• Composites Research
• /
• v.21 no.5
• /
• pp.15-22
• /
• 2008

This paper describes the results of structural integrity and crashworthiness of Automatic Guideway Transit(AGT) vehicle made of sandwich composites. The applied sandwich composite of vehicle structure was composed of aluminum honeycomb core and WR580/NF4000 glass fabric/epoxy laminate composite facesheet. Material testing was conducted to determine the input parameters for the composite facesheet model, and the effective equivalent damage model fer the orthotropic honeycomb core material. The finite element analysis using ANSYS v11.0 was dont to evaluate structural integrity of AGT vehicle according to JIS E 7105 and ASCE 21-98. Crashworthiness analysis was carried out using explicit finite element code LS-DYNA3D with the lapse of time. The crash condition was frontal accident with speed of 10km/h at rigid wall. The results showed that the structural integrity and crashworthiness of AGT vehicle were proven under the specified loading and crash conditions. Also, the modified Chang-Chang failure criterion was recommended to evaluate the failure modes of composite structures after crashworthiness event.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.4
• /
• pp.1488-1495
• /
• 2012

In this study, the fracture behaviour of DCB(double cantilever beam) specimen with aluminum foam composite materials is analyzed by simulation. The used model is 3D configuration on the basis of British industrial standard and ISO international standard. As the thickness of model is increased, the length of propagated crack is increased and the load becomes higher. The analysis result obtained by this study can be applied at the practical composite structure bonded with aluminum foam materials. The fracture behaviour is analyzed and the mechanical property can be understood.

• Composites Research
• /
• v.17 no.5
• /
• pp.54-60
• /
• 2004

A new three-dimensional model for predicting the relationship between the prestrain of the composite and the amount of phase transformation of shape memory alloy inducing shape memory effect has been proposed by using Eshelby's equivalent inclusion method with Mori-Tanaka's mean field theory. The model composite is aluminum matrix reinforced with short TiNi fiber shape memory alloy, where the matrix is work-hardening material of power-law type. The analytical results predicted by the current model show that most of the prestrain is induced by the plastic deformation of the matrix, except the small prestrain region. The strengthening mechanism of the composite by the shape memory effect should be explained by excluding its increase of yield stress due to the work-hardening effect of the matrix.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.1
• /
• pp.48-57
• /
• 2007

The fatigue crack growth behavior of a cracked and patch-repaired Ah2024-T3 panel has been monitored by acoustic emission(AE). The overall crack growth rate was reduced The crack propagation into the adjacent hole was also retarded by introducing the patch repair. AE signals due to crack growth after the patch repair and those due to debonding of the plate-patch interface were discriminated by usiag the principal component analysis. The former showed high center frequency and low amplitude, whereas the latter showed long rise tine, low frequency and high amplitude. This type of AE signal recognition method could be effective for the prediction of fatigue crack growth behavior in the patch-repaired structures with the aid of AE source location.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.4
• /
• pp.632-637
• /
• 2003

In this study, the effect of surface treatment of CFRP and aluminum on the fracture toughness of CFRP/aluminum composites was investigated. CFRP was surface-treated by Ar$^{+}$ ion beam under oxygen environment, and the aluminum was surface-treated by DC plasma. CFRP was adhesively bonded to aluminum using the secondary bonding procedure. Cracked lap shear specimens were used to determine fracture toughness. Three cases of cracked lap shear specimens were made depending on the surface treatment. The values of fracture toughness of three cases were compared to each other It was found that the fracture toughness of ion beam-treated CFRP/aluminum composites was almost 72 % higher than that of unrented CFRP/aluminum composites. The fracture toughness of CFRP/plasma-treated aluminum composites was 50 % higher than that of untreated CFRP/aluminum composites.s.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.192.2-192.2
• /
• 2012

