This study was made to determine the advantages of the use of epoxy resins in the industrial arts laboratory. The purpose of this study was to determine the feasibility of using epoxy resins as a wood adhesive. Data was gathered from texts, periodicals, and unpublished data. Tests were conducted using epoxy samples acquired from three epoxy manufacturers on three different woods and joints. The study discusses the advantages and disadvantages of using epoxy resins as a wood adhesive and the material and equipment necessary for the use of epoxy resins. Strength tests were performed on the joints adhered with epoxy and on joints adhered with white glue. A hand operated high tensile strength machine was used to conduct the tests. Epoxy Resins were found, in most cases, to give a more durable bond than white glue. Further studies should be made using epoxy resins as adhesives for metal, glass, plastic, and other materials used in the industrial arts laboratory.

L'assemblage de matériaux par collage pour l'aéronautique est une solution à laquelle les industriels pensent depuis longtemps pour alléger les structures. Cependant, les adhésifs développés de nos jours ne sont pas suffisamment performants pour remplacer les méthodes traditionnelles (rivetage, boulonnage, etc..). Notamment, la température de service limite la performance d'un joint adhésif. Pour élargir l'opérabilité d'un assemblage collé, la première solution proposée a consisté à utiliser deux adhésifs dans un même joint : c'est le concept du joint multi-adhésif. Plus récemment, plusieurs travaux de recherche ont fait évoluer ce concept en utilisant un joint adhésif avec des propriétés variables discontinues le long de la surface encollée. Le présent manuscrit propose une nouvelle évolution de ce concept, où cette fois-ci la variation de propriétés est continue le long du joint adhésif : on parlera de concept de joint adhésif aux propriétés graduées (JAPG). L’idée du concept du JAPG réside dans la possibilité de diffusion de copolymères au sein d’une résine époxyde-amine, créant ainsi un gradient de concentration en copolymères, et donc un gradient de propriétés le long du joint. Suite à l’optimisation de la mise en œuvre de ce type de joint, le cœur du travail s’est articulé autour de la définition de méthodes de caractérisation d’assemblages collés sensibles à la modularité des propriétés d’adhérence induites par ces adhésifs hybrides. Plus précisément la puissance d’adhérence a été quantifiée lors de la phase d’encollage dans laquelle l’adhésif est sous forme de gel, puis lorsque l’adhésif est rigide au sein de la structure collée en service. Les tests choisis sont un test de tack à poinçon plat et un test de clivage en coin. Cette volonté de suivre l’évolution de l’adhérence durant toute la transformation de l’état physique de l’adhésif s’explique par la nécessité de maitriser la compétition entre forces de cohésion internes à l’adhésif qui prédominent quand l’adhésif est rigide et forces d’adhésion qui se créent lors de la mise en contact de l’adhésif avec le substrat. Les tests mécaniques sélectionnés et adaptés se sont finalement révélés être des outils sensibles et fiables pour caractériser l'adhérence d'un JAPG. Cette étude a montré qu’un tel joint possède des propriétés d’adhérence supérieures à celles de ses contreparties mono-adhésives de par la distribution hétérogène des copolymères dans le joint. / Bonded assemblies are a solution for which the aeronautical industry is looking forward to lighten airplanes since a long time. However, adhesives used nowadays are not equivalent to traditional methods, performance-wise. Particularly, in life temperature is one of the parameters that limit the performance of adhesive joints. A first attempt to solve this problem saw the birth of the multi adhesive joint, where two adhesive are used in the same joint. Recently, several works proposed an evolution of this concept, where the properties are changed gradually along the joint. This thesis moves one step forward by proposing yet another evolution. We designed an adhesive joint where the properties are continually graded over the joint: an adhesive joint with a gradient of properties (AJGP). Continuous grading is obtained by designing an adhesive joint with two adhesives. One of those is obtained from a classical epoxy-amine system. The other adhesive is made with the same epoxy-amine matrix, with the addition of amphiphilic tribloc copolymers. The latter is a nanostructured adhesive, which exhibit higher toughness than the former. When those adhesives are placed in the same joint, an interdiffusion phenomenon occurs. This allows copolymers diffusion along the joint. This work is split in two complementary research axis: first, a AJGP joint is designed and realized, to be tested either during bonding or in-life. Second, experimental tests are used to assess fracture toughness of the AJGP joint, with the challenge in mind to be able to detect an adherence variation along the joint. We chose a probe tack test and two wedge tests (cleavage test and driven wedge test) as mechanical tests. Those mechanical tests proved useful to assess adherence properties of an AJGP, which exhibits higher properties than its mono-adhesives counterpart

In this work, epoxy resins were modeled using all atom representations in nanoscale simulation boxes. Tetrafunctional epoxy and corresponding multifunctional amine were chosen as model materials. Algorithms of constructing interconnected network structures were invented developed to properly account for the chemical structures and computational cost. Monomers were generated in diamond lattice and crosslinked to model complex epoxy multifunctional network. The initial configurations were relaxed and equilibrated using molecular dynamics and suitable force field. Physical, thermal and mechanical properties resulting from equilibrated simulation box are in good agreement with experimental results. Possible impact of chemical degradation was studied by adopting oxidation and hydrolysis algorithms. Mechanism of degradation was based on bonds reaction probability and chemical structures of epoxies. Both oxidation and hydrolysis were found to decrease materials performances by reducing number of crosslinking points. Elastic modulus of materials was directly related to crosslinking density. Interfaces between two types of epoxies were constructed to study interactions at interfaces. Covalent bonds linking two components play an important role in interfacial strength. Free volume calculation helps to identify and monitor nucleation of crazes and voids within materials. It was found voids and cracks prefer to initiate and grow at 2 interfaces and lead to failures. Additional compatibilizer layers can improve overall composite performances by preventing void growth at interfaces. Diffusion pattern of water in epoxy resins was studied by tracking displacement of single molecules during certain time intervals. The characteristic of water diffusion in epoxies was interpreted by free volume theory. Reactive force field was introduced to study thermal degradation behavior of epoxy resins. Number of molecules and variation of different types of covalent bonds during heating processes were tracked and analyzed to uncover the degradation mechanism of epoxy resins.

