비직교이방성 조성방정식을 이용한 직물강화 열가소성 복합재료의 액압성형공정 해석

유웅렬,정관수,강태진,Pourboghrat Farhang 한국섬유공학회 2002 한국섬유공학회지 Vol.39 No.4

A new constitutive model has been developed based on the homogenization method considering the micrcostructures of composites including both the mechanical and structural properties of fabric reinforcements. In particular, the current model aims to account for the effect of the fiber stiffness difference and orientation on anisotropy and also to simulate shear deformation without significant length change, as common in FRT(fabric reinforced thermoplastics) composite forming. For validation purposes, the model was implemented in an explicit dynamic finite element ocde and tested for pure shear. Using the new constitutive equation, the deformation behavior of woven fabric reinforced thermoplastic composites in hydroforming process was also analyzed.

전분 발포체의 제조조건과 압축성질에 관한 연구

유웅렬,이영목,김의환,이대훈 한국섬유공학회 1999 한국섬유공학회지 Vol.36 No.7

For the development of the biodegradable packaging material, expanded starch of loose-fill type was produced on a twin screw extruder. The processing variables were the mixture ratio between starch and additives (PVA, CaCO$_3$), temperature and screw speed. The physical and compressional properties of the expanded starch were examined against processing variables. The content of CaCO$_3$ was a very important factor affecting the physical, structural and compressional properties of the expanded starch. The interior structure of the expanded starch showed closed cell structure with increase in the content of CaCO$_3$. But the compressional energy and rate linearly decreased with the increase in the content. The compressional resilience was increased with the increase in the temperature at the front extruding zone, but it decreased at high temperature.

전단강성이 고려된 직물강화 열가소성 복합재료 조성방정식

유웅렬 한국섬유공학회 2002 한국섬유공학회지 Vol.39 No.4

A new constitutive model has been developed based on the homogenization method by considering the micrcostructure of composites including both the mechanical and structural properties of woven fabric reinforcements. The constitutive equation enables to simulate the deformation behavior of thermoplastic composites in forming processes as reported in the previous paper. In the previous formulation for the constitutive equation, the warp and weft yams over crossover were assumed to freely rotate without considering frictional behaviors. This assumption is released in this study to simulate the shear behavior of fabric reinforcements due to the frictional behavior of crossing points between the warp and the weft. A simple but effective way to add the shear resistance of woven fabrics into the constitutive model is discussed. Based on literatures, several examples were simulated for validation purposes in this study.

비선형 굽힙거동을 고려한 직물의 처짐

서장일,유웅렬,정관수,강태진 한국섬유공학회 2000 한국섬유공학회지 Vol.37 No.5

A fabric deflection model was developed based on the nonlinear beam bending theory to predict fabric deflection under its own weight. The nonlinear bending properties of fabrics were measured from the KES bending test, assuming that the bending moment is a function of curvature. Compared to the results based on the linear bending theory, the results showed better agreement with experimental results.

PA6/MWNT Nanocomposites Fabricated Using Electrospun Nanofibers Containing MWNT

이병선,유웅렬 한국고분자학회 2010 Macromolecular Research Vol.18 No.2

The electrospinning process with an applied electric field is used to extrude submicron fibers from polymeric solutions and has been recognized as a viable method for dispersing and aligning nanoparticles into a nanofibrous polymer matrix. In this study, electrospun nanofibers containing multi-walled carbon nanotubes (MWNTs)were used as a preform to fabricate MWNT reinforced polymer nanocomposites. The electrospun nanofibers were prepared by electrospinning a solution of polyamide 6 (PA6) and multiwalled carbon nanotubes (MWNTs). Raman spectroscopy, TGA, DSC, XRD, and TEM showed that the MWNTs were well dispersed and aligned in the electrospun nanofibers. The electrospun nanofibers in mat form were then consolidated into a solid composite by a thermal pressing. The initial modulus and tensile strength of the nanocomposites were improved by the reinforcement of the MWNTs. However, their breaking strain was lowered. This shortcoming was overcome by introducing a functional group onto the MWNTs through a surface treatment. Overall, the current method (modification of MWNTs, electrospinning,and thermal fabrication) can improve the tensile properties, including initial modulus, tensile strength and breaking strain, of PA6/MWNTs nanocomposites.

