입자를 보강한 탄소 폼의 열적ㆍ전기적 성질

송승아(Seung A Song),김성수(Seong Su Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.4-1

Microwave 를 이용한 활성탄 강화 페놀 폼의 제조 및 특성

송승아(Seung A Song),이현철(Hyun Chul Lee),김성수(Seong Su Kim) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

The foam industry has been challenged in recent years from recyclability and the depletion of earth’s ozone layer by the chlorofluorocarbon blowing agents. For conventional foaming methods, the extensive time is required to fabricate large volumes and environmental regulations limit the use of blowing agents. For that reason, Phenolic foams are preferred as a thermal insulator due to a lower flammability and lower gas generation than other polymeric insulation foams. In this study, a new foaming method for the AC reinforced microcellular phenolic foams was developed to decrease the cell size and density of the forms using microwaves. The mechanical properties and the cell structures of the phenolic foam were characterized based on the degree of cure of the phenolic resin before the microwave foaming process. We found that the microcellular phenolic foams fabricated under these optimum foaming conditions had low thermal conductivities and low densities that are suitable for insulating foams.

탄소폼의 기계적 · 열적 물성 향상을 위한 연구

송승아(Seung A Song),김성수(Seong Su Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

Porous carbon foams are used as insulation materials at high temperature. The carbon foams are fabricated by pyrolyzing thermosetting resin derived from polymer foams. Phenolic resins are a good source of carbon foams due to low level of toxic gas emission and high heat resistance. However, the carbon foams based on the phenolic foams have inferior mechanical strength and electrical conductivity because of glassy carbon formed after the carbonization procedure. There are many researches about the nano-particles reinforced the phenolic foams to improve the mechanical strength and electrical conductivity of the carbon foam. When the conductive nano-particles were reinforced in the precursor foam before carbonization, it leads to high cell density and cell uniformity affecting the physical and electrical properties of carbon foam. However, conductive nano-particles such as graphene and carbon nanotube in the carbon foam are easily aggregated, which causes low mechanical properties of the carbon foam. In addition, high weight fraction of particle was required to improve the electrical properties. In this study, the MWCNT embedded polyimide particle (Composite particles; CP) which has high thermal stability, mechanical properties and carbon yield by intermolecular cyclization after carbonization process was reinforced to improve the mechanical and electrical properties of carbon foam. The MWCNT embedded polyimide particle was fabricated by removing the solvent of PI varnish mixed with MWCNT and by grinding the MWCNT embedded polyimide pellet. The CP reinforced phenolic foams were carbonized at 1000°C under nitrogen atmosphere. The cell morphology of the carbon foams were observed by scanning electron microscope (SEM) images. The physical properties and electrical characteristics of carbon foams were characterized by measuring compressive strength and electrical conductivity.

탄소 나노입자 보강에 따른 페놀폼의 물성 변화에 대한 연구

송승아(Seung A Song),김성수(Seong Su Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

Phenolic foams have high fire resistance, thermal stability at high temperature and maintaining performance over a broad temperature range, which have led to a broad range of applications as an insulating material. However, phenolic foam is needed to improve the mechanical properties for more extensive application. These problems can be improved by controlling the cell morphology because the properties of phenolic foam are determined by the cell morphologies such as cell shape, cell wall thickness and cell density. And the cell morphologies are affected by various factors that are viscosity of the phenolic resin, degree of cure before the foaming and the type of particle for reinforcement. In this work, the phenolic foam was fabricated by reinforcing the nano-particles, multiwall carbon nanotube (MWNT) and graphene, to improve the thermal and mechanical properties of the phenolic foam. The optimal weight percent of particle formed the proper cell morphology of the phenolic foam. And optimal aging time before microwave foaming of each particle reinforced phenolic resin were investigated by cure monitoring using a dielectric sensor to obtain the optimal cell morphology. From the experimental results, optimal weight percent of the each carbon nanoparticle was found based on the cell morphology, thermal and mechanical properties of the phenolic foams.

폴리프로필렌과 탄소섬유 사이의 계면 결합력 향상을 위한 ZnO nanorods 성장

송승아(Seung A Song),김성수(Seong Su Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.4

용제 휘발 속도에 따른 결정 형태가 탄소섬유/Polyamide66 복합재료의 계면 특성에 미치는 영향

박고은(Go Eun Park),송승아(Seung A Song),김성수(Seong Su Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.4

탄소섬유를 이용한 열가소성 복합재료 시트 제조 및 특성

이윤선 ( Yun Seon Lee ),송승아 ( Seung A Song ),김완진 ( Wan Jin Kim ),김성수 ( Seong Su Kim ),정용식 ( Yong Sik Jung ) 한국복합재료학회 2015 Composites research Vol.28 No.4

