Effect of Embedded Optical Fiber Sensors on Transverse Crack Spacing of Composite Laminates

In this study the effect of the presence of embedded optical fiber sensors on the transverse cracking of cross-ply laminates was investigated. The transverse crack spacing of cross-ply laminates with embedded optical fiber sensors was predicted using modified shearlag analysis considering the presence of optical fibers and compared with experimental results. The effect of the orientation and quantity of optical fibers was evaluated and the effect of coating of optical fiber was also investigated. Specimens were made with transparent Glass/Epoxy prepreg because the transverse crack and other damages such as delimitation, splitting and bleeding of laser can be examined directly and visually. It has been found that the transverse crack spacing was not affected significantly by the embedding of optical fibers at low volume fraction of optical fibers. However, the following trend was found that specimens with embedded optical fibers showed earlier crack initiation and smaller crack spacing than specimens without embedded optical fibers. The theoretical crack spacing evaluated from the shear lag analysis showed good agreements with experimental results

Fatigue crack growth behavior and crack monitoring of cracked aluminum plate with bonded composite patch repair

학위논문(박사) - 한국과학기술원 : 기계공학전공, 2002.2, [ viii, 118 p. ]한국과학기술원 : 기계공학전공

Effect of embedded optical fibers on matrix crack spacing in smart structures

학위논문(석사) - 한국과학기술원 : 기계공학과, 1995.2, [ ii, 54 p. ]한국과학기술원 : 기계공학과

Effect on the structural integrity and fatigue damage monitoring of smart composite structures with embedded intensity based optical fiber sensors

본 연구에서는 복합재료에 삽입된 광섬유센서의 인장하중하에서의 정적 물성치와 피로하중하에서의 동적 물성치를 실험적인 방법과 유한요소해석을 통하여 고찰하였다. 결과에 의하면 삽입된 광섬유센서는 인접한 강화섬유에 수직한 방향으로 삽입된 피로하중의 경우를 제외하고 복합재료의 기계적인 물성치에 큰 영향을 끼치지 않는다고 결론지을 수 있다. 광강도형 광섬유센서를 복합재료 적층판에 삽입하여 복합재 적층판의 강성저하를 측정함으로써 직교적층판 피로손상을 검출하였다. 이 실험의 결과에 의하면 광강도형 광섬유센서는 간단하고 저렴한 장치와 측정된 신호의 복잡한 후처리 과정이 필요 없다는 장점으로 인하여 구조물의 강성저하를 측정하여 피로손상을 감시하는데 있어서 큰 잠재력을 가진다고 할 수 있다. 또한 삽입된 광강도형 광섬유센서는 우수한 내 피로성과 넓은 강성측정 범위를 보였다

Finite Element Analysis of Carbon Steel according to Shape and Distribution of Phase

In this study, the stress-strain relations of steels have been calculated as a function of microstructural morphologies of each phase by use of FEM program(i.e. ABAQUS). The mechanical behavior of low carbon steels is affected by the microstructural factors such as yield ratio, volume fraction, shape and distribution of each phase and so on. The effects of shape, volume fraction and yield ratio of each phase on the mechanical behavior were analyzed by using unit cell and whole specimen size models. Results obtained are summarized as follows. As the yield ratio of hard phase to that of soft phase and volume fraction of hard phase were increased, stress level of flow curves were increased. It was found that in whole specimen size model, as the particle size was decreased, higher stress level was shown. Lastly the relationship between microstructure and tensile properties was examined by using the steels with various microstructural morphologies

Staged Approach for Stent-Assisted Coiling of Cerebral Aneurysms after Failure of Initial Intra-Saccular Catheterization

Purpose: Microcatheter navigation into an aneurysm sac can present difficulties through negative interactions between the deployed stent mesh and microcatheter. We hypothesized that endothelialization of the stent mesh would minimize these interactions. We aimed to assess the feasibility of staged coiling after stenting by reviewing our experiences with unavoidably staged embolization cases.Materials and Methods: Between 2011 and 2019, 7 patients (mean age 57.2 years, range 49?76 years) including 5 females, experienced 9 unruptured aneurysms treated with staged stenting and coiling due to unstable microcatheter navigation into the aneurysm after stent placement. The aneurysms were in the paraclinoid internal carotid artery (ICA) (n=3), ophthalmic origin ICA (n=1), superior cerebellar artery origin (n=2), basilar tip (n=2), and the middle cerebral artery bifurcation (n=1). The stents used were the Neuroform Atlas (n=4), Neuroform EZ (n=2), and Low-profile Visualized Intraluminal Support Blue (n=1).Results: The mean interval between stenting and coiling was 15 weeks (range, 12?21 weeks). The average navigation time between the first roadmap imaging and microcatheter insertion in the sac was 14 minutes (range, 8?20 minutes). One aneurysm was occluded without further coiling on follow-up. Staged coiling successfully treated the remaining aneurysms (n=8). No complications were identified.Conclusion: In cases of difficult intra-saccular catheterization, intentional staged coiling may be a feasible option for stent-assisted coiling of the cerebral aneurysms

Rare Neurovascular Diseases in Korea: Classification and Related Genetic Variants

Rare neurovascular diseases (RNVDs) have not been well-recognized in Korea. They involve the central nervous system and greatly affect the patients' lives. However, these diseases are difficult to diagnose and treat due to their rarity and incurability. We established a list of RNVDs by referring to the previous literature and databases worldwide to better understand the diseases and their current management status. We categorized 68 RNVDs based on their pathophysiology and clinical manifestations and estimated the prevalence of each disease in Korea. Recent advances in genetic, molecular, and developmental research have enabled further understanding of these RNVDs. Herein, we review each disease, while considering its classification based on updated pathologic mechanisms, and discuss the management status of RNVD in Korea