Ohio Aerospace Institute

Abstract This article demonstrates the complementary value of combining electron backscatter diffraction (EBSD) and x-ray diffraction (XRD) for materials characterization through two case studies. EBSD provides localized crystallographic information from micron to millimeter-scale areas within a scanning electron microscope, while XRD characterizes larger centimeter-sized regions using a diffractometer, with both techniques capable of revealing texture and phase composition. The first case study examined texture measurements in oxide dispersion strengthened (ODS) and non-ODS additively manufactured nickel-based superalloys. The second case study focused on phase identification of desert soil samples serving as lunar analogues for radio frequency property investigations. Together, the studies illustrate how EBSD's site-specific sensitivity and XRD's bulk representativeness create a comprehensive characterization approach where each technique validates and complements the other, ensuring that neither minor phases nor overall composition are overlooked in materials analysis.

Fused Filament Fabrication (FFF) is an additive manufacturing technique that constructs parts by extruding material layer by layer. It offers advantages such as rapid prototyping, cost-effectiveness, and the ability to produce complex geometries. This study investigates the mechanical behavior of a composite filament composed of silicon carbide (SiC) ceramic particulates embedded in a polylactic acid (PLA) matrix, fabricated via FFF. Pure PLA specimens were also printed and tested to serve as a baseline. A Design of Experiments (DOE) methodology was employed to evaluate the influence of key printing parameters on mechanical properties, including Young’s modulus, yield strength, and ultimate strength. Microstructural analysis was performed on printed specimens using scanning electron microscopy (SEM). For compression testing, the parameters studied were infill percentage, number of shells, and print orientation. For tensile testing, the parameters included layer height, number of shells, and infill angle. Results indicated that infill percentage had the most significant impact on compressive properties, while layer height was the dominant factor in tensile performance. These findings provide insights into optimizing FFF process parameters for ceramic-particulate-reinforced polymer composites.

Effective thermal management is essential for the safe and efficient operation of lithium-ion battery packs, particularly in compact, airflow-sensitive applications such as drones. This study presents a comprehensive thermal analysis of a 16-cell lithium-ion battery pack by exploring seven geometric configurations under airflow speeds ranging from 0 to 15 m/s and integrating nano-carbon-based phase change materials (PCMs) to enhance heat dissipation. A Computational Fluid Dynamics (CFD) approach was employed using Ansys Discovery and Workbench 2024 R1 to simulate airflow and heat transfer processes with high spatial resolution. Using high-fidelity 3D simulations, we found that the trapezoidal wide-base configuration, combined with a 5-inlet and 1-outlet airflow design, achieved the most balanced cooling performance across all speed regimes. This configuration maintained battery temperatures within the optimal operating range (∼45 °C) in both low- and high-speed airflow conditions, with a maximum temperature reduction of up to 8.3 °C compared to the standard square configuration. Additionally, PCM integration extended the thermal regulation duration to approximately 12.5 min, effectively buffering thermal spikes during peak loads. These findings underscore the critical role of CFD-driven geometric optimization and advanced material integration in designing high-efficiency, compact cooling systems for energy-dense battery applications in drones and portable electronics.

Abstract Silicon carbide (SiC) is a candidate material for high‐temperature structural aerospace applications due to its thermal and mechanical properties. Joining technologies enable the fabrication of complex shaped components needed for such applications. Various interlayers and processing conditions were used to form diffusion bonds between SiC substrates. Interlayers of titanium (Ti) foils and physically vapor deposited Ti coatings were used in the thicknesses of 10 and 20 μm with processing hold times of 1, 2, and 4 h. Polished cross sections of resulting diffusion bonds were analyzed using scanning electron microscopy (SEM) coupled with energy‐dispersive spectroscopy (EDS) and using transmission electron microscopy (TEM). From the TEM analysis, selected‐area diffraction patterns for Ti3SiC2, Ti5Si3Cx, and TiSi2 were observed. Moreover, TiC and an unknown phase were present in diffusion bonds formed with metallic titanium foil. From the SEM/EDS analyses, intermediate phases of Ti5Si3Cx and TiC were found to be present in microcracked diffusion bonds. With the thinner Ti interlayers and/or longer processing time, microcracking was alleviated or eliminated due to the presence of the more stable and lower thermal expansive phases of Ti3SiC2 and TiSi2. Detailed analysis of microstructures and the probable phases that formed in the bonded regions is presented.

Fused filament fabrication (FFF) systems utilize a wide variety of commercially available filaments, including Acrylonitrile Butadiene Styrene (ABS), as well as their variants. However, the effect of filament composition, reinforcements (chopped fibers and nanotubes), and 3-D printing variables on the microstructure and thermomechanical behavior is not well understood, and systematic studies are needed. In this work, different types of ABS materials with and without carbon fiber and carbon nanotube reinforcements were printed with multiple print layer heights. The microstructure, elastic behavior, tensile behavior, and fracture toughness of 3-D printed materials were characterized. ABS material systems printed at a low print layer height of 0.1 mm outperformed those printed at a larger height of 0.2 mm. Carbon nanotube reinforcements result in significant improvement in the strength and elastic modulus of ABS materials. Printed coupons of ABS with carbon nanotubes achieve an ultimate strength of 34.18 MPa, while a premium grade ABS coupon achieved 28.75 MPa when printed with the same print layer heights. Samples of ABS with chopped carbon fiber show an ultimate strength of 27.25 MPa, due primarily to the significant porosity present in the filament. Elastic moduli and fracture toughness measured using dynamic and mechanical methods show similar trends as a function of layer height. The effects of different materials, reinforcements, and printing parameters on the microstructure and mechanical properties are discussed in detail.

Abstract Joining and integration technologies are integral to manufacturing of components based on ultrahigh‐temperature ceramics (UHTCs) such as transition metal diborides. Brazing is a particularly attractive joining technique because of its simplicity and versatility, but its use to join the UHTCs demands knowledge of the complex interplay among high‐temperature wettability, interfacial reactions, and chemical and thermoelastic compatibilities. This paper summarizes the research and development activities carried out over the last two decades to characterize the wettability and interfacial phenomena in brazing of refractory diboride ceramics. The contact angle data of various metal alloys on diboride‐based ceramics have been collected and critically evaluated in conjunction with an analysis of the chemistry and structure of the interface to understand the underlying mechanisms and phenomena that govern interface formation. It explores how solid–liquid interactions impact and are impacted by physical, chemical, and mechanical properties of joined materials. It also describes how this knowledge has been successfully utilized to create liquid‐phase bonded diboride‐based joints. The paper concludes with a summary of the current state of the art and highlights integration challenges and future research and technology development needs in the area.