Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2007. / Committee Chair: Mulalo Doyoyo; Committee Co-Chair: Reginald Desroches; Committee Member: Laurence J. Jacobs.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 139-150).

Abstract In this thesis, the effect of the orientation of trussed honeycomb core design on the stiffness of a composite honeycomb plate is presented. A commercial finite element (FEM) package ¡¥MSC-MARC¡¦ is employed in the stiffness simulation. To illustrate the feasibility and accuracy of the proposed FEM model, the measured and calculated data for two different sizes regular honeycomb plates (with regular hexagonal cell) are compared. Results show that a good agreement between the simulated and the measured static deflections and dynamic characteristics is found. Numerical results indicate that different orientations of trussed honeycomb core design may improve the stiffness/density ratio of a composite honeycomb plate significantly. The effects of other design parameters of composite honeycomb plate, e.g. width and height of plate, thickness of truss, cell wall and faces, and material of truss, on the stiffness/density ratio have also been investigated in this study.

This thesis presents the results for measured and predicted rotordynamic coefficients and leakage for a convergent-tapered honeycomb seal (CTHC). The test seals had a diameter of 114.968 mm (4.5263 in) at the entrance, and a diameter of 114.709 mm (4.5161 in) at the exit. The honeycomb cell depth was 3.175 mm (0.125 in), and the cell width was 0.79 mm (0.0311 in). Measurements are reported with air as the test fluid at three different speeds: 10,200, 15,200, and 20,200 rpm; with a supply pressure of 69 bar (1,000 psi), with exit-to-inlet pressure ratios from 20% to 50%, and using two rotors that are 114.3 mm (4.500 in) and 114.5 mm (4.508 in) respectively; this enables the same seals to be tested under two different conditions. The q factor, which is just a simple way to quantify taper is defined as the taperangle seal parameter and is calculated using the inlet and exit radial clearance. Two taper-angles parameters were calculated; q = 0.24 for the 114.3 mm (4.500 in) rotor, and q = 0.386 for the 114.5 mm (4.508 in) rotor. The q = 0.24 condition was compared to a constant clearance honeycomb seal (CCHC q = 0) because both sets of data were taken with the same rotor diameter. The direct stiffness, effective stiffness, and direct damping coefficients were larger for q = 0.24. The CTHC q = 0.24 eliminates the direct negative static stiffness obtained with CCHC ( q = 0). The cross-coupled stiffness and damping also were larger for q = 0.24, especially at low frequencies. Effective damping is one of the best indicators in determining the stability of a roughened stator annular gas seal. The frequency at which it changes sign is called the cross-over frequency. In applications, this frequency needs to be lower than the rotorsystem’s first natural frequency. Otherwise, the seal will be highly destabilizing instead of highly stabilizing. The magnitude of effective damping and the cross-over frequency also increases with q for all frequencies. Constant clearance honeycomb seals have less leakage than convergenttapered honeycomb seals. CTHC ( q = 0.24), has approximately 20 percent more leakage than CCHC ( q = 0). The experimental results for rotordynamic characteristics and leakage were compared to theoretical predictions by the two-control-volume developed by Kleynhans and Childs. All rotordynamic coefficients were reasonably predicted for all cases. The model does a better job predicting the cross-coupled stiffness and damping coefficients rather than the direct stiffness and damping coefficients. Also, the two-control-volume model predicts the dynamic characteristics of CCHC ( q = 0) better, and does not predict well the effective stiffness and damping for CTHC q = 0.386.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 102-111).

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In recent times, it was divulged that highly ordered honeycomb structured porous films from a variety of polymers could be fabricated by breath figures (water droplets) templating technique. In contrast to existing macroporous fabrication techniques, this technique is simple, more versatile and very cost effective. Amphiphilic block copolymers composed of a hydrophobic and a hydrophilic block were employed in this research to examine the process of porous film formation and the outcome of films generated using breath figure technique. A customized film casting system, established according to the casting parameters affecting the outcome of films was used to generate honeycomb structured porous films for the studies. The casting method best suited to generate highly ordered honeycomb structured porous films and the procedures to manipulate the size of the pores in films generated from amphiphilic block copolymers were also investigated and identified. Analyses into the formation process of the honeycomb structured porous films revealed that the airflow casting method where the cast of polymer solution was supplied with a flow of moist air was the most suitable method to generate highly ordered honeycomb structured porous films from amphiphilic block copolymers. Variations to the casting conditions of the airflow casting method such as the rate of moist airflow could only provide limited alterations to the size of pores on films generated. However, changes to the chemical system of the casting solution such as the concentration and the molecular weight of polymers in the polymer solvent was more prominent in manipulating the size of pores in the generated films. On the other hand, any extreme variations to either the physical conditions or the chemical system could devastate the hexagonal arrangement of pores in these films. In the synthesis of amphiphilic block copolymers in this research, RAFT polymerization technique was used to generate the hydrophobic polymer block followed by the subsequent chain extension polymerization of the hydrophilic polymer block. The polymerization 'process, especially the hydrophilic chain extension polymerization, was investigated in details. It was established that there were significant dependence on the composition of the initial polymer block used, particularly the molecular weight and the type of chain transfer (RAFT) end group in the hydrophobic polymer chain. Incompatible RAFT end group and high polymer molecular weights of the initial block usually lead to slower rate of subsequent chain extension coupled with increased terminations. These copolymers generated were usually bimodal in molecular weight distributions and broad in polydispersity indexes. Honeycomb structured porous films generated from one of these amphiphilic block copolymers were assessed as scaffoldings for cell culture to regenerate cells. In particular, the effects of cellular attachments and proliferations on the honeycomb porous structures were investigated. The assessment of these honeycomb structured porous films indicated that not only were these films not cytotoxic but they also enhanced the quantity of cellular proliferation (2.7x) when used as cell culture substrate compared to standard non-porous polystyrene cell culture surfaces. Finally, this research had shown a simple way to generate a new class of highly ordered porous material that could be customized individually for a wide range of applications. The synthesis of amphiphilic block copolymers to generate these films could be achieved by RAFT polymerization with a board selection of polymers choices according to applications. A porous cell substrate such as honeycomb structured porous films could enhance cellular growth when used as a cell culture substrate.