Este trabalho apresenta conceitos da fabricação de compósitos com o objetivo de avaliar a influência das condições do processo de fabricação nas propriedades mecânicas do laminado. É comum utilizar ensaios mecânicos para determinar as propriedades do produto final a fim de otimizar e adicionar confiabilidade ao projeto e o objetivo deste trabalho é estudar uma das fontes de variação das características em compósitos estruturais, que é o processo de cura. Embora pela regra das misturas se considere que a relação ponderada entre os elementos de matriz e reforço resulte na propriedade final do laminado, é necessário entender que existe influência do processo de fabricação para a obtenção deste potencial. O processo de cura é uma das etapas mais importantes na fabricação de componentes em polímeros reforçados e consiste na utilização de certo nível de energia que propicia a polimerização da matriz e formação da estrutura monolítica do material compósito. Para a simulação desta variação, através de ensaios laboratoriais são definidas condições de cura que reflitam uma diferença razoável de temperatura de transição vítrea. Com a definição dos parâmetros de cura, laminados bi diagonais são fabricados por processo de moldagem por transferência de resina assistida por vácuo e as características mecânicas destes laminados são mensuradas em ensaios que seguem padrões normalizados pela ISO em condições de tração, compressão e flexão. Os resultados destes ensaios são comparados entre si, a fim de direcionar o projetista em compósitos para a relevância e impacto do processo produtivo na vida do componente. / This work introduces manufacturing concepts for composites parts targeting to evaluate the influence of manufacturing process conditions in the final mechanical properties of the laminates. It is usual to utilize mechanical tests to define and predict properties of the actual component aiming to optimize and add reliability to the design. The main purpose of this study is to evaluate one of the main sources of variation that becomes form the curing process. Although from the mixture rules is possible to consider the final product property as the weighted relation between matrix and reinforcement properties, its needed to understand that the manufacturing process affects the achievement of this potential. Curing is one of the most important steps on the composites manufacturing and consists in the use of some source of energy to start matrix polymerization and formation of a monolithic structure with at least two phases from when becomes the composites concept. To simulate this variation through laboratorial tests, firstly the curing condition was defined to reflect a reasonable difference of glass transition temperature between the samples. After the definition of the curing condition bi diagonal laminate panels were prepared through vacuum assisted resin transfer molding and their mechanical characteristics evaluated by laboratory tests following international ISO standards in tensile, compression and flexural trials. Results of the tests are compared for the purpose of guiding composites designers for the relevance of manufacturing process and its impact on the component life.

abstract: Deformation during hydration of concrete includes curling at joints and terminations. Previous research has explored mix designs, chemical additives, and other material factors to minimize slab distortion due to curling. This research study explores the development and use of externally applied silicone-based compounds after both the placing and cutting of joints. This exploratory study presents the results of controlled testing and a field study results that include distortion of contraction joints as measured with a Spectra LL300N under existing environmental conditions. Specifically, the study presents the results of a side-by-side test of two slabs, a base case, and a silicone-altered case, as well as field measures of two large commercial buildings using the developed methods. The results of the study show reduced distortion due to curling as compared to standard comparative slabs and warrant the continued exploration and testing of the concept. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

