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Polymeric materials are popular in civil infrastructure due to their durability, strength, and resistance to corrosion and environmental degradation. However, the long-term performance of such materials in civil infrastructure is still being researched and investigated. This thesis will focus on the long-term performance of two civil infrastructure applications: 1) high-density polyethylene (HDPE) above-ground storage tanks (AST) and 2) silicone and self-healing polymeric concrete sealants. HDPE is a strong and durable plastic material that is commonly used to store a wide range of liquids ASTs. Currently, there are no established protocols for carrying out non-destructive testing (NDT) and assessment of HDPE ASTs for regular inspections, so this study investigated the viability of using infrared thermography (IRT) and ultrasonic testing (UT) for routine inspection. The study discovered that environmental parameters, such as temperature, wind, and humidity, can affect IRT accuracy, and that a proper heating-cooling cycle can aid in defect detection. Concrete joints in pavement systems are often susceptible to deterioration. They are engineered cracks that enable concrete slabs to expand and contract in response to temperature. They serve the dual purpose of preventing water infiltration and improving ride quality, while extending the pavement's service life. Bridge joints, in particular, are susceptible to water and liquid penetration, which can result in extensive damage over time. By applying sealants to these connections, concrete structures can be protected from such damage, thereby extending their service life. Consequently, a better comprehension of sealant performance and additional research are required to develop effective solutions to address these issues and ensure the safety and longevity of concrete structures prone to cracking. In this study, samples of the two commercial silicone joint sealants were sandwiched between Portland cement mortar specimens and tested using a specially designed fixture to imitate the fatigue performance of the joint under simulated field conditions. The results of the study indicated that the fatigue life of the two silicone sealants were different, with Sealant 2 showed better performance than Sealant 1. Both sealants exhibited adhesive failure initiating debonding along the weak interface of cement mortar cube and joint sealant. The results of commercial sealants are then compared with self-healing polysulfide sealants. This indicates that the performance of sealants can vary, and additional research may be required to develop effective solutions to address these issues. / Master of Science / Polymeric materials are widely utilized in construction due to their durability, strength, and resistance to corrosion and environmental degradation. However, the long-term performance of these materials in civil infrastructure is still under investigation. This thesis specifically examines the long-term performance of two civil infrastructure applications: 1) high-density polyethylene (HDPE) above-ground storage tanks (ASTs) and 2) silicone and self-healing polymeric concrete sealants. HDPE is a robust and durable plastic material commonly employed for storing various liquids in ASTs. Currently, there are no established protocols for conducting non-destructive testing (NDT) and assessment of HDPE ASTs during regular inspections. Therefore, this study investigates the viability of utilizing infrared thermography (IRT) and ultrasonic testing (UT) for routine inspections. The findings reveal that environmental factors such as temperature, wind, and humidity can impact the accuracy of IRT, and implementing a proper heating-cooling cycle can help in detecting such defects inside the tank structure. Concrete joints in pavement systems are susceptible to deterioration. These engineered cracks allow concrete slabs to expand and contract in response to temperature changes, while preventing water infiltration and enhancing ride quality, thus prolonging the pavement's service life. Bridge joints, in particular, are prone to water and liquid penetration, leading to extensive damage over time. Applying sealants to these connections safeguards concrete structures, extending their service life. Consequently, understanding sealant performance and conducting further research are crucial for developing effective solutions to address these issues and ensure the safety and durability of concrete structures prone to cracking. This study involves testing two commercially available silicone joint sealants by sandwiching them between Portland cement mortar specimens. A specially designed fixture is employed to simulate the fatigue performance of joints under field-like conditions. The performance of commercial sealants was also compared with self-healing polysulfide sealants. These findings highlight the variability in sealant performance, emphasizing the need for additional research to develop effective solutions.

