• Composites Research
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• 제34권6호
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• pp.421-425
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• 2021

본 연구에서는 동일한 열가소성 수지(PEEK)와 각기 다른 탄소섬유(Type A, Type B) UD 테이프를 이용하여 열가소성 복합재를 제작하고 제작된 각각 2개의 복합재를 유도가열 용접방식에 따라 접합 특성 및 기계적 특성에 대하여 고찰하였다. 복합재의 접합 특성과 기계적 특성은 비파괴검사인 C-Scan, B-Scan과 전단 강도(Single lap shear)를 각각 측정하였고, 열화상 카메라를 이용하여 시편 표면의 온도를 모니터링 하였다.

• 방사선산업학회지
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• 제17권3호
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• pp.225-232
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• 2023

In this study, poly(ethylene-co-vinyl acetate)/magnesium hydroxide (EVA/MDH) composites were prepared by electron beam crosslinking. EVA as a matrix resin and MDH as a flame retardant were melt-blended and compression molded to prepare EVA/MDH composites. The prepared EVA/MDH composites were electron beam-irradiated at various absorbed doses of 50~200kGy. The effects of electron beam irradiation on the gel content, tensile strength, elongation-at-break, thermal properties, and flame retardancy of the composites were investigated. The gel content and tensile strength increased, while the elongation-at-break decreased with an increase in the absorbed dose due to the formation of crosslinked network structures. In addition, the thermal stability and flame retardancy improved as the absorbed dose increased. Therefore, the EVA/MDH composites prepared in this study can be used as an insulation material for flame-retardant and heat-resistant wires and cables.

• 한국재료학회지
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• 제26권10호
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• pp.521-527
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• 2016

Geopolymers have many advantages over Portland cement, including energy efficiency, reduced greenhouse gas emissions, high strength at early age and improved thermal resistance. Alkali activated geopolymers made from waste materials such as fly ash or blast furnace slag are particularly advantageous because of their environmental sustainability and low cost. However, their durability and functionality remain subjects for further study. Geopolymer materials can be used in various applications such as fire and heat resistant fiber composites, sealants, concretes, ceramics, etc., depending on the chemical composition of the source materials and the activators. In this study, we investigated the thermal properties and microstructure of fly ash and blast furnace slag based geopolymers in order to develop eco-friendly construction materials with excellent energy efficiency, sound insulation properties and good heat resistance. With different curing times, specimens of various compositions were investigated in terms of compressive strength, X-ray diffraction, thermal property and microstructure. In addition, we investigated changes in X-ray diffraction and microstructure for geopolymers exposed to $1,000^{\circ}C$ heat.

• 한국분말재료학회지
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• 제17권2호
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• pp.123-129
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• 2010

The fabrication of interconnect from titanium powders and $TiN_x$ powders is investigated. Corrosion-resistant titanium and $TiN_x$ are used as reinforcement in order to reveal high heat and corrosion resistance at the elevated temperature. We fabricated the plates for interconnect reinforced with $TiN_x$ by mixing titanium powders with 10 wt.% of nano-sized $TiN_x$. Spark Plasma Sintering (SPS) was chosen for the sintering of these composites. The plate made of titanium powders and $TiN_x$ powders demonstrates higher corrosion resistance than that of the plate of titanium powders alone. The physical properties of specimens were analyzed by performing hardness test and biaxial strength test. The electrochemical properties, such as corrosion resistance and hydrogen permeability at high temperature, were also investigated. The microstructures of the specimens were investigated by FESEM and profiles of chemical compositions were analyzed by EDX.