This study is to evaluate the effect of curing and casting methods on the physicochemical properties of polymeric coating systems. Aqueous-dispersion-based and organic-solvent-based Kollicoat® SR30D (poly(vinyl acetate)) and Kollicoat® MAE100P (poly(methacrylic acid-ethyl acrylate)) free films or film-coated pellets were used to evaluate the physicochemical properties resulting from different solvents and different curing treatments. Diffusion coefficients of water in organic-solvent-based films were lower than those in aqueous-dispersion-based films. Increases in curing temperature and curing time decreased the diffusion coefficient. Regardless of preparation method, the tensile strengths of films increased with an increase in curing temperature and curing time. Changes in elongation percentage of the films were dependent on the polymer and curing. The tensile strengths of aqueous-dispersion-based SR30D films are lower compared to those of organic-solvent-based SR30D films. However, the “core-shell” structure is preserved in the aqueous-dispersion-based MAE100P film and formed a rigid frame, which greatly increased the mechanical properties of the films. Therefore, the tensile strength of aqueous-dispersion-based MAE100P films is greater than in the case of organic-solvent-based films. In swelling studies, water uptake and weight loss for all of the films increased with an increase in incubation time. The water uptake and weight loss of SR30D films cast from water were higher than those of organic-solvent-based films. However, contradictory results were observed for MAE100P films due to the core-shell structure in the aqueous-dispersion-based MAE100P films. An increase in curing time and temperature increased the Tg of SR30D films. Curing treatments led to a second glass transition temperature for MAE100P films, which may result from microphase separation. Curing decreased acetaminophen release from pellets coated with an aqueous-dispersion-based SR30D film. Curing effects are also dependent on the coating formulation and coating parameters. The drug release rate from organic-solvent-based film-coated pellets was slower in comparison to pellets coated with aqueous-dispersion-based films. Acetaminophen release in 0.1 N HCl from aqueous-dispersion-based MAE100P coated pellets was reduced after the curing treatment. Curing has no effect on drug release for acetaminophen-containing pellets coated with organic-solvent-based SR30D or MAE100P films. The ionization of surface carboxylic-acid groups on MAE100P polymer particles alters the properties of polymer films by increasing ionic aggregates and solubilizing the polymer chains. Increased ionic aggregates improve the mechanical properties of films. However, solubilizing polymer chains will change the film formation mechanism from a dispersion-based film to a solution-based film. Therefore, tensile strength was decreased with an increase in ionization degree. The drug release rates were continuously increased when the degree of ionization of surface acid groups increased. Overall, curing and casting methods have significant effects on the physicochemical properties of SR30D and MAE100P films and on the drug release behavior from film-coated, drug-loaded pellets. The core-shell structure in aqueous-dispersion-based MAE100P films also greatly changed the properties of this film or coat.

This dissertation presents a literature review of the state-of-practice for the use of IC in concrete mixtures and how structural engineers and construction engineers can adapt IC to their present and future work. Current high early strength concrete mixtures have natural cracking and shrinkage problems due to the high content of cementitious material or their chemical components. Using IC allows for early strength, enhanced durability, reduced shrinkage and a better curing by providing water that can be absorbed by the cement past after the final set. Rapid hydration and high early strength Portland cement and calcium sulfoaluminate (CSA) concretes are commonly used as pavement repair media. The fresh properties (slump, setting time), mechanical properties (elastic modulus, compressive and tensile strength), and volume stability (autogenous shrinkage, drying shrinkage, restrained ring shrinkage, and creep) of rapid repair media were evaluated with and without internal curing with saturated lightweight aggregate. Significant improvements in volume stability were also noted. Results indicate that internal curing can successfully improve volume stability and mitigate restrained shrinkage cracking in rapid repair media without compromising fresh properties or ultimate mechanical strength. Maturity was observed for CSA mixtures and exhibited a correlation with compressive strength development which could be beneficial for rapid repair media on the field.

Increasing demands for more reliability and functionalities in electronic devices have pushed the electronics industry to adopt newly developed materials and reduce interconnect sizes and spacing. These adaptations have led to concerns of reliability failures caused by conductive anodic filament formation (CAF). CAF is a conductive copper-containing salt that forms via an electrochemical process. It is initiated at the anode and grows along the epoxy/glass interface to the cathode, and once CAF reaches the cathode a short circuit will occur. The objective of this research is to evaluate and compare the effects of curing agents (DICY vs. phenolic-cured epoxy) and drilling methods (laser vs. mechanical drilling) on CAF formation using an insulation resistance test at 85 ºC, relative humidity of 85%, and a voltage gradient of 0.4V/µm. Time-to-failure for DICY-cured and phenolic-cured epoxy with laser drilled microvias and mechanically drilled vias were determined using the insulation resistance test. The failed coupons were cross-sectioned and examined using a Scanning Electron Microscope equipped with Energy-dispersive X-ray spectroscopy to verify the existence of CAF. Weibull analysis was used to compare the reliability and identify the failure modes of the failed coupons. Test results show that DICY-cured epoxy is a better CAF resistant material than phenolic-cured epoxy. It is believed that the brittleness of phenolic-cured material might enhance the damage to the epoxy/glass fiber interface during drilling; and hence, facilitate subsequent CAF formation. The study also shows that laser drilled microvias are less prone to CAF formation than mechanically drilled vias, because there is less mechanical damage and lower glass fiber content. Finally, using Weibull analysis, it is determined that laser drilled microvias experienced infant-mortality failure, whereas mechanically drilled vias exhibited a wear-out type failure.