Subconcussive impacts have become a growing concern particularly with respect to contact sports. It is believed that minimal head impacts can cause cerebral perturbations that initiate an immune response creating a window of vulnerability. Evidence suggests that additional head insults sustained during this window of vulnerability elicit an exaggerated inflammatory response and exacerbate cognitive deficits. Therefore, determining the lower limits of systematic perturbation resulting from low-level impacts is of critical importance in expanding our understanding of cerebral vulnerability and recovery. However, the vast majority of experimental investigations of subconcussion fail to model single impact events and instead focus on cumulative insults. Additionally, these animal models employ impact magnitudes used to model mild Traumatic Brain Injury. The present investigation aimed to address this gap in knowledge through the utilization of a pneumatically controlled, closed-head, blunt impact device capable of producing repeatable, defined, subconcussive head impacts within a rat model. Thermography was used as a noninvasive measure of inflammation and system perturbations with respect to local (head) and global (thorax and abdomen) temperature changes. Cognitive function was assessed using an Open Field Test and Novel Object Recognition test. Neuroinflammation was measured by assessment of GFAP and iba-1 within the hippocampus and corpus callosum. To investigate the tolerance and the persistence of cerebral vulnerability, measurement outcomes were assessed at six timepoints of recovery, 0, 0.5, 1, 4, 7, and 14 days. Thermal disturbances were detected directly after impact, followed by an apparent recovery, 0.5- and 1-day post-impact. A latent temperature increase was observed after 4- and 7-days of recovery coinciding with decreased risk-avoidance behaviors, a modest upregulation of iba-1, and a marked downregulation of GFAP. Short-term memory deficits became apparent after 7-days of recovery. A decrease in locomotor activity and an upregulation of GFAP was observed concomitant to a persistent decrease in risk-avoidance despite thermal, short-term memory, and iba-1 measurements recovery 14-days post-impact. Overall, these results indicate that low magnitude subconcussive impacts can produce latent thermal, behavioral, and histological disturbances uncharacteristic for a head injury model suggestive of a biomechanical threshold of altered pathodynamics that fail to fully recover after 14 days.

Effective mental workload measurement is critical because mental workload significantly affects human performance. A non-invasive and objective workload measurement tool is needed to overcome limitations of current mental workload measures. Further, training/learning increases mental workload during skill or knowledge acquisition, followed by a decreased mental workload, though sufficient training times are unknown. The objectives of this study were to: (1) investigate the efficacy of using thermography as a non-contact physiological measure to quantify mental workload, (2) quantify and describe the relationship between mental workload and learning/training, and, (3) introduce a method to determine a sufficient training time and an optimal human performance level for a novel task by using thermography. Three studies were conducted to address these objectives. The first study investigated the efficacy of using thermography to quantity the relationship between mental workload and facial temperature changes while learning an alpha-numeric task. Thermography measured and quantified the mental workload level successfully. Strong and significant correlations were found among thermography, performance, and subjective workload measures (MCH and SWAT ratings). The second study investigated the utility of using a psychophysical approach to determine workload levels that maximize performance on a cognitive task. The second study consisted of an adjustment session (participants adjusted their own workload levels) and work session (participants worked at the chosen workload level). Participants were found to fall into two performance groups (low and high performers by accuracy rate) and results were significantly different. Thermography demonstrated whether both group found their optimal workload level. The last study investigated efficacy of using thermography to quantify mental workload level in a complex training/learning environment. Experienced drivers’ performance data was used as criteria to indicate whether novice drivers mastered the driving skills. Strong and significant correlations were found among thermography, subjective workload measures, and performance measures in novice drivers. This study verified that thermography is a reliable and valid way to measure workload as a non-invasive and objective method. Also, thermography provided more practical results than subjective workload measures for simple and complex cognitive tasks. Thermography showed the capability to identify a sufficient training time for simple or complex cognitive tasks.

