• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.373-384
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• 1999

The shell structures with composite materials have the advantages in strength, corrosion resistance, and weight reduction. The objective of this study is to analyze anisotropic composite circular cylindrical shells with shear deformation theory. In applying numerical methods to solve differential equations of anisotropic shells, this paper use finite difference method. The accuracy of the numerical method can be improved by taking higher order of interval ${\Delta}$ to reduce error. This study compares the results of finite difference method with the results of ANSYS based on finite element method. Several numerical examples show the advantages of the stiffness increasement when the composite materials aroused. Therefore, it is expected that results of this study give various guides for change of the subtended angles, load cases, boundary conditions, and side-to-thickness ratio.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.17-17
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• 2012

수송용 섬유소재는 자동차, 항공기 또는 선박 등의 교통 및 운송 분야에 기여하는 사용되는 섬유소재를 말하며, 내장재, 각종 호스류, 벨트류, 타이어, 안전용품, 필터류 등을 포함하고 일반적으로 섬유, 발포체, 고무, 플라스틱, 접착제 등 유기소재가 결합된 복합체이다. 기존 섬유기술의 혁신과 더불어 IT, NT, BT, ET 등 첨단 기술과의 융합에 의한 고성능 극한 슈퍼섬유, 나노 복합섬유 등의 신소재를 개발하여 산업 전반에서 플라스틱의 금속소재 대체수요를 증가시키고 산업자재의 고성능화, 고기능화, 다양화를 이루기 위해 다양한 노력이 진행하고 있다. 현재 수송용 섬유소재 산업은 기술의 연결고리가 부족하며, 선도기업 및 원천기술이 부족하며, 자동차용 섬유부품소재 관련 기업의 역량도 부족한 실정이다. 이에 광역경제권 연계협력사업을 통해 생산기반의 대경권(대구경북)과 수요중심의 동남권(부산경남)의 네트워크를 강화하여 완성품 업체 및 수요기업과의 네트워킹을 강화하고자 한다. 따라서 본 연구에서 수송용 섬유소재개발, 수송용 친환경 oam-skin 일체형 표피재 개발, 고속성형 복합소재 및 수송용 경량부품 개발, 초경량 고내열 고강도 섬유활용 하이브리드 wire & cable 개발 등 수송용 섬유소재를 개발하고, 또한 수송용 섬유소재의 생산-수요 연계를 통한 투자활성화, 기술개발, 소재 산업 육성을 강화하여, 산학연네트워크구축, 지역 간 협력 및 국제적 협력, 생산-수요기반의 연계협력시스템을 활용한 자립형 수송용 소재 공급기지 완비하는 데 목적이 있다.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.289-294
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• 2021

In this study, after measuring polarization characteristics of 97.3 wt% Ag, Au-Coated 97.3 wt% Ag (ACA) and 100 wt% Au wires in 1 wt% H₂SO₄ and 1 wt% HCl electrolytes at 25 ℃, corrosion rate and corrosion characteristics were comparatively analyzed. Comparing corrosion potential (E_CORR) values in sulfuric acid solution, ACA wire had more than six times higher E_CORR value than Au wire. Thus, it seems possible to use a broad applied voltage range of bonding wire for semiconductor packaging which ACA wire could be substituted for the Au wire. However, since the E_CORR value of ACA wire was three times lower than that of the Au wire in a hydrochloric acid solution, it was judged that the use range of the applied voltage and current of the bonding wire should be considered. In hydrochloric acid solution, 97.3 wt% Ag wire showed the highest corrosion rate, while ACA and Au showed similar corrosion rates. Additionally, in the case of sulfuric acid solution, all three types showed lower corrosion rates than those under the hydrochloric acid solution environment. The corrosion rate was higher in the order of 97.3 wt% Ag > ACA > 100 wt% Au wires.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.11-18
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• 2021