The objectives of the proposed research are to model, optimize, and control variable frequency microwave (VFM) curing of polymer dielectrics. With an increasing demand for new materials and improved material properties, there is a corresponding demand for new material processing techniques that lead to comparable or better material properties than conventional methods. Presently, conventional thermal processing steps can take several hours. A new thermal processing technique known as variable frequency microwave curing can perform the same processing steps in minutes without compromising the intrinsic material properties. Current limitations in VFM processing include uncertain process characterization methods, lack of reliable temperature measuring techniques, and the lack of control over the various processes occurring in the VFM chamber. Therefore, the proposed research addressed these challenges by: (1) development of accurate empirical process models using statistical experimental design and neural networks; (2) recipe synthesis using genetic algorithms; (3) implementation of an acoustic temperature sensor for VFM process monitoring; and (4) implementation of neural control strategies for VFM processing. and #8194;

Concrete curing has long been realized to be important to produce durable concrete. Curing compound is widely used to cure concrete in the field. The current curing membrane evaluation method ASTM C 156, however, is incapable of distinguishing the curing compound quality and guiding the curing practice in the field. A new laboratory curing membrane evaluation protocol is developed in this study. It has the ability to rank the quality of curing compound and guide curing practice in the field according to the field ambient weather conditions and the type of curing compound. A series of field tests were conducted to investigate the key factors that affect the curing effectiveness in the field conditions. A finite element program, temperature and moisture analysis for curing concrete (TMAC2), is updated to solve the coupled and nonlinear heat transfer and moisture transport problems in early-age concrete. Moisture capacity is induced into the TMAC2, which makes it unique to characterize the self-desiccation. A full scale concrete pavement test study was conducted at the FAA National Airport Pavement Test Facility (NAPTF) near Atlantic City, New Jersey. In this study, the material properties, i.e. thermal conductivity and moisture diffusivity, were backcalculated from field data. Thereafter, backcalculated material properties were used to forward-calculate the temperature and moisture histories of all other sections. High order shear deformable theory is used to model the concrete slab curling and warping behavior because of highly nonlinear temperature and moisture gradients. The maximum shear strain is obtained a couple of inches below the concrete slab. This might account for the occurrence of delamination.

Prime coats have been in use for many decades to help protect the base before the subsequent application of bituminous surface treatments. Prime coat is an application of a low viscosity binder onto the base to help protect the base from moisture, to provide an adequate bond between the bituminous surface coating and the base, to strengthen the base near the surface by binding the fines, and to protect the base from detrimental effects of weather and light traffic until the surface can be constructed. For a prime coat to function efficiently it should penetrate sufficiently into the base and should be cured before the application of subsequent layers. Evaluation of the time required for curing of prime coats and how the curing time depends on various weather parameters has received a lack of attention. In view of this, the time taken for curing of different prime coats and the dependence of curing time on weather parameters was studied. The prime coats most commonly used in Texas were selected for this study, namely; MC-30, EC-30, CSS-1H, SS-1H and AEP. All testing was done in real conditions, that is, samples were prepared and exposed to actual weather conditions. Since each prime coat is chemically very different, they were analyzed separately to determine the minimum curing time. Curing time was calculated in three different weather conditions to understand how the weather affects curing time. Further, two different application methods were used to determine the effect of application method on the curing time. In addition to determining curing times, other important engineering properties of prime coats that determine the performance of prime coats such as strength, permeability and penetration were also studied. Strength and permeability tests were done on cured specimens and the effect of application method on these values was also determined. Strength values were measured using a pocket penetrometer and penetration was determined by using sand penetration tests. A unique ranking system list was developed using curing time, strength, penetration and permeability as the key factors to determine the prime coat which would serve all the intended functions effectively and efficiently. / text