위성시스템 소형화, 탑재체 수용증대, 발사비용절감, 탐사임무 효율화 등의 요구로 인하여, 위성 설계에 있어 경량화는 오랜 기간 진행되어온 연구 주제였다. 이러한 연구결과로서, 위성 구조체를 복합재료로 대신하기 위한 구조 경량화 연구와 적용이 성과를 거두었으며, 현재 위성체 프레임이나 전개형 안테나, 광학구조물 등에 경량 탄소섬유 강화 복합재료의 적용은 보편화되어 있다. 한편, 위성시스템에서 전력, 통신, 명령/데이터처리, 자세제어 및 관측기기의 각종 전자장비를 보호하는 하우징 구조물에는 여전히 금속재료가 광범하게 적용되고 있다. 특히, 알루미늄 합금은 하우징 재료로 널리 사용되는데, 강도, 강성, 열전달, 우주방사, 전기전도도 및 EMI 차폐특성과 더불어 가공성이 우수하다는 장점을 지닌 반면에, 금속재료로서 중량이 상당하여 위성 경량화 관점에서는 한계를 갖게 하는 단점이 있다. 전자장비에 부여된 전자기능 측면에서 보면, 하우징은 기생 구조물로서, 경량으로 제공될수록 전자장비 전체 무게에서 전자유닛만의 무게가 차지하는 전기전자기능비가 향상되고 위성 경량화에 크게 기여할 수 있다. 구조 경량화를 위하여 전자장비 하우징을 경량 복합재로 대체하여 설계 및 제작하였으며, 복합재 하우징의 강도, 강성, 열전달, 우주방사, 전기전도도 및 EMI 차폐를 검증할 수 있는 방법에 대하여 검토하였다.

• Aerospace Engineering and Technology
• /
• v.10 no.2
• /
• pp.114-120
• /
• 2011

Thermal control of satellite is mainly based on passive ways, such as the radiator made of aluminum honeycomb core with aluminum skins and OSR (Optical Solar Reflector). Additionally, for the thermal control of high dissipation unit, the aluminum doubler and heat pipe are utilized. Recently, efforts to find advanced thermal materials have been carried out to enhance heat rejection capability without increasing satellite size, weight and cost. This paper handles the carbon composites have high thermal conductivity with light weigh and have been considered as future thermal control materials to replace aluminum based radiator and doubler. Thermal analysis of satellite panel using APG(Annealed Pyrolytic Graphite) and carbon-carbon composites were performed and temperature contours were compared with the conventional thermal control methods.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.81-85
• /
• 2006

Through-the-thickness properties of thick-walled cylindrical composites are required to determine structural performances because interlaminar tensile stress is primarily responsible for structural failure of the composites during their curing process. It is necessary for evaluating the tensile properties to find individual test methods to find appropriate methods because there are no recognised international standards(test methods and test specifications) available for generating reliable tensile properties in the direction. This paper has performed an experimental Study to measure that properties of carbon fabric/phenolic composites are produced by domestic company. Several test methods using an aluminum specimen were compared and evaluated. The best method, found out, was adopted to measure transverse through-the-thickness properties of composite materials. The results show that strain trends on four faces of composite specimen are the same.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.3
• /
• pp.48-52
• /
• 2006

Through-the-thickness properties of thick-walled cylindrical composites are required to determine structural performances because interlaminar tensile stress is primarily responsible for structural failure of the composites during their curing process. It is necessary for evaluating the tensile properties to find individual test methods to find appropriate methods because there are no recognised international standards(test methods and test specifications) available for generating reliable tensile properties in the direction. This paper has performed an experimental study to measure that properties of carbon fabric/phenolic composites which are produced by domestic company. Several test methods using an aluminum specimen were compared and evaluated. The best test method to measure transverse through-the-thickness properties of composite materials was developed by the experimental results that strain trends on all faces of composite specimen are the same.

• Composites Research
• /
• v.24 no.5
• /
• pp.9-16
• /
• 2011

This paper describes the crashworthiness evaluation and performance improvement of tilting train made of sandwich composites. The applied sandwich composite of carbody structure was composed of aluminum honeycomb core and glass/epoxy & carbon/epoxy laminate composite facesheet. Crashworthiness analysis of tilting train was carried out using explicit finite element analysis code LS-DYNA 3D. The 3D finite element model and 1D equivalent model were applied to save the finite element modeling and calculation time for crash analysis. The crash conditions of tilting train were conducted according to four crash scenarios of the Korean railway safety law. It found that the crashworthiness analysis results were satisfied with the performance requirements except the crash scenario-2. In order to meet the crashworthiness requirements for crash scenario-2, the stiffness reinforcement for the laminate composite cover and metal frames of cabmask structure was proposed. Consequentially, it has satisfied the requirement for crash scenario-2.