• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.57-60
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• 2003

Generally, normal concrete has the disadvantages of low tensile strength, low ductility and volume instability. To improve its performance, fiber reinforced cimentitious composite(FRCC) have been development. These composites are composed of cement, sand, water, a small amount of admixtures, and an optimal amount of fiber like synthetic fiber and steel fiber. This research investigates influence of sand, hybrid fiber and fiber volume fraction, and reports the test results of mechanical properties, fracture behavior and failure pattern of the FRCC. Our experiment was observed that sand mixed FRCC has lower compressive strength and higher bending strength than no sand mixed FRCC, and more steel fiber mixed FRCC has higher compressive strength and bending strength. Hybrid FRCC of steel and polypropylene had superior properties than FRCC of polypropylene only in same fiber volume fraction.

• Composites Research
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• 제26권4호
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• pp.245-253
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• 2013

본 연구에서는 입자형태인 두 가지 이상의 강화제가 기지 내에 무작위로 분포하여 하이브리드 복합재료를 이룰 때, 강화제의 함유량에 따른 복합재료의 인장강도 및 탄성계수를 예측할 수 있는 이론 모델을 제안하였다. 이를 위하여 연속적인 두 강화제가 기지 내에 평행하게 분포한 복합재료 모델에 입자형태의 한 가지 강화제가 무작위하게 분포한 복합재료 모델을 수정 적용하였다. 본 연구에서 제안한 모델의 정확성과 타당성을 논의하기 위해, 산업체에서 널리 쓰이고 있는 폴리프로필렌을 기지로 하고, 탈크와 유리단섬유를 서로 다른 강화제로 한 복합재료를 제작하여 인장강도 및 탄성계수를 측정하였다. 인장강도 값을 예측하는 경우, 이전의 이론 모델이 실험 측정값과 7배 이상의 오차를 보이는 반면 본 연구의 모델은 비슷한 값을 예측하였다. 탄성계수의 경우에도 본 연구의 모델은 비교적 정확하게 실험 측정 값을 예측할 수 있었다.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.877-887
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• 2015

본 연구진은 사출성형 공정에서 적용되는 미지 시료 및 고점도의 복합소재 점도를 추정하기 위한 새로운 방법을 제시한 바 있다. 본 논문에서는 사출성형 금형 캐비티 내압을 측정하는 장치를 개발하였다. 이는 사출성형 공정 중의 금형 내를 흐르는 용융체의 압력을 실시간으로 측정하고, 이를 CAE 해석 결과로부터 모사된 압력과 비교함으로써 CAE D/B내의 점도 데이터의 정확성을 검증할 수 있게 한다. 본 연구에서 사용한 재료는 PP(Polypropylene), PP/LGF30%(Polypropylene과 long glass fiber 50% composite), PA66/LGF50%(Polyamide 6,6와 long glass fiber 50% composite) 이다. 여기서 PP와 PP장섬유복합재료는 이미 점도 데이터가 구축되어 있으나, PA66장섬유복합재료는 새롭게 개발한 재료로써 기존의 점도 데이터가 없기에 본 시스템을 이용해서 새로운 점도 곡선을 추정하였다. 그리고, 일반 점도 측정장치로 구한 점도 곡선과도 비교하였다. 한편, 이미 점도 데이터를 갖고 있는 경우인 PP는 신뢰성을 확인할 수 있었으나, PP/LGF50%의 경우는 높은 점도와 구조의 복잡성으로 인해 기존 점도 데이터의 개선이 필요하였다.

• 공업화학
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• 제10권1호
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• pp.46-50
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• 1999

본 연구에서는 표면이 개질된 목분으로 강화된 PP수지 복합체의 $(NH_4)_2HPO_4$과 boron 혼합물($Na_2B_4O_7:H_3BO_3=5:1\;ratio$)에 대한 난연특성에 관해 알아보았다. 또한 m-phenylene dimaleimide(PDMI)로 개질된 PP수지와 비개질된 PP수지 복합체의 기계적 특성을 비교하였다. $(NH_4)_2HPO_4$로 개질된 복합체의 난연성은 boron 혼합물로 개질된 복합체의 난연성보다 우수하였다. 복합체의 충격강도는 목분의 함량이 증가함에 따라 증가되었고, 인장강도는 감소하였다. 개질된 PP수지 복합체의 기계적 강도는 비개질된 수지의 복합체보다 개선되었다. 또한 난연제의 농도가 증가함에 따라 인장강도는 점진적으로 증가되었고, 25 wt %에서 최대값을 나타내었으며, PDMI의 함량이 증가함에 따라 목분-PP 복합체의인장강도는 16 wt %까지 증가되었다.

