• 대한기계학회논문집
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• 제8권5호
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• pp.425-434
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• 1984

본 연구에서는 ［0˚/90˚］$_{2s}$, Gr/Gp 복합 적층판에 대해서 접착면의 비율과 폴리에스테르 필름의 구멍의 형상이 적층판의 인장 성질과 파괴인성에 미치는 영향에 대한 실험적인 결과를 얻고자 한다.다.

• Structural Engineering and Mechanics
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• 제57권4호
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• pp.733-762
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• 2016

Based on a reduced displacement field, a layer-wise (LW) formulation is developed for analysis of thick shell panels which is subjected to axial tension. Employing the principle of minimum total potential energy, the local governing equations of thick panel which is subjected to axial extension are obtained. An analytical method is developed for solution of the governing equations for various edge conditions. The governing equations are solved for free and simply supported edge conditions. The interlaminar stresses in the panel are investigated by means of Hooke's law and also by means of integration of the equilibrium equations of elasticity. Dependency of the result upon the number of numerical layers in the layerwise theory (LWT) is studied. The accuracy of the numerical results is validated by comparison with the results of the finite element method and with other available results in the open literature and good agreement is seen between the results. Numerical results are then presented for the distribution of interlaminar normal and shear stresses within the symmetric and un-symmetric cross-ply thick panels with free and simply supported boundaries. The effects of the geometrical parameters such as radius to thickness and width to thickness ratio are investigated on the distribution of the interlaminar stresses in thick panels.

• 대한기계학회논문집
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• 제10권2호
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• pp.198-207
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• 1986

본 연구에서는 Fig.1과 같이 시편 부위에 균일응력분포가 작용하도록 M.Arcan 등에 의해 제시된 비대칭형상의 시편고정물에 층간균열을 가진 시편을 부착한 다음 하중각도를 바꾸어가며 모우드 II뿐 아니라 혼합모우드 및 모우드 I까지도 실험 할 수 있는 실험장치를 사용하여 균열면에서의 섬유방향이 〔0/0〕이고 초기균열길이비가 0.4, 0.5, 0.6인 시편의 모우드I, 혼합모우드 및 모우드II 층간파괴인 성치들을 실험 적으로 구해 혼합모우드 파괴결정조건식들에 적용시켜 보았다. 또한 균열면에서의 섬유방향이 〔0/0〕, 〔0/30〕, 〔0/45〕및 〔0/60〕인 경우의 층간파괴인성치와 이때 의 파괴현상에 대해 관찰하였다.

• Advanced Composite Materials
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• 제16권2호
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• pp.95-113
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• 2007

Experimental investigations of interlaminar mechanical properties for carbon fiber reinforced plastic (CFRP) laminates were carried out using aramid fiber ($Kevlar^{(R)}$-29 1000d) and carbon fiber (TR40-1K 612d, Mitsubishi Rayon) stitching. Various carbon fiber (CF) stitch densities were used to prepare a number of CF stitched CFRP laminates for double cantilever beam (DCB) tests. An insert tongue-type loading fixture, developed by the Japan Aerospace Exploration Agency (formerly the National Aerospace Laboratory of Japan), was also employed in the DCB test. Interlaminar tension tests were carried out under an out-of-plane directional loading using a single CF stitch thread in the CFRP laminates. The DCB test results clarified that the relationship between the volume fractions of the CF stitch thread ($V_{ft}$) and mode I critical energy release rate ($G_{Ic}$) showed a mostly linear function with a higher gradient than that of the $Kevlar^{(R)}$ stitched CFRP laminates. The CF stitched CFRP tension test results indicated that the consumption energy per unit area ($E_i$) was larger than that of $Kevlar^{(R)}$ stitched CFRP laminates.

• 한국안전학회지
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• 제17권3호
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• pp.7-12
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• 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.

• The Korean Journal of Pain
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• 제31권2호
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• pp.87-92
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• 2018

Background: An epidural steroid injection (ESI) is a commonly administered procedure in pain clinics. An unintentional lumbar facet joint injection during interlaminar ESI was reported in a previous study, but there has not been much research on the characteristics of an unintentional lumbar facet joint injection. This study illustrated the imaging features of an unintentional lumbar facet joint injection during an interlaminar ESI and analyzed characteristics of patients who underwent this injection. Methods: From December 2015 to May 2017, we performed 662 lumbar ESIs and we identified 24 cases (21 patients) that underwent a lumbar facet joint injection. We gathered data contrast pattern, needle approach levels and directions, injected facet joint levels and directions, presence of lumbar spine disease as seen on magnetic resonance images (MRI), and histories of lumbar spine surgeries. Results: The contrast pattern in the facet joint has a sigmoid or ovoid contrast pattern confined to the vicinity of the facet joint. The incidence of unintentional lumbar facet joint injection was 3.6%. The mean age was 68.47 years. Among these 21 patients, 14 (66.7%) were injected in the facet joint ipsilaterally to the needle approach. Among the 20 patients who received MRI, all (100%) had central stenosis and 15 patients (75%) had severe stenosis. Conclusions: When the operator performs an interlaminar ESI on patients with central spinal stenosis, the contrast pattern on the fluoroscopy during interlaminar ESI should be carefully examined to distinguish between the epidural space and facet joint.

