• Composites Research
• /
• v.30 no.6
• /
• pp.384-392
• /
• 2017

Sandwich panels with three different joint configurations were tested to design a novel sandwich joint structure that can effectively support both the tensile and compressive loads. The sandwich core was mainly aluminum flex honeycomb but the PMI foam core was limitedly applied to the ramp area which is transition part from sandwich to solid laminate. The face of sandwich panel was made of carbon fiber composite. For configuration 1, the composite flange and the sandwich panel were cocured. For configurations 2 and 3, an aluminum flange was fastened to the solid laminate by HI-LOK pins and adhesive. The average compressive failure loads of configurations 1, 2, and 3 were 295, 226, and 291 kN, respectively, and the average tensile failure loads were 47.3 (delamination), 83.7 (bolt failure), and 291 (fixture damage) kN, respectively. Considering the compressive failure loads only, both the configurations 1 and 3 showed good performance. However, the configuration 1 showed delamination in the corner of the composite flange under tension at early stage of loading. Therefore, it was confirmed that the structure that can effectively support tension and compressive loads at the same time is the configuration 3 which used a mechanically fastened aluminum flange so that there is no risk of delamination at the corner.

• Korean Journal of Optics and Photonics
• /
• v.19 no.1
• /
• pp.73-79
• /
• 2008

We propose a novel metal-waveguide structure for sustaining long-range surface-plasmon-polaritons (LRSPP). The LRSPP waveguides are composed basically of two asymmetric metal layers: a very thin, finite-width metal strip on top of a metal slab with a dielectric gap in between them. Mode cut-off of LRSPPs excited on the double-metal waveguides is characterized by consistently investigating their dispersion relations and mode profiles. We also confirm experimentally the existence of low-loss, well-confined LRSPP modes by measuring far-field outputs emerging from an edge of the asymmetric double-metal waveguides. In the experiment, we have fabricated several types of SPP waveguide devices including straight lines, S-bend, and Y-branch consisting of gold strips (20 nm-thick, $5{\mu}m$-wide). Overall propagation loss of the proposed double-metal waveguides is quite comparable to that of single metal-strip waveguides, in addition the mode sizes can be tuned by increasing the core-insulator gap between the metal layers to get a higher coupling efficiency with a single-mode fiber in telecom wavelength. The proposed LRSPP waveguides may open up realization of SPP-waveguide sensors or nonlinear SPP-devices by replacing the core-insulator with a bio-fluid or a nonlinear medium.

• Tribology and Lubricants
• /
• v.35 no.3
• /
• pp.158-168
• /
• 2019

This paper presents the investigation of two types of rotordynamic modeling issues for 2.2 kW-class, rated speed of 1,800 rpm, squirrel-cage type induction motors. These issues include the lamination structure of rotor cores, and the radial clearance of ball bearings that support the shaft of the motor. Firstly, we focus on identifying the effects of rotor core lamination on the rotordynamic analysis via a 2D prediction model. The influence of lamination is considered as the change in the elastic modulus of the rotor core, which is determined by a modification factor ranging from 0 to 1.0. The analysis results show that the unbalanced response of the rotor-bearing system significantly varies depending on the value of the modification factor. Through modal testing of the system, the modification factor of 0.079 is proven to be appropriate to consider the effects of lamination. Next, we investigate the influence of ball bearing clearance on the rotordynamic analysis by establishing a bearing analysis model based on Hertz's contact theory. The analysis results indicate that negative clearance greatly changes the bearing static behavior. Rotordynamic analysis using predicted bearing stiffness with various clearances from -0.005 mm to 0.010 mm reveals that variations in clearance result in a slight difference in the displacement of the system up to 18.18. Thus, considering lamination in rotordynamic analysis is necessary as it can cause serious analysis errors in unbalanced response. However, considering the effect of the bearing clearance is optional because of its relatively weak impact.

• Composites Research
• /
• v.29 no.4
• /
• pp.209-215
• /
• 2016

The failure of composite sandwich structures with thickness and material variation was studied. The main body of the structure is sandwich plate made of the carbon composite face and Aluminum honeycomb core. It is connected with composite laminated flange without core through transition region of tapered sandwich panel with foam core. Tension and compression tests were conducted for the total of 6 panels, 3 for each. Test results showed that the panels under compression are vulnerable to the face failure along the material discontinuity line between two different cores. However the failure load of which panel does not show such failure can carry 16% more load and fails in honeycomb core and face debonding. For the tensile load, the extensive delamination failure was observed at the corner radius which connects the panel and the flange. The average failure load for compression is about 7 times the tensile failure load. Accordingly, these sandwich structures should be applied to the components that endure the compressive loadings.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.8
• /
• pp.798-805
• /
• 2010

Whole composite structure small class (150kg) satellite, STSAT-3, was initially developed in Korea. The structure does have aluminum frames that support the structure, and it is composed of only composite sandwich panels. A number of electronic boxes and mechanical apparatus will be shielded within the compartments built up by the composite panels. This study focused on the random vibration responses of the satellite. For this objective, vibration tests and analyses have been successfully performed with respect to STM (structure and thermal model) of the satellite. Additionally, through the experiment and theoretical analyses, the both results' accuracy was verified by comparison each other.

