Showing papers by "Dai Gil Lee published in 2010"
TL;DR: In this article, the through-thickness compressive strength (TTCS) of a carbon/epoxy composite bearing material was measured with respect to weave type, stacking sequence, and direction of cut from the laminate.
41 citations
TL;DR: In this paper, the authors presented a new design of asymmetric composite sandwich endplates which are made of carbon fiber reinforced composite and glass fibre reinforced composite with a pre-curvature generated by the residual thermal deformation, which will yield the required pressure distribution in the stack when the endplates are fastened by the clamping device.
40 citations
TL;DR: In this article, a monocoque satellite structure composed of many composite sandwich panels, which consist of two carbon fiber/epoxy composite faces and an aluminum honeycomb core, was designed to reduce structural mass and to improve static and dynamic structural rigidity.
31 citations
TL;DR: In this article, a single-lap joint composed of aluminum adherends and epoxy adhesive was measured with respect to the condition of the silane solution and surface roughness obtained with grit blast.
Abstract: Aluminum adherends for the adhesive joints at cryogenic application such as LNG (Liquefied Natural Gas) containment tanks were silane treated to improve bond strength of the aluminum joints. The bond strengths of the single-lap joints composed of aluminum adherends and epoxy adhesive were measured with respect to the condition of the silane solution and surface roughness obtained with grit blast. The chemical composition of the silane treated aluminum surface was analyzed by XPS (X-ray photoelectron spectroscopy). Also, contact angles of appropriate liquids on the silane treated aluminum surface were measured with respect to treatment conditions. From the experiments, the optimum treatment conditions for the aluminum adherends were obtained for the adhesive joints at the cryogenic temperature.
25 citations
TL;DR: In this article, the authors measured the fracture toughness and crack resistance of aluminum adhesive joints at the cryogenic temperature of −150°C, with respect to the orientation and volume fraction of the E-glass fibers in the epoxy adhesive.
Abstract: Fracture toughness and crack resistance of aluminum adhesive joints were measured at the cryogenic temperature of −150°C, with respect to the orientation and volume fraction of the E-glass fibers in the epoxy adhesive. Cleavage tests on the DCB (Double Cantilever Beam) adhesive joints were performed using two different test rates of 1.67 × 10−2 and 8.33 × 10−4 mm/s to observe the crack propagation trends. From the experiments, it was found that the DCB joints bonded with the epoxy adhesive reinforced with E-glass fibers not only showed a stable crack propagation with a low crack propagation speed, but also higher fracture toughness and crack resistance than those of the DCB joints bonded with the unreinforced epoxy adhesive at a cryogenic temperature of −150°C.
24 citations
TL;DR: In this paper, a sandwich construction composed of carbon fiber reinforced composite faces and a thermal insulation foam core was employed for the endplate of a polymer electrolyte membrane fuel cell (PEMFC) to satisfy the two functional requirements, i.e. light weight and good cold-start characteristics.
20 citations
TL;DR: In this article, the surface of a glass/epoxy composite material was embedded with oxidized carbon black by heat treatment to enhance the adhesion strength of the composite structure, and the surface free energies and lap shear strengths were investigated in terms of the heat treatment conditions and the amount of embedding.
Abstract: The surface of a glass/epoxy composite material was embedded with oxidized carbon black by heat treatment to enhance the adhesion strength of the glass/epoxy composite structure. Quantitative chemical bonding analysis with X-ray photoelectron spectroscopy (XPS) was conducted to observe the chemical binding states of the surface of the carbon black particles with heat treatment. The morphological effects of the carbon black on the surface of the composite were observed using SEM and AFM. The surface free energies and lap shear strengths of the glass/epoxy adhesive joints whose adherends were embedded with oxidized carbon black were investigated in terms of the heat-treatment conditions and the amount of embedding. From the experimental results, embedding the heat-treated carbon black particles on the composite surface was found to greatly improve the adhesion strength of the composite due to the increased oxidation radicals on the carbon black surface.
