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Category: Publications: Geotechnical and Structures Laboratory (GSL)
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  • FIMOFs: Fiber-Integrated Metal–Organic Frameworks through Electrospinning

    Abstract: Green synthesis plays a crucial role in advancing sustainability within materials science. This study explores the integration of metal–organic frameworks (MOFs), obtained through green synthesis, using an electrospinning post-processing technique to develop MOF-based composite materials. The resulting novel multifunctional composites demonstrate enhanced stability and functionality, compared to their control counterparts. The integration of four types of MOFs into an electrospun fiber network was investigated using a specific polymer solution. Characterization and preliminary adsorption studies were conducted to elucidate the chemistry, morphology, and adsorptive capabilities of the resulting MOF composites. Electrospinning MOFs into polymer fibers improved their stability and dye removal capabilities. More specifically, optimization of MOF-to-polymer ratios and processing conditions yielded composites that are thermally stable, with modified surface area and porosity. Post-processing MOFs resulted in a fiber diameter increase of 44 and 109%, enhancing the composites by providing more MOF active sites and improved mechanical strength. Zirconium-based post-processed MOFs demonstrated superior dye removal, different from the copper-based dyes. Electrospinning technology has demonstrated significant potential in the fabrication of high-performance multifunctional MOF composites. This has helped to create advanced sustainable composites with tailored properties, paving the way for more targeted and efficient applications. The applications of these composites show promise for military engineering where durable, light weight, and multifunctional materials are critical in contributing to improved performance, operational efficiency, and safety.
  • Rapid Assessment of Airfield Pavements

    Abstract: The US Navy identified pavement assessment shortfalls under its Facilities Shore Readiness (FSR) program. Two assessment needs were related to (1) rapidly assessing the condition of existing concrete structures such as roads, parking lots, and airfields of port facilities and (2) using nondestructive devices to determine pavement thickness. The project described in this report evaluated the efficacy of two technologies: WayLink Systems Corporation’s automated pavement condition surveys and the MIRA Shear Wave 3D Tomographer, which identify real-time pavement surface conditions and pavement thicknesses, respectively. These commercial off-the-shelf systems offer great potential value, especially when historical construction and maintenance data are unavailable. Test data for this project were collected on asphalt and concrete runways, taxiways, aprons, parking lots, and roads. The overall results indicated that automated pavement surveys are not currently ready for full implementation on airfield pavements. The MIRA tomographer had success in estimating pavement thickness and is recommended for implementation in pavement evaluations.
  • Development of High-Performance Cold Mix Asphalt for Asphalt Patching

    Abstract: Cold mix asphalt (CMA) is commonly used to perform small asphalt patching repairs. It is readily available even when hot mix asphalt (HMA) is not due to distance from a plant or cold weather; it is convenient and can be kept on hand; and it can be used at ambient temperatures. Unfortunately, these advantages are generally offset by marginal performance, especially under heavy loads and at quick return-to-traffic times. For military airfields in particular, both logistical factors and adequate performance are critically important; typical CMAs cannot deliver both, and HMA is not always readily available. Consequently, the objective of this project was to develop a new high-performance CMA that combines convenience and logistical advantages of conventional CMA with the performance expected from HMA. This objective was met using an asphalt-modified polyurethane binder to design cold mix that far outperforms conventional CMA and rivals (exceeds, in some cases) HMA performance, based on both laboratory and full-scale field testing. This two-part material can be field mixed without special mixing equipment; once cured, it is highly elastic, exhibits little temperature sensitivity, and can withstand up to 300 passes of F-15E aircraft traffic with a 3 hr return-to-traffic time (1 in. rutting threshold).
  • Examination of Analytical Shear Stress Predictions for Coastal Dune Evolution

    Abstract: Existing process-based models for simulating coastal foredune evolution largely use the same analytical approach for estimating wind-induced surface shear stress distributions over spatially variable topography. Originally developed for smooth, low-sloping hills, these analytical models face significant limitations when the topography of interest exhibits large height-to-length ratios and/or steep, localized features. In this work, we utilize computational fluid dynamics (CFD) to examine the error trends of a commonly used analytical shear stress model for a series of idealized two-dimensional dune profiles. It is observed that the prediction error of the analytical model increases compared to the CFD simulations for increasing height-to-length ratio and localized slope values. Furthermore, we explore two data-driven methodologies for generating alternative shear stress prediction models, namely, symbolic regression and linear, projection-based, non-intrusive reduced-order modeling. These alternative modeling strategies demonstrate reduced overall error but still suffer in their generalizability to broader sets of dune profiles outside of the training data. Finally, the impact of these improvements on aeolian sediment transport fluxes is examined to demonstrate that even modest improvements to the shear stress prediction can have significant impacts on dune evolution simulations over engineering-relevant timescales.
  • Surface Oxide Removal in Preparation for Controlled Liquid Metal Embrittlement

    Abstract: During liquid metal embrittlement a liquid metal infiltrates grain boundaries of a compatible solid metal, interrupting the inter-grain bonds and weakening the metal. Ongoing research has proposed that this effect may be used to perform additive/subtractive hybrid machining to fabricate replacement components, using relatively simple equipment and low material and instrument costs. The gallium/aluminum pairing is of particular interest due to the usage of aluminum in a wide variety of structural and aerospace applications coupled with gallium’s nontoxicity and melting point just above room temperature, which facilitates storage and transport. To activate aluminum to gallium infiltration, the surface oxide formed on aluminum in atmosphere must first be removed simultaneously with a significant amount of bulk metal to promote flow control of the liquid metal. Three targeted techniques for oxide removal were tested and compared, specifically mechanical abrasion, chemical etching, and laser ablation. Mechanical abrasion is simple to implement but lower precision. Chemical etching requires significant prep work and cleanup but could operate on entire sheets of substrate simultaneously with proper masking. Although laser ablation requires the most complex instrumentation, it requires minimal prep work and provides the greatest precision, making it ideal for the manufacturing application under development here.
  • Tribological Properties of Synthetic and Biosourced Lubricants Enhanced by Graphene and Its Derivatives: A Review

    Abstract: This review explores the tribological properties of biosourced lubricants (biolubricants) enhanced by graphene (Gr) and its derivatives and hybrids. Friction and wear at mechanical interfaces are the primary causes of energy loss and machinery degradation, necessitating effective lubrication strategies. Traditional lubricants derived from mineral oils present environmental challenges, leading to an increased interest in biolubricants derived from plant oils and animal fats. Biolubricants offer high biodegradability, renewability, and low toxicity, positioning them as ecofriendly alternatives. This work extensively reviews the role of Gr-based nanoadditives in enhancing the lubrication properties of biolubricants. Gr with its exceptional physicomechanical properties has shown promise in reducing friction and wear. The review covers various Gr derivatives, including Gr oxide (GO) and reduced Gr oxide (r-GO), and their performance as lubrication additives. The discussion extends to Gr hybrids with metals, polymers, and other 2D materials, highlighting their synergistic effects on the tribological performance. The mechanisms through which these additives enhance lubrication, such as the formation of protective films and improved interactions between lubricants and tribopairs, are examined. Emphasis is placed on the environmental benefits and potential performance improvements of Gr-based biolubricants. Finally, by analyzing current research and technological trends, the paper outlines future prospects for optimizing lubricant formulations with Gr-based nanoadditives, aiming for more sustainable and efficient tribological applications.
  • Insight into the Photocatalytic Degradation Mechanism for “Forever Chemicals” PFNA by Reduced Graphene Oxide/WO3 Nanoflower Heterostructures

    Abstract: Water contamination with “forever chemicals” like per- and polyfluoroalkyl substances (PFAS) poses significant toxicity to the environment. Since they are the most persistent synthetic chemicals that hardly degrade in the natural environment and are carcinogenic to humans, there is an urgent need to discover novel processes for destroying PFAS. Herein, we report on the design of a reduced graphene oxide (r-GO)/WO3 nanoflower (WO3-NF)-based heterostructure for harnessing 365 nm light-driven photocatalytic oxidation and reduction process toward the photocatalytic degradation of perfluorononanoic acid (PFNA). Moreover, reported data reveal that using an r-GO/WO3-NF heterostructure photocatalyst, 100% PFNA degradation and 14% defluorination can be achieved in the presence of isopropyl alcohol as the hydroxy radical (•OH) quencher or glucose as a hot hole (h+) quencher after exposure to 365 nm light for 22 h. A reported mechanistic study shows synergistic oxidation and reduction processes are vital for the complete degradation of PFNA, where the hydrated electron (eaq−) plays a key role as a reducing agent and h+ and •OH act as oxidation agents. Furthermore, the photocatalytic destruction mechanism study indicates that chain shortening via C−C bond breaking and defluorination via C−F bond breaking are major pathways for PFNA degradation. A wavelength-dependent study shows that only 22% degradation can be achieved after exposure to 532 nm light for 22 h, which is due to the lack of the formation of hydrated electrons (eaq−). The current study sheds light on the construction of the r-GO/WO3 NF heterojunction for the highly efficient degradation of PFAS.
  • Erosion Test Database Reassessment with Application to Engineered Soils

    Abstract: This report presents a reevaluation of the soil erosion property relation-ships and a reanalysis of the data with a specific focus on compacted and engineered fill materials. Reinterpretation first centered on describing the parametric space of the database in which the models’ ability to predict critical shear stress and the erodibility coefficient parameter have the greatest uncertainty. Second, this work considered the smaller subset of the dataset with only engineered fill and compacted materials. However, considering only this subset was not found to reduce significantly the uncertainty in predictive capability. We recommend additional work to expand the dataset, focusing on materials in conditions more representative of the compacted and aged soils present on many flood control infrastructure projects.
  • An Investigation of Causes of Inaccuracy of Infrared Radiation Cameras for Large-Scale Additive Manufacturing Applications

    Abstract: In additive manufacturing, accurate temperature data are needed for both real-time feedback for print operators and understanding the thermomechanical behavior for prediction and part quality characterization. Through the collection of accurate temperature data, thermal models can be validated to predict process-induced properties of parts. Infrared radiation (IR) is used to determine the temperature of a surface. Because IR cameras measure thermal radiation from a distance without contact, they are safe to use in high-temperature environments like 3D printing. An investigation of reported temperature values for multiple cameras during one print showed a decreasing trend for cameras close to the printer’s heat sources, which was not reflective of the printing process, and a discrepancy of ±20°C when printing at 200°C across overlapping camera views. Two more prints were studied to determine whether this camera behavior was unique to that print and geometry. The analysis showed the same results across all three prints, with camera-reported values having inconsistencies for a single layer, a subset of layers, and the scale of the print. Multiple possibilities for the cameras’ variances were explored. The IR cameras were determined to require further calibration and experimentation before reported temperature values can be treated as physical temperature values.
  • Bridge Load Rating for US Army Installations: Guidance

    Abstract: This report summarizes Army policy and provides technical guidance for the load rating of vehicular and railroad bridges on US Army installations. These bridges must be load rated to determine and ensure their abilities to support the Army’s heavy military vehicles as well as all public-sector cars, trucks, or trains (in the case of railroad bridges). Installation bridge management and load ratings are accomplished under the Installation Management Command (IMCOM) Army Dams and Transportation Infrastructure Program (ADTIP), with technical support from the US Army Engineer Research and Development Center (ERDC).