A novel microwave dielectric composite material for ultra-low temperature co-fired ceramics (ULTCC) with (1-x)BaWO₄-xBaV₂O₆ (x=0.54~0.85) composition was prepared by firing a mixture of BaWO₄ and BaV₂O₆. Shrinkage tests showed that the ceramic composite begins to densify at a temperature as low as 550℃ and can be sintered at 650℃ with 98% of relative density under the influence of BaV₂O₆. X-ray diffraction analysis showed that BaWO₄ and BaV₂O₆ coexisted and no secondary phase was detected in the sintered bodies, implying good chemical compatibility between the two phases. Near-zero temperature coefficients of the resonant frequency (𝛕_f) could be achieved by controlling the relative content of the two phases, due to their positive and negative 𝛕_f values, respectively. With increasing BaV₂O₆ (x from 0.53 to 0.85), the 𝛕_f value of the composites increased from -7.54 to 14.49 ppm/℃, ε_r increased from 10.08 to 11.17 and the quality factor (Q×f value) decreased from 47,661 to 37,131 GHz. The best microwave dielectric properties were obtained for x=0.6 samples with ε_r=10.4, Q×f=44,090 GHz, and 𝛕_f=-2.38 ppm/℃. Chemical compatibility experiments showed the developed composites are compatible with aluminum electrode during co-firing process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.54-60
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• 2019

Recently, various composite materials for additive manufacturing are interested to expand the application field of 3D printing. 3D printing technique was mainly developed using polymer, and ceramic materials for 3D printing are still in the early stage of research due to the requirement of high solid content and post treatment process. In this study, silica particles with various diameters were surface treated with silane coupling agent, and synthesized as silica composite with photopolymer to apply DLP 3D printing process. DLP is an additive manufacturing technology, which has high accuracy and applicability of various composite materials. The rheological behavior of silica composite was analyzed with various solid contents. After DLP 3D printing was performed using silica composites, the printing accuracy of the 3D printed specimen was less than about 3 % to compare with digital data and he bending strength was 34.3 MPa at the solid content of 80 wt%.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.672-678
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• 2011

In this work, carbon fibers were electrolessly Ni-plated in order to investigate the effect of metal plating on the electromagnetic shielding effectiveness (EMI-SE) of Ni-coated carbon fibers-reinforced epoxy matrix composites. The surfaces of carbon fibers were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electric resistance of the composites was tested using a 4-point-probe electric resistivity tester. The EMI-SE of the composites was evaluated by means of the reflection and adsorption methods. From the results, it was found that the EMI-SE of the composites enhanced with increasing Ni plating time and content. In high frequency region, the EMI-SE didn't show further increasing with high Ni content (Ni-CF 10 min) compared to the Ni-CF 5 min sample. In conclusion, Ni content on the carbon fibers can be a key factor to determine the EMI-SE of the composites, but there can be an optimized metal content at a specific electromagnetic frequency region in this system.

• The Optical Journal
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• s.153
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• pp.47-62
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• 2014