14 citations
TL;DR: In this paper, the tribological behavior of carbon epoxy composites whose surfaces have many small grooves of 100 μm width were compared with respect to plasma treatment duration under dry sliding conditions.
12 citations
TL;DR: In this article, a selective surface preparation technology is developed using an electromagnetic field and carbon black (electromagnetic-carbon surface treatment), which can be applied for production of the composite bipolar plates in a fast and efficient process.
11 citations
Patent•
25 Jun 2010
TL;DR: In this paper, a composite separator for a polymer electrolyte membrane fuel cell (PEMFC) and a method for manufacturing the same is presented. But the method involves allowing graphite foil layers to be brought into direct contact with each other when graphite foils are stacked on both sides of a carbon fiber reinforced composite material prepreg, thereby improving electrical conductivity.
Abstract: The present invention provides a composite separator for a polymer electrolyte membrane fuel cell (PEMFC) and a method for manufacturing the same. The inventive method involves allowing graphite foil layers to be brought into direct contact with each other when graphite foils are stacked on both sides of a carbon fiber reinforced composite material prepreg, thereby improving electrical conductivity in the thickness direction of the separator.
7 citations
TL;DR: In this paper, the surface of glass/epoxy composite material was embedded with carbon black which was dispersed in methyl ethyl ketone (MEK) during the curing process to enhance the adhesion strength of the composite structure.
Abstract: The surface of glass/epoxy composite material was embedded with carbon black which was dispersed in methyl ethyl ketone (MEK) during the curing process to enhance the adhesion strength of the glass/epoxy composite structure. The morphological effect of the carbon black on the surface of composite was observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative chemical bonding analysis with X-ray photoelectron spectroscopy (XPS) was also performed to observe chemical bonding states on the surface. The lap shear strength of the glass/epoxy composite adhesive joints where composite adherends were embedded with carbon black was investigated with respect to the type and amount of embedment. Also, the tensile properties of the carbon black embedded glass/epoxy composites were measured to observe the mechanical degradation of the composite due to the MEK. The surface free energies of carbon black embedded composites were determined from the van Oss–Chaudhury–Good equation to...
TL;DR: In this article, a hybrid composite anchor composed of two stainless steel caps and a glass fiber composite body was developed and optimized for strength, thermal stress and heat loss of the anchor.
TL;DR: In this paper, the authors emphasized the application of composite technology to the design and fabrication of an all-composite spacecraft bus for small-class satellite STSAT-3.
Abstract: A satellite that has an all-composite structure, STSAT-3(science and technology satellite), was initially developed in Korea. Partially use of advanced composites in space applications such as solar panel is well developed, however the application of an all-composite satellite bus has never been achieved in Korea. This study emphasizes the application of composite technology to the design and fabrication of an all-composite spacecraft bus for small-class satellite STSAT-3. Moreover its structure design concept is totally different from the one that was used in the previous satellites developed in Korea.
01 Jan 2010
TL;DR: In this paper, the epoxy adhesive was modified by quartz nano-particles which have much higher piezoelectric properties than epoxy adhesives, which not only improved the joint strength but also increased the sensitivity of damage monitoring performance at cryogenic temperature.
Abstract: Recently, a piezoelectric method using piezoelectric characteristics of epoxy adhesives has been successfully developed for the adhesive joints, which can monitor continuously the damage of adhesively bonded structures without producing any defect induced by inserting a sensor. However, due to low piezoelectric properties of epoxy adhesives, the detection of micro crack was impossible. At the cryogenic temperature, the detection of micro crack is important to estimate the fatigue life because the polymeric adhesives become very brittle. Therefore, in this work, the epoxy adhesive was modified by quartz nano-particles which have much higher piezoelectric properties than the epoxy adhesives. To investigate the effects of quartz nano-particles, the static and dynamic tests of the tubular adhesive joints were performed to compare the joint strength and sensitivity of damage monitoring performance. From the experiment result, it was found that the quartz nano-particles not only improved the joint strength but also increased the sensitivity of damage monitoring performance at cryogenic temperature.