• Journal of the KSME
• /
• v.31 no.3
• /
• pp.293-299
• /
• 1991

단섬유보강 금속복합재료의 2차가공은 금속복합재료의 넓은 범위 응용을 위해 필히 요구된다. 여러 가공방법 중 하나인 열간압출시 보강섬유파괴 및 계면에서의 접합분리 및 균열발생이 없는 제조공정의 최적화를 위해서 가공시 내부조직의 소성변형 기구 규명보다 압출력에 의한 응력분 포와 기지재료와 보강섬유 사이 계면 변화 및 기계적 특성 관계규명이 정량적으로 요구된다. 본 글에서는 유한요소법을 이용하여 계면에서의 접합상태를 임의로 가정하여 압출조건에 따른 압 출후의 보강섬유 방향 및 계면균열 및 접합분리를 거시적으로 예측하고, advanced shear-lag을 이용하여 균열 전, 후의 응력. 변형관계를 미시적으로 규명할 수 있음을 제시하였다. 그러나 향후 현상적 모델인 shear-lag 모델을 수학적 모델인 균질화법에 도입하면 미시적. 거시적 거 동해석이 함께 요구되는 금속복합재료의 열간압출거동 해석을 일체적으로 행할 수 있어 효율적 이고 정확한 예측이 가능하리라고 사료된다.

• Composites Research
• /
• v.33 no.4
• /
• pp.198-204
• /
• 2020

In this study, we employ the full atomistic molecular dynamics simulation and finite element homogenization method to predict the thermo-mechanical properties of nanocomposites including carbon nanotube bundle. As the number of carbon nanotubes within the single bundle increases, the effective in-plane Young's modulus and in-plane shear modulus decrease, and in-plane thermal expansion coefficient increases, despite the same volume fraction of carbon nanotubes. To investigate the thickness of interphase zone, we employ the radial density distribution. It is investigated that the interphase thickness is almost independent on the number of carbon nanotubes within the single bundle. It is assumed that the matrix and interphase are isotropic materials. According to the predicted thermo-mechanical properties of interphase zone, the Young's modulus and shear modulus of interphase zone clearly decrease, and the thermal expansion coefficient increases. Based on the thermo-mechanical interphase behavior, we developed the multiscale homogenization model to predict the thermo-mechanical properties of PLA nanocomposites that include the carbon nanotube bundle.

• Elastomers and Composites
• /
• v.37 no.4
• /
• pp.258-264
• /
• 2002

In this work, the influence of thermal treatment on surface properties of silicas and mechanical interfacial properties of silicas/polyurethane composites was investigated. The surface properties of thermally treated silicas were studied in the context of Fourier Transform-IR (FT-IR), solid-state 29Si NMR spectroscopy, and contact angle. And the mechanical interfacial properties of the silica/polyurethane composites were evaluated by composite tearing energy (GIIIC). As a result, it was found that the thermally treated silica surfaces became hydrophobic in nature, due to the condensation of surface hydroxyls and the formation of siloxane bonds, resulting in increasing the London dispersive component of surface free energy. From which, the increase of the London dispersive component of the silicas led to an improvement of the dispersion of silicas in a polyurethane matrix, finally resulting in improving the tearing energy (GIIIC) of the silicas/polyurethane composites.

• Composites Research
• /
• v.20 no.1
• /
• pp.23-31
• /
• 2007

In order to improve the mechanical properties of jute fiber/polypropylene(PP) composites, the property change with the addition of a coupling agent, maleic anhydride polypropylene(MAPP) was examined experimentally. The maleated coupler acts as an intermediate to chemically connect the polar nature of the fiber and non-polar nature of the polyolefin polymer resin. Furthermore, the decrease in viscosity of the resin which results from the melting point reduction by the MAPP, leads to an increase of contact area with the fiber interface. We discussed the improvement of the PP composite blend of the maleated coupler with the 80mm jute long fiber mat in conjunction with the change of physical parameters in the thermoplastic resin. We confirmed the extent of contribution to the mechanical physical enhancement by using the following parameters: melting flow index(MI) and viscosity, contact angle, thickness of the composite, interfacial shear strength and morphology observation etc. Especially it was observed that the MI and viscosity, MAPP mixture had a very strong relationship with the tensile and flexural strength and modulus, and interfacial shear strength(IFSS).

• Applied Chemistry for Engineering
• /
• v.23 no.3
• /
• pp.313-319
• /
• 2012

In this work, the electroplating of copper was introduced on PAN-based carbon fibers for the enhancement of mechanical interfacial strength of carbon fibers-reinforced composites. The surface properties of carbon fibers were determined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and contact angle measurements. Its mechanical interfacial properties of the composites were studied by interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$). From the results, it was found that the mechanical interfacial properties of Cu-plated carbon fibers-reinforced composites (Cu-CFRPs) enhanced with increasing the Cu plating time, Cu content and COOH group up to Cu-CFRP-30. However, the mechanical interfacial properties of the Cu-CFRPs decreased dramatically in the excessively Cu-plated CFRPs sample. In conclusion, the presence of Cu particles on carbon fiber surfaces can be a key factor to determine the mechanical interfacial properties of the Cu-CFRPs, but the excessive Cu content can lead the failure due to the interfacial separation between fibers and matrices in this system.

• Polymer(Korea)
• /
• v.37 no.1
• /
• pp.61-65
• /
• 2013

In this work, the anodic oxidation of carbon fibers was carried out to enhance the mechanical interfacial properties of carbon fibers-reinforced epoxy matrix composites. The surface characteristics of the carbon fibers were studied by FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Also, the mechanical interfacial properties of the composites were studied with interlaminar shear strength (ILSS), critical stress intensity factor ($K_{IC}$), and critical strain energy release rate ($G_{IC}$). The anodic oxidation led to a significant change in the surface characteristics of the carbon fibers. The anodic oxidation of carbon fiber improved the mechanical interfacial properties, such as ILSS, $K_{IC}$, and $G_{IC}$ of the composites. The mechanical interfacial properties of the composites anodized at 20% sulfuric/nitric (3/1) were the highest values among the anodized carbon fibers. These results were attributed to the increase of the degree of adhesion at interfaces between the carbon fibers and the matrix resins in the composite systems.

• Composites Research
• /
• v.15 no.6
• /
• pp.16-23
• /
• 2002

In this work, the effect of anodic oxidation on surface characteristics of high strength PAN-based carbon fibers was investigated in mechanical interfacial properties of composites. The surface properties of the carbon fibers were determined by acid-base values, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angles. And their mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$). As a result, the acidity or the $O_{ls}/C_{ls}$ ratio of carbon fiber surfaces was increased, due to the development of the oxygen functional groups. Consequently, the anodic oxidation led to an increase in surface free energy of the carbon fibers, mainly due to the increase of its specific (or polar) component. The mechanical interfacial properties of the composites, including ILSS and $K_{IC}$, had been improved in the anodic oxidation on fibers. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between fibers and epoxy resin matrix.

• Rubber Technology
• /
• v.18 no.1
• /
• pp.13-23
• /
• 2017

• Proceedings of the KWS Conference
• /
• 2000.04a
• /
• pp.193-196
• /
• 2000

• Proceedings of the KWS Conference
• /
• 1999.05a
• /
• pp.98-99
• /
• 1999