Matching Items (3)
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- All Subjects: Carbon nanotubes
- Creators: Yekani Fard, Masoud
Description
Carbon nanotube (CNT) membranes (buckypaper) are manufactured with multiple procedures, vacuum filtration, surfactant-free, and 3D printing. A post-manufacturing process for resin impregnation is subjected to the membranes. The effects of manufacturing processes on the microstructure and material properties are investigated for both pristine and resin saturated samples manufactured using all procedures. Microstructural characteristics that are studied include specific surface area, porosity, pore size distribution, density, and permeability. Scanning electron microscopy is used to characterize the morphology of the membrane. Brunauer-Emmett-Teller analysis is conducted on membrane samples to determine the specific surface area. Barrett-Joyner-Halenda analysis is conducted on membrane samples to determine pore characteristics. Once the microstructure is characterized for each manufacturing process for both pristine and resin saturated samples, material properties of the membrane and nanocomposite structures are explored and compared on a manufacturing basis as well as a microstructural basis. Membranes samples are interleaved in the overlap of carbon fiber polymer matrix composite tubes, which are subjected to fracture testing. The effects of carbon nanotube membrane manufacturing technology on the fracture properties of nanocomposite structures with tubular geometries are explored. In parallel, the influences of manufacturing technology on the electromechanical properties of the membrane that effect a piezoresistive response are investigated for both pristine and resin saturated membranes manufactured using both methods. The result of this study is a better understanding of the relationships between manufacturing technology and the effected microstructure, and the resulting influences on material properties for both CNT membranes and derivative nanocomposite structures. Developing an understanding of these multiscale relationships leads to an increased capacity in designing manufacturing processes specific to optimizing the expression of desired characteristics for any given application.
ContributorsWoodward, John Michael (Author) / Chattopadhyay, Aditi (Thesis director) / Yekani Fard, Masoud (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Damage and failure of advanced composite materials and structures are often manifestations of nonlinear deformation that involve multiple mechanisms and their interactions at the constituent length scale. The presence and interactions of inelastic microscale constituents strongly influence the macroscopic damage anisotropy and useful residual life. The mechano-chemical interactions between constituents at the atomistic length scale play a more critical role with nanoengineered composites. Therefore, it is desirable to link composite behavior to specific microscopic constituent properties explicitly and lower length scale features using high-fidelity multiscale modeling techniques.In the research presented in this dissertation, an atomistically-informed multiscale modeling framework is developed to investigate damage evolution and failure in composites with radially-grown carbon nanotube (CNT) architecture. A continuum damage mechanics (CDM) model for the radially-grown CNT interphase region is developed with evolution equations derived using atomistic simulations. The developed model is integrated within a high-fidelity generalized method of cells (HFGMC) micromechanics theory and is used to parametrically investigate the influence of various input micro and nanoscale parameters on the mechanical properties, such as elastic stiffness, strength, and toughness. In addition, the inter-fiber stresses and the onset of damage in the presence of the interphase region are investigated to better understand the energy dissipation mechanisms that attribute to the enhancement in the macroscopic out-of-plane strength and toughness. Note that the HFGMC theory relies heavily on the description of microscale features and requires many internal variables, leading to high computational costs. Therefore, a novel reduced-order model (ROM) is also developed to surrogate full-field nonlinear HFGMC simulations and decrease the computational time and memory requirements of concurrent multiscale simulations significantly.
The accurate prediction of composite sandwich materials' thermal stability and durability remains a challenge due to the variability of thermal-related material coefficients at different temperatures and the extensive use of bonded fittings. Consequently, the dissertation also investigates the thermomechanical performance of a complex composite sandwich space structure subject to thermal cycling. Computational finite element (FE) simulations are used to investigate the intrinsic failure mechanisms and damage precursors in honeycomb core composite sandwich structures with adhesively bonded fittings.
ContributorsVenkatesan, Karthik Rajan (Author) / Chattopadhyay, Aditi (Thesis advisor) / Liu, Yongming (Committee member) / Jiao, Yang (Committee member) / Yekani Fard, Masoud (Committee member) / Stoumbos, Tom (Committee member) / Arizona State University (Publisher)
Created2021
Description
Carbon Fiber Reinforced Polymers (CFRP) are a promising engineering material because of their multifunctionality and desirable mechanical, electrical, and thermal properties. The mechanical and fracture properties of CFRPs rely on effective stress transfer from the bulk matrix to individual carbon fibers. Pristine carbon fibers (CF) are chemically unreactive and smooth, which inhibits stress transfer mechanisms and makes CF susceptible to matrix debonding. Current composite research aims to improve the synergy between the CF and surrounding matrix by engineering the interphase. The composite interphase is characterized by mechanical properties deviating from the fiber and matrix properties. Carbon nanotubes (CNT), graphene nanoplatelets, and other carbon nanofillers have been studied extensively for their interphase-enhancing capabilities.
ContributorsPensky, Alek R (Author) / Yekani Fard, Masoud (Thesis director) / Zhu, Haolin (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05