Establishing And Advancing Qualification Strategies For Aerospace Components Produced Using LPBF

The adoption of Laser Powder Bed Fusion (LPBF) for aerospace hardware requires qualification strategies that ensure repeatable, reliable, and certifiable performance. This dissertation focuses on a qualification effort for an aerospace titanium bracket to be used for a serial production aircraft, following a fixed-process, sample-centric methodology. The work was performed following industry expectations for mechanical performance, dimensional tolerance, and process control, and culminated in the successful qualification of the bracket for flight hardware installation. The qualification effort was divided into four primary objectives. Machine and parameter qualification was first to establish a baseline LPBF process on an SLM 280 HL system using Ti-6Al-4V powder feedstock. Results across repeated builds revealed spatial variations in mechanical performance, particularly in areas with insufficient gas flow. These findings led to a redesign of the gas flow system in collaboration with the OEM, which significantly improved build uniformity. Second, material, process, and supplier qualification were conducted using an extensive test matrix, which included tensile, shear, fatigue, fracture toughness, metallography, and chemistry assessments, all done at NADCAP-certified laboratories. All results met or exceeded aerospace OEM requirements, and the process was frozen for production use. Third, part qualification confirmed that the LPBF bracket satisfied all functional, dimensional, and material criteria. The first article underwent CMM-based dimensional inspection, tensile testing, and X-ray computed tomography, all of which passed the necessary quality metrics. Additional blue-light scanning during development revealed as-built distortion, informing optimization of build orientation and support strategy. Lessons learned included the impact of hot isostatic pressing on final geometry and the need to lock orientation early to avoid requalification. Fourth, recurring production testing monitored quality over time. Statistical process control tools (Cp, Cpk, Pp, Ppk) revealed that oxygen contamination (due to inconsistent purge practices) led to chemistry drift and degradation in ductility. A change was implemented to ensure purging reached a verified oxygen threshold before each build. Additionally, a comparative fatigue study demonstrated the feasibility of ultrasonic fatigue testing as a rapid, cost-effective screening tool. Equivalent results were achieved between traditional uniaxial fatigue (20 Hz) and ultrasonic testing (20 kHz), with a reduction in test time from almost six days to under ten minutes for 10 million cycles. This finding supports the integration of high-throughput fatigue methods into future qualification protocols. The dissertation concludes with a forward-looking proposal to evolve from a sample-centric to a subsystem-centric qualification model. Rather than relying solely on sample testing, this approach emphasizes the performance of core machine subsystems (mainly gas flow and atmosphere control). Additional recommendations include subsystem benchmarking, beam profiling, powder reuse management, and advanced fatigue characterization. In summary, this work not only qualifies a functional aerospace component but also contributes a robust case study in the maturation of LPBF process control and lays the groundwork for scalable, repeatable qualification methodologies that will support the broader industrialization of metal AM in aerospace

Tailoring Functional And Sensing Properties Of Polymer-Ceramic Composites Via 3d Printing

