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You searched for subject:(hexagonal cell). Showing records 1 – 2 of 2 total matches.

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Penn State University

1. Pontecorvo, Michael Eugene. CELLULAR STRUCTURES WITH INTERNAL FEATURES FOR ENHANCED STRUCTURAL PERFORMANCE .

Degree: 2011, Penn State University

In classical cellular structures the unit cells have typically not had any inclusions. In the current research, unit cells with various types of inclusions or internal features are envisaged. Different types of internal features such as linear springs or dashpots, and a wide variety of nonlinear elements (buckling beams which display softening behavior, mechanical stops or contact elements which display stiffening behavior, and bistable elements which display negative stiffness or snap-through behavior) can be introduced into the unit cell. These internal features will strongly impact the behavior of the unit cell. Unit cells with different types of inclusions can then be thought of as ``Lego blocks'. A structure can be assembled using specific types of ``blocks' in specific arrangements, to provide desired system level behavior. The current study is based on the concept of a two-dimensional cellular structure with hexagonal cells made of pinned-pinned rigid links. Since such a cell has no stiffness of its own, the behavior of the internal feature dominates. The study presents the necessity to include three constraints within the hexagonal cell for its stability. Of the different elements/inclusions that can be used, this thesis focuses on two: a linear spring, and a bistable elastic arch. The selection of the linear spring is based on its being the simplest possible inclusion. For different spring arrangements, closed-form analytical expressions are derived for the in-plane modulus and Poisson's ratio of the hexagonal cell (and by extension, of a cellular structure with that unit cell repeated). The analytical expressions are validated using NASTRAN finite element simulations, as well as against tensile/compressive tests of unit cells with internal springs in an Instron machine. When the spring stiffness exceeds certain values, the rigid cell wall assumption is no longer valid, and these bounds are established. The validated analysis is used to conduct design studies on how the cell modulus (nondimensionalized by the spring stiffness) would vary with cell geometric parameters such as cell angle and cell wall length ratio. An in-plane cell modulus as high as 1.15 GPa was calculated using springs that were stiff but yet compliant enough so as not to violate the rigid cell wall assumption. The second part of the study focused on a bistable elastic arch. This is of interest because of the negative stiffness or snap-through behavior it can display. The large stroke and velocity of the arch, when transitioning from one stable equilibrium condition to the other, can be exploited for enhanced energy dissipation when coupled to a damping element. In the present study a finite element model of the arch is developed and its bistable behavior examined. Experiments on Nitinol and Delrin arches are used to validate the finite element analysis. The analysis is further used to conduct a parametric study on how variation in arch height, thickness or restraining spring stiffness influences the critical snap-through… Advisors/Committee Members: Farhan Gandhi, Thesis Advisor/Co-Advisor, Farhan S Gandhi, Thesis Advisor/Co-Advisor.

Subjects/Keywords: cellular structure; elastic arch; bistable; hexagonal cell; internal features; cell modulus

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Pontecorvo, M. E. (2011). CELLULAR STRUCTURES WITH INTERNAL FEATURES FOR ENHANCED STRUCTURAL PERFORMANCE . (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/12616

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Pontecorvo, Michael Eugene. “CELLULAR STRUCTURES WITH INTERNAL FEATURES FOR ENHANCED STRUCTURAL PERFORMANCE .” 2011. Thesis, Penn State University. Accessed April 18, 2021. https://submit-etda.libraries.psu.edu/catalog/12616.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Pontecorvo, Michael Eugene. “CELLULAR STRUCTURES WITH INTERNAL FEATURES FOR ENHANCED STRUCTURAL PERFORMANCE .” 2011. Web. 18 Apr 2021.

Vancouver:

Pontecorvo ME. CELLULAR STRUCTURES WITH INTERNAL FEATURES FOR ENHANCED STRUCTURAL PERFORMANCE . [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Apr 18]. Available from: https://submit-etda.libraries.psu.edu/catalog/12616.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Pontecorvo ME. CELLULAR STRUCTURES WITH INTERNAL FEATURES FOR ENHANCED STRUCTURAL PERFORMANCE . [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/12616

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Delft University of Technology

2. Loef, Thomas (author). Periodic-Random Modulated Surface Textures For Efficient Light Trapping in Thin-Film Silicon Solar Cells.

