Sun Ho Ko

A Study on Impact Strength of CFRP Using Infrared Thermography

Of the advanced composite materials for aerospace structures such as aircrafts and space devices, the carbon fiber reinforced plastics (CFRP) is applied to many sectors that require lightweight materials for its high strength and stiffness. One of the disadvantages of the CFRP, however, is that it is weak against impact. In this study, impact test specimens were manufactured with five fiber stacking angles (0°/0°, 0°/15°, 0°/30°, 0°/45°, 0°/90°) according to ASTM D7136[15], and a falling weight test was performed to analyze the correlation between their mechanical and thermal characteristics. As a result, the impact energy applied to the five test specimens with different fiber stacking angles was almost constant at 30.63 J - 30.78 J. The absorbed energy increased with the increase in the fiber stacking angle, and decreased after 0°/45°. The average temperature on the fractured surface increased with the increase in the fiber stacking angle in all specimens other than the 0°/0° specimen.

A Study on the Bending Analysis of the Al Honeycomb Core Sandwich Composite Panel Bearing Large Bending Load

Al honeycomb core sandwich composite panels have different core and plate materials. The core is the Al honeycomb core, and the thin plate is GFRP sheets with fibers laminated in the 0°/90° symmetric structure. The Al honeycomb core sandwich composite panel is used for structures, which involve relatively high bending load. Before designing the structures, their stability is evaluated via the finite element analysis. In this study, an analysis method that is closest to the reality was proposed for designing the structures with Al honeycomb core sandwich composite panels. For that purpose, the modulus was reviewed. In the finite element analysis, the tensile modulus is generally used. In the results of this study, however, the tensile modulus led to significant deviations from the test results, whereas the bending modulus led to a closer value to the test results.

Stability Evaluation for Polymer Electrolyte Membrane Eletrolyzer

Recently, polymer electrolyte membrane (PEM) electrolyzers consist of the layered structure of membrane and electrode assembly (MEA), titanium flow field plate, gasket, end plate, and others. Among these components, MEA and titanium flow field plate take account for most of the device cost. The cost and time for manufacturing device can be reduced with the gasket-integrated 3-D mesh-applied PEM electrolyzer (Fig. 3), while maintaining the same performance as that of the existing titanium flow field plate devices. The 3-D mesh is found to perform the roles of the existing flow plate which ensures the smooth fluid flow and uniform power supply. The voltage shows 19.3V at current density (0.5 A/cm2), a little lower than 19.6V that is 10 times of 1.96V which is the average cell voltage at the same current density. In addition, hydrogen production and stability for performance are equal to or higher than that of the device for titanium flow field plate.

A Study on the Nondestructive Evaluation of Carbon/Carbon Brake Disks Using Infrared Thermography

Carbon/carbon brake disks that use carbon fibers impregnated in a carbon matrix are widely utilized in aircrafts and automobiles owing to their high strength, high heat conductivity, low density, and excellent overall mechanical properties. Carbon/carbon brake disks are high cost products and require multi-process manufacturing. The safety and material efficiency of defective products reduces significantly and nondestructive testing is required to monitor the quality, homogeneity, and integrity of the material. In general, radiographic evaluations pose safety problems owing to the use of radiation in such evaluations and ultrasonic flaw detection is difficult to use because of its dependence on the surface of the specimen. This study uses an infrared thermography camera technique, which is not influenced by the sample surface, to monitor the heterogeneity of materials during the manufacturing process and to thus prove the reliability of the method.

A Study on the Structure Analysis of Skate for Transportation Using Composite Materials

As society became more complex, the logistics also increased, demanding for logistics transport vehicles and feeder has increased. Because the self-weight of skate for cargo transport used in this study is heavy, it needs to be weight lightening. However there is a lack of capital and technology not to improve lasting. We conducted FEM studies about weight lightening applying composites on cargo transport skate and the stiffness can be obtained at the same time. However, due to the presence of discontinuities such as holes in the parts. If you are applying composite, Because this causes the degradation of the strength of the material under static and fatigue load induced stress concentration in parts. In order to examine the safety of the cargo transport skate, you must consider the impact of the static strength damage on the stress concentration because of the discontinuous parts. In this study, therefore, the cargo skate was performed to evaluate the structural analysis through the FEM analysis. As a result, it was found that CFRP compared to existing SM45C is superior 25% when considering the characteristics. It indicated the best results in about 30% of the weight lightening.

Mechanical and Thermal Analysis of Topological Optimization for Load Bearing Skate

Load bearing skate for the current weight is heavy and requires its own weight, but persist without improvement in the lack of capital and technology, but it is a reality. In this study, carried out phase optimal design to remove unwanted elements that do not have a stress to reduce the weight of skating that is being used for cargo transportation for, it reduces the weight of the objective function, we examined the safety associated with it.Using the FEM analysis Lets examine the effect on the failure strength by extreme temperatures that are used in the field of stress concentration due to discontinuity in the analysis at the time, structure - was carried out thermal analysis.Further, while ensuring safety through safety factor 2.1 and 20% weight reduction by the phase volume of for weight reduction.