Papers by Author: Oh Heon Kwon

Abstract: The crack formation and propagation remain as major issues regarding the mechanical crack behavior of solid oxide fuel cell (SOFC), due to the thermomechanical mismatch and the porous nature of the SOFC components. The SOFC consisting of brittle ceramic materials can be damaged by the cracking due to high-temperature during the manufacturing and operation. The crack generated during the manufacturing were can cause the cell performance degradation during operation. For crack evaluation because the SOFC products the required power density through the stack considering the interconnector is required. The purpose of this study is to investigate the effect of the vertical crack at the cathode electrode, and also the effects of the crack on the interconnect channel position in operation for the crack behavior and stress field.

Abstract: Fiber reinforced metal matrix composites (MMCs) are recently used in automobile, ship, aerospace and manufacturing industry because they have high stiffness and strength. The effective utilization of the strength and stiffness of the fiber reinforced MMCs depends on efficient load transfers from the matrix to fibers through the interfacial region. However, during the fabrication and afterward utilization of composites, so many numbers of micro crack may extend, especially at the interface, even before any load has been applied. Thus, in this study, the interfacial stress state and behavior of the interfacial perpendicular crack for transversely loaded unidirectional fiber reinforced MMCs investigated by using the elastic-plastic finite element analysis.

Abstract: Recently, composite materials are used in many fields because their properties are high strength, high stiffness, and they have light weight, good corrosion resistance and good thermal conductivity. However, composite materials have relatively a lot of problems, especially delamination, compared with common materials such as a steel and aluminum, etc. Therefore, having the interlaminar fracture toughness for a laminate composite is important. In this study, the end notched flexure (ENF) specimens are employed in order to evaluate modeⅡ interlaminar fracture toughness for CFRP laminate composites. Three kinds of a/L ratio were applied to these specimens under the different pressure level. Also, we discuss the relation of crack growth and the interlaminar fracture toughness in terms of AE characteristics using ENF test.

Abstract: The strong continuous fiber reinforced metal matrix composites (MMCs) are recently used in aerospace and transportation applications as an advanced material due to its high strength and light weight. However, MMC is significantly affected by the interface under the transverse loading. Furthermore, the crack at the interface induces weakness of the characteristics of the overall mechanical response and strength of the MMCs. In order to be able to utilize these MMCs effectively and with safety, it must be determined their elastic plastic fracture behaviors at the interface. The influence of different regular fiber arrangement as like square and hexagonal arrangement on the strength of transversely loaded fiber reinforced matrix is analyzed. And the interface of fiber and matrix is modeled as thin multi layers with properties linearly gradient to distinguish the interface from the fiber and matrix. Different fiber arrangement of square and hexagon type is studied. And fiber volume fraction is changed for several kinds (5%-60%).