlations constant for consistency limits. Data from geotechnical projects often display a considerable scatter and deviate from established empirical correlations. In this thesis, statistical analyses are performed and evaluated qualitatively on direct simple shear, constant rate of strain and fall cone test data from 146 sampling points with a total of 596 soil samples from Stockholm, Gothenburg and Uppsala. The aim is to investigate the correlation between shear strength and the preconsolidation pressure. The thesis evaluates the normalized shear strength’s dependency on liquid limit, how the data corresponds to Hansbo’s (1957) and Swedish Geotechnical Institute’s (2007) linear empirical correlations, and the correction factor applied to shear strength measured by the fall cone test. The results of the study show that the correction factor typically reduces the shear strength from fall cone tests too much with respect to shear strength from direct simple shear tests. The normalized shear strength’s dependency on liquid limit may be rejected for the fall cone test data. The results for direct simple shear test data however, indicates a correlation with liquid limit. The data scatter is considerable, especially for fall cone test data, and the relevance of describing the normalized shear strength from fall cone test with a linear empirical correlation to liquid limit may conclusively be questioned. / Skjuvhållfasthet och förkonsolideringstryck är två viktiga jordparametrar för lösa leror. Båda parametrar reflekterar lerans struktur och spänningstillstånd, och empiriska korrelationer för odränerad skjuvhållfasthet, normaliserad mot förkonsolideringstrycket, används därför ofta för att bedöma en leras egenskaper. De empiriska korrelationerna är vanligen kopplade till flytgräns eller plasticitetsindex. Dessa korrelationer har däremot ifrågasatts av studier som i vissa fall istället föreslagit ett konstant förhållande mellan normaliserad odränerad skjuvhållfasthet och plasticitetsgränser. Mätvärden från geotekniska projekt i Sverige visar allmänt stor spridning avseende dessa parametrar och data avviker ofta från etablerade empiriska korrelationer. I examensarbetet har data från direkta skjuvförsök, ödometerförsök och fallkonförsök utvärderats statistiskt och kvalitativt. Totalt omfattar studien 596 jordprover från 146 provtagningspunkter från Stockholm, Göteborg och Uppsala. Syftet med studien är att undersöka korrelationen mellan odränerad skjuvhållfasthet och förkonsolideringstryck. Studien behandlar den normaliserade skjuvhållfashetens flytgränsberoende, Hansbos (1957) och Statens Geotekniska Instituts (2007) empiriska korrelationer, samt den korrektionsfaktor som ska tillämpas på skjuvhållfastheter från fallkonförsök. Resultatet visar att korrektionsfaktorn reducerar skjuvhållfastheten för mycket och att korrigerade skjuvhållfastheter är i sämre samstämmighet med skjuvhållfastheter från direkta skjuvförsök än okorrigerade. Data från fallkonförsök uppvisar inget tydligt flytgränsberoende, medan resultaten från direkta skjuvförsök indikerar ett beroende. Spridningen i data är dock påfallande, särskilt för fallkonförsöket. Relevansen i att tillämpa en linjär empirisk korrelation för odränerad normaliserad från fallkonförsök mot förkonsolideringstryck beroende av flytgräns bör ifrågasättas.

Literature shows that production of cottonseed adhesives is feasible to develop an environmentally friendly and competitive bio-based wood adhesive. Defatted cottonseed and water-washed cottonseed meals were prepared from glandless cottonseed and were used in adhesive formulations to produce three-ply yellow poplar (Liriodendron tulipifera) plywood panels as the first objective. These two cottonseed meals were compared with the properties of plywood panels made with an adhesive formulated from a commercial soybean meal, as a control. Adhesive resins were prepared from each protein meal with sodium metabisulfite (Na2S2O5) and one of two polyamido-amine-epichlorohydrin (PAE) wet strength agents, and the plywood panels were produced by hot pressing for 7, 8.5 and 10 minutes at 135°C with a constant pressure of 1.241 MPa. Panels prepared from three protein meals had comparable shear strengths. The combinations of the two cottonseed preparations and the two wet strength agents produced panels with acceptable wet resistant properties, whereas the soybean meal only produced acceptable panels with one of the wet strength agents. Because the panels prepared from the two cottonseed meals had comparable properties, there appears to be no benefit to including a water-washing step to increase the meal’s protein level. The second objective of this research was to reduce the hot press time and develop cottonseed meals into adhesives to become comparable to commercial soybean-based adhesives. New cottonseed, water-washed cottonseed, and commercial in-house soybean meals were separately prepared with deionized water, sodium metabisulfite, and PAE to produce three-ply yellow poplar plywood panels. The panels were hot pressed for 4, 5, and 6 minutes at 135°C with a constant pressure of 1.241 MPa. Panels prepared from the three meals and commercial soybean plywood panels had comparable mechanical shear strengths and water resistance properties. Results indicated that press time, meal types, and interactions were statistically significant. Shear strength results indicate that cottonseed could be used alternatively to soybean. The new cottonseed panels were more resistant to delamination than soybean. The cottonseed meals showed great promise for applicability as a formaldehyde-free, bio-based, and environmentally friendly hardwood plywood wood-based adhesives product for use in interior type applications.

