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Full-Text Articles in Engineering

Feasibility Of Thermoplastic Extrusion Welding As A Joining Method For Vacuum-Assisted Additively Manufactured Tooling, Chase C. Flaherty May 2023

Feasibility Of Thermoplastic Extrusion Welding As A Joining Method For Vacuum-Assisted Additively Manufactured Tooling, Chase C. Flaherty

Electronic Theses and Dissertations

In recent years, additive manufacturing (AM) has been successfully utilized for the production of large-scale composite tooling. Within these endeavors, however, limited research has focused on joining methods between printed sections. This work evaluates the feasibility of thermoplastic extrusion welding as a joining method for additively manufactured tooling structures. This joining method was assessed based on industry specifications of conventional thermoset tooling for wind blade manufacturing utilizing the vacuum-assisted resin transfer molding (VARTM) process. The specifications include requirements for the mechanical strength, vacuum integrity, roughness, and hardness of the tool surface. The feasibility of this welded polymer joint was demonstrated …


Investigation Into Sintered Lunar Regolith Construction Methods And Novel Usability Evaluation, Thomas A. Cox May 2023

Investigation Into Sintered Lunar Regolith Construction Methods And Novel Usability Evaluation, Thomas A. Cox

Electronic Theses and Dissertations

Since the Apollo missions in the late 1960's, there has been a growing interest shared by many countries around the world to return to the Moon and establish a permanent Lunar settlement. The first phase of temporary Lunar bases will be established over the next several years. For a permanent human presence on the Moon, it will be necessary to use locally available resources for the construction of Lunar habitats and other infrastructure. Sintering Lunar regolith has been shown to be a promising method for producing structural material with a variety of desirable properties from strength to radiation shielding. While …


Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. Mcdermott Dec 2019

Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. Mcdermott

Electronic Theses and Dissertations

Composite materials have been adopted into primary aircraft structures by virtue of their great strength-to-weight and stiffness-to-weight ratios, fatigue insensitivity, and corrosion resistance. These characteristics are leveraged by aircraft designers to deliver improved fuel effciency and reduced scheduled maintenance burdens for their customers. These benefits have been impressively realized in the Boeing 787 and Airbus A350 XWB, with airframes utilizing about 50% composites by weight. Tempering these successes, however, are the inherent vulnerabilities of carbon-fiber reinforced composites. When compared to conventional metallic structure, composite laminates are more sensitive to stress concentrations at mechanical fastenings and damage due to low-velocity impact. …


Structural Behavior Of Inflatable, Reinforced, Braided, Tubular Members, Joshua Clapp Aug 2017

Structural Behavior Of Inflatable, Reinforced, Braided, Tubular Members, Joshua Clapp

Electronic Theses and Dissertations

The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) system being developed by the National Aeronautics and Space Administration (NASA) is an inflatable structure composed of multiple, concentric, pressurized tori, load straps, and a thermal protection system. The HIAD overcomes limitations inherent with the use of rigid decelerators since the deployed diameter is much larger than the packed size, which makes it an enabling technology for new opportunities in space exploration. The HIAD is designed to decelerate and protect spacecraft during atmospheric re-entry. The objective of this research was to improve understanding of structural behavior of HIAD components through material testing, structural testing …


Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook Dec 2016

Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook

Electronic Theses and Dissertations

This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared …