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A thin wire Ag/AgCl reference electrode was prepared using 50 μm Ag wire in dilute FeCl3. The wire was embedded beneath the polyurethane topcoat of two sacrificial coating systems to monitor their corrosion potential. This is the first report of a reference electrode embedded between organic coating layers to monitor substrate health. The embedded reference electrode (ERE) successfully monitored the corrosion potential of Mg primer on AA 2024-T3 for 800 days of constant immersion in dilute Harrison’s solution. Zn primer on steel had low accuracy in comparison. This is in part due to short circuiting by Zn oxidation products, which are much more conductive than Mg corrosion products. Data interpretation was improved through statistical analysis. On average, ERE corrosion potentials are 0.1 to 0.2 V and 0.2 to 0.3 V more positive than a saturated calomel electrode (SCE) in solution for AA 2024-T3 and steel coating systems, respectively. Further research may confirm that ERE obtains corrosion potential information not possible by an exterior, conventional reference electrode. The ERE is stable under polarization. AA 2024-T3 was polarized to -0.95 V vs ERE to emulate controlled potential cathodic protection (CPCP) applications. Polarizations of -0.75 V vs ERE are recommended for future experiments to minimize cathodic delamination. The ERE was utilized to analyze coating mixtures of lithium carbonate, magnesium nitrate, and Mg metal on AA2024-T3. Corrosion potential, low frequency impedance by electrochemical impedance spectroscopy (EIS), and noise resistance by electrochemical noise method (ENM) were reported. Coating performance ranking is consistent with standard electrochemical characterization and visual analyses. The results suggest anti-corrosion resistance superior to a standard Mg primer following 1600 hours of B117 salt spray. Both lithium carbonate and magnesium nitrate are necessary to achieve corrosion protection. Unique corrosion protective coatings for aluminum could be designed through continued mixture optimization. The Ag wire ERE has been utilized for the characterization and ranking of experimental coatings on metal substrates. Structural health monitoring and corrosion potential feedback of cathodic protection systems are additional uses. There is some indication that CPCP may be applied by ERE to control the substrate polarization for an organic coating system.

Fiber-reinforced composite (FRC) materials are ideal for the aerospace and automotive industries which require high-strength structures with exceptional specific properties. The unfortunate reality is composite materials are susceptible to complex failure modes and difficult-to-predict damage growth as a result of their heterogeneity and anisotropy. Thus, robust structural health monitoring (SHM) for in-operation tracking of damage formation and accumulation is important for these materials. Self-sensing materials are a strong candidate to replace traditional composite SHM because they do not suffer from the disadvantages of point-based sensing. The piezoresistive effect in nanofiller-modified materials is a common approach to material self-sensing. Research to date in piezoresistivity has predominantly focused on the direct current (DC) response of such materials. This is an important limitation because alternating current (AC) has important advantages – it inherently possesses more information (AC data can relate both impedance magnitude and phase to damage), AC effects can be leveraged for improved damage sensitivity, and AC interrogation can reduce power requirements. Therefore, to develop knowledge that will facilitate the transition to AC, this work explores the effect of high-cycle<br>fatigue loading on the AC response of carbon nanofiber (CNF)-modified glass fiber/epoxy laminates. In this study, impedance magnitude and phase angle are measured along the length and through the thickness of composite specimens with an open-hole stress concentration<br>subjected to tension fatigue-loading up to 10 MHz. The collected impedance data is fit to an equivalent circuit model as a function of cycle. These results show that high-cycle fatigue loading does indeed have an appreciable effect on the equivalent circuit behavior of the material. However, clear and definitive trends were not observed thereby suggesting that further research is needed into the basic mechanisms of AC transport in nanocomposites if frequency-dependent transport is to be used to track fatigue loading. <br>

The main goal of this research is to investigate vulnerability of levees to future slump slides. In the first part, polarimetric synthetic aperture radar (PolSAR) imagery is used as input in an automated classification system for characterizing areas on the levee having anomalies. In addition, a set of in-situ soil data is collected to provide detailed soil properties over the study area. In-situ soil properties of different classes characterized by the classifier are analyzed to determine how similarities between different areas. The second part, a database including of 34 slump slides that occurred in the lower Mississippi River levee system over a period of two years is used. The impacts of rainfall as well as several spatial geometrical and geomorphological variables (including channel width, river sinuosity index, riverbank erosion, channel shape condition and distance to river) are analyzed and tested for significance and used for developing a logistic regression model.

As the use of polymer matrix composites for structures increases, there is a growing need for monitoring these structures. Distributed strain sensing using optical fibers shows promise for monitoring composite structures due to optical fiber's small size, light weight, and ability to obtain continuously distributed strain data. This study investigates the feasibility of using embedded optical fibers using two case studies: embedding the fibers in the adhesive layer of double lap shear composite specimens, and within composite end-notched flexure specimens to locate a growing crack front. To establish a repeatable fabrication methodology, manufacturing techniques for embedding the optical fibers were investigated. The measured strain distribution from the optical fibers compares well with data obtained from finite element analyses for both the double lap shear and end-notch flexure specimens. Additionally, the embedded optical fibers do not seem to impact the failure loads or fracture behavior of the specimens.

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<p dir="ltr">The research in this thesis focuses on developing an alert system to detect damage or impact on bridge. It employs Raspberry Pi and accelerometers for real-time health monitoring. The methodology includes bridge model creation, testing under no damage, impact, and structural damage conditions, and data processing for vibration frequency analysis. The aim is to differentiate between normal bridge conditions, collisions, and structural damages, providing timely notifications for necessary investigations or repairs. The study addresses the challenges in bridge safety and aims to improve maintenance efficiency and reliability.</p><p><br></p>