An Effective Method for Manufacturing Hollow Carbon Nanofibers and Microstructural Analysis

이병선,유웅렬,박규민,육지호 한국고분자학회 2012 Macromolecular Research Vol.20 No.6

Hollow carbon nanofibers (HCNFs) were successfully manufactured by co-axial (core/shell) electrospinning of poly(styrene-co-acrylonitrile) (SAN) and poly(acrylonitrile) (PAN) solutions. The shell component (PAN)was converted into a turbostratic carbon structure by thermal treatment, whereas the sacrificial core component (SAN) was eliminated. SAN was found to be a very suitable material for the sacrificial core. SAN exhibited excellent co-axial electrospinnability to produce a uniform core/shell nanofiber precursor because of its immiscibility with PAN. Also, SAN had a good thermal sustainability that prevented the PAN shell from shrinking during the stabilization and carbonization processes, thus maintaining the shell structure. These two predominant properties of SAN enabled the manufacturing of uniform HCNFs with controlled inner diameters and wall thickness that ranged from 120-510 nm and 52-145 nm, respectively. The core solution properties, such as solution concentration and flow rate,were mostly effective in controlling both the outer diameters and the wall thicknesses of HCNFs. The microstructure of these HCNFs was investigated using high resolution transmission electron microscopy. The crystallite size and crystallinity of HCNFs were dependent on their wall thicknesses. As the wall thicknesses of HCNFs decreased, they developed smaller crystallites and higher crystallinities.

피복과학분과 1 : 화상분석을 이용한 천의 드레이프성 평가방법 및 응용

박창규,유웅렬,이대훈,김성민 한국의류학회 2000 한국의류학회 학술대회논문집 Vol.2000 No.-

비뉴턴 유체를 이용한 스마트 과속방지턱 소재 개발

정인준,김은정,유웅렬,나원진 한국복합재료학회 2022 Composites research Vol.35 No.4

본 연구에서는 저가 재료인 전분과 물 기반의 현탁액을 이용하여 과속방지턱에 응용 가능한 스마트 소재를 개발하고 물성을 평가하였다. 유변물성측정기를 이용하여 전단율에 따른 점도 및 전단력을 측정하여 전분 농도별 전단농화 발생 현상을 확인하였다. 물체의 낙하 시험과 5-25 km/h의 주행 속도로 충격 후 진동을 측정한 자전거 주행 시험을 통해 거시적인 전단농화현상을 확인하였고, 과속방지턱의 적용 가능성을 확인하였다. 점도 측정 결과, 초기에 전단담화 구간에 이어 전단농화가 발생하였고, 전단농화 현상을 유발하는 임계 변형률은 농도가 증가함에 따라 감소하였다. 또한 전분 농도 증가에 따라 점도와 전단력이 크게 증가하였다. 낙하시험과 자전거 주행시험 결과 현탁액이 단시간에 고체 상태로 바뀌었고 충격 에너지가 유체에 흡수되었다. 유체의 농도와 가하는 충격(속도)이 증가할수록 전단농화현상이 쉽게 발생하였다. 최종적으로 물과 전분 기반의 비뉴턴 유체로 5-25 km/h 범위에서 구동하는 스마트 과속방지턱 재료의 개발을 제안하였다.

Preparation and Characterization of nanoporous shape memory membranes

신상진,유영창,유웅렬,류희욱,육지호 한국고분자학회 2012 한국고분자학회 학술대회 연구논문 초록집 Vol.2012 No.10

Simple design of a Si–Sn–C ternary composite anode for Li-ion batteries

양호성,이병선,유웅렬 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.98 No.-

Previous research established that Si–Sn–C ternary composite electrodes composed of carbon nanofibers(CNFs) having robust double-hole structuresfilled with Si and SnOx nanoparticles displayed excellentelectrochemical performance due to the thermodynamic contribution of Sn. This study reports simpleand highly commercial ternary composite electrodes. By electrospinning and subsequent thermaltreatment, Si and Sn nanoparticles were dispersed in solid CNFs to form Si–Sn–SC nanofibers, or theywere incorporated into a core of hollow CNFs to form Si–Sn HC nanofibers. The rate performances ofthese two ternary electrodes displayed quite good retention because of the ternary composition, but theirrate performances differed at high current densities (5000 and 10,000 mA g–1); the core/shell structure ofthe Si–Sn HC nanofibers was more beneficial for rate performance retention than the Si–Sn–SCnanofibers having intimate electrical contact of Sn and Si with the carbon matrix. Improved cyclingperformances also resulted from the structure of the Si–Sn HC nanofibers. The core/shell structuredSi–Sn–C ternary composite anode thus has an advantageous structure for high-power Li-ion batterieshaving long-term stability.