• 폴리머
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• 제24권6호
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• pp.777-786
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• 2000

본 연구에서는 범용 열가소성 수지인 폴리프로필렌 (virgin polypropylene, VPP)과 폴리프로필렌을 주성분으로 하는 재생플라스틱의 난연성을 향상시키기 위하여, 난연제 decabromodiphenyl oxide (DBDPO)와 chlorinated paraffin wax (CPW)를 혼합하여 이것들의 난연 특성을 정량적으로 비교 분석 연구하였다. 난연성 평가 측정으로 콘 칼로리미터 (cone calorimeter, ASTM E1354, ISO 5660), 한계산소지수 측정 (LOI, ASTM D2863, ISO 4589) 등을 사용하였고, 콘 칼로리미터를 이용하여 DBDPO와 CPW의 난연효율을 정량적으로 측정하였다. 콘 칼로리미터의 결과로 난연제의 난연효율을 측정한 결과, DBDPO가 CPW보다는 약 2배의 난연효율을 가지고 있다는 것을 확인하였고, 한계산소지수 측정 결과와 유사한 난연효율을 보임을 확인하였다. 열중량 분석 (TGA) 측정결과 난연제 DBDPO를 첨가하였을 때 약 30~5$0^{\circ}C$의 열분해 온도의 상승을 확인할 수 있었다.

• Advances in nano research
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• 제16권2호
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.

• Composites Research
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• 제36권4호
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• pp.264-269
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• 2023

Spent coffee grounds (SCG) are a ubiquitous byproduct of coffee consumption, representing a significant waste management challenge, as well as an untapped resource for economic development and sustainability. Improper disposal of SCG can result in environmental problems such as methane emissions and leachate production. This study aims to investigate the physicochemical properties of SCG and their potential as a reinforcement material in polypropylene (PP) to fabricate an eco-friendly composite via extrusion and injection molding, with SCG filler ratios ranging from 5-20%. To evaluate the effect of SCG on the morphological and mechanical properties of the bio- composite, thermogravimetric analysis, SEM, tensile, flexural, and impact tests were conducted. The results demonstrated that the addition of SCG lead to a slight increase in brittleness of the composite but did not significantly affect its mechanical properties. Impressively, the presence of a significant organic component in SCG contributed to the enhanced thermal performance of PP/SCG composites. This improvement was evident in terms of increased thermal stability, delayed onset of degradation, and higher maximum degradation temperature as compared to pure PP. These findings suggest that SCG has potential as a filler material for PP composites, with the ability to enhance the material's properties without compromising overall performance.

• 소성∙가공
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• 제31권1호
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• pp.29-38
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• 2022

Recently, the composite material market is gradually growing. Various composite forming processes have been developed in order to reduce the production cost of the composite material. Unlike the conventional forming process, the microwave composite forming process has the advantage of reducing the processing time because the composite material is heated directly or indirectly at the same time. Due to this advantage, in this study, a double cantilever beam test was conducted with specimens manufactured by the microwave composite forming process. The purpose of this study was to compare mode-I energy release rate for specimens manufactured by prepreg compression forming and microwave composite forming processes. First, a microwave oven was proposed to conduct the microwave composite forming process. Double cantilever beam specimens were manufactured. After that, the double cantilever beam test was conducted to obtain the mode-I energy release rate. Mode-I energy release rates of specimens manufactured by the microwave composite forming and prepreg compression forming processes were then compared. As a result, mode-I energy release rates of specimens fabricated by the microwave composite forming process were similar to those fabricated with the prepreg compression forming process with a relatively reduced process time.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1993년도 ACT 93
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• pp.605-611
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• 1993

• 소성∙가공
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• 제25권6호
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• pp.402-408
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• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.