http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
일방향 혼합방사형 탄소섬유/폴리아미드 6 복합재료판의 제작조건과 굽힘파괴거동
최낙삼,Choi, Nak-Sam 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.2
Unidirectional commingled-yarn-based carbon fiber(CF)/polyamide(PA) 6 composite was fabricated under molding pressures of 0.4, 0.6 and 1.0 MPa to study its flexural deformation and fracture behavior. Fiber/matrix interfacial bonding area became larger with an increase of molding pressure from 0.4 to 0.6 MPa. For molding pressures .geq. 0.6 MPa, good flexural performance of similar magnitudes was attained. For the fracture test, four kinds of notch direction were adopted : edgewise notches parallel (L) and transverse (T) to the major direction of fiber bundles, and flatwise notches parallel(ZL) and perpendicular(ZT) to this direction. Nominal bend strength for L and ZL specimens exhibited high sensitivity to notching. ZL specimens revealed the lowest values of the critical stress intensity factor $K_c$ which was slightly superior to those of unfilled PA6 matrix. Enlargement of the compression area for T specimens was analyzed by means of the rigidity reduction resulting from the fracture occurrence.
모드 I 하중조건하에 있는 다방향 적층 복합재료의 층간파괴거동
최낙삼,Choi, Nak-Sam,Kinloch, A.J. 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
The delamination fracture of multidirectional carbon-fiber/epoxy laminates under the Mode I condition has been studied using the modified beam analysis for a fracture mechanics approach. It was found that the variation of fracture energy $G_IC$ with increasing length of the propagating crack exhibited a minimum for the pure interlaminar fracture and a maximum for the intraply fracture,i.e. a rising "R-curve", which was strongly affected by the degree of fiber bridging and crack-tip splitting arising in the global delamination. The maximum $G_IC$ value was significantly dependent on such types of delamination as no crack jumping, crack jumping into the adjacent ply and edge-delamination. It was shown also that the value of "effective flexural modulus" estimated from the modified beam analysis increased much with the development of fiber bridging behind the crack tip.ehind the crack tip.
서모트로픽 액정폴리머와 폴리아미드6으로 성형된 얇은 복합재료의 미세구조형태
최낙삼,최기영,하성규,Choe, Nak-Sam,Choe, Gi-Yeong,Ha, Seong-Gyu 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.7
Microstructural morphology of molded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) has been studied as a function of epoxy fraction. Injection-moulding of a thin composite plaque at a temperature below the melting point of the LCP fibrils by suing the extruded LCP/PA6 pellets produced multi-layered structures: 1) the surface skin layer with thickness of 65-120 ym exhibiting a transverse orientation, 2) the sub-skin layer with an orientation perpendicular to the surface skin, i.e. in the flow direction, 3) the core layer with arc-curved flow patterns. Similar microstructural orientations were observed in the respective layers for the composite plaques with different fractions of epoxy.
최낙삼,Choe, Nak-Sam 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.11
The delamination behavior of multidirectional carbon-fiber/epoxy composite laminates under 10NA intermediate and high rates of test, up to rate of about 11.4m s has been investigated using the double cantilever beam specimens. The mode I loading under rates above l.0m/s showed considerable dynamic effects on the load-time curves and thus higher values of the average crack velocity than that expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Based on the assumption of constant flexural modulus, values of $G_{IC}$ at the crack initiation and arrest were decreased with an increase of the test rate up to 5.7m/s, but the maximum $G_{IC}$ was increased at 11.4m/s.
복합 적층 박판의 열응력 파손에 대한 진동 활용 비파괴평가
이성혁,이정기,최낙삼 韓國非破壞檢査學會 1999 한국비파괴검사학회지 Vol.19 No.5
두께 1mm의 얇은 복합적층판의 자유경계단부에서 열응력으로 인해 발생하는 미세손상을 진동거동과 관련된 비파괴평가의 가능성을 연구하였다. 유한요소 열응력해석을 통해 예상되는 손상발생영역을 초음파 C-스캔과 광학현미경을 이용하여 관찰하였다. 사인 스윕시험을 이용한 적층보 시험편의 횡진동 해석결과, 미세한 내부손상으로 인해 고유주파수가 확실히 감소하였으며 감쇠비도 상당히 증가하였다. 길이가 짧은 적층보 시험편과 2차 모드의 공진주파수를 이용하여 얇은 적층판에서 열응력으로 유기된 미세손상을 매우 민감하게 평가할 수 있음을 알았다. A feasibility investigation on vibration-based nondestructive evaluation of thermal stress-induced micro failure in the free edge region of thin composite laminates(1mm thick) has been carried out. The failure occurrence and damage zone, which were predicted by the three-dimensional finite-element thermal stress analysis, were observed using the ultrasonic C-scan and optical microscopy. Analysis of the vibration spectrum measured from the laminate beam specimens by the vibration sweep test exhibited that the obvious decrease in resonancy frequency and some considerable increase in damping factor were associated with the micro-failure formation. The vibration technique utilizing short beam and high resonant frequency was found to be very sensitive to the thermal stress-induced damage in the thin laminates.