• Computational Structural Engineering
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• v.9 no.4
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• pp.15-26
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• 1996

항공기용 복합재료는 여전히 많은 응용의 여지를 갖고 있으나 또한 시급히 해결하여야 할 많은 기술적인 문제점을 갖고 있다. 즉 복합재료 항공기용 구조물은 반드시 인증 절차를 밟아야 실제 항공기에 장착/판매될 수 있는데 수치해석 기법에 의한 구조해석을 거친 기본/상세 설계과정과 성형 제작된 실물 구조물에 대해 가혹환경 조건하(95% 상대습도, 70.deg. C 온도에서 30일간의 방치)에서 설계에서 제시한 최대 하중의 150%를 견디어야 하는 까다로운 full-scale testing 및 각종 복합재료관련 coupon test(표 7 참조)들을 수행하여야 한다. 이와 같은 기술적인 문제점들은 향후 연구결과에 따라 충분히 극복할 수 있으나 이와 더불어 현재 각각의 항공기 제작사가 보유하고 있는 material specification, design manual, process standard 등의 규격이 전세계적으로 통일될 수 있는 제도적인 보완이 뒷받침 된다면 복합재료의 응용도 훨씬 앞당겨질 수 있을 것으로 예상된다.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.42-48
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• 2009

There are a number of factors affecting the continued airworthiness of composite structure. Unlike metal structure, damages made in manufacturing processes or maintenance repair procedures need to be considered. The different levels of degradation and damage, which may occur, must be considered for structural substantiation of static strength, stiffness, flutter, and damage tolerance. This can start with an evaluation of environmental effects for the particular composite material. Matrix-dominated composite properties, such as compressive strength, are most sensitive to moisture absorption and temperatures. Static strength substantiation includes the smaller damages that will not be detected in production or maintenance inspection while damage tolerance addresses larger damages that need to be repaired once discovered. In this paper, we intend to list the airworthiness regulations and advisory circular that are deemed closely related to the certification of composite airplanes.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.203-206
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• 2005

The objective of study on composite cylinder for alternative fuel vehicle is to develop safe, efficient, and commercially viable, on-board fuel storage system for the fuel cell vehicle or natural gas vehicle that use highly compressed gaseous fuel such as hydrogen or natural gas. This study presents the whole procedure of development and certification of a type 3 composite cylinder of 207bar service pressure and 70 liter water capacity, which includes design/analysis, processing of filament winding, and validation through various testing and evaluation. Design methods of liner configuration and winding patterns are presented. Three dimensional, nonlinear finite element analysis techniques are used to predict burst pressure and failure mode. Design and analysis techniques are verified through burst and cycling tests. The full qualification test methods and results for validation and certification are presented.

• Composites Research
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• v.25 no.4
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• pp.105-109
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• 2012

Recently, development of a small aircraft has been carried out for the BASA(Bilateral Aviation Safety Agreement) program in Korea. This aircraft adopted all composite structures for environmental friendly by low fuel consumption due to its lightness behavior. However the composite structure has disadvantage which is very weak against impact damages. Therefore, damage allowable design of aircraft structure must be performed considering compressive fracture strength. This point is very important for certification of composite structure aircraft. In this paper, it is performed the research on damage tolerance of thick laminate adopting aircraft structure. The damage tolerance of three different types of thick laminates such as no damage, open hole and impact damage is evaluated under compression loading.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.1-7
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• 2017

The development of effective design allowable values for unmanned composite aircraft is an issue of paramount concern for the industry. The application of conventional manned aircraft structural certification methods to unmanned aircraft such as prototype and technology demonstrators, can lead to excessively long development time and costs. In this paper, the determining method of composite structure design allowable values for light composite unmanned aircraft is presented to reduce to the structural weight. This paper seeks to show the applicability of composite B-basis material values as a design allowable of light composite unmanned aircraft structures. A review of different civil and UAV targets failure probability is given. From the results, the researchers can know that the requirements of light composite unmanned aircraft design allowable should be alleviated, compared to manned composite aircrafts.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.933-935
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• 2017

This paper deals with the influence of fungi for the thermal protective cork-based exterior insulator which protect a missile system from aerodynamic loads and heating during flight of missile. We consider the adhesion of cork-based composite on the composite motor case which fabricated by filament winding process. We also consider the importance of the requirement analysis for effective, successful system development under given system conditions. In order to develop the basic requirement analysis for the thermal protective cork-based exterior insulator, an experimental requirement analysis was accomplished, and some experimental comparing results, the study for preventing fungi are presented.

• Composites Research
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• v.24 no.1
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• pp.10-16
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• 2011

Many tests are required to predict the fatigue life of composite laminates made of various materials and having different layup sequences. Aiming at reducing the number of tests, a methodology was presented in this paper to predict fatigue life of composite laminates based on fatigue life prediction of constituents, i.e. the fiber, matrix and interface, using micromechanics of failure. For matrix, the equivalent stress model which is generally used for isotropic materials was employed to take care of multi-axial fatigue loading. For fiber, a maximum stress model considering only stress along fiber direction was used. The critical plane model was introduced for the interface of the fiber and matrix, but fatigue life prediction was ignored for the interface since the interface fatigue strength was presumed high enough. The modified Goodman equation was utilized to take into account the mean stress effect. To check the validity of the theory, the fatigue life of three different GFRP laminates, UDT[$90^{\circ}2$], BX[${\pm}45^{\circ}$]S and TX[$0^{\circ}/{\pm}45^{\circ}$]S was examined experimentally. The comparison between predictions and test measurements showed good agreement.

• New & Renewable Energy
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• v.4 no.3
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• pp.45-50
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• 2008

GFRP based composite rotor blades were developed for 750 kW & 2 MW wind turbines. The blade sectional geometry was designed to have a general shell-spar and shear web structure. For verifying the structural safety under all relevant extreme loads specified in the GL guidelines, the structural analysis of the rotor blades was performed using commercial FEM codes. The static load carrying capacity, blade tip deflections and natural frequencies were evaluated to satisfy the strength and stability requirements. Full-scale proof tests of rotor blades were carried out with optical fiber sensors for real-time condition monitoring. Finally, the prototype of each rotor blade passed all proof tests for GL certification.

• Korean Journal of Construction Engineering and Management
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• v.9 no.4
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• pp.84-91
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• 2008

"Eco-friendly construction" is an emerging issue in the building industry. Main purpose of the eco-friendly construction is to sustain the health and environment of building residents and to minimize the harmful effect on their environment. Apartment residents have great concern on eco-product, since many cases are reported that Sick Building Syndrome is caused by toxic substance from building materials. Environmental performance is to meet through using the highest grade eco-friendly materials. However, generally eco-friendly materials are more expensive than normal materials, Therefore, using eco-friendly materials at public housing project is limited to economical aspect. The purpose of this paper is development of eco-friendly material selection model considered cost efficiency. The selection of Eco-friendly finishing materials and their methods are constructed to consider environmental performance level and cost index compositively. Development of eco-friendly material selection method is economic and reasonable one when public housing is constructed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.7 s.166
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• pp.1104-1111
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• 1999

A brake pedal for the flight control system of the Korean primary trainer is developed using composite material. The development includes the structural design, stress analysis, manufacturing and the qualification tests. A FEM analysis is used for the structural design and stress analysis. Autoclaving process is used to fabricate the composite brake pedal. For the qualification tests, modular fixtures are developed and applied. It is shown that the composite brake pedal developed meets all the structural integrity requirements specified in the military specification for aircraft parts.