ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- All Subjects: Deformations (Mechanics)
- All Subjects: structural sections
- Creators: Mobasher, Barzin
Description
Composite materials are now beginning to provide uses hitherto reserved for metals in structural systems such as airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. These structural systems are often subjected to impact loads and there is a pressing need for accurate prediction of deformation, damage and failure. There are numerous material models that have been developed to analyze the dynamic impact response of polymer matrix composites. However, there are key features that are missing in those models that prevent them from providing accurate predictive capabilities. In this dissertation, a general purpose orthotropic elasto-plastic computational constitutive material model has been developed to predict the response of composites subjected to high velocity impacts. The constitutive model is divided into three components – deformation model, damage model and failure model, with failure to be added at a later date. The deformation model generalizes the Tsai-Wu failure criteria and extends it using a strain-hardening-based orthotropic yield function with a non-associative flow rule. A strain equivalent formulation is utilized in the damage model that permits plastic and damage calculations to be uncoupled and capture the nonlinear unloading and local softening of the stress-strain response. A diagonal damage tensor is defined to account for the directionally dependent variation of damage. However, in composites it has been found that loading in one direction can lead to damage in multiple coordinate directions. To account for this phenomena, the terms in the damage matrix are semi-coupled such that the damage in a particular coordinate direction is a function of the stresses and plastic strains in all of the coordinate directions. The overall framework is driven by experimental tabulated temperature and rate-dependent stress-strain data as well as data that characterizes the damage matrix and failure. The developed theory has been implemented in a commercial explicit finite element analysis code, LS-DYNA®, as MAT213. Several verification and validation tests using a commonly available carbon-fiber composite, Toyobo’s T800/F3900, have been carried and the results show that the theory and implementation are efficient, robust and accurate.
ContributorsHoffarth, Canio (Author) / Rajan, Subramaniam D. (Thesis advisor) / Goldberg, Robert (Committee member) / Neithalath, Narayanan (Committee member) / Mobasher, Barzin (Committee member) / Liu, Yongming (Committee member) / Arizona State University (Publisher)
Created2016
Description
Pultrusion manufacturing technique stands at the forefront for efficient production of continuous, uniform concrete composites for use in large scale structural applications. High volume and low labor, among other benefits such as improved impregnation and better sample consistency, stand as some of the crucial advances found in automated pultrusion. These advantages introduce textile reinforced concrete (TRC) composites as a potential surrogate for wood, light gauge steel, and other common structural materials into an ever changing and broadening market of industrial grade structural sections. With the potential modifications of textile geometry, textile type, section geometry, and connection type, the options presented by TRC sections seem nearly boundless. Automated pultrusion presents the ability to manufacture many different TRC composite types in at a quickened rate opening up a new field of study of structural materials.
The objective of this study centered on two studies including the development of an automated pultrusion system for the manufacturing of TRC composites and ultimately the assessment of composites created with the pultrusion technique and their viability as a relevant structural construction material. Upon planning, fabrication, and continued use of an automated pultrusion system in Arizona State University’s Structures Lab, an initial, comparative study of polypropylene microfiber composites was conducted to assess fiber reinforced concrete composites, manufactured with Filament Winding Technique, and textile reinforced concrete composites, manufactured with Automated Pultrusion Technique, in tensile and flexural mechanical response at similar reinforcement dosages. A secondary study was then conducted to measure the mechanical behavior of carbon, polypropylene, and alkali-resistant glass TRC composites and explore the response of full scale TRC structural shapes, including angle and channel sections. Finally, a study was conducted on the connection type for large scale TRC composite structural sections in tension and compression testing.
The objective of this study centered on two studies including the development of an automated pultrusion system for the manufacturing of TRC composites and ultimately the assessment of composites created with the pultrusion technique and their viability as a relevant structural construction material. Upon planning, fabrication, and continued use of an automated pultrusion system in Arizona State University’s Structures Lab, an initial, comparative study of polypropylene microfiber composites was conducted to assess fiber reinforced concrete composites, manufactured with Filament Winding Technique, and textile reinforced concrete composites, manufactured with Automated Pultrusion Technique, in tensile and flexural mechanical response at similar reinforcement dosages. A secondary study was then conducted to measure the mechanical behavior of carbon, polypropylene, and alkali-resistant glass TRC composites and explore the response of full scale TRC structural shapes, including angle and channel sections. Finally, a study was conducted on the connection type for large scale TRC composite structural sections in tension and compression testing.
ContributorsBauchmoyer, Jacob Macgregor (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2017