Section 1.1. Abstract This chapter investigates the use of direct ink write (DIW) additive manufacturing to control grain orientation in non-toxic barium titanate (BTO) ceramics by blending spherical and platelet-shaped particles in the ink. A series of inks containing 0–40 wt.% BTO platelets were formulated with poly(vinyl alcohol), polyethylene glycol, poly(acrylic acid-co-maleic acid), and ammonium hydroxide to ensure printability and homogeneous dispersion. Cylindrical specimens (20 mm × 3 mm) were printed using a Hyrel 30M DIW system and subjected to de-binding (650 °C, 2 h) followed by a two-step sintering schedule (T₁: 1200–1350 °C; T₂: 700–850 °C; 24 h dwell). Relative density peaked at 85.9 % for 0 wt.% platelets (1300 °C/800 °C) and decreased with increasing platelet content due to inhibited grain-boundary diffusion. SEM and XRD analyses confirmed platelet alignment parallel to the build plate, with Lotgering factors (F₂₀₀) rising from 0.00 (0 wt.%) to 0.63 (40 wt.%). This texturization produced a 29.6 % enhancement in dielectric constant compared to randomly oriented ceramics. The results demonstrate that DIW-induced shear alignment coupled with optimized thermal processing can tailor microstructure and functional performance of BTO ceramics for sensor and energy-storage applications. Section 2.1. Abstract This chapter presents the development of multifunctional lattice structures fabricated from a novel PEEK–carbon fiber (CF)/carbon nanotube (CNT) composite filament for fused filament fabrication (FFF). An optimized melt-blend extrusion process produced filaments with 11.6 wt.% CF and 12 wt.% CNT, yielding uniform dispersion and robust interfacial bonding. Two lattice geometries—truncated octahedron and re-entrant auxetic—were selected to exploit plateau stress regions (5–15 % strain) for decoupling piezoresistive and thermoresistive responses. Printed specimens exhibited surface roughness as low as ~20 µm Ra, compressive strengths up to 60 MPa, and electrical conductivities reaching 0.067 S/m. Cyclic loading under controlled temperatures (25–100 °C) confirmed stable resistance during plateau stress and a positive temperature coefficient of resistance with \u3c 0.3 % variation, achieving 99.7 % repeatability. These results demonstrate that lattice architecture, combined with tailored composite formulation, enables selective force and temperature sensing in a single-material system. Section 3.1. Abstract This chapter introduces Hybrid PIZCAL, a multi-material lattice architecture enabling programmable directional piezoelectric sensing via fused filament fabrication (FFF). Using an ABS–BaTiO₃ composite filament with 20 vol.% ceramic loading co-printed alongside pure PLA, we create geometrically anisotropic lattices that concentrate mechanical strain along the Z-axis while passivating the X–Y planes. Thermal poling (3 kV/mm at 85 °C) aligns dipoles in the active regions, yielding a Z-axis voltage-per-mass output of 13.7 mV/g—293 % higher than a monolithic piezoelectric cube—while suppressing transverse responses by \u3e20 %. Finite-element simulations confirm compliance contrasts exceeding 5× between axes, and SEM micrographs demonstrate homogeneous BaTiO₃ dispersion within the ABS matrix. The Hybrid PIZCAL thus combines topological control with material zoning to deliver high-fidelity, single-axis sensing in a single-step AM process, paving the way for advanced wearable, robotic, and structural-health-monitoring applications

Thermal Inkjet Bioprinting Of Human Fibroblasts Into Stem Cell Environment Leads To Stem-Like Gene And Protein Expression And Changes In Hippo Pathway Effectors Yap/taz

Thermal inkjet bioprinting (TIB) has emerged as a powerful tool with many potential applications, such as organ regeneration, drug testing, and cell differentiation, among others. Despite the forces and stress that cells are subjected to during the printing process, there is little research that investigates in detail the combined effects of the TIB process and the surrounding environment on cells. Furthermore, a cell\u27s biological environment greatly influences its behavior. Therefore, understanding the effects of bioprinting on cells in a particular environment at a genetic level can provide clues regarding changes in cell characteristics. Bioprinting could potentially be used as a tool for reprogramming or differentiation into different cell types. We hypothesize that using a thermal inkjet bioprinter to bioprint human fibroblasts into induced pluripotent stem cell (iPSC) media will stress the cells, induce disruption of their membranes, and encourage them to upregulate stem-cell-related genes and proteins in response to their environment. Apart from assessing TIB-related changes in gene and protein expression, this work also assesses changes seen in the Hippo pathway effectors YAP/TAZ, as nuclear localization of these has been shown to have positive effects in reprogramming to pluripotency.In this study, we investigated changes in thermal inkjet bioprinted human dermal fibroblasts printed into a stem cell environment using different techniques. We performed immunocytochemistry to assess changes in stem related proteins, lamin A/C, and Hippo pathway effectors. RNA sequencing analyses were conducted at different time points to assess changes in gene expression dynamics at different time points. Finally, DNA methylation studies and analyses on DNA integrity were conducted to examine the impacts of TIB on DNA. Results from RNA sequencing experiments showed differential expression of genes involved in pluripotency-relevant pathways and upregulation of some genes associated with stemness. Immunocytochemistry experiments revealed increases in stem cell markers, particularly for the earlier stem cell marker Lin28b in bioprinted cells, which was particularly prominent at the 24-hour time point post-printing. Analysis of YAP and TAZ localization behavior revealed increased nuclear expression of both YAP and TAZ in TIB cells compared to control cells. Further analyses on YAP dynamics as a result of TIB revealed that stresses on the cell during the TIB process could be influencing YAP phosphorylation at serine 128 and allowing it to enter the nucleus. Finally, DNA methylation analysis revealed decreases in DNA methylation right after printing. The results of this study reveal fundamental changes in gene and protein expression that should be taken into account when using TIB cells in other experiments and that could be used to our benefit to develop new methods of cell engineering and cell reprogramming