Degree: 2018, Delft University of Technology

Thin-film silicon solar cells make use of relatively thin layers of active material compared to wafer based solar cells. The main advantage of thin absorber layers is the possibility to fabricate flexible solar cells. However, due to limited absorber layer thickness and weak absorption coefficients at long wavelengths, light management techniques need to be implemented in order to increase the device performance. Advanced substrate texturisation is one of the promising light management techniques that have drawn much attention recently. In state-of-the-art devices, randomly textured interfaces are often used to increase the optical performance. However, the introduction of periodic diffraction gratings resulted in world record conversion efficiencies for hydrogenated amorphous/nanocrystalline silicon (a-Si:H/nc-Si:H) tandem solar cells. A different method of advanced texturisation is introducing modulated surface textures (MST). These MST structures combine various surface morphologies (random and/or periodic) to reach higher levels of light scattering over a broader wavelength range. Modulated surface textures based on large periodic gratings and small random textures have been successfully employed in single junction nc-Si:H solar cells, resulting in a world record efficiency of 11.8 %. An MST structure based on large random features and small periodic gratings, however, has not been reported yet. The aim of this work is to investigate the possibility of fabricating MST structures based on micro-textured glass with superimposed periodic gratings, and to obtain a functioning n-i-p nc-Si:H solar cell, based on an MST substrate. An optical and morphological analysis of randomly textured substrates, periodic gratings, and modulated surface textures was carried out. It was found that MST substrates can be fabricated using ITO induced, wet-etched glass substrates, and a photolithography process. MST structures resulted in light scattering into greater, less distinct angles, when compared to either one of the individual surface morphologies. Therefore, these structures show promising light scattering behaviour for application in nc-Si:H solar cells. Hydrogenated nanocrystalline silicon solar cells were fabricated on randomly textured glass substrates and MST structures. Two-dimensional (2D) periodic gratings, with square and hexagonal lattice structures, were superimposed on randomly textured glass to obtain MST substrates. nc-Si:H solar cells based on hexagonal MST structures seemed to outperform their square lattice counterparts. A functioning device with an active area efficiency of 6.46 % and short-circuit current density (Jsc) of 19.74 mA/cm2 was fabricated. This work reports the first functioning nc-Si:H solar cell, based on a periodic-random modulated surface texture substrate. The best performing solar cell on randomly textured glass, however, exceeded this performance with an active area efficiency of 7.67 % and JSC of 23.2 mA/cm2. It can be concluded that functioning nc-Si:H… Advisors/Committee Members: Isabella, Olindo (mentor), Vismara, Robin (mentor), Zeman, Miro (graduation committee), Mastrangeli, Max (graduation committee), Delft University of Technology (degree granting institution).

Subjects/Keywords: PVMD; Solar Cell; Thin-Film; light management; modulated surface texture; random; periodic; light trapping; grating; texture; square; hexagonal

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Loef, T. (. (2018). Periodic-Random Modulated Surface Textures For Efficient Light Trapping in Thin-Film Silicon Solar Cells. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:d48a285f-cf84-40a3-b806-3211afa9c45e

Chicago Manual of Style (16th Edition):

Loef, Thomas (author). “Periodic-Random Modulated Surface Textures For Efficient Light Trapping in Thin-Film Silicon Solar Cells.” 2018. Masters Thesis, Delft University of Technology. Accessed April 18, 2021. http://resolver.tudelft.nl/uuid:d48a285f-cf84-40a3-b806-3211afa9c45e.

MLA Handbook (7th Edition):

Loef, Thomas (author). “Periodic-Random Modulated Surface Textures For Efficient Light Trapping in Thin-Film Silicon Solar Cells.” 2018. Web. 18 Apr 2021.

Vancouver:

Loef T(. Periodic-Random Modulated Surface Textures For Efficient Light Trapping in Thin-Film Silicon Solar Cells. [Internet] [Masters thesis]. Delft University of Technology; 2018. [cited 2021 Apr 18]. Available from: http://resolver.tudelft.nl/uuid:d48a285f-cf84-40a3-b806-3211afa9c45e.

Council of Science Editors:

Loef T(. Periodic-Random Modulated Surface Textures For Efficient Light Trapping in Thin-Film Silicon Solar Cells. [Masters Thesis]. Delft University of Technology; 2018. Available from: http://resolver.tudelft.nl/uuid:d48a285f-cf84-40a3-b806-3211afa9c45e

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