Interest in the use of mass timber in building and construction is growing worldwide, this is due to the structural integrity and reduced environmental footprint of timber-based structures. Concerns associated with the biological and environmental degradation of mass timber necessitate the development of adequate protection strategies to ensure the durability of these products. Preservative treatment is a proven technique that increases the durability and performance of wood in-service and can also be applied to large-sized timber panels such as cross-laminated timber (CLT). Therefore, this study focused on investigating the feasibility of treating prefabricated 3- and 5-layer CLT panels with Copper-azole type C (CA-C) and micronized copper azole (MCA) preservatives. Further, we studied the effects of panel layup and thickness on the preservative impregnation in CLT. Based on the experimental results, we found adequate preservative penetration and retention in the treated 3- and 5-layer CLT panels, particularly in CA-C treated panels. Also, the lengthwise layup shows better treatment results in both CA-C and MCA-treated panels. In addition to the preservative-treatment of CLT panels, this dissertation covers the development of lignin-reinforced polyurethane adhesive (PUR) for bonding glue-laminated timber (Glulam). Herein, the glulam were fabricated and bonded using lignin-reinforced PUR at different wt% (1, 2, and 3) and tested for shear strength, wood failure and delamination. The lignin-treated PUR samples showed improved adhesion properties via high shear strength and reduced delamination compared to the control specimens. Thus, the lignin-reinforced PUR adhesive shows great potential as a bio-based and environment-friendly wood adhesive for producing glulam used in structural applications.

Advances in wide-bandgap semiconductor devices have increased the allowable operating temperature of power electronic systems. High-temperature devices can benefit applications such as renewable energy, electric vehicles, and space-based power electronics that currently require bulky cooling systems for silicon power devices. Cooling systems can typically be reduced in size or removed by adopting wide-bandgap semiconductor devices, such as silicon carbide. However, to do this, semiconductor device packaging with high reliability at high temperatures is necessary. Transient liquid phase (TLP) die-attach has shown in literature to be a promising bonding technique for this packaging need. In this work TLP has been comprehensively investigated and characterized to assess its viability for high-temperature power electronics applications. The reliability and durability of TLP die-attach was extensively investigated utilizing electrical resistivity measurement as an indicator of material diffusion in gold-indium TLP samples. Criteria of ensuring diffusive stability were also developed. Samples were fabricated by material deposition on glass substrates with variant Au–In compositions but identical barrier layers. They were stressed with thermal cycling to simulate their operating conditions then characterized and compared. Excess indium content in the die-attach was shown to have poor reliability due to material diffusion through barrier layers while samples containing suitable indium content proved reliable throughout the thermal cycling process. This was confirmed by electrical resistivity measurement, EDS, FIB, and SEM characterization. Thermal and mechanical characterization of TLP die-attached samples was also performed to gain a newfound understanding of the relationship between TLP design parameters and die-attach properties. Samples with a SiC diode chip TLP bonded to a copper metalized silicon nitride iv substrate were made using several different values of fabrication parameters such as gold and indium thickness, Au–In ratio, and bonding pressure. The TLP bonds were then characterized for die-attach voiding, shear strength, and thermal impedance. It was found that TLP die-attach offers high average shear force strength of 22.0 kgf and a low average thermal impedance of 0.35 K/W from the device junction to the substrate. The influence of various fabrication parameters on the bond characteristics were also compared, providing information necessary for implementing TLP die-attach into power electronic modules for high-temperature applications. The outcome of the investigation on TLP bonding techniques was incorporated into a new power module design utilizing TLP bonding. A full half-bridge inverter power module for low-power space applications has been designed and analyzed with extensive finite element thermomechanical modeling. In summary, TLP die-attach has investigated to confirm its reliability and to understand how to design effective TLP bonds, this information has been used to design a new high-temperature power electronic module.