• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.491-496
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• 2001

In recent years, the research and development about the new material proceed rapidly and actively in the building industry. As building structures become bigger, higher and more specialized, so does the demand for material with higher strength. In the future, we will need to research repair and rehabilitation to make high strength concrete mixed steel fibrous building safe. The carbon fiber reinforced plastic bonding method is widely used in reinforcing the existing concrete structure among the various methods. The repair of initiate loaded reinforced high-strength concrete beams mixed steel fibrous with epoxy bonded Carbon Fiber Sheets(CFS) was investigated experimentally. The CFS thickness and length were varied to assess the peel failure at the curtailment of CFS, The behaviour of the repaired beams was represented by load-longitudinal steel strain relation and failure modes were discussed. The test results indicate that CFS is very effective for strengthening the demand beams and controlling deflections of reinforced high strength concrete beams mixed steel fibrous happen diagonal crack, the increase in the number of CFS layers over two layers didn't effect the increase in the strength of beams.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.557-558
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• 2008

This paper presents the effects of via losses to be connected with an embedded DPDT(Double Pole Double Thru) in a substrate. The substrate consists of two ABF(Ajinomoto Bonding Film) and a Epoxy core. In order to verify and test effects of via, via chains in a substrate using SoP-L process are proposed and measured. Via loss can be calculated as averaging the total via holes. The exact loss of a DPDT switch embedded in substrate are extracted by using the results of via chain and measured data from embedded DPDT. The calculated one via insertion loss is about 0.0005 dB on basis of measured via chains. This result confirms very low loss in via. So the inserti on loss of the embedded switch is confirmed only switch loss as loss is 0.4 dB.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.104-107
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• 2004

In this work, the blend of diglycidylether of bisphenol A (DGEBA) and modified polyurethane (PU) was prepared and characterized in the cure behaviors and mechanical interfacial properties. The N-benzylpyrazinium hexafluoroantimonate was used as a cationic initiator for cure, and the content of PU was varied within 0-20 phr. The cure behaviors and mechanical interfacial properties were studied by DSC, near­IR, and the critical stress intensity actor $(K_{IC})$ measurements. Also thermal stabilities were carried out by TMA and TGA analyses. As a result, the cure activation energy $(E_a)$ and the conversion $(\alpha)$ were slightly increased with increasing the PU content, and a maximum value was found at 10 phr PU. The mechanical interfacial properties measured from $K_{IC}$ showed a similar behaviors with the results of conversion. These results were probably due to the increase of the hydrogen bonding between the hydroxyl groups of DGEBA and isocyanate groups in PU.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.204-209
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• 2001

In this research, the effects of fiber stacking sequence on damage behaviors of FML(Fiber Metal Laminates) subject to indentation loading. SOP (Singly Oriented Ply) FML and angle ply FML were fabricated to study fiber orientation effects and angle ply effects. FML were fabricated by using 1050 aluminum laminate and carbon/epoxy prepreg. To increase adhesive bonding strength, Al laminate was etched using FPL methods. The static indentation test were conducted by using UTM(5ton, Shimadzu) under the 2side clamped conditions. During the tests, load and displacement curve and crack initiation and propagation behaviors were investigated. As fiber orientation angle increases, the crack initiation load of SOP FML increases because the stiffness induced by fiber orientation is increased. The penetration load of SOP FML is influenced by the deformation tendency and boundary conditions. However, the macro-crack of angle ply FML was initiated by fiber breakage of lower ply because angle plies in Angle ply FML prevents the crack growth and consolidation. The Angle ply FML has a critical cross-angle which prevent crack growth and consolidation. Damage behavior of Angle ply FML is changed around the critical cross-angle.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.4
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• pp.241-250
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• 1997

The velocity dispersion of surface acoustical wave(SAW) of Si layer/mesh Au/Si substrate was measured by the frequency analysis technique of backward radiation at liquid/solid interface. The difference of backward radiation patterns depending on used transducers (2, 5, 10MHz) confirmed that the backward radiation phenomenon was caused by the energy radiation from SAW generated in surface region. An ultrasonic goniometer was constructed to measure continuously the angular dependence of backscattered intensity. The angular dependences of backward radiation(5MHz) were measured for Ni layer/Al substrate specimens that were bonded by epoxy involving different content of Cu powder. It was known that the width and pattern of backward radiation had informations such as the velocity dispersion, bonding quality and structure of surface region.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.165-172
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• 2005

In MEMS (Micro-Electro-Mechanical System), packaging induced stress or stress induced structure deformation becomes increasing concerns since it directly affects the performance of the device. In the decoupled vibratory MEMS gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, packaged using the anodic bonding at the wafer level and EMC (epoxy molding compound) molding, has a deformation of MEMS structure caused by thermal expansion mismatch. This effect results in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) process technology. It uses a silicon wafer and two glass wafers to minimize the wafer warpage. Thus the warpage of the wafer is greatly reduced and the frequency difference is more uniformly distributed. In addition. in order to increase robustness of the structure against deformation caused by EMC molding, a 'crab-leg' type spring is replaced with a semi-folded spring. The results show that the frequency shift is greatly reduced after applying the semi-folded spring. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.81-86
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• 2000