• Korean Journal of Optics and Photonics
• /
• v.18 no.1
• /
• pp.14-18
• /
• 2007

Photonic crystal fibers(PCFs) with silica cores within an away of air holes have unique properties. Broad band single-mode and the octave-spanning supercontinuum generation, impossible to achieve in classical fibers, can be realized. The design of PCFs is very flexible. There are two parameters to manipulate: air hole diameter, and lattice pitch. We introduced a fabrication process for control of the parameters to obtain endlessly single mode PCF, which is single mode in a large wavelength range, and highly nonlinear PCF. The numerical analysis and experiments are included.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.1
• /
• pp.68-72
• /
• 2004

The integrated voltage-controlled-oscillator(VOC) operating at 1.75 ㎓ is designed using the InGaP/GaAs HBT process. The proposed noise removal circuit and FR-4 substrate structure in this letter show the better characteristic of the phase noise and reduce the size of the VCO. The frequency tuning range of the VCO is about 200 ㎒ and the phase noise at 120 ㎑ offset is -119.3 ㏈c/㎐. The power consumption of the VCO core is 11.2 ㎽ at 2.8 V supply voltage and the output power is -2 ㏈m. The calculated figure of merit(FOM) is 191.7, which shows the best performance compared with the previous FET or HBT VCO.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2011.11a
• /
• pp.15-15
• /
• 2011

본 연구는 기존의 하우스 랩이 가지는 방풍, 방수 기능 외에 복사열 차단성, 열반사성, 통기성, 투습성, 난연성, 방수성 및 단열성 등의 다기능성이 발현되는 우수한 건축용 하우스 랩을 제조하는 목적으로 시스-코어 섬유로 이루어진 부직포층, 통기성 합성수지 필름층, 니들펀칭 복합 부직포층 및 고분자 필름이 일면 또는 양면에 코팅된 내식성 알루미늄 필름층이 순차적으로 적층되고 핫-멜트 라미네이팅에 의하여 합지 된 다기능성 하우스 랩 및 그의 따른 제조방법에 관한 것이다. 상기 니들펀칭 부직포 내부에 포함 된 아라미드 섬유에 의해 우수한 난연효과를 가지며, 통기성 필름에 의하여 투습방수 기능을 가질 수 있으며, 니들펀칭 부직포층에 다량의 공기가 함유되어 보온성이 우수하고, 내식성 알루미늄 필름층이 가진 빛에 대해 우수한 방사성으로 복사열을 차단하여 단열효과를 나타내는 하우스 랩을 제조하였다.

• Restorative Dentistry and Endodontics
• /
• v.33 no.3
• /
• pp.169-176
• /
• 2008

The purpose of this study was to evaluate the effect of thickness, filling methods and curing methods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Bis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 mm (bulky filled), 4 mm (bulky filled), 6 mm (bulky and incrementally filled) and 8 mm (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at $37{\circ}C$ for 24 hours, the Knoop hardness values (KHN) of top and bottom surfaces were measured and the microhardness ratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA and Scheffe multiple comparison test, with ${\alpha}$= 0.05. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 mm groups, the KHN of two materials were not affected by thickness. However, in 8 mm group of MultiCore Flow, the KHN of the bottom surface was lower than those of other groups (p < 0.05). The effect of filling methods on the polymerization of dual cured composites was different by their thickness or materials. In 6 mm thickness, there was no significant difference between bulk and incremental filling groups. In 8 mm thickness, Bis-Core showed no significant difference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling group was lower than that of incremental filling group (p < 0.05). The effect of curing methods on the polymerization of dual cured composites showed material specific results. In Bis-Core, the KHN of dual cured group were higher than those of self cured group at both surfaces (p < 0.05). However, in MultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured group showed higher KHN than that of self cured group (p < 0.05). However, in the bottom surface, dual cured group showed lower value than that of self cured group (p < 0.05).

• Proceedings of the KACD Conference
• /
• 2008.05a
• /
• pp.169-176
• /
• 2008

The purpose of this study was to evaluate the effect of thickness, filling methods and curing methods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Bis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 mm (bulky filled), 4 mm (bulky filled), 6 mm (bulky and incrementally filled) and 8 mm (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at $37^{\circ}C$ for 24 hours, the Knoop hardness values (KHN) of top and bottom surfaces were measured and the microhardness ratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA and Scheffe multiple comparison test, with ${\alpha}=0.05$. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 mm groups, the KHN of two materials were not affected by thickness. However, in 8 mm group of MultiCore Flow, the KHN of the bottom surface was lower than those of other groups (p < 0.05). The effect of filling methods on the polymerization of dual cured composites was different by their thickness or materials. In 6 mm thickness, there was no significant difference between bulk and incremental filling groups. In 8 mm thickness, Bis-Core showed no significant difference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling group was lower than that of incremental filling group (p < 0.05). The effect of curing methods on the polymerization of dual cured composites showed material specific results. In Bis-Core, the KHN of dual cured group were higher than those of self cured group at both surfaces (p < 0.05). However, in MultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured group showed higher KHN than that of self cured group (p < 0.05). However, in the bottom surface, dual cured group showed lower value than that of self cured group (p < 0.05).