• 한국안전학회지
• /
• 제17권3호
• /
• pp.7-12
• /
• 2002

The object of this paper is to investigate collapse characteristics of CF/Epoxy(Carbon Fiber/Epoxy resin) composite tubes on the change of interlaminar number and fiber orientation angle of outer and to evaluate reappearance of collapse characteristics on the change of tension strength of fibers under static and impact axial compression loads. When a CF/Epoxy composite tube is mushed, static/impact energy is consumed by friction between the loading plate and the splayed fiends of the tube, by fracture of the fibers, matrix and their interface. In general, CF/Epoxy tube with 6 interlaminar number(C-type) absorbed more energy than other tubes(A, B, D-types). The maximum collapse load seemed to increase as the interlaminar number of such tubes increases. The collapse mode depended upon orientation angle of outer of CF/Epoxy tubes and loading status(static/impact). Typical collapse modes of CF/Epoxy tubes are wedge collapse mode, splaying collapse mode and fragmentation collapse mode. The wedge collapse mode was shorn in case of CF/Epoxy tubes with 0$^{\circ}$ orientation angle of outer under static and impact loadings. The splaying collapse mode was shown in only case of CF/Epoxy tubes with 90$^{\circ}$ orientation angie or outer under static loadings, however in impact tests those were collapsed in fragmentation mode. So that CF/Epoxy tube with 6 interlaminar number and 90$^{\circ}$ outer orientation angle presented to the optimal collapse characteristics.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1993년도 추계학술대회 논문집
• /
• pp.656-659
• /
• 1993

The failure phenomenon of Dual Basalt Fibers Reinforced Epoxy Composites(DFC) under tensile load was studied using acoustic emission(AE) technique. AE amplitude and AE energy were mainly associated with the internal microscopic failure mechanism of DFC specimen, such as fiber fracture, matrix cracking, and fiber/matrix debonding. Fiber failures in the DFC specimens were distinguishable by showing the highest AE energy amplitude. They were dependant on the fiber diameters. Matrix cracking was determined from the relatively lower AE amplitude and AE energy, whereas fiber/matrix debonding could not be successfully isolated. AE method, however, can be applicable to the fragmentation method for interfacial strength(IFSS) in DFC specimens with adjusting the threshold to isolate fiber breaks from matrix crack and debonding.

• 접착 및 계면
• /
• 제2권1호
• /
• pp.9-17
• /
• 2001

전기저항 측정법과 인장 및 압축 시험을 이용하여, 탄소섬유/에폭시 복합재료의 정화특성과 계면물성을 평가하였다. 계면이 존재하지 않는 탄소섬유 자체만을 사용했을 경우에는 경화 초기와 최종단계의 저항차이는 없었으며, 계면이 존재하는 탄소섬유/에폭시 시편의 경우에는 매트릭스 경화 수축에 의해 저항차가 크게 나타났다. 인장 하충하의 저항 변화 측정에서, 전기증작된 시편은 섬유의 첫 파단에 의해 저항이 무한대로 도달하는 시간이 미처리에 비해 다소 지연되는 현상을 보였다. 인장 및 압축 시험에서 표면처리된 시연은 미처리섬유에 비해 계면전단 강도가 현저히 크게 증가하였다. 인장의 경우, 미처리 섬유에서는 debonding 형태, 그리고 표면처리된 섬유에서는 cone 형태의 판단이 관찰되었다. 압축에서는 부러진 섬유 끝에서 대각선으로 미끄러지는 파단 현상이 두 경우 모두에서 나타났는데, 미처리섬유는 창 끝과 같은 예리한 파단이 일어나며, 전기증착된 섬유는 다소 둔한 판단이 나타났다. 이를 통해 전기증착에 의한 표면처리가 계면접착력과 미세파괴구조에 인장 및 압축하에서 각각 다른 영향을 주는 것을 확인하였다.

• Macromolecular Research
• /
• 제8권4호
• /
• pp.153-164
• /
• 2000

By electrodeposition (ED) using a monomeric- and two polymeric coupling agents, the interfacial shear strength (IFSS) of carbon fiber/epoxy composites was investigated by fragmentation test. ED results were compared with the dipping and the untreated cases under dry and wet conditions. Multi-fiber composites (MFC) were used for the direct comparison for the untreated and the treated cases. Various treating conditions including time, concentration and temperature were evaluated, respectively. Under dry and wet conditions ED treatment exhibited much higher IFSS improvement compared to the dipping and the untreated cases. Monomeric- and polymeric coupling agents exhibited the comparative IFSS improvement. Adsorption mechanism between coupling agents and carbon fiber was analyzed in terms of the electrolyte molecular interactions during ED process based on to the chain mobility. The microfailure modes occurring from the fiber break, matrix and interlayer cracks were correlated to IFSS.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
• /
• pp.199-202
• /
• 2002

Interfacial properties and electrical sensing for fiber fracture in carbon and SiC fibers/epoxy composites were investigated by the electrical resistance measurement and fragmentation test. As fiber-embedded angle increased, interfacial shear strength (IFSS) of two-type fiber composites decreased, and the elapsed time was long to the infinity in electrical resistivity. The initial slope of electrical resistivity increased rapidly to the infinity at higher angle, whereas electrical resistivity increased gradually at small angle. Furthermore, both fiber composites with small embedded angle showed a fully-developed stress whitening pattern, whereas both composites with higher embedded angle exhibited a less developed stress whitening pattern. As embedded angle decreased, the gap between the fragments increased and the debonded length was wider for both fiber composites. Electro-micromechanical technique can be a feasible nondestructive evaluation to measure interfacial sensing properties depending on the fiber-embedded angle in conductive fiber reinforced composites.

