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CNT-polymer composite의 유효강성 예측을 위한 Digimat의 활용
최기평(Ghi Pyoung Choi),우창희(Chang Hee Woo),이세환(Se-Hwan Lee),안상현(Sang Hyun Ahn),조용상(Yong Sang Cho),조영삼(Young-Sam Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4
In this paper, we predicted the effective stiffness of CNT-polymer composite using Digimat and ABAQUS which are commercial numerical analyzing programs. Nano-inclusion in composite is important factors which decide stiffness and properties. Therefore, we modeled RVE of CNT-polymer composite using Digimat for the numerical analysis using ABAQUS. Using RVE model constructed via Digimat, we have analyzed the effective modulus through the asymptotic homogenization scheme. To estimate the effective stiffness of various CNT-polymer composite, we constructed RVEs which have different CNT contents and direction in matrix. Obtained effective stiffness is used in homogenized finite element model to compare with the reference solution from the full model of CNT-polymer composites.
최기평(Ghi Pyoung Choi),안상현(Shang Hyun An),조영삼(Young-Sam Cho) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
We fabricated hollow-cylinder particle with thickness and length of several hundred micrometers using PCL (polycaprolactone). Firstly, we put the SUS needle having diameter of 500 micrometer into the hole having diameter of 0.9 millimeter. Moreover, this SUS needle was immersed into a melted PCL. After that, we pull the needle out of the hole. This procedure made a PCL coated needle with thickness of 200 micrometer. Secondly, we could fabricate PCL coated needle with thickness of 200 and 200 micrometer, respectively. After removal of SUS needle, we diced the hollow cylinder with a length of 400 micrometer and finally we could get hollow-cylinder PCL particles. Using these particles, we fabricated porous scaffolds using PCL-only-melting procedures.
AEH(Asymptotic expansion homogenisation)을 이용한 MWCNT-polymer composite 의 유효강성 예측
최기평(Ghi Pyoung Choi),손동우(Dongwoo Sohn),우창희(Chang Hee Woo),이세환(Se-Hwan Lee),안상현(Sang Hyun Ahn),조영삼(Young-Sam Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, we predicted effective stiffness modulus using the developed in-house code which applied AEH(Asymptotic expansion homogenization). Firstly, we designed RVE model with rectangular structure which have different CNT direction in matrix, X, X&Y, X&Y&Z, respectively. Inclusion in matrix is very important factor which influence effective modulus of composite. Therefore, we designed inclusions of various structures. The shape of inclusion were designed with straight and curve cylindrical shape. Inclusions have a diameter of 5 nm. In addition, CNT in matrix were designed to long and short CNT, respectively. Five different stiffness moduli of matrix were given for application to various materials. Moreover, 720 different RVE models are analyzed with variation of inclusion direction, inclusion volume percent, and inclusion type. Consequently, we proposed some equation to predict experiment results of nano-composite using analyzed result of AEH in-house code.
ABS/MWCNT 복합재료의 분산 영향에 따른 마모 특성 분석
우창희(Chang Hee Woo),최기평(Ghi Pyoung Choi),이세환(Se Hwan Lee),조영삼(Young-Sam Cho) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Firstly, we fabricated several types of ABS/MWCNT composites using mechanical stirrer. MWCNT was prepared with acetone and sonication treatment to enhance the dispersion characteristics. After that, we added several different weight percent of MWCNT into melted ABS polymer to fabricate ABS/MWCNT composite. For the several different dispersion rate of MWCNT, we varied the operation time of mechanical stirring. With fabricated ABS/MWCNT composite, we analyzed the wear characteristics using abrasion tester. Consequently, we proposed a empirical fitted wear model for ABS/MWCNT composites.
우창희(Chang Hee Woo),최기평(Ghi Pyoung Choi),이세환(Se Hwan Lee),조영삼(Young-Sam Cho) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Firstly, we fabricated PCL (polycaprolactone) wire with 400 and 600 micrometer using extrusion technique. After that, one layer was composed with (PCL wire/ metal wire) repeatedly. Moreover, we stamped nano-patterned mold on the surface of composed layer. The second layer was composed by same process but 90 degree rotated and nano-patterned mold-stamping procedure is also repeated. This layer stacking process was executed repetitively when the height is reached at the designed height. After that, PCL wires became a porous scaffold under the environmental temperature over 60 degrees Celcius. Subsequently, each metal wire was removed from the repeated (PCL wire/metal wire) composition. Consequently, we fabricated the 3D porous PCL scaffold with porosity of 400 or 600 micrometer and surface pattern of dozens nanometers.
