Showing papers by "Dai Gil Lee published in 2009"

Tensile Strength of Joints Bonded With a Nano-particle-Reinforced Adhesive

Abstract: In order to improve the tensile lap shear strength of adhesively bonded joints, nano-particles were dispersed in the adhesive using a 3-roll mill. The dispersion states of nano-particles in the epo...

The Sliding Friction of Hybrid Composite Journal Bearing under Various Test Conditions

Abstract: Composite journal bearings are becoming more popular for marine applications because they eliminate the possibility of seizure to steel journals, which is a drawback of white-metal bearings. However, the reliability of composite bearings should be verified by various tests before its commercialization. In this study, hybrid composite journal bearings composed of carbon/phenolic and glass/epoxy laminated composites were manufactured and tested under various operating conditions and compared with white-metal journal bearings. The friction coefficient of the hybrid composite journal bearing was similar to that of white-metal bearing under transient and hydrodynamic lubrication. However, the hybrid composite journal bearing could be operated up to 30 min under severe dry condition, whereas the white metal gets seizure to the steel journal during the bearing operation.

Strength of Double Lap Joints Bonded With Carbon Black Reinforced Adhesive Under Cryogenic Environment

Abstract: In order to improve the tensile lap shear strength and durability of adhesively bonded joints, nano-size carbon black particles were dispersed in the adhesive using a 3-roll mill. The effect of nano-particles on the mechanical properties of the adhesive and the lap shear strength of the adhesively bonded joints composed of glass/epoxy composite were investigated at room and cryogenic temperatures. From the experimental and FE analysis results, it was found that the carbon black particles improved the mechanical property of the adhesive at room temperature, but there was no reinforcing effect at cryogenic temperature. However, since the carbon black reinforced adhesive decreased thermal residual strain in the adhesively bonded joint, the lap shear strength was improved at both room and cryogenic temperatures. Also it was found that the reinforcement with carbon black improved durability of the adhesively bonded joints under thermal loadings.

Improvement of Bonding Characteristics Between the Frequency Selective Surface and E-Glass/Epoxy Composites for Stealth Radomes

Abstract: Radomes of weapon systems such as aircraft, warships, and missiles have been manufactured using FSS (Frequency Selective Surface) for the stealth performance and E-glass/epoxy composite to protect the radar antenna from weather and mechanical impact and to minimize the loss of EM (electromagnetic) waves transmitted through the radome. In this work, the FSS was manufactured from an FCCL (Flexible Copper Clad Laminate) composed of a copper foil of 20 μm thickness and a polyimide film of 40 μm thickness. The bonding characteristics between the FSS and E-glass/epoxy composite were determined for different surface treatments of copper such as atmospheric pressure plasma treatment and nitric acid/ferric chloride treatment. The EM transmission characteristics of the FSS were also measured by the free space measurement system before and after surface treatments. Nitric acid/ferric chloride treatment of the FSS was found to be a promising method to enhance the bonding characteristics between the FSS and the E-glas...

Optimum Design of Aramid-phenolic/Glass-phenolic Composite Journal Bearings

Abstract: Composite journal bearings are increasingly employed in large journal bearings for marine applications because composite materials can eliminate the seizure problem between the journal and the bearing during the start and stop periods of journals. Recently, aramid/glass reinforced phenolic composite journal bearings have been employed rather than the asbestos-phenolic composite bearings due to the health hazard of asbestos. In this work, the mechanical properties of aramid/glass reinforced phenolic composite were measured in order to analyze the stress on the journal bearing using the finite element (FE) method. The failure modes of the aramid/glass reinforced phenolic composite journal bearings were observed. The modified dimensions of aramid/glass reinforced phenolic composite journal bearings and the optimum interference fit amount were suggested using the FE-analysis results.

Durability Improvement of Co-cured Carbon/Epoxy Composite-Aluminum Laminate With Nano-size Carbon Black at Cryogenic Temperature

Abstract: Since metal foils such as aluminum, copper or nickel foils have been used in composite structures for radiation shielding and EMI protection in space environments, high adhesive bonding strength and durability between metal foils and composites under large temperature variations are very important. In this study, the strength of co-cure bonded joint between an aluminum foil and a composite has been investigated, with three different aluminum surface treatments such as standard PAA (Phosphoric Acid Anodization) procedure, abrasion with sandpaper, and carbon black pasting on the metal foils. From the double cantilever beam (DCB) tests, it was found that the interlaminar peel strength with carbon black pasting improved 60% compared to the laminate without any surface treatment. Also it was found that the interlaminar peel strength of the co-cure carbon/epoxy composite-aluminum foil hybrid laminate with the carbon black pasting on the aluminum foil did not decrease after many thermal cycles from 30°C to –196°C.

Trennplatte für einen Brennstoffzellenstapel und Verfahren zur Herstellung

Abstract: Die vorliegende Erfindung stellt eine Trennplatte fur einen Brennstoffzellenstapel und ein Verfahren zum Herstellen einer Trennplatte bereit, und insbesondere eine Trennplatte fur einen Brennstoffzellenstapel und ein Verfahren zum Herstellen einer Trennplatte, in welchem die Trennplatte, die den Brennstoffzellenstapel formt, derart gebildet ist, so dass eine Anordnung von Metallrohren zwischen zwei Platten aus einem Verbundwerkstoff einfugbar ist, und eine Dichtung, die an die Trennplatte angrenzt, derart gebildet ist, um Wasserstoff- und Luftstromungskanale zu umgrenzen, um dadurch einen Kontaktwiderstand zwischen zwei benachbarten Trennplatten zu beseitigen, die Elementarzellen formen, um den Wirkungsgrad der Brennstoffzelle entsprechend zu verbessern.

Probe card and manufacturing method therefor

Abstract: PROBLEM TO BE SOLVED: To provide a probe card for performing a visual test by bringing it into contact with an electrode pad of a body to be inspected collectively, and to provide a manufacturing method for the probe card. SOLUTION: The probe card comprises a plurality of probes where contact parts, having elasticity to contact the electrode pad of the body to be inspected are formed of folded conductive wires and are aligned in the same direction and is aligned in parallel, to prevent short-circuitings; an insulating block for fixing a part close to one end of the probe; a second insulating block for fixing a part close to the other end of the probe; and a mounting plate for fixing the first insulating block and the second insulating block, respectively, so that the contact parts of the probes project. COPYRIGHT: (C)2009,JPO&INPIT