Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 262-271). Also available via the Internet

The influence of thickness and hole radius on the fracture strengths of Narmco V 5245C-G40-600 graphite/bismaleimide laminates was studied. Tests were run on 8 ply, 40 ply, and 80 ply quasi-isotropic laminates of stacking sequence [0/ ± 45/90]. Both unnotched and notched laminates were tested. Unnotched strength was found to be inversely proportional to thickness. Notched strengths were compared to three different failure models based on the stress distribution around the hole. Damage development around the holes was studied using x-ray radiography. In general, the small holes created more damage than the large holes and the thin laminates were more susceptible to damage than the thick laminates. All notched specimens exhibited matrix cracking in the 90° plies around the hole and vertical splitting in the 0° plies at the edge of the hole. / Master of Science

The miniaturization of energy, chemical and biological systems for distributed and portable applications, known as process intensification, is realized by the enhancement in heat and mass transfer performance within high surface-to-volume ratio microchannels. Fabrication of devices for process intensification is achieved in part by microlamination techniques. These techniques consist of patterning, aligning, and bonding thin layers of material into monolithic devices. Even though the fabrication techniques used in microlamination are generally accurate and consistent, small amounts of dimensional variation in microlaminated structures can strongly affect the device performance. One significant finding of this dissertation is that fin warpage, which is commonly induced during bonding, generally has more adverse device performance effects than misalignment. A heat exchanger that contains fin warpage as small as 25 percent of the microchannel height (on the order of 10 ��m) needs to almost double the number of flow channels to gain the same thermal effectiveness as the uniform one. Therefore, the focus of this dissertation is to investigate, understand, and learn how to control the cause and effect of buckling warpage produced within microlaminated structures. The microlamination discussed in this dissertation is performed with a thermally-controlled registration process, which facilitates metallic bonding at elevated temperatures. Another finding of this dissertation is that the tolerance limits of the fixture used in this registration process exceed the accuracy of the machine tools used to produce the fixture. Fixture tolerance limits on the order of 10 ��m are necessary to align and bond laminae with thicknesses below 100 ��m. An alternative technique based on the compliance of the fixture is proposed in order to improve these limits. This technique helps compensate for the excessive registration force due to over-constrained bonding, which extends the range of fixture tolerance limit to over 100 ��m well within current process capability of machine tools. Another approach to controlling fin warpage, based on the induction of higher modes of fin buckling, is also discussed. An analytical evaluation shows that the effect of fin warpage is minor as the mode of buckling reaches mode 10. A preliminary experiment confirms that the induction of fin buckling into a higher mode can be achieved by constraining the fin at specific locations along the fin during microlamination. / Graduation date: 2002

Due to the increasing competition from developing countries, companies are struggling to reduce their manufacturing costs. In the field of tool manufacturing, manufacturers are under pressure to produce new products as quickly as possible at minimum cost with high accuracy. Laminated tooling, where parts are manufactured layer by layer, is a promising technology to reduce production costs. Laminated tooling is based on taking sheets of metal and stacking them to produce the final product after cutting each layer profile using laser cutting or other techniques. It is also a powerful tool to make complex tools with conformal cooling channels. In conventional injection moulds and casting dies the cooling channels are drilled in straight paths whereas the cavity has a complex profile. In these cases the cooling system may not be sufficiently effective resulting in a longer cooling time and loss of productivity. Furthermore, conventional cooling channels are limited to circular cross sections, while conformal cooling channels could follow any curved path with variable and non circular cross sections. One of the issues in laminated tooling is the surface jaggedness. The surface jaggedness depends on the layers' thicknesses and surface geometry. If the sheets are thin, the surface quality is improved, but the cost of layer profile cutting is increased. On the other hand, increasing the layers' thicknesses reduces the lamination process cost, but it increases the post processing cost. One solution is having variable thicknesses for the layers and optimally finding the set of layer thicknesses to achieve the minimum surface jaggedness and the number of layers at the same time. In practice, the choice of layers thicknesses depends on the availability of commercial sheet metals. One solution to reduce the number of layers without compromising the surface jaggedness is to use a non-uniform lamination technique in which the layers' thicknesses are changed according to the surface geometry. Another factor in the final surface quality is the lamination direction which can be used to reduce the number of laminations. Optimization by considering lamination direction can be done assuming one or multiple directions. In this thesis, an optimization method to minimize the surface jaggedness and the number of layers in laminated tooling is presented. In this optimization, the layers' thicknesses are selected from a set of available sheet metals. Also, the lamination direction as one of the optimization parameters is studied. A modified version of genetic algorithm is created for the optimization purpose in this research. The proposed method is presented as an optimization package which is applicable to any injection mould, hydroforming or sheet metal forming tool to create an optimized laminated prototype based on the actual model.

Laminated glass is comprised of multiple glass plates coupled together in a sandwich construction through the use of a polymorphous interlayer that acts as a bonding agent between the glass plates. Laminated glass offers several advantages over monolithic glass including the ability to resist post fracture collapse, improved sound insulation, lower ultraviolent light trans-mission, and improved thermal insulation. Because the stiffness of the interlayer is often many orders of magnitude less than that of the glass, plane sections prior to loading do not remain plane throughout the laminate?s thickness after load is applied. The behavior of laminated glass is controlled by the stiffness of the interlayer. This behavior rules out the use of classical theoretical formulations for thin plates. In such cases, it is necessary to use specially formulated equations or finite element analyses to evaluate the performance of laminated glass. Previous attempts have been made to develop procedures to quantify the interlayer stiffness for use in laminated glass design. However, there is no widely accepted technique that can be referenced for use. It is known that the interlayer stiffness is a function of both temperature and load duration. The primary objective of this thesis is to formalize a standard procedure to estimate the in situ interlayer shear modulus through the use of nondestructive testing. Physical experiments were carried out on simply supported laminated glass beams subject to three point loading in a temperature controlled environmental testing chamber. Strains and temperatures were recorded as a function of time. These data were used in combination with results from finite element analyses to quantify the variation of the interlayer stiffness as a function of temperature and load duration for a given laminated glass beam. This procedure was applied to three common types of interlayer materials: freshly man-factured polyvinyl butyral (PVB), over a decade old PVB, and freshly manufactured SentryGlas Plus (SGP). Results from these efforts provide specific design guidance for laminated glass that incorporates these interlayer materials. Further, the procedure was applied to various data presented in open literature by previous researchers. In addition, a standardized procedure to estimate interlayer stiffness is provided for the development of additional interlayer properties as required.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Okenwa Okoli, Florida State University, College of Engineering, Dept. of Industrial & Manufacturing Engineering. Title and description from dissertation home page (viewed 6/16/04). Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiv, 180 p. : ill. Includes abstract. Includes bibliographical references (p. 115-118).

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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