• Composites Research
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• 제17권6호
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• pp.1-7
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• 2004

입자강화복합재료에 관한 연구는 오래 전부터 수행되어왔다. 최근 활발한 연구가 이루어지고 있는 나노복합재료도 역시 입자강화복합재료의 한 종류라 할 수 있다. 본 연구에서는 섬유강화 복합재료의 모재로서 사용되어질 수 있는 다중벽탄소나노튜브/에폭시 복합재료를 제작하고 그 물성을 고찰하였다. 본 연구에서 정립한 제작 공정을 사용하여 제작 된 다중벽 탄소나노튜브/에폭시 복합재료의 인장 물성을 MWNT의 첨가량에 따라 고찰하였다 0.5wt%의 MWNT를 첨가 하였을 때, 인장강성은 19%, 인장강토에서는 12%의 증가를 보였다. 또한 경화시 발생하는 재응집 현상을 관찰하고, 기계적 물성을 더 높이 항상시키기 위해서는 이 현상을 억제해야 함을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.131-138
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• 2014

Highly conductive bipolar plate for polymer electrolyte membrane fuel cell (PEMFC) was prepared using phenol novolac-type epoxy/graphite powder (GP)/carbon fiber filament (CFF) composite, and a rubber-modified epoxy resin was introduced in order to give elasticity to the bipolar plate graphite fiber (GF) was incorporated in order to improve electrical conductivity. To find out the cure condition of the mixture of novolac-type and rubber-modified epoxies, differential scanning calorimetry (DSC) was carried out and their data were introduced to Kissinger equation. And tensile and flexural tests were carried out using universal testing machine (UTM) and the surface morphology of the fractured specimen and the interfacial bonding between epoxy matrix and CFF or GF were observed by a scanning electron microscopy (SEM).

• 한국정밀공학회지
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• 제16권8호
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• pp.149-154
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• 1999

FRMLs(Fiber Reinforced Metal Laminates) is a new type of hybrid materials. FRMLs consists of high strength metal and fiber which are laminated using a structural adhesive bond(epoxy resin). The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical property of Aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA) was cured with methylene dianiline(MDA) with or without accelerator(K-54). Eight kinds of resin mixture ratio were tested for the experiment ; five kinds of FRMLs(1))epoxy & curing agent) and three kinds of FRMLs(2)(epoxy & curing agent & accelerator). FRMLs(2) have a more effective characteristics on the fatigue crack propagation behavior and mechanical property than FRMLs(1)

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.79-83
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• 2000

Interfacial and microfailure properties of carbon liber/bismaleimide (BMI) composites were evaluated using both tensile fragmentation and compressive Broutman tests with acoustic emission (AE). Since BMI is rather difficult matrix to apply for the conventional fragmentation test because of its too low elongation and too brittle and high modulus properties, dual matrix composite system was applied. After carbon fiber/BMI composite was prepared for rod shape by controlling differing curing stage, composites rod was embedded in toughened epoxy as outer matrix. The typical microfailure modes including fiber break, matrix cracking, and interlayer failure were observed during tensile testing, whereas the diagonal slippage in fiber ends was observed during compressive test. On the other hand, AE amplitudes of BMI matrix fracture were higher than carbon fiber tincture under tensile test because BMI matrix has very brittle and high modulus. The waveform of signals coming from BMI matrix fractures was consistent with AE amplitude result under tensile tests.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1495-1498
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• 2003

Recently, self-healing methods of a cracked matrix, especially polymeric composite materials, became the center of engineering researchers. In this paper, we summarized the self-healing concept for polymeric composite materials and investigated the effect of microparticle on the crack growth behavior in colorless and transparent matrix by experimental observation to describe the crack propagation around the microparticle inside epoxy matrix composite. Compression splitting test for the specimen involving microparticle was conducted. In addition, FE analysis was pursued to present the stress contour around microparticle in the matrix. Through the experiments and FE analysis, we found that the size. relative position, bonding condition and relative stiffness of microparticle are important parameters to decide the direction of crack propagation, which is related to the rupture of microparticle for self-healing