Humboldt County

Danny Marquez, a police sergeant for the Los Angeles Police Department, takes his family on a vacation to Seattle, Washington. On the way, they stop in Humboldt County, and Danny is captivated by the beauty and serenity of this county. He imagines moving his family to Humboldt County and leaving the troubles of big city life behind. He applied for the position of Chief Inspector for the Humboldt Police. By the time he is hired, he loses both his son to Fentanyl and his wife to suicide. He is hired for the position but finds himself alone. He considers suicide. His only consideration is where to do it. When the body of a foreign college student is found in Samoa Dunes, he decides he has must find justice for her. While constantly reminded that he is wasting his time and resources, he remains vigilant. He decides he must stand up for this student, and he takes on the challenge of solving this murder mystery. In doing so, he discovers that suffering can lead to redemption and grace

BIM Assessment for State Departments of Transportation

Building Information Modeling (BIM) has been used by the Architecture, Engineering, and Construction (AEC) industry to enhance the efficiency and quality of work across various stages, including planning, design, construction, and operation and maintenance (OM) of projects. Despite widespread adoption in vertical construction, BIM implementation in infrastructure projects is still falling behind. This disparity can be attributed to several factors, including the complexity and scale of infrastructure projects and varying levels of BIM adoption and integration within organizations. Efforts to standardize BIM practices and enhance the digital capabilities of infrastructure projects are essential to bridge this gap and ensure the industry can benefit from the efficiencies and improvements that BIM offers. This study aims to assess BIM maturity at the organizational level for transportation agencies. The BIM Maturity Index (BMI) sub-elements were grouped based on existing literature and mapped to the National Strategic Roadmap published by the Federal Highway Administration (FHWA) to standardize the terms used in evaluating BIM maturity. A survey questionnaire and BIM maturity tool was developed and administered to several state departments of transportation to assess the current state of BIM implementation in those states. The results indicate that BIM use is still in the initial stages for many of the sub-elements of the BIM Maturity Index and that a lack of standardization of terms remains the most significant challenge among transportation agencies

Exploring Willingness To Seek Help And Well-Being In Rural Veterans With Health Conditions: A National Rural Health Study

The population of Veterans in the United States has increased significantly, with a substantial number residing in rural areas. This study aims to highlight and understand the correlation between military service members\u27 physical and mental well-being and the quality/access to care they receive. This study also aims to explore mental health-seeking behaviors, health, and well-being in rural Veterans with health conditions. The study included 400 rural-dwelling Veterans with documented physical and mental health conditions. Data was collected through surveys distributed via various media channels, including social media platforms, and the results demonstrated that willingness to seek psychological help was positively correlated with rural Veteran\u27s well-being. The results highlight the critical role of willingness to seek mental health support and access to mental health and substance use care services for rural Veterans. These findings can inform policies and interventions aimed at enhancing overall well-being and quality of life for this population

Evaluating Extrusion Model Accuracy Using Laser Profilometry In Ceramic Robocasting Via Custom G-Code