탄소섬유 강화 복합재료는 높은 비강도 및 비강성을 가지기 때문에 자동차 산업, 선박, 우주 항공 산업과 같은 다양한 산업 분야에 적용되어 왔으며, 수요가 점차 증가하고 있다. 탄소섬유 강화 복합재료에는 기지재로 주로 에폭시(Epoxy)와 같이 점도가 낮고 젖음 특성이 우수하며 강도가 양호한 열경화성(Thermosetting) 수지가 사용된다. 열경화성 수지는 우수한 물리적 특성을 나타내지만 재사용이 어렵다. 이러한 문제를 해결하기 위하여 재사 용이 가능한 탄소섬유 강화 열가소성 수지(Thermoplastic) 복합재료 개발 및 탄소섬유 재사용에 관한 많은 연구들이 진행되고 있다. 본 연구에서는 열분해 방법을 사용하여 탄소섬유/에폭시 복합재료로부터 탄소섬유와 수지를 분리하여 탄소섬유를 재활용하였다. 에폭시의 분해도(Degree of decomposition)는 열중량분석기(TGA)와 시차 주사현미경(SEM)을 통해 확인하였다. 수지로부터 분리해낸 탄소섬유는 절단(Cutting)과 그라인딩(Grinding) 방법을 거쳐 탄소섬유 복합재료 시트(Sheet)를 제조하였다. 재활용 탄소 섬유로 제조된 탄소섬유 시트는 각각 다른 냉각 조건에서 결정화 엔탈피(Crystallization enthalpy)와 기계적 특성, 표면과 단면의 형태를 분석하였다. Recently, the applications of carbon fiber reinforced plastics (CFRPs) have become broader than ever when it comes to such industries as automotive, ships, aerospace and military because of their lightweight-ness and high mechanical properties. Thermosetting plastics like epoxy are frequently used as the binding matrix in CFRPs due to their high hardness, wetting characteristics and low viscosity. However, they cannot melted and remolded. For this reason, thermosetting plastic wastes have caused serious environmental problems with the production of fiber reinforced plastics. Thus, many studies have focused on the carbon fiber reinforced thermoplastics (CFRTPs) and recycling carbon fiber. In this study, recycled carbon fiber (RCF) was prepared from CFRPs using a pyrolysis method, which was employed to separate resin and carbon fiber. The degree of decomposition for epoxy resin was confirmed from thermal gravimetric analysis (TGA) and scanning electron microscope (SEM). The RCF was cut and ground to prepare a carbon fiber composite sheet (CFCS). CFCS was manufactured by applying recycled carbon fibers and various thermoplastic fibers. Various characterizations were performed, including morphological analyses of surface and cross-section, mechanical properties, and crystallization enthalpy of CFCS at different cooling conditions.

AlOOH와 실란 커플링 에이전트 적용을 통한 탄소섬유/폴리프로필렌 복합체의 계면 강도 증가

함수진(Soo Jin Ham),송승아(Seung A Song),김성수(Seong Su Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.4

OpenCV를 이용한 캐리커처 자동 생성 프로그램

서유경(Yu-Gyung Seo),김송(Song Kim),송승아(Seung-A Song),오세은(Se-eun Oh),정진영(Jin-Yung Jung),이경명(Gyung-Myung Lee),황예원(Ye-one Hwang) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.11

터보 컴프레셔용 복합재료 틸팅 패드 저널 베어링의 오일 공급 중단 상황에서의 내구성 연구

최강영 ( Kang-yeong Choe ),정민혜 ( Min-hye Jung ),유준일 ( Jun-il You ),송승아 ( Seung-a Song ),김성수 ( Seong-su Kim ) 한국복합재료학회 2016 Composites research Vol.29 No.3

터보/컴프레셔(Turbo compressor)용 틸팅 패드 저널 베어링(Tilting pad journal bearing)은 고속, 고하중의 주축(Rotor)을 지지하는 역할을 하며, 화이트 메탈(White metal)이 대표적인 소재로 널리 사용되어왔다. 그러나 예기치 않은 윤활유 공급 중단 상황(Oil cut situation) 또는 베어링과 주축 사이에 유막(Oil film)이 제대로 형성되지 않을 경우, 기존의 화이트 메탈 베어링은 융착(Seizure) 현상에 의해 바로 정지하게 되고 주축에 심각한 손상을 유발한다. 이러한 융착 문제를 해결하기 위해 기존의 화이트 메탈에 비해 높은 비강성, 비강도 그리고 뛰어난 마찰 특성(Tribological characteristic)을 가지는 탄소섬유 강화 복합재료(Carbon fiber reinforced composite)가 틸팅 패드 저널 베어링에 사용될 수 있다. 본 연구에서는 고 내열성 탄소섬유/에폭시 복합재료 틸팅 패드 저널 베어링의 오일공급 중단 상황에서의 내구성에 대한 연구를 진행하였다. 이를 위해 상온 및 오일공급 중단상황의 고온에서 인장, 압축, 전단 등의 기초적인 복합재료 물성 실험을 진행하였고, 복합재료 틸팅 패드 저널 베어링에 있어 가장 중요한 물성인 층간 계면 강도를 측정하기 위해 Short Beam Shear 실험을 진행 하였다. 오일 공급 중단 상황에서 복합재료 틸팅 패드 저널 베어링의 파손(Failure) 가능성을 알아보기 위해 유한 요소 해석(Finite element analysis)을 진행함으로써 베어링 표면에 가해지는 최대 응력을 도출하였고, 해석 결과와 물성 시험으로부터 측정된 강도 값을 이용하여 Tsai-Wu Failure index를 계산하였다. 해석 결과를 검증하기 위해 산업용 테스트 벤치를 이용하여 탄소섬유/에폭시 복합재료로 제조된 틸팅 패드 저널 베어링의 오일 공급 중단 실험을 진행하였다. The tilting pad journal bearing for the turbo compressor application has a role to support high speed and heavy loading rotor. White metal has been widely used for the bearing material but the conventional bearing is immediately suspended and induces serious serious damage to the rotor under the unexpected oil cut situation or the insufficient oil film formation. The carbon fiber reinforced composite having high specific stiffness, specific strength and excellent tribological characteristics can solve these seizure problems. In this work, the study on the durability of high thermal resistance carbon fiber/epoxy composite tilting pad journal bearing under oil cut situation was conducted. The material properties of the composite materials including tensile, compressive and interlaminar properties were measured at room and high temperature of oil cut situation. To investigate the possibility of failure of composite tilting pad journal bearing under oil cut situation, the stress distribution of the composite bearing was analyzed via finite element analysis and the Tsai-Wu Failure index was calculated. To verify the failure analysis results, the oil cut tests for the composite tilting pad journal bearing were conducted using industrial test bench.