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2001년도 제16회 학술발표회 논문초록집
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• pp.1-6
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• 2001

In this paper, edge delaminations in cracked composite plates are analytically investigated. A theoretical model based upon a sub-laminate approach is used to determine the strain energy release rate, $G^{ed}$, in [$\pm$$\theta_m$/$90_n$]$_s$ carbon/epoxy laminates loaded in tension. The analysis provides closed-form expressions for the reduced stiffness due to edge delamination and matrix cracking and the total energy release rate. The parameters controlling the laminate behaviour are identified. It is shown that the available energy for edge delamination is increased notably due to transverse ply cracking. Also thermal stresses increase substantially the strain energy release rate and this effect is magnified by the presence of matrix cracking. Prediction for the edge delamination onset strain is presented and compared with experimental data. The analysis could be applied to ceramic matrix composite laminates where similar mechanisms develop, but further experimental evidence is required.

• 대한기계학회논문집
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• 제16권2호
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• pp.200-206
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• 1992

The effect of fiber diameter and gauge length on pull-out test for the interfacial properties in fiber reinforced resin composites have been investigated and these results have been arranged as statistical analysis. The fiber and matrix resins used for this study were stainless steel fiber (SUS316) and carbon fiber (high strength type), epoxy and high density polyethylene resin. From this study, it has been found that shear strength are constant regardless of gauge length of pull-out test and coefficient of variation depend on fiber diameter. In addition, it has been found that the interfacial shear strength decreased with the increasing fiber diameter, and in all case, Weibull parameter (m) has approximately 1.2/C.O.V.

• 폴리머
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• 제25권4호
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• pp.587-593
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• 2001

본 연구에서는 red mud(RM)를 0.1, 1, 그리고 5M 의 H$_3PO_4$ 용액으로 화학적 표면처리하여 에폭시/RM 나노복합재료를 제조하였으며, RM 표면의 pH, 표면 산-염기도, 표면적, 그리고 기공도를 이용하여 표면처리에 의한 영향을 분석하였다. 또한, 임계응력 세기인자(K$_{IC}$)를 통하여 제조된 복합재료의 기계적 계면물성을 조사하였다. 실험결과로부터, 표면처리에 의한 RM의 표면은 hydroxyl 등의 산성관능기 그룹의 생성과 금속산화물의 반응으로 인하여 표면 산도가 증가하고, 미세기공 및 중기공 구조가 발달하여 비표면적이 증가되었다. K(IC)를 이용한 RM의 기계적 계면성질은 비표면적이 증가함과 동시에 표면산도가 증가함으로 염기성 매트릭스와의 계면결합력이 증대되어 순수 에폭시와 처리되지 않은 에폭시/RM 복합재료보다 더 우수한 기계적 계면물성을 나타내었다.

• 폴리머
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• 제26권5호
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• pp.623-633
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• 2002

적인을 이용한 ortho-cresol novolac (OCN)과 biphenyl계 혼합 에폭시 수지 조성물의 열적 특성과 난연 특성을 검토하였다. OCN과 biphenyl 에폭시의 부피비에 따라 5가지 조성물을 디자인하였으며, TGA 및 DTG, 그리고 UL-94V 테스트를 통해 난연 효과를 평가하였다. 충전제와 적인의 함량이 증가할수록 열적 성질 및 우수한 난연 효과를 보였으나, 과량의 적인을 적용하였을 경우에는 열안정성의 저하를 유발하였다. 복합재료의 기저 수지호서 OCN/biphenyl 혼합 에폭시를 사용하였을 경우 OCN의 내열특성과 biphenyl 에폭시의 높은 발포 특성에 기인하여 보다 향상된 난연 특성을 확보할 수 있었다. 적인을 적용한 에폭시 수지 조성물의 난연 기구는 표면에서 형성된 발포성 탄화층 (char-layer)의 열적 방어 효과로 판단할 수 있었다.

• 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.