Browse Topic: Graphite

Items (264)
ABSTRACT The ability to construct a composite, semimonocoque, damage-resistant, cargo floor for a rotary wing application using an IM7 graphite/polyetheretherketone (PEEK) composite with in-situ tape-placement fabrication technology has been demonstrated. Through an evolutionary process, a damage-tolerant thermoplastic composite cargo floor was designed according to realistic requirements, and subelement representative structures were developed to verify the design viability and approach. The fabricated and tested structural composite floor subelements demonstrated the feasibility of the technology, illustrated the ability to customize the design to meet unique cargo floor properties (e.g., cargo-loading features), and validated the maturity of the approach and fabrication technology for rotary-wing applications.
Luzetsky, HarryMichasiow, John
ABSTRACT The ability to construct a multifunctional material that provides electromagnetic (EM) hardening on an aircraft structure integral to the material form has been demonstrated. The material's key attribute is the integration of a high level of EM shielding directly into a structural fiber-reinforced graphite composite in a manner that has minimal to no impact on the mechanical characteristics of the host composite. The material form has demonstrated the EM shielding equivalency of an aluminum electronics enclosure structure on a composite alternative for 25% of the weight without impacting structural characteristics. This material form provides a lightweight alternative to traditional means of providing aircraft EM protection from existing and emerging threats, such as high-power microwaves (HPMs) and EM pulse (EMP)/high-altitude EMP (HEMP), without incurring parasitic weight penalties. Its multifunctionality provides a weight-efficient means to address EM shielding in a
Luzetsky, HarryOstrander, GrahamKlein, Martha
ABSTRACT The ability to construct a composite, damage-resistant, highly survivable drive shaft for a rotary-wing application using an IM7 graphite/polyetheretherketone (PEEK) composite and in-situ tape-placement fabrication technology has been demonstrated. Through an evolutionary process, highly survivable, damage-tolerant shafts were developed, design tools and data were validated, and test shafts developed to evaluate the design viability in a dynamic application. The drive shafts demonstrated the feasibility of the technology, illustrated the ability to customize the design to meet unique shaft properties (e.g., frequency), and validated the maturity of the technology for rotary-wing applications.
Luzetsky, HarryMichasiow, JohnPhifer, Ellen
Strength and life prediction of a nonlinear tapered hybrid composite flexbeam under combined axial tension and bending is a challenging problem due to the presence of a complex geometry, a hybrid composite material system with a combination of glass/epoxy and graphite/epoxy composites, and a variable thickness profile along the beam longitudinal direction. A hybrid approach based on the combination of discrete crack network (DCN) and continuum damage mechanics (CDM) is applied for fatigue damage prediction under pure bending and bending with axial loading. Abaqus solid shell elements (SC8R) with composite section were used to capture the stress distribution and its concentration at the ply drop location. A hybrid modeling strategy is developed based on Abaqus solid shell elements (SC8R) with a user-defined material model for non-critical damage zones, user-defined phantom paired solid elements for critical damage zones, and Abaqus elements for non-damaged regions. A comparative study
Lua, JimPhan, NamFang, EugeneRahman, Anisur
NASA has an ongoing need for high-temperature solid lubricant coatings to reduce friction and wear in turbine engines, rocket engines, and other mechanical systems. Such lubricants must be thermally and chemically stable in air, vacuum, and reducing environments like hydrogen. Traditional lubricants like oil, grease, and PTFE (Polytetrafluoroethylene), and even more exotic solid lubricants like graphite and molybdenum disulphide, lack such capabilities. The key problem is to identify and formulate a material that possesses good mechanical properties, long-term environmental durability, and acceptable friction and wear-reducing characteristics while being practical to apply to bearings, seals, and other mechanical components.
This paper presents a new nanolubricant for the intermediate gearbox of the Apache aircraft. Historically, the intermediate gearbox has been prone for grease leaking and this natural-occurring fault has negatively impacted the airworthiness of the aircraft. In this study, the incorporation of graphite nanoparticles in mobile aviation gear oil is presented as a nanofluid with excellent thermo-physical properties. Condition-based maintenance practices are demonstrated where four nanoparticle additive oil samples with different concentrations are tested in a full-scale tail rotor drive-train test stand, in addition to, a baseline sample for comparison purposes. Different condition monitoring results suggest the capacity of the nanofluids to have significant gearbox performance benefits when compared to the base oil.
Gouda, KareemBayoumi, AbdelTarbutton, JoshuaMcVay, Jacob
Medical electronic devices can run the gamut from imposing MRI and x-ray imaging machines to miniscule implantable circuits designed to detect physical conditions and deliver programmed therapy. As is the case with most electronic gadgets, there is a growing trend in medical electronics toward miniaturization. Advances in circuit miniaturization, low-power architectures, and lightweight components are facilitating improvements to hearing aids, pacemakers, and other devices, while giving rise to promising new applications.
Items per page:
1 – 50 of 264