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Transition is an important phenomenon in large scale, commercial, wind tunnel testing at low speeds because it is an excellent indicator of an airfoil performance. It is difficult to estimate transition through numerical techniques because of the complex nature of viscous flow. Therefore experimental techniques can be essential. Over the transition region the rate of heat transfer shows significant increases which can be detected using infrared thermography. This technique has been used predominantly at high speeds, on small models made of insulated materials, and for short test runs. Large scale testing has not been widely undertaken because the high sensitivity of transition to external factors makes it difficult to detect. The present study records the process undertaken to develop, implement and validate a transition detection system for continual use in the Virginia Tech Stability Wind Tunnel: a low speed, commercial wind tunnel where large, aluminium models are tested. The final system developed comprises of two high resolution FLIR A655sc infrared cameras; four 63.5-mm diameter circular windows; aluminium models covered in 0.8-mm silicone rubber insulation and a top layer of ConTact© paper; and a series of 25.4-mm wide rubber silicone fiberglass insulated heaters mounted inside the model and controlled externally by experimenters. This system produces images or videos of the model and the associated transition location, which is later extracted through image processing methods to give a final transition location in percentage chord. The system was validated using two DU96-W-180 airfoils of different chord lengths in the Virginia Tech Stability Wind Tunnel, each tested two months apart. The system proved to be robust and efficient, while not affecting the airfoil performance or any other system in use in the wind tunnel. Transition results produced by the system were compared to measurements obtained from pressure data and stethoscope tests as well as the numerical predictions of XFOIL. The transition results from all four methods showed excellent agreement with each other for the two models, for at least two Reynolds numbers and for several angles of attack on both suction and pressure side of the model. The agreement of data obtained under such different conditions and at different times suggests that the infrared thermography system efficiently and accurately detects transition for large aluminium models at low speeds. / Master of Science

Statistics released in the fall 1989 showed that 238,357 (41%) of the nation's 577,710 bridges are either structurally deficient or functionally obsolete. New materials, such as fiber reinforced polymeric composites (FRP), are being suggested for use in bridge systems to solve some of the current problems. These materials are thought to be less affected by corrosive environmental conditions than conventional civil engineering materials. Therefore they may require less maintenance and provide longer life spans. More specifically, glass fiber reinforced vinyl ester matrix composites are considered possible replacements for deteriorating conventional bridge decks due to their durability, decreased weight, and relative affordability. In order to facilitate rapid acceptance of FRP structural components into the world of civil structural engineering, effective and efficient NDE techniques must be explored and documented in these situations. This thesis will discuss the use of Infrared Thermography (IRT) as a means of detecting debonds and voids caused by conditions encountered both in fabrication and in the field. As forced convective hot air is applied within the bridge deck, debonds between bridge deck components near the riding surface appear cold while imperfections near the bottom of the deck give rise to concentrations of heat. These variations in thermal propagation patterns are observed by the infrared camera and indicate possible structural deficiencies. Results of experimentation and thermal analyses from laboratory studies of a model bridge deck and some from in situ full-scale investigations are presented. / Master of Science

Les composites thermoplastiques sont de plus en plus privilégiées dans les structures aérospatiales au vue de leur tolérance aux dommages améliorée par rapport aux résines thermodurcissables. Néanmoins, ils restent sensibles à l’impact car il produit des endommagements complexes au sein du matériau, dont le délaminage est le plus critique. La propagation de ces endommagements en compression après impact (CAI) entraîne une réduction de la tenue résiduelle. D’abord, des essais ENF ont été menés afin de déterminer la ténacité interfaciale par le biais de la méthode de la complaisance et de la technique de thermographie infrarouge. Ensuite, l’essai « Short Beam Shear » est proposé afin d’investiguer le couplage entre la fissuration matricielle et le délaminage. L’effet de la vitesse de sollicitation a été également étudié. La valeur de ténacité mesurée semble indépendante à la vitesse de sollicitation car, lors des essais réalisés, la propagation est instable. Ensuite, le comportement d’une éprouvette académique été étudié à l’aide du « Discrete Ply