• 한국자동차공학회논문집
• /
• 제10권4호
• /
• pp.149-157
• /
• 2002

This paper is to investigate collapse mechanisms of CFRP(Carbon Fiber Reinforced Plastics)composite tubes and to evaluate collapse characteristics on the change of interlaiminar number and ply orientation angle of outer under static and impact axial compression loads. When a CFRP composite tube is crushed, static/impact energy is consumed by friction between the loading plate and the splayed fronds of the tube, by fracture of the fibers, matrix and their interface. These are associated with the energy absorption capability. In general, CFRP tube with 6 interlaminar number(C-type), absorbed more energy than other tubes(A, B, D-types). The maximum collapse load seemed to increase as the interlaminar number of such tubes increases. The collapse mode depended upon orientation angle of outer of CFRP tubes and loading status(static/impact). Typical collapse modes of CFRP tubes are wedge collapse mode, splaying collapse mode and fragmentation collapse mode. The wedge collapse mode was shown in case of CFRP tubes with 0° orientation angle of outer under static and impact loadings. The splaying collapse mode was shown in only case of CFRP tubes with 90°orientation angle of outer under static loadings, however in Impact tests those were collapsed in fragmentation mode .

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
• /
• pp.42-45
• /
• 2005

Interfacial evaluation of various combinations of both Flax and Hemp fibers/polypropylene were performed by using micromechanical test and nondestructive acoustic emission (AE). It can be because interfacial adhesion between the natural fiber surface and matrix plays an important role in controlling the overall mechanical properties of polymer composite materials by transferring the stress from the matrix to the fiber. It is necessary to characterize the interphase and the level of adhesion to understand the performance of the composites properly. Microfailure mechanism of single Flax fiber bundles were investigated using the combination of single fiber tensile test and nondestructive acoustic emission. Microfailure modes of the different natural fiber/polypropylene systems were observed using optical microscope and determined indirectly by AE and their FFT analysis.

• 한국축산식품학회지
• /
• 제39권6호
• /
• pp.988-999
• /
• 2019

To investigate the relationship between muscle fiber characteristics and meat quality traits by age of Korean native black goat (KNBG), four muscles (longissimus dorsi, LD; psoas major, PM; semimembranosus, SM; gluteus medius, GM) were obtained from five adult goat (AG; 18 months old) and five young goat (YG; 9 months old). PM muscle had the highest fiber number percentage (FNP) and fiber area percentage (FAP) of type I, followed by SM, GM, and LD muscles. FNP and FAP of type IIB were significantly (p<0.001) higher in AG than those in YG. YG had higher L^* values but lower b^* values than AG. The highest L^* and b^* values were observed in LD muscle (p<0.001). Age and muscle type had detrimental (p<0.001) effect on shear force and collagen content for all muscle in AG as compared to YG. YG had significantly (p<0.001) higher myofibrillar fragmentation index (MFI) than AG for all four muscles. These results suggest that muscle fiber compositions of different muscle types of KNBG depend on age, resulting in variations of meat color, MFI, collagen content, and shear force.

• 한국섬유공학회:학술대회논문집
• /
• 한국섬유공학회 1997년도 춘계학술발표회 논문집
• /
• pp.26-31
• /
• 1997

유리섬유/nylon 6 복합재료의 계면결합강도를 증가시키기 위하여 r-APS(r-Aminopropyltriethoxysilane)로 유리섬유의 표면을 처리 하였다. 이때 표면처리의 최적 조건을 찾기위해서 처리후 기기분석과 계면결합강도 측정 등을 하였다. 농도, pH, 처리시간, 온도를 변화시키면서 표면처리를 한 후 흡착량을 살펴본 결과 처리 농도에 의해서는 흡착량이 단조증가하였으며 처리시간에 따라서는 5분정도에서, 처리온도에 의해서는 30C 부근에서 최대 흡착량을 보였다. 또한 pH에 따른 흡착량은 silane의 고유 pH인 10.5부근에서 최대치를 나타냈다. FR-IR 분석에 의하면 NH2의 NH3 bending mode가 1607cm-1, 1575cm-1에서 나타났으며 SiOH의 SiO band는 960cm-1에서 나타났다. XPS를 통해서는 N ls와 Si 2p의 존재를 확인할 수 있었다. 표면처리된 유리섬유와 matrix인 nylon 6를 이용해 단섬유내장시편을 만들어 fragmentation test를 한 결과 계면결합강도는 약 5분의 처리시간과 1%(wt%)의 농도에서 최대값을 보였다.

• Annals of Clinical Neurophysiology
• /
• 제9권2호
• /
• pp.43-50
• /
• 2007

Analysis of intraepidermal nerve fibers using skin biopsy is a recently developed technique, providing diagnostic information on small fiber neuropathies. The specimens are obtained by 3 mm punch biopsy, which is safe and minimally invasive. Immunohistochemical staining by Protein gene product (PGP) 9.5 demonstrate not only intraepidermal nerve fibers but dermal structures, such as sweat gland and erector papillae. Up to now, many studies agree that intraepidermal nerve fiber density is dramatically reduced in various sensory neuropathies. The utility of density measure was confirmed with high sensitivity in the diagnosis of sensory neuropathy, comparable to sural nerve biopsy or quantitative sensory testing. Besides quantitative methods, morphological changes like axonal swelling and fragmentation can be used as predegenerative markers. This article reviews the technique of skin biopsy and clinical and experimental usefulness of skin biopsy in diagnosing and monitoring peripheral neuropathies.