This paper was carried out to investigate the characteristics of interlaminar fracture toughness of foam core sandwich structures under opening loading mode by using the double cantilever beam (DCB) specimens in Carbon/Epoxy and foam core composites. instead of using symmetric geometry of DCB specimen non-symmetric DCB specimen was used to calculate the interlaminar fracture toughness. Three approaches for calculating the energy release rate({{{{ {G }_{IC } }}}}) were compared. Fracture toughness of foam core sandwich structures by autoclave vacuum bagging and hotpress were compared and analyzed. Experiment nonlinear beam bending FEM method were performed. Suggested bonding surface compensation and equivalent area inertia moment was used to calculate the energy release rate in nonlinear analytical results. The conclusions among experimental nonlinear analytical and FEM results was observed. The vacuum bagging method was shown to be able to substitute method in stead of autoclave without serious loss of Mode I energy release rate({{{{ {G }_{IC }}}}}) to be able to substitute method in stead of autoclave without serious loss of Mode I energy release rate({{{{ {G }_{IC }}}}}).

• The Journal of Korean Academy of Prosthodontics
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• v.20 no.1
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• pp.7-17
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• 1982

In order to investigate the internal adaptability and cytotoxicity for porcelain fused to metal Ni-Cr alloy, two commercial alloys (Generic Gold-R alloy, Aalba Dent- Valloy)were employed and compared with new developed beryllium free Ni-Cr alloy (KIST-K alloy). After cementation of each crown to abutment die before and after ceramic bonding respectively, dies were mounted to epoxy resin and the internal space was measured between crown and die of each point on sagittal section. The results were as follows: 1) The results show that the space between the crown and the die was largest at the incisal edge, followed by the shoulder or the bevel and chamfer. The least was to be in the axial surface. 2) There were no significant difference in the adaptability of the compared alloys. 3) On day 2 of the experiment the cell multiplication was slightly inhibited by R and K alloys. However, observations taken at day 4 and 7 showed normal cell multiplication process compared to control group. 4) Alloy V exhibited the most severe cell toxicity among the alloys tested on day 2. By day 4 and 7 it showed a decrease level in toxicity, however it did not exhibit normal cell growth as compared to control group.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.2
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• pp.92-98
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• 2015

The magnetoelectric characteristics on layered Ni-PZT-Ni, Co, Fe composites by epoxy bonding for magnetic field sensor were investigated in the low-frequency range. The ME coefficient of Ni-PZT-Ni, Ni-PZT-Co and Ni-PZT-Fe composites reaches a maximum of $200mV/cm{\cdot}Oe$ at $H_{dc}=110$ Oe, $106mV/cm{\cdot}Oe$ at $H_{dc}=90$ Oe and $87mV/cm{\cdot}Oe$ at $H_{dc}=160$ Oe, respectively. A trend of ME charateristics on Ni-PZT-Co, Ni-PZT-Fe composites was similar to that of Ni-PZT-Ni composites. The ME output voltage shows linearly proportional to ac field $H_{ac}$ and is about 0~150 mV at $H_{ac}$=0~7 Oe and f=110 Hz in the typical Ni-PZT-Ni sample. The frequency shift effect due to the load resistance $R_L$ shows that the frequency range for magnetic field sensor application can be modulated with appropriate load resistance $R_L$. This sample will allow for a low-magnetic ac field sensor in the low-frequency (near f=110 Hz).

• Advanced Composite Materials
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• v.16 no.2
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• pp.181-194
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• 2007

This paper presents the mechanical properties of a composite consisting of acrylonitrile-butadiene-styrene (ABS) resin mixed with carbon fiber reinforced plastics (CFRP) pieces (CFRP/ABS). CFRP pieces made by crushing CFRP wastes were utilized in this material. Nine kinds of CFRP/ABS compounds with different weight fraction and size of CFRP pieces were prepared. Firstly, tensile and flexural tests were performed for the specimens with various CFRP content. Next, fracture surfaces of the specimens were microscopically observed to investigate fracture behavior and fiber/resin interface. Finally, the tensile modulus and strength were discussed based on the macromechanical model. It is found that the elastic modulus increases linearly with increasing CFRP content while the strength changes nonlinearly. Microscopic observation revealed that most carbon fibers are separated individually and dispersed homogeneously in ABS resin. Epoxy resin particles originally from CFRP are dispersed in ABS resin and seem to be in good contact with surrounding resin. The modulus and strength can be expressed using a macromechanical model taking account of fiber orientation, length and interfacial bonding in short fiber composites.