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The synthesis of two types of metallocenophanes is described: strained, ring-tilted [1]metallocenophanes with Al and Ga in bridging positions and Fe and Ru as transition elements and unstrained [1.1]ferrocenophanes with Al, Ga and In in bridging positions. [1]Metallocenophanes are potential monomers for the synthesis of organometallic polymers via ring-opening polymerization (ROP). After the successful synthesis of various starting monomers using the concept of intramolecular coordinating ligands, four different pathways of ROP were investigated. However, only one of these pathways proved successful in obtaining polymeric material. The starting monomers showed a surprising stability against commonly used initiators. This was attributed to an overly steric protection by the intramolecular coordinating ligands, thereby blocking the initiators, and a reduced ring strain, a consequence of the size of the bridging element.<p>[1.1]Ferrocenophanes belong to a class of dinuclear complexes where the two redox-active iron atoms are in close proximity with restricted flexibility. [1.1]Ferrocenophanes with Al, Ga and In in bridging positions were investigated. The redox properties of previously published [1.1]ferrocenophanes showed a fully reversible, stepwise, one-electron oxidation (FeII/FeII → FeII/FeIII → FeIII/FeIII). After the initial oxidation of the first iron center, a stable, mixed-valent monocationic species is created. The removal of a second electron from the second iron center therefore is more difficult, and occurs at higher potential to create the dicationic species. The difference in potential for the stepwise oxidation is directly related to the delocalization of the charge in the mixed-valent species. This delocalization mainly depends on the electronic properties of the bridging element. Depending on the bridging group 13 element, very different electrochemical properties were observed. For the alumina[1.1]ferrocenophane, no delocalization was detected, and a one-step, two-electron oxidation at the same potential was observed. For the inda[1.1]ferrocenophane, a more complex electrochemistry was observed that we attributed to an isomerization of the compound in solution. Only the investigated galla[1.1]ferrocenophane showed the expected stepwise oxidation-reduction behavior.

The synthesis of two types of metallocenophanes is described: strained, ring-tilted [1]metallocenophanes with Al and Ga in bridging positions and Fe and Ru as transition elements and unstrained [1.1]ferrocenophanes with Al, Ga and In in bridging positions. [1]Metallocenophanes are potential monomers for the synthesis of organometallic polymers via ring-opening polymerization (ROP). After the successful synthesis of various starting monomers using the concept of intramolecular coordinating ligands, four different pathways of ROP were investigated. However, only one of these pathways proved successful in obtaining polymeric material. The starting monomers showed a surprising stability against commonly used initiators. This was attributed to an overly steric protection by the intramolecular coordinating ligands, thereby blocking the initiators, and a reduced ring strain, a consequence of the size of the bridging element.<p>[1.1]Ferrocenophanes belong to a class of dinuclear complexes where the two redox-active iron atoms are in close proximity with restricted flexibility. [1.1]Ferrocenophanes with Al, Ga and In in bridging positions were investigated. The redox properties of previously published [1.1]ferrocenophanes showed a fully reversible, stepwise, one-electron oxidation (FeII/FeII → FeII/FeIII → FeIII/FeIII). After the initial oxidation of the first iron center, a stable, mixed-valent monocationic species is created. The removal of a second electron from the second iron center therefore is more difficult, and occurs at higher potential to create the dicationic species. The difference in potential for the stepwise oxidation is directly related to the delocalization of the charge in the mixed-valent species. This delocalization mainly depends on the electronic properties of the bridging element. Depending on the bridging group 13 element, very different electrochemical properties were observed. For the alumina[1.1]ferrocenophane, no delocalization was detected, and a one-step, two-electron oxidation at the same potential was observed. For the inda[1.1]ferrocenophane, a more complex electrochemistry was observed that we attributed to an isomerization of the compound in solution. Only the investigated galla[1.1]ferrocenophane showed the expected stepwise oxidation-reduction behavior.

The goal of this study is to design and analyze a sandwich composite panel with lightweight graphite foam core and carbon epoxy face sheets that can function as a radiator for the given payload in a satellite. This arrangement provides a lightweight, structurally efficient structure to dissipate the heat from the electronics box to the surroundings. Three-dimensional finite element analysis with MSC Visual Nastran is undertaken for modal, dynamic and heat transfer analysis to design a radiator panel that can sustain fundamental frequency greater than 100 Hz and dissipate 100 W/m2 and withstand launch loads of 10G. The primary focus of this research is to evaluate newly introduced graphite foam by Poco Graphite Inc. as a core in a sandwich structure that can satisfy structural and thermal design requirements. The panel is a rectangular plate with a cutout that can hold the antenna. The panel is fixed on all the sides. The objective is not only to select an optimum design configuration for the face sheets and core but also to explore the potential of the Poco foam core in its heat transfer capacity. Furthermore the effects of various parameters such as face sheet lay-up, orientation, thickness and material properties are studied through analytical models to validate the predictions of finite element analysis. The optimum dimensions of the sandwich panel are determined and structural and thermal response of the Poco foam is compared with existing aluminum honeycomb core.