공동입자조립기법과 salt leaching 을 이용한 PCL / NaCl 이중기공 세포지지체 제작
안상현(Sang Hyun Ahn),최기평(Ghi Pyoung Choi),조영삼(Young-Sam Cho) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
We fabricated hollow-cylinder particle with thickness and length of several hundred micrometers using NaCl and PCL (polycaprolactone) with dozens micrometers of pore. Firstly, we put the SUS needle having diameter of 500 micrometer into the hole having diameter of 1.3 millimeter. Moreover, this SUS needle was immersed into a melted PCL/NaCl. After that, we pull the needle out of the hole. 75wt% of NaCl was dispersed in PCL using mechanical mixing with melting temperature and the diameter of NaCl is dozens micrometers. After removal of SUS needle, we diced the hollow cylinder with a length of 400 micrometer and finally we could get hollow-cylinder PCL/NaCl particles. Using these particles, we fabricated porous scaffolds using PCL-only-melting procedures. Finally, NaCl particles in the fabricated scaffold were leached out with D. I. water.
기공률과 기공크기에 따른 salt-leaching 과 bio-plotter 방법으로 제작된 PCL 세포 지지체의 가속분해 평가
이세환(Se Hwan Lee),우창희(Chang Hee Woo),최기평(Ghi Pyoung Choi),송기명(Ki Myoung Song),조아라(A-Ra Jo),조영삼(Young-Sam Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, we assessed the degradation behavior of PCL (Polycarprolactone, Mn=80,000) scaffolds (salt-leaching and bio-plotter) via accelerated degradation using NaOH. Firstly, we fabricated porous PCL scaffold with different pore size and porosity respectively using ‘salt-leaching using thermoplastic powder’ technique that is proposed by our team and bio-plotter PCL scaffold is fabricated by bio-plotter. We carried out an accelerated degradation experiment with the two kinds of above-mentioned PCL scaffolds using 5MNaOH solution. Firstly, we put 5ml 5M-NaOH solution into vial with the PCL scaffold. After that, for the maintaining temperature constantly, we submerged vials into the waterbath with 37 Celsius degrees. We take out 7 specimens per each 12 hours to analyze the weight loss, the change of molecular weight, and the morphology. To assess the change of molecular weight, we used Gel Permeation Chromatography (GPC) analysis. For the imaging of degradation morphology, we used SEM equipment. As a result, we expect the accelerated experiment could be used to predict the weight loss estimation. However, according to the GPC result, the molecular weight does not change attentively with respect to the time in the accelerated experiment. Therefore, accelerated experiment could not be used to predict the molecular weight change as the scaffold is resolved.
Polymer/MWCNT 복합재료의 제작과 분산영향에 따른 기계적 특성 평가
우창희(Chang Hee Woo),이세환(Se Hwan Lee),최기평(Ghi Pyoung Choi),안상현(Sang Hyun Ahn),송기명(Ki Myoung Song),조영삼(Young-Sam Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4
In the study, we fabricated several types of polymer/MWCNT composites using mechanical stirrering. Firstly, MWCNT was dissolved in acetone by the aid of sonication treatment to enhance the dispersion characteristics. After that, the mixture of polymer and solvent was sonicated and the prepared CNT is added into the mixture. Subsequently, with the mechanical stirrer, we fabricated the composite which is composed with polymer and MWCNT. We investigated the dispersion status using TEM. Furthermore, we analyzed the mechanical characteristics using tensile test and wear test.
새로운 와이어 네트워크 몰딩 기법을 활용한 Scaffold 제작 및 특성평가
우창희 ( Chang Hee Woo ),김태영 ( Tae Young Kim ),이세환 ( Se Hwan Lee ),최기평 ( Ghi Pyoung Choi ),이승재 ( Seung Jae Lee ),김범수 ( Beom Su Kim ),유형근 ( Hyung Keun You ),조영삼 ( Young Sam Cho ) 한국조직공학·재생의학회 2012 조직공학과 재생의학 Vol.9 No.2s
In this study, we proposed a novel method which has several merits: guaranteed interconnectivity, solvent free, and unnecessary expensive devices. For the proposed novel method named as Wire-Network Molding, firstly, we prepare a mold with designed shape. Secondly, rectangular wires with thickness size 300 μm, 400 μm or 620 μm are inserted to make space for interconnected pore. After that, melted PCL (polycaprolactone) which is one of synthetic polymers with biocompatibility is filled in the mold and the mold is cooled at room temperature. Subsequently, wires are separated from the mold and the mold is removed from PCL. Consequently, the remained PCL has interconnected pores with a configuration of wire-network. To analyze the compressive modulus of the fabricated scaffold, UTM compression test is carried out. Moreover, we compare the compressive modulus of the fabricated scaffold with that of bio-plotter scaffold. Additionally, for scaffolds with 300 μm, 400 μm pore size, cell culture experiments are carried out using human.