This thesis presents an experimental validation of a simplified extrusion model intended to predict dimensional accuracy in ceramic Direct-Ink Writing (DIW). Given the inherent complexity of ceramic paste formulations, extrusion processes, and shape retention during additive manufacturing, it is crucial to validate simplified models that can accurately forecast bead geometry and subsequent dimensional fidelity. A custom-designed force tester was developed to emulate ram extrusion conditions and determine key parameters using the Benbow-Bridgwater equation while attempting to be a low-cost alternative. This approach is meant for rapid, affordable assessment of ceramic paste extrusion characteristics without the need for complex rheological testing. The force tester fell short of expectations due to the number of tests necessary to acquire the paste characteristics of a single formulation. Single-line, single-layer, and multi-layer prints were produced and assessed using a laser profilometry scanning system. Bead and layer geometries were measured, evaluating the predictive accuracy of the simplified volumetric extrusion calculation typically employed in polymer extrusion slicers. Experimental results demonstrated that the simplified model accurately predicted bead width and height to within approximately 5-10% of targeted dimensions under stable extrusion conditions. Through these investigations, the study identified critical processing parameters that influence dimensional fidelity, including optimal nozzle dimensions, infill overlap and layer spacing. Additionally, the presence of extrusion defects such as bead discontinuities, pressure fluctuations, and liquid-phase migration were characterized and related directly to paste formulation and printing parameters. Ultimately, this research confirms the practical utility of simplified extrusion models in ceramic DIW, highlighting their capabilities and limitations. The insights gained provide a solid foundation for future advancements in slicer development and extrusion control, aimed at enhancing the predictability, consistency, and dimensional accuracy of printed ceramic parts

The Bullied Prairie Vole: Modeling Depression And Anxiety Through Social Defeat Stress

Stress-induced illnesses, such as major depression and anxiety, are significant global causes of disability. This highlights the need for reliable animal models that accurately mimic social stress-induced maladaptations, thus, allowing the experimental study of the etiology of such disorders. Prairie voles (Microtus ochrogaster), known for their human-like bi-parental behavior and monogamous partner preferences, are a relevant model for the study of stress-induced psychopathologies. For this reason, in this dissertation, I examined whether exposing voles to the social defeat stress (SDS) paradigm, an experimental approach that captures bullying behavior, would result in both depression and anxiety-related profiles. To do this, experimental voles were exposed to 10-minute agonistic interactions with a paired male aggressor over 10 consecutive days, as it is conventionally done in laboratory mice. Control animals were housed under similar conditions but did not experience stress. To evaluate the effects of SDS on depression-related behavior, I adopted (1) the social interaction test, (2) sucrose preference, and (3) Morris water maze tests, which are validated approaches to assess depressive-relevant phenotypes (i.e., social withdrawal, anhedonia, and spatial memory impairment, respectively). Additionally, I evaluated responses to open-space exploratory behavior on the (4) light/dark box and (5) elevated plus-maze tests, since they are commonly adopted to study anxiety-related behavior across rodent species. I found that SDS decreased body weight, sociability, sucrose preference (anhedonia), exploratory behavior, and impaired spatial memory performance. No changes in general locomotor activity were noted between the experimental groups. Collectively, the findings of this dissertation support the notion that the SDS model, in male prairie voles, is a valuable tool for studying stress-induced phenotypes that resemble human-like depression and anxiety-relevant profiles

Mechanical Characterization of M Plane (10-10) and C Plane (0001) Gallium Nitride Semiconductors via Spherical Nanoindentation

Gallium nitride\u27s (GaN) mechanical characterization is essential for evaluating its performance and long-term dependability, especially when subjected to mechanical stress and irradiation. The design and optimization of GaN-based devices, which are extensively employed in high-power electronics and optoelectronics, depend on an understanding of these characteristics. Mechanical characterization allows for the evaluation of key characteristics, including stress distributions, representing the spatial variation of internal stresses under applied loading, and pop-in events, which correspond to abrupt displacements associated with the onset of dislocation nucleation and slip. These features are essential for understanding the anisotropic (direction-dependent) response of the material to external forces and environmental conditions. Additionally, the use of GaN in harsh environments, such as those exposed to radiation, can lead to degradation, which may affect its structural integrity and functionality. Through the examination of load-displacement responses acquired using a spherical indenter, the mechanical characteristics of gallium nitride wafers with c-plane (0001) and m-plane (10-10) orientations are examined in this work. A useful method for assessing important mechanical traits like hardness, elastic modulus, and plastic deformation behavior is spherical indentation, which offers a more even stress distribution than sharp indenters. By utilizing this technique, the research aims to enhance the understanding of orientation-dependent mechanical behavior, emphasizing the variations in elastic and plastic responses that are essential for maximizing performance in a range of applications, particularly those where directional properties are significant