Mechanical Engineering Commons^™

Molecular Modeling Of High-Performance Thermoset Polymer Matrix Composites For Aerospace Applications, Prathamesh P. Deshpande

Dissertations, Master's Theses and Master's Reports

The global efforts from major space agencies to transport humans to Mars will require a novel lightweight and ultra-high strength material for the spacecraft structure. Three decades of research with the carbon nanotubes (CNTs) have proved that the material can be an ideal candidate for the composite reinforcement if certain shortcomings are overcome. Also, the rapid development of the polymer resin industry has introduced a wide range of high-performance resins that show high compatibility with the graphitic surface of the CNTs. This research explores the computational design of these materials and evaluates their efficacy as the next generation of aerospace …

Multiscale Modeling Of Carbon Fibers/Graphene Nanoplatelets/Epoxy Hybrid Composites For Aerospace Applications, Hashim Al Mahmud

Dissertations, Master's Theses and Master's Reports

Significant research effort has been dedicated for decades to improve the mechanical properties of aerospace polymer-based composite materials. Lightweight epoxy-based composite materials have increasingly replaced the comparatively heavy and expensive metal alloys used in aeronautical and aerospace structural components. In particular, carbon fibers (CF)/graphene nanoplatelets (GNP)/epoxy hybrid composites can be used for this purpose owing to their high specific stiffness and strength. Therefore, this work has been completed to design, predict, and optimize the effective mechanical properties of CF/GNP/epoxy composite materials at different length scales using a multiscale modeling approach. The work-flow of modeling involves a first step of using …

3d Printing Of Iron Oxide Incorporated Polydimethylsiloxane Soft Magnetic Actuator, Rasoul Bayaniahangar

Dissertations, Master's Theses and Master's Reports

Soft actuators have grown to be a topic of great scientific interest recently. As the fabrication of soft actuators with conventional microfabrication methods are tedious, expensive, and time consuming, employment of 3-D printing fabrication methods appears promising as they can simplify fabrication and reduce the production cost. Complex structures can be fabricated with 3-D printing such as helical coils can achieve actuation performances that otherwise would not be possible with simpler geometries. In this thesis development of soft magnetic helical coil actuators of iron-oxide embedded polydimethylsiloxane (PDMS) was achieved with embedded 3-D printing techniques. Composites with three different weight ratios …

Nanotextured Titanium Surfaces For Implants: Manufacturing And Packaging Aspects, Sachin Bhosle

Dissertations, Master's Theses and Master's Reports

It has been shown that nanotexturing the surface of otherwise smooth titanium orthopedic materials increases osteoblast proliferation in vitro, and the bone-implant contact area and pullout force in vivo. However, this prior work has not focused on the requirements for scale-up to industrial processes. This dissertation reports on titanium surface modifications by electrochemical anodization using a benign NH₄F electrolyte, and a hybrid electrolyte also containing AgF, rather than hazardous hydrofluoric acid used elsewhere. Nanotube fabrication of Ti6Al4V foils, rods, thermal plasma sprayed commercial implants, and laser and e-beam melted powder materials was demonstrated.

It was found …

An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur

Dissertations, Master's Theses and Master's Reports

Evaporation is ubiquitous in nature and occurs even in a microgravity space envi- ronment. Long term space missions require storage of cryogenic propellents and an accurate prediction of phase change rates. Kinetic theory has been used to model and predict evaporation rates for over a century but the reported values of accommodation coefficients are highly inconsistent and no accurate data is available for cryogens. The proposed study involves a combined experimental and computational approach to ex- tract the accommodation coefficients. Neutron imaging is used as the visualization technique due to the difference in attenuation between the cryogen and the metallic …

Multiscale Modeling Of Liquid Crystalline/Nanotube Composites, Sharil Patrale

Dissertations, Master's Theses and Master's Reports - Open

The objective of this research is to synthesize structural composites designed with particular areas defined with custom modulus, strength and toughness values in order to improve the overall mechanical behavior of the composite. Such composites are defined and referred to as 3D-designer composites. These composites will be formed from liquid crystalline polymers and carbon nanotubes. The fabrication process is a variation of rapid prototyping process, which is a layered, additive-manufacturing approach. Composites formed using this process can be custom designed by apt modeling methods for superior performance in advanced applications. The focus of this research is on enhancement of Young's …

Co-Electrophoretic Deposition Of Liquid Metal And Silicon For Lithium-Ion Battery Application, Hanfei Zhang

Dissertations, Master's Theses and Master's Reports - Open

A low cost electrophoretic deposition (EPD) process was successfully used for liquid metal thin film deposition with a high depositing rate of 0.6 µ/min. Furthermore, silicon nano-powder and liquid metal were then simultaneously deposited as the negative electrode of lithium-ion battery by a technology called co-EPD. The liquid metal was hoping to act as the matrix for silicon particles during lithium ion insertion and distraction. Half-cell testing was performed using as prepared co-EPD sample. An initial discharge capacity of 1500 mAh/g was reported for nano-silicon and galinstan electrode, although the capacity fading issue of these samples was also observed.

High Voltage Electrophoretic Deposition For Electrochemical Energy Storage And Other Applications, Sunand Santhanagopalan

Dissertations, Master's Theses and Master's Reports - Open

High voltage electrophoretic deposition (HVEPD) has been developed as a novel technique to obtain vertically aligned forests of one-dimensional nanomaterials for efficient energy storage. The ability to control and manipulate nanomaterials is critical for their effective usage in a variety of applications. Oriented structures of one-dimensional nanomaterials provide a unique opportunity to take full advantage of their excellent mechanical and electrochemical properties. However, it is still a significant challenge to obtain such oriented structures with great process flexibility, ease of processing under mild conditions and the capability to scale up, especially in context of efficient device fabrication and system packaging. …