• Composites Research
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• 제21권4호
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• pp.15-21
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• 2008

단일 탄소섬유에 부착된 반구형 미소본드 시험편을 제사하여 에폭시수지와 난소섬유사이의 계면전단강도를 평가하였다. 반구형 미소시험편의 경우, 드랍레트 미소접합시험편 및 역반구형 미소접합시험편과 비교하여 계면강도측정값들이 높은 회귀계수 및 삭은 편차를 보여주었다. 이는반구형 시험편의 메니스커스 부분이 다른 미소시험편보다 작으며 핀홀 부하장치의 선단과 접촉하고 있는 수지부분에서 응력집중이 감소했기 때인 것으로 사료된다. 이들 시험에 대한 유한요소해석결과, 반구형시험편에서는 수지/섬유의 계면부를 따라 전단응력분포가 응력모드의 전환이 없이 안정하였다. 또한 이들 계면강도 측정데이터는 미소 바이스의 선단과 핀홀 판의 선단과 같은 부하장치의 종류에 따라 달라졌음을 알았다.

• 한국안전학회지
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• 제12권4호
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• pp.57-62
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• 1997

The combined structure of hybrid composite made through the bonding process of materials of different properties greatly defines its mechanical characteristics, as the results of the experiments on materials of different properties show much dissimilarity. When carbon/epoxy materials are applied to hybrid composite, the carbon materials helps to improve the mechanical properties of the hybrid composite, and the epoxy reduces its fracture strain and impact resistance. Carbon fiber which is now in general commercialization is classified as high modulus or high strength system, and its manufacturing methods are various. The study of the materials having combined structure is focused on the numerical analysis of the layers of bonding surface in materials with difference modulus. The hybrid composite made through the multilayered bonding of reinforced aluminium sheets with aramid fiber now faces the marketing phase, and especially its excellent fatigue resistance and mechanical properties promote active researches on the similar products of hybrid composite. This study aims to investigate the effects of CFRP volume ratio and fiber's orientation over the properties of mechanical strength and fatigue life of the hybrid composite, AI7075/CFRP. To carry out this study, static tensile and fatigue tests were given to some of the panels which, made through the co-cure processing in an autoclave, have different CFRP volume ratio and carbon fiber orientations.

• 대한기계학회논문집A
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• 제32권11호
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• pp.918-923
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• 2008

Since crack detection for laminated composites in-service is effective to improve the structural reliability of laminated composites, it have been tried to detect cracks of laminated composites by various nondestructive methods. An electric potential method is one of the widely used approaches for detection of cracks for carbon fiber composites, since the electric potential method adopts the electric conductive carbon fibers as reinforcements and sensors and the adoption of carbon fibers as sensors does not bring strength reduction induced by embedding sensors into the structures such as optical fibers. However, the application of the electric method is limited only to electrically conductive composite materials. Recently, a piezoelectric method using piezoelectric characteristics of epoxy adhesives has been successfully developed for the adhesive joints because it can monitor continuously the damage of adhesively bonded structures without producing any defects. Polymeric materials for the matrix of composite materials have piezoelectric characteristics similarly to adhesive materials, and the fracture of composite materials should lead to the fracture of polymeric matrix. Therefore, it seems to be valid that the piezoelectric method can be applied to monitoring the damage of composite materials. In this research, therefore, the feasibility study of the damage monitoring for composite materials by piezoelectric method was conducted. Using carbon fiber epoxy composite and glass fiber composite, charge output signals were measured and analyzed during the static and fatigue tests, and the effect of fiber materials on the damage monitoring of composite materials by the piezoelectric method was investigated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.613-617
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• 1998

This study deals with the effect on adhesive strength properties of fiber sheet layer and maintenance position of coccrete structure reinforced using epoxy resin carbon and aramit fiber sheet. Properties of epoxy resin adhesive strength of the concrete bridge slab, tunnel and wall etc. reinforced using fiber sheet under many different environment change according to condition of concrete substrate, temperature, moisture, curing, cleaning, and chemical effects and so on. The purpose of this study is that it makes the estimation value of adhesive strength of concrete substrate and fiber sheet reinforcing layer penetrated epoxy resin under high temperature(9$0^{\circ}C$), chemical attack and condition of curing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.785-792
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• 2000

Repair and retrofit system of concrete structures has been developed from conventional reinforced concrete overlaying, steel plate bonding and recently to fiber composite systems. Research and study on carbon, aramid, and glass fiber composite system has been actively carried out from all over the world Glass fiber composite is proved to be competitive technically and enconomically, among fiber composite system. CAF system is a system developed locally using all domestic materal, glass fabric and epoxy, and improved in shear bonding property by utilizing silica fume mixed with epoxy. All the tests on material properties, structural behavior, constructiveness at site and quality control procedure proved to be most appropriate system so far developed. Futher research work is and will be under progress for utilization of this system which will be applied to more adverse situation.