${\blacksquare}$ 목적 * 우리나라 주력산업분야(자동차, 조선, 항공, 기계, 로봇, 반도체 등)에 절단, 가공, 용접, 리소그라피, 마킹, 열처리, 합성, 표면처리 등의 방식으로 활용되고, 융 복합산업(의료, 에너지, 영상, 군수, 신소재, 센서)에 광원으로 응용되는 산업용 고출력 레이저의 산업 생태계 분석을 통하여 기존 산업의 고부가화와 신산업의 경쟁력을 견인 ${\blacksquare}$ 주요현황 * (시장현황) 2011년부터 2014년까지 고출력 레이저의 시장규모는 4,452백만불(5조 463억원)에서 5,255백만불(5조 9,565억원)으로 연평균 5.7% 성장 전망 * (제품기술동향) 3세대 레이저인 광섬유 레이저와 고출력 다이오드 레이저, DPSS 레이저 등이 기술혁신을 거듭하면서 1, 2세대 레이저를 대체해 가면서 높은 수준의 성장을 거듭할 것으로 전망. 산업용레이저의 주요선진국 대비 국내 기술수준은 전체적으로 44.5%정도로 취약 * (기업동향) Coherent, Trumpf, Cymer, IPG Photonics, Rofin-Sinar 5개사가 전체시장의 55%이상을 점유하고 있으며 대부분 수직계열화를 통해 경쟁력 확보. 최근 중국의 Han's 사가 자국정부의 지원을 통해 급 부상 ${\blacksquare}$ 시사점 * 산업용 레이저를 이용한 응용기술 부분 투자가 과거에는 단기 경제적 성취는 이로웠으나, 현재에 이르러 레이저 혹은 레이저 시스템이 필요할 때마다 외국에서 관련 핵심부품, 모듈 등을 수입해야하는 실정에 이르렀음. 향후 레이저 국산화를 위한 노력과 함께 후방 소재.부품의 전략적 투자를 통해 산업의 건강한 선순환생태 환경을 조성하여 산업 경쟁력을 갖추어야 함.

• Current Industrial and Technological Trends in Aerospace
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• v.6 no.2
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• pp.60-68
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• 2008

The characteristic and properties of materials are rapidly degraded when subjected to the synergistic effects of the space environment such as atomic oxygen, radiation, vacuum and thermal cycling. In order to understand the mechanism of material property variation in space environment and to develop new space materials applicable to the future space program, advanced space organizations such as NASA, ESA and JAXA have been continuing many researches on material test specimens used on ISSE(International Space Station Experiment) or LDEF(Long Duration Exposure Facility). In this paper, the selection requirements and verification trend of materials in space applications

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.388-394
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• 2005

A typical honeycomb sandwich panel consists of two thin, high-strength facings bonded to a thick, light-weight core. Each component by itself is relatively weak and flexible, but when it combind in a sandwich panel they produce a structure that is stiff, strong, and lightweight. In addition to use in honeycomb sandwich panels, honeycomb is used for energy absorption, radio frequency shielding, light diffusion, and to direct air flow.Accordingly, the usage of honeycomb sandwich structure is very widely applied to the aircraft, the automobile, and marine industry, etc., because of these advantages. Generally, this honeycomb sandwich structure is manufactured by autoclave process.In this study, the honeycomb sandwich structure was produced by prepreg. To prove the suitability the honeycomb sandwich structure with prepreg, The optimum design of the skin materials and honeycomb sandwich structure were evaluated with the theory of stress analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.387.2-387.2
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• 2014

최근 이동통신 LED 에너지 자동차 산업분야에서 제품의 고기능화 고성능화를 위한 신소재 개발 및 친환경적인 신공정 개발에 있어, PI 또는 PET와 같은 유연성 소재 위에 선택적 패턴 도금 기술, 고기능성 나노/복합 도금 등이 주목 받고 있다. 또한 전 세계적으로 유해물질의 수 출입 규제 움직임이 강력하게 제기되고 있다. 본 연구에서는 유연성 소재인 PET 위에 친환경적 방법으로 구리를 선택적으로 도금하기 위한 실험을 진행하였다. 준비된 PET 필름 위에 Ag paste를 Screen Printing법을 이용하여 Ag 전극을 패턴하고, 그 위에 무전해 도금방식을 이용하여 Ni과 Cu가 도금 되도록 하였다. Ni 무전해 도금은 pH6.5, 65도에서 시행되었으며, Cu 무전해 도금은 환경규제물질인 포름알데히드 대신에 차아인산나트륨을 사용하여 70도에서, 중성근처의 pH 농도(pH7과 pH8)에서 시행되었다. 이들 다층 박막에 대해 X-ray diffraction (XRD), SEM (Scanning Electron Microscope), XPS (X-ray Photoelectron Spectroscopy) 등을 이용하여 물리-화학적/전기적 특성들을 이용하여 조사 분석하였다.