• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집A
• /
• pp.596-602
• /
• 2001

Structures in current use are required of weight reduction and strength in many instances. This naturally necessitates frequent applications of composite materials in many areas. Elastic constants are one of key parameters in determining design guidelines for the specific applications of particular materials. In this research two vibratory techniques (acoustic resonance method and impulse technique)are utilized to evaluate elastic constants. Both techniques are suitable for the measurements of dynamic elastic constants. The Impulse technique provides a quick method for the measurement while the acoustic resonance method produces the values of elastic constants which agree better with theoretical values.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 C
• /
• pp.1436-1438
• /
• 2003

In this paper thermal and mechanical properties of elastic epoxy for applying high voltage products were investigated. Glass transition temperature(Tg) of elastic epoxies can't find form room temperature to $200^{\circ}$ by DSC. It occurred weight reduce on $285^{\circ}$ and $451^{\circ}$ by thermo-gravimeter. The first temperature was effected on addictives and the other was epoxy's character. Max, tensile strain showed $28.3kgf/cm^2$ at 20% of mechanical stress in addictives 35phr. SEM micrograph of the fracture surface observed in void and tearing of elastic epoxy at addictives 35phr. The other side, SEM micrograph of rigid epoxy showed the trace which broke.

• 한국재료학회지
• /
• 제9권8호
• /
• pp.763-767
• /
• 1999

자동차, 항공기 및 기타 산업에서 복합재료의 사용은 증가되어 왔고 활발한 연구가 진행되고 있다. 이러한 복합재료중의 하나인 Carbon-epoxy 복합재료의 열 특성에 관하여 알아보았다. 반복적인 냉각과 가열이 부가되는 열 피로에서 복합재료의 탄성계수의 변화를 관찰하여 봄으로써 복합재료가 가지고 있는 여러 열 특성에 관하여 연구하였다. 일반적으로 복합재료는 온도가 증가하면 탄성계수가 감소한다고 알려져 있다. 이러한 결과와는 달리 본 연구에서 수행한 실험에서는 열 피로가 부가되었을 때에는 어느 정도 온도까지는 탄성계수가 증가하다가 다시 감소하는 특이한 현상을 관찰할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
• /
• pp.248-251
• /
• 2003

In this paper, it was experimented about thermal and mechanical insulation properties of a elastic epoxy specimen. We made elastic epoxy specimen adding a ratio of 0[phr], 20[phr], 35[phr] and 53[phr] with modifier to existing epoxy. Each specimen was absorbed by 25h, 196h, 361h 484h with water. In water-absorption state, it was experimented a change of heat flows by temperature of elastic epoxy and changes of thermal expansion coefficient. Also, a hardness-change of each specimen was experimented by change of water-absorption time. In this experiment DSC (Differential Scanning Calorimetry) and TMA (Thermomechanical Analysis) were used. A temperature range of DSC was changed from -0[$^{\circ}C$] to 200[$^{\circ}C$], TMA was changed from -0[$^{\circ}C$] to 350[$^{\circ}C$]. In addition, we investigated structural analysis of water absorbed specimen using SEM (Scanning electron microscope).

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권11호
• /
• pp.556-560
• /
• 2004

In this paper, thermal and structural properties of epoxy/elastomer blend were measured by DSC, TGA and FESEM. Specimens were made of dumbbell forms by the ratio of 5, 10, 15, and 20[phr] by changing elastomer content. The measuring temperature ranges of DSC were from -20[℃] to 150[℃] and heating rate was 4[℃/min]. And the measuring temperature ranges of TGA were from 0[℃] to 800[℃], and heating rate was 5[℃/min]. Also we observed structure of specimens through FESEM with magnification of 1000 times and voltage of 15[kV] by breaking quenched specimens. As experimental results, we could know that thermal and structural properties were improved according to decrease of elastomer content. Because it increased glass transition temperature, high temperature and structure of elastic epoxy.

• 대한기계학회논문집A
• /
• 제22권3호
• /
• pp.540-544
• /
• 1998

Compliance calibration method is frequently used to determine $G_IC$ from the DCB composite specimen. However, the method requires at least 4 to 5 fracture test (loading-unloading) records. In this study, $G_IC$ of unidirectional graphite/epoxy DCB composites was determined from the elastic work factor approach which uses a single fracture test record. In order to inspect the validity of the elastic work factor approach, $G_IC$ determined from the elastic work factor approach was compared to that of determined from the compliance calibration method. It was shown that $G_IC$ determined from the elastic work factor approach was comparable to that determined from the compliance calibration method. That is, the elastic work factor approach can be used to determine $G_IC$ of unidirectional graphite/epoxy DCB specimen from a single fracture record.

• Coupled systems mechanics
• /
• 제5권4호
• /
• pp.355-369
• /
• 2016

Changes in chemical structure have profound effects on the physical properties of epoxy-based materials, and eventually affect the durability of the entire system. Microscopic structural voids generally existing in the epoxy cross-linked networks have a detrimental influence on the epoxy mechanical properties, but the relation remains elusive, which is hindered by the complex structure of epoxy-based materials. In this paper, we investigate the effect of structural voids on the epoxy-based materials by using our developed mesoscale model equipped with the concept of multiscale modeling, and SU-8 photoresist is used as a representative of epoxy-based materials. Developed from the results of full atomistic simulations, the mesoscopic model is validated against experimental measurements, which is suitable to describe the elastic deformation of epoxy-based materials over several orders of magnitude in time- and length scales. After that, a certain quantity of the structure voids is incorporated in the mesoscale model. It is found that the existence of structural voids reduces the tensile stiffness of the mesoscale epoxy network, when compared with the case without any voids in the model. In addition, it is noticed that a certain number of the structural voids have an insignificant effect on the epoxy elastic properties, and the mesoscale model containing structural voids is close to those found in real systems.

• 한국정밀공학회지
• /
• 제23권11호
• /
• pp.103-107
• /
• 2006

It is well-known that the mechanical properties of MMT(montmorillonite) nanocomposites are better than those of conventional composites. In this study, tensile tests were performed to determine the effect of silane modification of MMT and its weight ratio on the tensile properties of MMT/epoxy nanocomposites. It was found that the tensile strength and the elastic modulus of MMT/epoxy nanocomposites increased with increasing weight ratio of MMT. The elastic modulus of silane-modified MMT/epoxy nanocomposites was higher than that of untreated MMT/epoxy nanocomposites, irrespective of weight ratio.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.259-260
• /
• 2008

In this paper, we fabricated elastomer epoxy specimens by added liquid elastomer to improve the mechanical and electrical properties instead of previous high-voltage epoxy materials. As increased additive contents, glass transient temperature (Tg) was continually decreased in DSC (differential scanning calorimetry). Among specimens, 15 phr sample showed the mechanical and electrical properties similar of high-voltage epoxy in modulus, break-down and arc test. From the optimized condition of elastic epoxy, we confirmed a chance of application for high-voltage materials and power electrical instruments.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.46-49
• /
• 2001

In this paper. tile validity of work factor approach was investigated to determine compressive fracture toughness of unidirectional graphite/epoxy composites under hydrostatic pressure environment. The elastic work factor was determined under various pressures as a function of delamination length. It was found that elastic work factor was not affected by hydrostatic pressure.