• 대한기계학회논문집A
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• 제22권3호
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• pp.588-594
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• 1998

Reliable three-dimensional models of woven fabric composites had scarcely been proposed for their geometric complexity. Simplified models, mostly one- or two-dimensional, currently used are not considered effective enough because of their oversimplifications. In this paper, the equivalent thermal conductivities and elasticity properties of woven fabric composites are computed using homogenization technique. The computational results show that the strength and thermal conductivity linearly increase with fiber volume fraction and that the variations of undulation of fibers has little effect on equivalent material properties. Homogenization technique is proved useful in the study of woven fabric composites and may find a lot more applications in the area.

• 항공우주시스템공학회지
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• 제16권6호
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• pp.8-17
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• 2022

항공기 날개에 사용되는 스킨-스트링거 패널은 기계적 체결과 접착 체결로 인하여 응력 집중과 접착 분리가 발생할 수 있다. 이를 고려하여, 3차원 직조 복합재료를 이용해 스킨과 스트링거를 일체시킨 패널을 설계하였다. 본 논문에서는 일체형 패널의 기계적 물성을 예측하기 위하여 기하학적 모델링 기법을 제안하였다. 시편의 기하학적 변수를 측정하고 섬유 다발의 패턴을 함수식으로 정의해 기하학적 모델링을 수행하였다. 이를 검증하기 위하여 iso-strain, iso-stress 가정을 사용한 가중평균모델을 통해 각 부재의 기계적 물성을 예측하고 유한요소해석을 수행해 압축시험 결과와 비교하였다. 제안한 기하학적 모델링 기법을 통해 스킨-스트링거 일체형 패널의 기계적 물성을 실험적 방법보다 효율적으로 예측하였다.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1757-1764
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• 1997

The geometric and elastic models based on the unit cell have been proposed to predict the geometric characteristics and the engineering constants of plain and satin woven composites. In the geometric model, length and inclined angle of the yarn crimp and the fiber volume fraction of woven composites have been predicted. In the elastic model, the coordinate transformation has been utilized to transform the elastic constants of the yarn crimp to those of woven composites, and the effective elastic constants have been determined from the volume averaging of the constituent materials. Good correlations between the model predictions and the experimental results of carbon/epoxy and glass/epoxy woven composites have been observed. Based on the model, the effect of various geometric parameters and materials on the three-dimensional elastic properties of woven composites can be identified.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.64-69
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• 2001

In general, laminate effective orthotropic thermal conductivities are dependent on fiber and matrix material properties, fiber volume fraction and fabric geometric parameters. This paper deals with the predicting method of the transverse and the in-plane thermal conductivities of plain weave fabric composites based on the three dimensional series-parallel thermal resistance network. Thermal resistance network was applied to unit cell model that characterizes the periodically repeated pattern of plain weave. Also, an experiment apparatus is setup to measure the thermal conductivities of composite material. The numerical and experimental results of carbon/epoxy plain weave are compared.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.83-86
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• 2003

Complete prediction of second order permeability tensor for three dimensional preform such as plain woven fabric and braided preform is critical to understand the resin transfer molding process of composites. The permeability can be obtained by various methods such as analytic, numerical, and experimental methods. For several decades, the permeability has studied numerically to avoid practical difficulty of many experiments. However, the predicted permeabilities are a bit wrong compared with experimentally measured data. In this study, numerical calculation of permeability was conducted for two kinds of preforms i.e., plain woven fabric and circular braided preform. In order to consider intra-tow flow in the unit cell of preform the proposed flow coupled model was used for plain woven fabric and the Brinkman equation was solved in the case of the braided preform.

