• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.93-96
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• 2000

The theory of non-prismatic folded plate structures was reported by the senior author in 1965 and 1966. Fiber reinforced composite materials are strong in tension. The structural element for such tension force is very thin and weak against bending because of small bending stiffnesses. Naturally, the box type section is considered as the optimum structural configuration because of its high bending stiffnesses. Such structures can be effectively analyzed by the folded plate theory with relative ease. The "hollow" bending member with uniform cross-section can be treated as prismatic folded plates which is a special case of the non-prismatic folded plates. Tn this paper, the result of analysis of a folded plates with one box type uniform cross-section is presented. Each plate is made of composite laminates with fiber orientation of [ABBCAAB]$_r$, with A=-B=$45^{\circ}$, and C=$90^{\circ}$. The influence of the span to depth ratio is also studied. When this ratio is 5, the difference between the results of folded plate theory and beam theory is 1.66%. is 1.66%.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.124-132
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• 2003

This paper described the structural design and the fabrication procedure of KSR-III composite pressure tank. The type of the composite pressure tank was COPV(Composite Overwrapped Pressure Vessel). A non-load sharing liner was made of aluminum 6061-0 and the liner provided a helium gas seal. The composite pressure tank was winded using T700 carbon/epoxy on the liner. Because the aluminum liner was thin, multiple cure cycles were applied to the filament winding technique. The multiple cure cycles prevented the liner-cylinder from losing a circular shape. A fitting force at the metallic boss was spread to the carbon fiber by a boss ring. The boss ring also prevented a local deformation at the boss part.

• Journal of Mechanical Science and Technology
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• v.19 no.4
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• pp.947-957
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• 2005

In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

• Journal of Chest Surgery
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• v.26 no.6
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• pp.457-462
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• 1993

We retrospectively studied 34 patients who underwent operations of ascending aortic aneurysm and aortic valve replacement from August 1979 to July 1992 at the Yonsei Cardiovascular Center. Eight patients underwent supracoroanry non-composite graft replacement and separate aortic valve replacement[group I]. Twenty six patients underwent valved composite graft replacement with reimplantation of coronary arteries[group II]. Two cases in group II died within 1 month after the operation. Among the 32 survivors 28 patients have been followed up for an average of 59 months ranging from 1 months to 159 months. During the follow up periods, a pseudoaneurysm around the ascending aorta and a newly developed dissecting aneurysm in remaining aorta were noted in group II. There were 6 late deaths: 2 cases in group I and 4 cases in group II. Three cases among the 6 late deaths have stigmata of Marfan`s syndrome[1 cases in group I and 2 case in group II]. There was no statistically significant difference in actuarial survival rates between group I and group II[p > 0.05]. This study suggests that non-composite supracoronary graft interposition with separate aortic valve replacement is a safe surgical technique in patients who have normal aortic annulus and normal position of coronary ostia. However in degenerative disease such as cystic medial necrosis, composite graft replacement is recommended because this procedure eliminates entire abnormal tissue.But it seems to be important that the suture technique and strict follow-up in patients with diseased aortic wall.

• Advances in aircraft and spacecraft science
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• v.3 no.1
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• pp.29-43
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• 2016

Composite materials are rapidly gaining popularity as an alternative to metals for structural and load bearing applications in the aerospace, automotive, alternate energy and consumer industries. With the advent of thermoplastic composites and advances in recycling technologies, fully recyclable composites are gaining ground over traditional thermoset composites. Stamp forming as an alternative processing technique for sheet products has proven to be effective in allowing the fast manufacturing rates required for mass production of components. This study investigates the feasibility of using the stamp forming technique for the processing of thermoplastic, recyclable composite materials. The material system used in this study is a self-reinforced polypropylene composite material (Curv$^{(R)}$). The investigation includes a detailed experimental study based on strain measurements using a non-contact optical measurement system in conjunction with stamping equipment to record and measure the formability of the thermoplastic composites in real time. A Design of Experiments (DOE) methodology was adopted to elucidate the effect of process parameters that included blank holder force, pre heat temperature and feed rate on stamp forming. DOE analyses indicate that feed rate had negligible influence on the strain evolution during stamp forming and blank holder force and preheat temperature had significant effect on strain evolution during forming.

• Journal of Korean society of Dental Hygiene
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• v.19 no.2
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• pp.307-315
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• 2019

Objectives: The aim of this study was to investigate the characterization of composite resin inlay surface with silane and non-thermal atmospheric pressure plasma treatment. Methods: Composite resin inlay was used as a specimen, which was treated by sandblasting + silane and sandblasting + plasma. The untreated specimens were assigned to the control group. Specimens were analyzed for surface roughness, color change, and chemical composition. Statistical analyses were performed using one-way ANOVA test (p<0.05). Results: The present findings showed that the roughness and color changes of the plasma-treated surface were significantly lower than those of the silane-treated surface. In addition, a change in the chemical composition was observed on the plasma-treated surface. Conclusions: Based on the results, non-thermal atmospheric pressure plasma could be a potential tool for the cementation of composite resin inlay.