Model » (DPM) permettant d’enchaîner la simulation d’impact et de CAI. Ce modèle est basé sur une approche semi-discrète modélisant le délaminage et la fissuration matricielle par des éléments cohésifs, permettant de prendre en compte le couplage entre ces deux endommagements. Une vaste campagne d'essais expérimentaux d’impact et de CAI a été mise en place sur quatre empilements différents impactés à trois niveaux d’énergie. Le modèle DPM a prouvé sa capacité à prédire correctement les endommagements d’impact et de CAI. Finalement, afin de se rapprocher des conditions de structures réelles, le comportement en compression après impact d’une plaque trouée a été investigué. / High-performance thermoplastic composite have been increasingly used in aerospace applications because of their advantageous mechanical properties. Nevertheless, impact damage leads to significant reduction in structure compressive strength although damage may remain unnoticed. Delamination is the most critical damage. Short Beam Shear (SBS) test has been proposed to reproduce impact damage chronology and characterize delamination toughness. Infrared thermography is used for local measuring of fracture toughness in this unclassical test showing unstable fracture growth. Mode II fracture toughness (GIIC) values are comprised between 0.9 and 1.7 N/mm and there was no influence of the loading rate in GIIC values. Discrete Ply Model (DPM) is therefore used to model impact and compression after impact tests on laminated composite structures. Tests have been conducted in order to validate DPM capacity to capture the effects of progressive damage and failure. Impact damage and specimen’s compressive strength is well predicted by DPM. CAI damage propagation is driven by the buckling of the structure. DPM is finally employed to study impact on an industrial sample with a large diameter hole. Impact damage correlates with tests but buckling is difficult to estimate, meaning that rupture of the specimen does not correlate to tests. Nevertheless, DPM shows a good ability to predict damage in thermoplastic composite.

The removal of water is an integral part of tissue paper production. Through air drying (TAD) is used for water removal when producing premium tissue grade products, however, at the price of higher energy demand. A better understanding of TAD may therefore lower the energy demand. The objective was to investigate the influence of formation, pulp type and grammage on non-uniform drying and air flow through sheets. A laboratory method, based on infrared thermography, was used to determine drying time and area-specific and mass-specific drying rates. Air flow rate and pressure drop were used to determine flow resistance and modified permeability. Pulp type had a large influence on the air flow through the sheet. Modified permeability, i.e. the material property describing the air flow through the fibre network, was strongly dependent on grammage for lower grammages, while it approached a constant value for higher grammages. In contrast to that, mass-specific drying rates were similar for the different pulp types at lower grammages, but proved to be grammage-dependent for higher grammages. Formation did not influence the drying speed to any large extent. The results illustrate that industrial TAD processes operate under very special process conditions due to the low grammage sheets.

O controle ambiental nas instalações pecuárias é um fator importante a ser levado em consideração para promover o bem-estar e otimizar a produção animal. Como o clima brasileiro é predominantemente tropical, sistemas de resfriamento são essenciais em instalações pecuárias em todo o país. Diferentes sistemas de resfriamento estão disponíveis no mercado brasileiro e, apesar de possuírem o mesmo objetivo, de atenuar a temperatura dentro do galpão, podem ser percebidos pelos animais de modos diferentes. O objetivo principal deste trabalho foi avaliar a percepção de suínos através de sua preferência em relação a diferentes sistemas de resfriamento do ambiente em uma câmara de preferência ambiental. Esta avaliação foi feita por meio do teste de preferência, que consiste em fornecer alternativas entre diferentes situações ou recursos, para que os animais transmitam suas respostas. Para tanto, foi utilizada uma câmara de preferência ambiental composta por quatro compartimentos interligados entre si por uma área neutra. Cada compartimento teve seu ambiente controlado independentemente, podendo assim fornecer, quatro diferentes tipos de sistemas de resfriamento: nebulização associada à ventilação forçada, ventilação forçada, aspersão e aspersão associada a ventilação forçada. Nesse estudo de preferência, dois grupos principais de suínos foram utilizados: os suínos-teste e os suínos-companhia. Os suínos-teste foram os animais com livre acesso aos distintos compartimentos da câmara e os suínos-companhia, por sua vez, ficaram confinados em seus respectivos sistemas. Para caracterização do ambiente no interior e no exterior da câmara, foram utilizados data-loggers para coleta das variáveis: temperatura ambiental, umidade relativa, temperatura de globo negro e ponto de orvalho; para determinação dos índices de conforto térmico: índice de