• The Korean Journal of Pain
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• 제31권4호
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• pp.277-288
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• 2018

Background: Neck and back pain are leading sources of disability placing substantial burden on health care systems. Surgical interventions in managing chronic neck pain secondary to various disorders continue to increase. Even though surgical interventions are effective, a significant proportion of patients continue to have symptomatology and develop cervical post-surgery syndrome. This study was performed to know the effectiveness of cervical interlaminar epidural injections with or without steroids. Methods: The effectiveness of fluoroscopic cervical interlaminar epidural injections in post-surgery syndrome was evaluated in a randomized, active controlled trial. The study population included 116 patients assigned to 2 groups. Group 1 received cervical interlaminar epidural injections with local anesthetic alone and Group 2 received injection with local anesthetic and steroids. The main outcomes were defined as significant improvement (greater than 50%) of pain relief using the numeric rating scale and/or functional status improvement using the Neck Disability Index (NDI). Results: Both groups had similar results with significant improvement (${\geq}50%$ pain relief and functional status improvement) in 69% of the patients in Group I, whereas, in Group II, 71% of the patients showed significant improvement at the end of 2 years. During a 2-year period, the average number of procedures was 5 to 6, with an average of approximately 12 weeks of significant improvement per procedure. Conclusions: Fluoroscopic cervical interlaminar epidural injections administered in cervical post-surgery syndrome using local anesthetic, regardless of the use of steroids, may be effective in approximately 70% of the patients at 2-year follow-up.

• Composites Research
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• 제24권5호
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• pp.34-38
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• 2011

탄소나노튜브가 발견된 이후로, 고분자 수지의 기계적, 전기적 물성을 증대시키는 보강재로서 많은 연구가 수행되어 왔다. 더 나아가, 탄소나뉴튜브를 탄소섬유복합재 (CFRP)의 기지가 되는 수지를 보강시키는 데 이용하는 연구도 최근 활발해지고 있는 추세이다. 단일벽탄소나노튜브가 각각 0.2 %, 0.5 %의 중량비로 에폭시 수지에 먼저 분산, 혼합되었다. 이 혼합액을 CFRP를 제작하는데 주로 쓰이는 방법 중 하나인 진공 수지 충전 공정법 (vacuum assisted resin transfer molding, VARTM)으로 탄소섬유 프리폼에 주입하는 방법과 습식 현장 적층법 (wet lay-up)의 두가지 다른 방법으로 복합재를 제작 하였다. 각각의 제작된 시편에 대하여, 층간전단강도 (interlaminar shear strength, ILSS)를 측정하여, 층간전단강도와 공정의 상관관계, 탄소나노튜브의 보강효과에 대하여 조사했다. 탄소나노튜브/에폭시 복합재의 경우 기계적 물성의 향상을 가져왔으나 이를 기지재로 사용한 탄소섬유복합재의 층간전단강도는 특히 VARTM 공정의 경우, 탄소나노튜브의 첨가에 따른 수지의 점도 증가로 인한 공정상의 문제로 기대만큼의 물성향상을 가져오지는 못한 것을 확인하였다.

• 대한기계학회논문집
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• 제13권5호
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• pp.911-920
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• 1989

본 연구에서는 층간균열면에서의 보 두께비를 달리함에 따라 다양한 혼합 모우드 층간파괴인성을 평가할 수 있는 Fig.1과 같은 층간균열 시편에 대해 3점 굽힘하중 하중이 작용될 때의 전체어너지방출률을 전단변형을 고려한 보이론에 의해 유도하고 이를 층간균열면에서의 보 두께비에 따라 모우드I 성분과 모우드II 성분의 분리된 형태로 나타내었다. 또 한 여러가지 시편두께에 대해 전체에너지방출률을 구해 전단변형에 의한 에너지방출률이 전체에너지방출률에 미치는 영향도 조사하였다. 그리고 층간 균열면에서의 보 두께비가 0.3, 0.5, 0.6, 0.7, 그리고 0.9인 경우의 층간균열시편에 대해 실험적으로 혼합모우드 층간 파괴인성을 평가하고 혼합 모우드 변형을 받을 때의 층간파괴 거동도 조사하였다.

• Composites Research
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• 제21권2호
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• pp.1-7
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• 2008

복합재료는 현재 항공-우주산업, 스포츠와 레저 산업에서 널리 사용되고 있으나, 흡습에 의해 기계적 성질이 저하하는 문제점을 가지고 있다. 본 연구에서는 이러한 문제점에 대한 규명을 위해 $80^{\circ}C$의 수 환경(담수/해수)에서 $100{\sim}200일$ 동안 침지/침지 - 건조한 시편으로 전단강도를 평가하였다. 그 결과, 전단강도의 하락은 초기에는 수지부의 흡습과 실란부의 흡습에 의한 물성저하 그리고 나중에는 실란부와 섬유와의 기계적 결합의 파괴가 주요원인으로 판단되었다. 결론적으로, 복합재료 내의 수분으로 인해 비가역구간을 넘어서게 되면 수분으로 인한 계면 파괴가 일어나 전단강도 회복이 어려워지는 것으로 판단된다.