• Steel and Composite Structures
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• v.42 no.2
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• pp.151-159
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• 2022

This study discusses a hypothetical method for tracking the propagation damage of Carbon Reinforced Fiber Plastic (CRFP) components underneath vibration fatigue. The High Cycle Fatigue (HCF) behavior of composite materials was generally not as severe as this of admixture alloys. Each fissure initiation in metal alloys may quickly lead to the opposite. The HCF behavior of composite materials is usually an extended state of continuous degradation between resin and fibers. The increase is that any layer-to-layer contact conditions during delamination opening will cause a dynamic complex response, which may be non-linear and dependent on temperature. Usually resulted from major deformations, it could be properly surveyed by a non-contact investigation system. Here, this article discusses the scanning laser application of that vibrometer to track the propagation damage of CRFP components underneath fatigue vibration loading. Thus, the study purpose is to demonstrate that the investigation method can implement systematically a series of hypothetical means and dynamic characteristics. The application of the relaxation method based on numerical simulation in the Artificial Intelligence (AI) Evolved Bat (EB) strategy to reduce the dynamic response is proved by numerical simulation. Thermal imaging cameras are also measurement parts of the chain and provide information in qualitative about the temperature location of the evolution and hot spots of damage.

• Steel and Composite Structures
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• v.18 no.4
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• pp.873-887
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• 2015

The continuous composite I-girder should have a sufficient rotation capacity (or ductility) to redistribute the negative bending moment into an adjacent positive bending moment region. However, it is generally known that the ductility of the high strength steel is smaller than that of conventional steel, and application of high strength steel can cause ductility problems in a negative moment region of the I-girder. In this study, moment redistribution of the continuous composite I-girder with high strength steel was studied, where high strength steel with yield stress of 690 MPa was considered (the ultimate stress of the steel was 800 MPa). The available and required rotation capacity of the continuous composite I-girder with high strength steel was firstly derived based on the stress-strain curve of high strength steel and plastic analysis, respectively. A large scale test and a series of non-linear finite element analysis for the continuous composite I-girder with high strength steel were then conducted to examine the effectiveness of proposed models and to investigate the effect of high strength steel on the inelastic behavior of the negative bending moment region of the continuous composite I-girder with high strength steel. Finally, it can be found that the proposed equations provided good estimation of the requited and available rotation capacity of the continuous composite I-girder with high strength steel.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.315-317
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• 2013

To analyze vertical fire spreadability of aluminum composite panel, real scale test of aluminum composite panel and fire retardant aluminum composite panel was conducted as well as analysis of domestic code, test and domestic reaserch resulted in following conclusion. Fire spread risk assessment of aluminum Composite Panel is impossible with the current regulations (Cone Calorimeter Test). It need to changes of regulatory and combustion expanded risk assessment and regulatory changes in the test methods need to be judged. Also, there is quite a big different between the general aluminum Composite Panel and semi-non combustible of aluminum Composite Panel. However it is also deemed to be danger when present in the sidewall to the top consisting of fire spread. From now on, it is needed the study about interpretation of fire spread and sidewall of vertical fire spread analysis not only experiments for aluminum Composite Panel.

• Steel and Composite Structures
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• v.21 no.6
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• pp.1307-1325
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• 2016

Nonlinear behavior of two-span, continuous composite steel-concrete girders strengthened with Carbon Fiber Reinforced Polymers (CFRP) bonded to the top of concrete slab over the negative moment region was evaluated using a non-linear Finite Element (FE) model in this paper. A three-dimensional FE model of continuous composite girder using commercial software ABAQUS simulated and validated with experimental results. The interfacial regions of the composite girder components were modeled using suitable interface elements. Validation of the proposed numerical model with experimental data confirmed the applicability of this model to predict the loading history, strain level for the different components and concrete-steel relative slip. The FE model captured the different modes of failure for the continuous composite girder either in the concrete slab or at the interfacial region between CFRP sheet and concrete slab. Through a parametric study, the thickness of CFRP sheet and shear connection required to develop full capacity of the continuous composite girder at negative moment zone have been investigated. The FE results showed that the proper thickness of CFRP sheet at negative moment region is a function of the adhesive strength and the positive moment capacity of the composite section. The shear connection required at the negative moment zone depends on CFRP sheet's tensile stress level at ultimate load.