• Korea-Australia Rheology Journal
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• 제19권1호
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• pp.17-25
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• 2007

In liquid composite molding (LCM), composites are produced by impregnation of a dry preform with liquid resin. The resin flow through the preform is usually described by Darcy's law and the permeability tensor must be obtained for filling analysis. While the resin flow in the thickness direction can be neglected for thin parts, the resin flow in the transverse direction is important for thicker parts. However, the transverse permeability of the preform has not been investigated frequently. In this study, the transverse permeability was measured experimentally for five different fiber preforms. In order to verify the experimental results, the measured transverse permeability was compared with numerical results. Five different fiber mats were used in this study: glass fiber woven fabric, aramid fiber woven fabric, glass fiber random mat, glass fiber braided preform, and glass/aramid hybrid braided preform. The anisotropic braided preforms were manufactured by using a three dimensional braiding machine. The pressure was measured at the inlet and outlet positions with pressure transducers.

• Composites Research
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• 제32권5호
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• pp.206-210
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• 2019

직조 구조의 복합재의 쓰임이 자동차, 항공 산업 등 여러 분야로 확장됨에 따라, 직조 복합재의 신뢰성 문제 및 물성예측에 대한 필요성이 대두되었다. 본 연구에서는 직조 구조가 다른 복합재료의 물성 예측을 위한 유한요소해석을 수행하여 실험으로 얻은 정적 물성과의 유사성을 검증하였고, 효과적인 모델링 방법을 개발하였다. 직조 구조의 특성을 반영하기 위하여 모델링은 메소 스케일의 대표 체적 요소(RVE)를 이용하였다. 섬유 다발과 순수 기지를 분리하여 3차원 모델링을 진행하였다. 하신 파괴 기준(Hashin's failure criteria)을 적용하여 요소의 파괴 유무를 판단하였고, 해석 모델은 복합재에 적합한 점진적 파괴 모델을 사용하였다. 최종적으로, 직조 구조에 따른 복합재의 물성을 성공적으로 예측하여 본 모델링 및 해석 기법에 대한 적합성을 검증하였다.

• Earthquakes and Structures
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• 제16권3호
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• pp.369-373
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• 2019

Construction industry is one of the largest markets for composite materials. Composite materials are mostly utilized as surface coatings or concrete reinforcements, and they can hardly be found as a load bearing member in buildings. The three-dimensional composite structures with considerable bending, compressive and shear strengths are capable to be used as construction load bearing members. However, these composites cannot compete with other materials due to higher manufacturing costs. If the cost issue is resolved or their excellent performance is taken into consideration to overcome disadvantages related to economic-competitive challenges, these 3D composites can significantly reduce the construction time and result in lighter and safer buildings. Sandwich composite panels reinforced with 3D woven glass fabrics are amongst composites with highest bending strength. The current study investigates the possibility of utilizing these composite materials to construct ceilings and their application as slabs. One-to-one scale experimental loading of these composite panels shows a remarkable bending strength. Simulation results using ABAQUS software, also indicate that theoretical predictions of bending behavior of these panels are in good agreement with the observed experimental results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.91-94
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• 2003

Laminated composites are liable to fatal damage under impact load due to the fact that they have no reinforcement in the thickness direction. To overcome the inherent weakness, three dimensional (3D) textile reinforcements have drawn much interests. In this paper, impact performance of 2D and 3D textile composites has been characterized. For 2D composites, fiber bundle size and fiber pattern have been varied. For 3D composites, orthogonal woven preforms of different density and type of through-thickness fibers have been studied. To assess the damage after the impact loading, specimens were subjected to C-scan nondestuctive inspection. Compression after impact (CAI) were also conducted in order to evaluate residual compressive strength.

• Steel and Composite Structures
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• 제38권6호
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• pp.717-737
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• 2021

A theoretical energy-based model to capture the mechanical response of thick woven composite laminates, which are used in such applications as maritime or aerospace, to high-velocity impact was developed. The dependences of the impact phenomenon on material and geometrical parameters were analysed making use of the Vaschy-Buckingham Theorem to provide a non-dimensional framework. The model was divided in three different stages splitting the physical interpretation of the perforation process: a first where different dissipative mechanisms such as compression or shear plugging were considered, a second where a transference of linear momentum was assumed and a third where only friction took place. The model was validated against experimental data along with a 3D finite element model. The numerical simulations were used to validate some of the new hypotheses assumed in the theoretical model to provide a more accurate explanation of the phenomena taking place during a high-velocity impact.