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<p>The exploitation of sandwich structures as a means toachieve high specific strength and stiffness is relatively new.Therefore, the knowledge of its damage tolerance is limitedcompared to other structural concepts such as truss bars andmonocoque plate solutions.</p><p>Several aspects of the damage tolerance of sandwichstructures are investigated. The influence of impact velocityonresidual strength is investigated. Sandwich panels withfaces of glass fiber reinforced vinylester are impacted bothwith very high velocity and quasi static. The residual strengthafter impact is found to be similar for both cases of impactvelocity.</p><p>Curved sandwich beams subjected to opening bending momentare studied. Faceñcore debonds of varying size areintroduced between the compressively loaded face sheet and thecore. Finite element analysis in combination with a pointstress criterion is utilized to predict the residual strengthof the beams. It is shown that it is possible to predict thefailure load of the beams with face-core debond.</p><p>Using fractography the governing mode of failure ofcompressively NCF-carbon is characterized. Sandwich panelssubjected to compression after impact are shown to fail byplastic micro buckling.</p><p>The residual compressive strength after impact of sandwichpanels is investigated. Sandwich panels with face sheets ofnon-crimp fabric (NCF) carbon are subjected to different typesof impact damages. Predictions of residual strength are madeusing the Budiansky, Soutis, Fleck (BSF) model. The residualstrength is tested, and the results are compared topredictions. Predictions and tests correlate well, and indicatethat the residual strength is dependent on damage size and notthe size of the damaged panel.</p><p>A study of the properties of a selection of fiberreinforcements commonly used in sandwich panels is conducted.The reinforcements are combined with two types of core materialand three types of matrix. Also the influence of laminatethickness is tested. Each combination materials is tested inuni-axial compression, compressive strength after impact andenergy absorption during quasi static indentation. Thespecimens which are tested for residual strength are eithersubjected to quasi-static or dynamic impact of comparableenergy level. Prediction of the residual strength is made andcorrelates reasonably whith the test results. The tests showthat if weight is taken into account the preferred choice offiber reinforcement is carbon.</p>

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Feb. 8, 2010). Additional advisors: Uday Vaidya, Talat Salama, Wilbur Hitchcock, Ashraf Z. Al-Hamdan. Includes bibliographical references (p. 144-155).

This bachelor thesis has been carried out at GKN Aerospace. GKN is a member of European Space Agency, designing and manufacturing rocket-nozzles for the Ariane rockets. The manufacturing process entails many welds. Weld-simulations have been made to investigate stresses and plastic strains on simplified geometries. Plastic strains have been evaluated parallel and normal to the weld for plate geometries of shell-elements with rectangular cross-section and sandwich-cross-section, using the FEM-program MSC.marc. Results shows that plate width and length have negligible effect on the plastic strains when one weld is made. A comparison between a sandwich-sector cone and a sandwich plate was made, to investigate how plastic strains and stresses were affected of geometry. Plastic strains and stresses parallel the weld are the same. Plastic strains and stresses normal the weld are affected by changing geometry. Studies on differences in stresses between solid and shell elements propose use of solid elements near the weld region, if stresses are of interest.

The focus of this research is characterizing a new material system composed of carbon and graphite foams, which has potential in a wide variety of applications encompassing aerospace, military, offshore, power production and other commercial industries. The benefits of this new material include low cost, light weight, fire-resistance, good energy absorption, and thermal insulation or conduction as desired. The objective of this research is to explore the bulk material properties and failure modes of the carbon foam through experimental and computational analysis in order to provide a better understanding and assessment of the material for successful design in future applications. Experiments are conducted according to ASTM standards to determine the mechanical properties and failure modes of the carbon foam. Sandwich beams composed of open cell carbon foam cores and carbon-epoxy laminate face sheets are tested in the flexure condition using a four point setup. The primary failure mode is shear cracks developing in the carbon foam core at a critical axial strain value of 2,262 με. In addition to flexure, the carbon foam is loaded under tensile and shear loads to determine the respective material moduli. Computational analysis is undertaken to further investigate the carbon foam's failure modes and material characteristics in the sandwich beam configuration. Initial estimates are found using classical laminated plate theory and a linear finite element model. Poor results were obtained due to violation of assumptions used in both cases. Thus, an additional computational analysis incorporating three dimensional strain-displacement relationships into the finite element analysis is used. Also, a failure behavior pattern for the carbon foam core is included to simulate the unique failure progression of the carbon foam on a microstructure level. Results indicate that displacements, strains and stresses from the flexure experiments are closely predicted by this two parameter progressive damage model. The final computational model consisted of a bond line (interface) study to determine the source of the damage initiation, and it is concluded that damage initiates in the carbon foam, not at the bond line.

Undesirable cabin noise has an adverse physiological effect on passengers and crews in an aircraft. In order to reduce the noise level, a passive approach using a truss-core sandwich (TCS) panel as a sound insulator is proposed. Design guidelines and analysis methodologies were developed in order to explore the vibro-acoustic characteristics of TCS structure. Its sound isolation properties can be thereby assessed. Theoretical analyses show that the transmission-loss and sound radiation properties of a TCS structure can be represented by the root-mean-square velocity of its surface, and a beam structure analysis is sufficient to reveal many of the important aspects of TCS panel design. Using finite element analysis, a sensitivity study was performed to create design guidelines for TCS structures. Transmission-loss experiments show that the analytical and numerical analyses correctly predict the trend of TCS structure’s vibro-acoustic performance.