Thesis--Auburn University, 2010. / Abstract. Includes bibliographic references.

Thesis (M.S.)--Mississippi State University. Department of Chemical Engineering. / Title from title screen. Includes bibliographical references.

Ce travail a pour objectif d'évaluer l'impact de la nanostructuration de résines d'imprégnation, destinées aux isolations statoriques d'alternateur de puissance, sur leurs propriétés électriques et thermiques. La première étape concerne l'étude de résines d'imprégnation aux propriétés physiques supérieures à celles des résines actuellement utilisées. La seconde étape concerne la détermination des caractéristiques de prototypes industriels développés par les sociétés Von Roll et Alstom ; ces prototypes sont composés d'un substrat « ruban » (composé de papier micacé et de tissu de verre) imprégné d'une résine innovante. Les améliorations apportées par les modifications des résines et des rubans permettent d'obtenir, dans le meilleur des cas, des augmentations respectives pouvant aller jusqu'à 14 % pour la rigidité diélectrique, 30 % pour la diffusivité thermique et 100 % pour l'endurance en tension. Une diminution de 33% des niveaux de charges d'espace accumulées est aussi observable. Les résultats obtenus lors de ce travail de thèse montrent qu'il est possible, dans certains cas, d'améliorer les propriétés électriques et/ou thermiques des isolations en modifiant les résines de référence par l'ajout de particules submicroniques de nitrure de bore (BN) et/ou de nanoparticules de dioxyde de silicium (SiO2). Cependant, il est également montré que ces propriétés peuvent être fortement influencées par le processus de fabrication, notamment par les paramètres de polymérisation. / This work aims to access the impact of nanostructuring over the impregnation resin, developed for the electrical insulation of alternator stator bars, on their electrical and thermal properties. The first step of this study concerns the analysis of impregnation resins with improved physical properties with respect to the usual resins. The second part concerns the characterization of prototypes which are manufactured by Alstom and Von Roll companies; these prototypes are composed by a tape (mica paper and glass fabric) impregnated with the innovative resin.In the best case, the modifications of the resins and the prototypes led to respective improvements up to 14 % for the dielectric strength, 30 % for the thermal diffusivity and 100 % for the voltage endurance. A decrease up to 33 % of the space charge levels can be also observed.The results obtained show that it is possible, in some cases, to improve the electrical and the thermal properties of the insulation by modifying the impregnation resin and the prototypes, with the addition of boron nitride (BN) submicron particles and/or silicon dioxide (SiO2) nanoparticles. However, it is shown that these properties can be highly influenced by the manufacture process of the resin and the prototypes, in particular by the curing parameters.

This research explores the use of carbon/epoxy and fiberglass/epoxy fiber-reinforced polymer (FRP) composite rebar manufactured on a three-dimensional braiding machine for use as reinforcement in concrete beams under four-point bending loads. Multiple tows of prepreg composite fibers were pulled to form a unidirectional core. The core was consolidated with spirally wound Kevlar fibers which were designed to also act as ribs to increase pullout strength. The rebar was cured at 121â—¦C (250â—¦F) in an inline oven while keeping tension on the fibers. Five configurations of reinforcing bars were used in this study as reinforcement in concrete beam specimens: carbon/epoxy rebar and fiberglass/epoxy rebar were manufactured on the three-dimensional braiding machine and cured in an inline oven while still under tension immediately after production; carbon/epoxy rebar was manufactured by IsoTruss industries on the three-dimensional braiding machine and was rolled and stored before curing; fiberglass/epoxy rebar was purchased from American Fiberglass; conventional No. 4 steel rebar was also purchased. All bars were embedded in 152 cm (60 in) long, 11 cm (4.5 in) wide, and 15 cm (6.0 in) tall concrete beams. Beams were tested under four-point bending loads after which three 30 cm (12 in) specimens were taken from the ends of each configuration to be tested under axial compression loads in order to investigate the effects of the concrete voids on the concrete strength. Concrete beams reinforced with BYU glass/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 5% greater compression bending stress and 11% greater tension bending stress than concrete beams reinforced with industry manufactured glass/epoxy rebar. Concrete beams reinforced with BYU carbon/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 18% lower compression bending stress and 64% lower tension bending stress than concrete beams reinforced with industry manufactured carbon/epoxy rebar. BYU glass/epoxy rebar has a 3% greater stiffness and 1% greater displacement than industry manufactured glass/epoxy rebar and BYU carbon/epoxy rebar has a 40% greater bending stiffness and 19% lower displacement than industry carbon/epoxy rebar. BYU carbon/epoxy rebar has 49% lower compression bending stress, 1% lower tension bending stress, 28% lower displacement, and a 68% greater bending stiffness than BYU glass/epoxy rebar. BYU glass/epoxy rebar has 38% greater compression bending stress, 30% lower tension bending stress, 26% greater center displacement, and a 105% lower bending stiffness than conventional steel. BYU carbon/epoxy rebar has 8% lower compression bending stress, 31% lower tension bending stress, and 22% lower bending stiffness than steel. The deflections of steel reinforced concrete and BYU carbon/epoxy reinforced concrete are comparable with steel rebar displaying a 1% greater center displacement than BYU carbon/epoxy rebar.

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No description available.