• 한국항공우주학회지
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• 제48권12호
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• pp.961-968
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• 2020

본 연구에서는 미시역학 전산 모형을 통해 열 보호 시스템에 사용되는 내열 코팅 재료의 유효 열전도도와 탄성 계수를 산출하고 분석하였다. 상용 프로그램 Simpleware를 이용하여 HfC로 코팅된 탄소/탄소 복합재료의 삼차원 전산 모형을 생성한 후 유한요소 해석을 수행하였다. 유효 물성의 경향을 확인하기 위해 코팅층의 기공도와 두께 변화를 고려하였다. 또한, 실제 시편을 제작하여 실험에서 온도에 따라 측정된 열전도도와 해석에서 산출된 열전도도를 서로 비교하였으며 해석 결과가 측정값에 근접하였다. 이를 통해 내열 코팅 재료의 유효 물성을 산출하는데 있어서 미시역학 전산 해석이 적절함을 확인하였다.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2134-2140
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• 1996

This study was carried out to anlayze the heat-resistant characteristics of functionally gradient material(FGM) composed with ceramic and metal. The thermal fracture behavior of plasma-sprayed FGM and conventional coating material(NFGM) was exaimined by acoustic emession technique under heating and cooling. Furnace cooling and rapid cooling tests were used to examine the effect of temperature change under various conditions, respectively. At the high temperature above $800^{\circ}C$, it was shown that FGM gives higher thermal resistance compared to NFGM by AE signal and fracture surface analysis.

• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.

• Elastomers and Composites
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• 제22권4호
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• pp.324-332
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• 1987

PMMA와 TBBA의 혼합비를 변화시킨 시료를 질소기류 하에서 비등온 열중량 분석법으로 가열속도 $1-20^{\circ}C/min$, 등온분해온도 $200-300^{\circ}C$로 열분해시킨 시료를 적외선 분광분석한 결과 TBBA의 함량 증가에 따라 활성화에너지 값은 Friedman법으로 28-46 Kcal/mol, Ozawa법으로 28-38 Kcal/mol로 증가 하였다. PMMA에 TBBA의 첨가에 따른 열분해반응은 주쇄 분해반응으로 이루어지며 실제 열중량곡선과 거의 일치되는 최적의 분해반응 모델식을 산출할 수 있었다.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1571-1579
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• 1997

The development of a new material which should be continuously use under severe environment of very high temperature has been urgently requested. For the development of such super-heat resistant materials, the main problem is not only to make the superior thermal barrier properties but also to actively release thermal stress. So, a new concept of functionally graded material(FGM) has been proposed to overcome this problem. A composition and microstructure of FGM are varied continuously from place to place in ways designed to provide it with the maximum function of mitigating the induced thermal stress. So, FGM can be applied in the aerospace, the electronic and the medical field, etc.. In this study, thermal stress analysis of sintering PSZ/NiCrAlY graded material was conducted theoretically using a finite-element program. The temperature condition was sintering temperature assuming a cooling-down process up to room temperature. Fracture damage mechanism was anlayzed by the parameters of residual stress. It could be known that FGM provided with the function of mitigating the induced thermal stress.

• Elastomers and Composites
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• 제46권2호
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• pp.164-170
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• 2011

본 연구에서는 실리콘 고무의 내열 및 내화 특성과 같은 열적 특성을 향상시키기 위해 실리콘 고무와 친환경 재료인 펄라이트를 기계적인 방법으로 혼합하여 실리콘 고무/펄라이트 복합체를 제조하였다. 다양한 분석 방법을 통하여 실리콘 고무/펄라이트 복합체의 특성은 펄라이트의 함량에 의존한다는 것을 확인하였다. 열중량 분석에서 순수한 실리콘 고무보다 실리콘 고무/펄라이트 복합체가 더 높은 온도에서 분해가 시작됨을 확인하였다. 가스 토치 시험을 통하여 펄라이트가 첨가된 복합 재료의 후면 온도가 순수한 실리콘 고무에 비하여 현저히 낮음을 알 수 있었고, RABT(Richtlinien fur die Ausstatung und den Betrieb won Stra${\beta}$entunneln) 조건에 따른 내화로 시험 그리고 탄화로 시험에서 펄라이트의 함량이 5 wt% 와 10 wt%인 복합체가 뛰어난 열적 안정성을 나타내었다. 주사전자현미경 (SEM)으로 실리콘 고무 내에서 펄라이트의 분산정도를 관찰하였다. 또한 한계산소지수(LOI)는 펄라이트의 함량에 따라 증가함을 확인하였다.