• 한국안전학회지
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• 제19권4호
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• pp.31-35
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• 2004

The A17075/CFRP multi-layered hybrid laminate material consists of the alternating A17075-T6 sheets and carbon/epoxy prepregs of M40 fade. The influence of volume fraction and fiber orientation of A17075/CFRP layer on flexural properties of A17075/CFRP laminate alternating A17075-T6 and carbon/epoxy prepreg was investigated. The results obtained from the experimental analysis are as follows: 1. In the $0^{\circ}$ fiber orientation, the mont of increase of the flexural rigidity was $20.5\%$ at the $26.5\%$ volume fraction and $38.0\%\;at\;the\;35.7\%$ volume fraction compared with the flexural rigidity level(20.0GPa) of the $10\%$ volume fraction of CFRP. 2. In the $\pm45^{\circ}$ fiber orientation the amount of decrease of the flexural rigidity was $23.5\%\;at\;the\;20.0\%$ volume fraction and $31.5\%\;at\;the\;33.3\%$ volume fraction compared with the flexural rigidity level of the $10\%$ volume fraction of CFRP. 3. In the $0^{\circ}$ fiber orientation, the flexural strength was 481.5MPa at the $10\%$ volume fraction of CFRP and 583.8MPa at the $26.5\%$ volume fraction and 653.7MPa at the $35.7\%$ volume faction. 4. In the $\pm45^{\circ}$ fiber orientation, the flexural strength was 354.0MPa at the $20.0\%$ volume fraction of CFRP and 340.5MPa at the $33.3\%$ volume fraction.

• Advanced Composite Materials
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• 제18권3호
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• pp.251-264
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• 2009

Nonlinear mechanical behaviors of unidirectional carbon fiber-reinforced plastic (CFRP) laminates using cup-stacked carbon nanotubes (CSCNTs) dispersed epoxy are evaluated and compared with those of CFRP laminates without CSCNTs. Off-axis compression tests are performed to obtain the stress-strain relations. One-parameter plasticity model is applied to characterize the nonlinear response of unidirectional laminates, and nonlinear behaviors of laminates with and without CSCNTs are compared. Clear improvement in stiffness of off-axis specimens by using CSCNTs is demonstrated, which is considered to contribute the enhancement of the longitudinal compressive strength of unidirectional laminates and compressive strength of multidirectional laminates. Finally, longitudinal compressive strengths are predicted based on a kink band model including the nonlinear responses in order to demonstrate the improvement in longitudinal strength of CFRP by dispersing CSCNTs.

• 콘크리트학회논문집
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• 제23권4호
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• pp.405-411
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• 2011

철근콘크리트 구조물의 보강에 자주 사용하는 탄소 섬유나 유리 섬유 대신에 이 두 가지 섬유를 동시에 사용하여 하이브리드 효과를 얻기 위한 연구를 시도하였다. 하이브리드 효과를 얻기 위해서는 탄소 섬유와 유리 섬유를 적절한 비율로 조합해야 되며, 이러한 비율로 제작된 실험체를 이용하여 하이브리드 FRP 직접 인장 실험을 수행할 수 있다. 하이브리드 FRP 실험체는 직조된 섬유 시트를 이용하는 현장과 다르게, 섬유를 직접 조합해야 하는 이유로 작업이 쉽지 않다. 따라서 이 연구에서는 고강도 탄소 섬유와 E형 유리 섬유의 조합에 따른 1축 직접 인장 실험체의 제작 방법을 제안하여 실험을 통하여 하이브리드 효과를 분석하였다. 하이브리드 FRP로 가장 적합한 섬유 조합은 연성 지수, 탄성계수 및 응력-변형률 곡선을 비교한 결과 연성 K형 에폭시를 사용한 유리 섬유 : 탄소 섬유 = 9 : 1(체적비)가 가장 적합한 것으로 평가되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.180-183
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• 2009

Composite bipolar plates offer several advantages of low cost, light weight, and ease of manufacturing compared to traditional graphite plate. However, it is difficult to achieve both high electrical conductivity and high flexural strength. In this study, the hybrid carbons filled epoxy composite bipolar plates were fabricated to test electrical conductivity and flexural properties. Graphite powders were used as the main conducting filler and continuous carbon fiber fabrics were inserted to improve the mechanical properties of the composite. This hybrid composite showed improved in-plane electrical conductivity and flexural property. The moldability of the hybrid composite was also improved comparing to the continuous prepreg composite. This study suggested that the continuous carbon fiber inserted graphite/epoxy composites can be a potential candidate material to overcome the disadvantages of conventional graphite composite or continuous prepreg composite bipolar plates.

• Carbon letters
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• 제25권
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• pp.43-49
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• 2018

This study suggests the novel thermoplastic toughening agent, which can be applied in the monomer forms without increasing the viscosity of the epoxy resin and polymerized during the resin curing. The diazide (p-BAB) and dialkyne (SPB) compounds are synthesized and mixed with the epoxy resin and the carbon fiber reinforced epoxy composites are prepared using vacuum infusion process (VIP). Then, flexural and drop weight tests are performed to evaluate the improvement in the toughness of the prepared composites to investigate the potential of the novel toughening agent. When 10 phr of p-BAB and SPB is added, the flexural properties are improved, maintaining the modulus as well as the toughness is improved. Even with a small amount of polytriazolesulfone polymerized, due to the filtering effect of the solid SPB by the layered carbon fabrics during the VIP, the toughening and strengthening effect were observed from the novel toughening agent, which could be added in monomer forms, p-BAB and SPB. This suggests that the novel toughening agent has a potential to be used for the composites prepared from viscosity sensitive process, such as resin transfer molding and VIP.