temperatura de globo e umidade e entalpia. Também foi coletada a velocidade do ar com anemômetro digital. Foram verificadas medidas fisiológicas: frequência respiratória e temperatura de superfície corporal na região da nuca no horário das 14 horas. Para analisar o desempenho dos animais foi avaliado ganho de peso diário e conversão alimentar, além das medidas in vivo de espessura de toucinho, rendimento de carne magra e profundidade da área do lombo. Para avaliação do teste de preferência foram considerados dias que caracterizassem condições climáticas em que os sistemas de resfriamento estivessem em operação. Para isto vídeos coletaram e registraram as imagens e estas foram analisadas automaticamente e interpretadas como preferência por (ou rejeição de) certos ambientes através de frequência e tempo do suíno-teste em cada um dos ambientes. A câmara conseguiu atender os valores recomendados para o índice de temperatura de globo e umidade, temperatura ambiental e umidade relativa ao longo dos períodos do dia, os valores obtidos para entalpia estiveram acima do recomendado na literatura. Porém o desempenho da câmara foi satisfatório, uma vez que as medidas fisiológicas de frequência respiratória e temperatura superficial, e as variáveis de desempenho indicaram que os animais estavam em conforto térmico e obtiveram medidas de espessura de toucinho, rendimento de carne magra e profundidade da área do lombo característicos para a categoria. Em relação à preferência dos suínos-teste, observou-se a maior frequência de permanência nos sistemas de aspersão (40%) e aspersão associada à ventilação forçada (34,7%). Assim os resultados obtidos validaram o uso da câmara de preferência ambiental para experimentação com suínos a fim de verificar sua preferência em relação a diferentes ambientes térmicos com diferentes sistemas de resfriamento. / Environmental control in livestock buildings is an important factor to be taken into account to promote the welfare and optimize the animal production. As the Brazilian climate is predominantly tropical, cooling systems are essential in animal facilities across the country. Different cooling systems are available in the Brazilian market and, despite having the same goal, to mitigate the temperature inside the shed, they can be perceived by the animals in different ways. The aim of this study was to evaluate the perception of pigs through their preference in relation to the different environment of the cooling systems in an environmental preference chamber. This assessment was made by the preference test, which is to provide alternatives between different situations or resources, so that the animals transmit their responses. An environmental preference chamber was used, and consisted of four compartments connected to each other by a neutral area. Each compartment has its environmental conditions controlled independently, and may thus provide four different types of cooling system: nebulizer associated to forced ventilation, forced ventilation, sprinkler and sprinkler associated to forced ventilation. In this preference study, two main groups of pigs were used: the test-pigs and companion-pigs. The test-pigs were the animals with free access to the chamber and companion-pigs, in turn, were confined in their respective systems. To characterize the environment inside and outside the chamber, data-loggers were used to collect the variables: ambient temperature, relative humidity, black globe temperature and dew point; to determine the levels of index thermal comfort: globe temperature and humidity index and enthalpy. The air speed with digital anemometer also was collected. Physiological measures were also registered: respiratory rate and body surface temperature in the neck region in the schedule at 2pm. Daily gain and feed conversion were evaluated to analyze the performance of the animals in addition to the measures in vivo backfat thickness, lean yield and depth of loin area. The preference test considered days that characterize climatic conditions in which the cooling systems were in operation. The video images were collected and recorded and they were automatically analyzed and interpreted as a preference (or rejection) of certain environments through the frequency and time that test-pig in each environment. The environmental preference chamber conditions attended the recommended values for globe temperature and humidity index, ambient temperature and relative humidity over the periods of the day, and the values obtained for enthalpy were slightly above the recommended literature. The chamber performance was satisfactory since the physiological measures respiratory rate and body surface temperature and the performance variables indicated that the animals were in thermal comfort and obtained backfat thickness, lean yield and depth of loin area measures, characteristic for the category. Regarding the preference of the test-pigs, the highest frequency was observed in sprinkler (40%) and sprinkler associated to forced ventilation (34,7%) systems. Thus the results validated the use of the environmental preference chamber for experimentation with pigs in order to verify their perception to different thermal environments with different cooling systems.