CO2 absorption behaviour of four commonly used cement based building products: cement paste, concrete block, expanded polystyrene bead (EPB) and cement-bonded cellulose fiberboard are studied. Cement products are manufactured following industry formulation and process, and carbonation curing takes place in a chamber under a pressure of 0.5 MPa, at ambient temperature, for durations of mostly 2 to 8 hours with both pure carbon dioxide gas and flue gas. The flue gas of 13.8% CO2 content is collected from a typical cement kiln without separation. Influencing factors on carbon uptake, long-term strength as well as microstructure development are studied. / It is found that the CO2 uptake ability of those cement-based products follows the same order when exposed to either pure gas or flue gas: fiberboard has the highest uptake capacity, followed by cement paste, bead board and concrete. For fiberboard, the best CO2 uptake in flue gas is 8.1%, it reaches 23.6% if pure gas used. Introduction of cellulose fiber in the fiberboard significantly increases voids volume and cement paste surface area through dispersing the paste onto fiber surface, effectively increasing carbonation reaction sites and thus CO2 uptake. / For pure gas carbonation with high reaction rate, it takes longer time for carbonated products to further develop strength from subsequent hydration, due to the high water loss during carbonation, the densified cement matrix structures and even fast decalcified cement minerals. Fast carbonation with pure gas is detrimental to cement paste in its long-term strength. For flue gas carbonation, both immediate strengths and long-term strength of the products are comparable with those by pure gas carbonation, although with less CO 2 uptake ability. / Five CO2 uptake determination methods are evaluated. Weight gain method is suitable for both pure gas and flue gas carbonation systems. Mass curve method is more suited for pure gas carbonation. For flue gas carbonation, CO2 concentration method agreed well with the weight gain method. Pressure drop method is relatively less accurate because of water vapor generation during carbonation.

Isobutylene-rich elastomers bearing functional groups that engage N-arylmaleimides in C-H bond addition and/or alternating copolymerization are described. While inactive to cross-linking when treated at high temperature with peroxide alone, these co-curing elastomers can be cross-linked substantially when combined with bis-maleimide coagents such as N,N’-m-phenylene dimaleimide (BMI). Poly(isobutylene-co-isoprene) (IIR) samples containing relatively high amounts of residual isoprene unsaturation are shown to provide relatively low coagent cure reactivity, whereas IIR derivatives bearing pendant polyether or vinyl ether functionality are shown to provide exceptional cross-linking rates and extents when treated with identical BMI formulations. The design of such co-curing elastomers is discussed, along with the physical properties of the resulting vulcanizates. Isobutylene rich elastomers bearing oligomerizable (C=C) functional groups, macromonomers, that are activated in the presence of free-radical initiators are described. The criteria for determining the macromonomers that are best suited for preparing thermosets of IIR is discussed. While IIR derivatives bearing pendant acrylic, styrenic and maleimide functionality are shown to provide exceptional cross-linking rates and extents, they are also shown to suffer from instability in the absence of peroxide. IIR carrying pendant methacrylic and itaconate functionality are shown to provide a good balance of cure rates and stability. Nitroxyl based radical trap that provides scorch protection to the macromonomers while regenerating the cure extent is discussed. Functional macromonomer derivatives of IIR bearing containing multi-functional pendant groups are discussed. IIR derivatives with itaconate and low amounts of BHT pendant groups is shown to act as bound anti-oxidant while IIR containing pendant fluoro groups are shown to have reduced surface energy. Ionic coagents are used to cross-link IIR containing itaconate pendant groups and their physical properties are discussed. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2012-07-06 11:20:56.915