Master of Science in Engineering, Youngstown State University, 2018, Department of Civil/Environmental and Chemical Engineering

The incorporation of additive manufacturing (AM) enables the ability to fabricate composite tooling molds rapidly and in a cost effective manner. This work has demonstrated the practice of an additive technology for manufacturing composite processing tools. In particular, this work has addressed tooling that is functional in the range of autoclave temperatures around 180°C. This has led to the use of Invar and ceramic materials for use in composite molding tools because of their relatively low coefficient of thermal expansion (CTE) performance, which is in range to that commonly displayed by carbon fiber reinforced composites during their solidifying curing process. In this project, three main approaches have been considered. The first innovative approach was based on printing a mold based on silica sand and infiltrating it with a polymer to yield a robust ceramic composite tooling. The second approach investigated the use of binder jetting to 3D print sand molds to cast molten Invar to produce the composite tooling. Indeed, 3D sand printing offers the ability to cast complex geometries without the geometric limitations associated with conventional pattern making. An additional technology using a Hybrid Direct Energy Deposition (DED) System for cladding Invar upon a steel molding structure has also been considered for producing potential composite tooling. Indeed, this unique approach could represent a promising technology for producing low cost composite tooling since only a small layer of Invar would be cladded to a non-expensive substrate. The results have shown that the aforementioned processes have successfully resulted in low CTE composite tooling molds. This work presents innovative AM processes by initially investigating additive manufacturing processes for composite tooling.

Committee: Pedro Cortes PhD (Advisor); Brett Conner PhD (Committee Member); Jason Walker PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy (PhD), Ohio University, 2009, Integrated Engineering (Engineering and Technology)

Carbon foams are porous materials which are attractive for many engineering applications because their thermal and mechanical properties can be customized by varying manufacturing process parameters. However, a highly random geometry at pore level makes it very difficult to analyze the properties and the behavior of this material in an application. Published research work on the analysis of foams has employed various ideal geometries to approximate the pore microstructure. However, these models are unable to predict accurately the foam properties and behavior in engineering applications.The objective of this research work is to determine thermal and mechanical properties of carbon foam on the basis of its true microstructure. A new approach is proposed by creating a three dimensional (3D) solid model based on an accurate representation of the real geometry of carbon foam. Finite element models are then developed to investigate the bulk thermal and mechanical properties of carbon foam using the three dimensional solid model. On the basis of the true 3D model of carbon foam, a study is undertaken to examine the effect of the unique microstructure on the flow field within the foam pores and the resultant convective heat transfer. A finite volume model is developed using the accurate representation of carbon foam microstructure inside a flow channel. The fluid flow and heat transfer is simulated to evaluate pressure drop and heat transfer capabilities. The carbon foam permeability, inertial coefficient and friction coefficient are determined and found to be in good agreement with experimental and semi-empirical models. The results also show a large enhancement in the heat transfer due to the presence of carbon foam in the channel. These results are comparable to the experimental results available in published literature. Another application that has been analyzed in this study is the use of carbon foam as tooling material for manufacturing advanced composite material (open full item for complete abstract)

Committee: M. Khairul Alam (Advisor) Subjects: Engineering; Technology