• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.243-250
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• 2018

In this paper, design technique using genetic algorithms(GA) for design optimization of composite leaf springs is presented here. After the initial design has been validated by the car plate spring as a finite element model, the genetic algorithm suggests the process of optimizing the number of layers of composite materials and their angles. Through optimization process, the weight reduction process of leaf springs and the number of repetitions are compared to the existing algorithm results. The safety margin is calculated by organizing a finite element model to verify the integrity of the structure by applying an additive sequence optimized through the genetic algorithm to the structure. When GA is applied, layer thickness and layer angle of complex leaf springs have been obtained, which contributes to the achievement of minimum weight with appropriate strength and stiffness. A reduction of 65.6% original weight is reached when a leaf steel spring is replaced with a leaf composite spring under identical requirement of design parameters and optimization.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.1
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• pp.1-7
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• 2011

In this study the optimal stacking section was selected by pendulum impact test for six different stacking sections of the composite safety barrier. The beam cross-section shape was determined through the poll on six different beam cross-section shapes. The six kinds of stacking design for the determined beam cross-section were suggested. CSM, DB, DBT and Roving fibers were used for stacking design. Horizontal beam and 3:1 sloped beam were modeled by using LS-DYNA. The fall impact simulation was carried out by using rectangular pendulum and cylinder pendulum. Optimal stacking section was determined by comparing and analyzing the impact simulation results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.276-279
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• 2010

유리섬유 복합소재 바닥판은 고강도, 경량 그리고 고내구성을 가지고 있으므로, 현재 국내 및 해외에서 교량에 꾸준히 적용되고 있다. 국내외에서 기존에 사용하고 있는 복합소재 데크는 주로 수평방향의 암수접착을 통한 결합을 실시하고 있으나 본 연구진에 의해 획기적인 착탈결합방식 연결이 가능한 복합소재데크를 개발하였다. 복합소재 적층설계를 통해 설계된 복합소재 데크의 물성치를 ESAComp에 의한 적층해석과 시편시험을 통해 추정하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.308-315
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• 2009

Because the attenuation of AE signal in composite materials is relatively higher than that of metallic materials, it is required to develop a damage assessment technique less affected by the attenuation property of composite materials in order to use AE sensing as a damage detection method. In the signal processing procedure, it is profitable to use the leading wave that arrives first because the leading wave is less influenced by the boundary conditions. Using wavelet transform, we investigated the frequency characteristics of impact induced AE signals focused on the leading wave in advance and chose the key factors to discriminate the damaged condition quantitatively. In this research, we established a damage assessment technique using the sharing percentage of the wavelet detail components of AE signal, and conducted a low-velocity impact test on composite laminates to confirm the feasibility of the proposed signal processing method.

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.75-83
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• 2010

Laminated composite plates have shown their superiority over metals in applications requiring high specific strength, high specific modulus, and so on. Therefore, they have used in various industry. However, they have poor resistance to impact compared to typical metal materials. So, many researchers have investigated about impact behavior of laminated composite plate. To investigate impact behavior of laminated composite plate, we have to calculate contact force between impactor and laminated composite plate at the first. Impactor's equation of motion, plate's equation of motion and correlations for indentation were solved to know the contact force at the same time. In this study, low velocity impact behavior of composite plate was investigated using the finite element program which is involved the classical Hertzian law, Sun's law and Sun & Yang's experimental law and Sun & Tan's experimental law considering the stacking method.

• Composites Research
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• v.32 no.2
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• pp.108-112
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• 2019

There has been a continuous study on the weight reduction of structure by composites. Unlike isotropic materials, the physical properties of composites vary according to the direction of laminate and the order of lamination. Therefore, in the case of composite ladders, it is essential to perform structural analysis to verify the planned design. In this study, ladder was designed by applying fabric material. In addition, the effect of loading position on the ladder was analyzed through finite element analysis, and structural performance was analyzed by selecting the most problematic location. We analyzed the effect of stacking order on the structural strength of the ladder by analyzing the structure by applying various stacking sequence and measuring the failure value in each layer.

• Composites Research
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• v.30 no.5
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• pp.297-302
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• 2017

Finite element analysis of T-beam laminate structure under bending-torsional loading was conducted to prevent the delamination which is the major failure behavior on laminated composites. Three-dimensional preform, which is that fabric is braided through thickness direction, is suggested from the laminate analysis. The analysis aimed to optimize the fiber ratio in laminated composites. After it is suggested that guideline for design of T-beam structure using commercial software ANSYS Composites PrePost. The results show that strength of T-beam structure is increased 21.6% when the fiber density along with beam length direction is two times bigger than transverse direction. It is expected that development of high strength T-beam structure using designed three-dimensional preform.

• Composites Research
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• v.29 no.6
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• pp.321-327
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• 2016

In this study, tests and finite element analyses were performed regarding compression after impact strength for laminated composite structures of unidirectional carbon fiber reinforced plastic widely used in structural materials. Two lay-up sequences of composite laminates were selected as test specimens and four impact energy conditions were applied respectively. Impact and compressive strength tests were conducted in accordance with ASTM standards. Impact damages in test specimens were analyzed by using non-destructive inspection method of C-Scan, and compression after impact strengths were calculated with compressive test results. Progressive failure analysis method that can progressively simulate damages and fractures of fiber/matrix/lamina/laminate level was used for impact and compressive strength analyses. All analysis results including contact force, deflection, impact damages, compressive strengths, etc. were compared to test results, and the validity of analysis method was verified.

• Computational Structural Engineering
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• v.6 no.1
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• pp.117-125
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• 1993

In general, the strength and stiffness of laminated composite cylindrical shells are very sensitive to the variation of slenderness parameters, some coupling-stiffness parameters, lamination angles, stacking sequence and number of layers. In this paper, the effects of these factors on the strength and buckling reliabilities of GFRP laminated cylindrical shells are investigated based on the proposed strength and buckling limit state models. As these factors have various and complicated effects on the strength and buckling reliabilities of GFRP laminated cylindrical shells, the results should be incorporated into the design formula such that optimum design technique and design code which provide uniform consistent reliability for balanced design in practice

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.17-24
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• 2002

인발성형 적층 FRP 복합소재의 재료상수는 일반적으로 시편실험을 통해 구해지고 있으나, 본 논문에서는, 실험에서 구한 탄성계수가 부재일 경우를 위해, Micromechanics와 Classical Laminate Theory (CLT)를 이용한 적층 FRP 복합재료의 탄성계수(E/sub L/과 E/sup b//sub L/) 예측모델을 제시하였다 또한 예측모델로부터 구한 값과 실험으로부터 얻은 실측값을 비교하여 그 적정성을 검증하였고, 예측모델의 민감도 및 확률적인 특성을 구성소재 (Constituents)의 재료특성에 근거해 평가하였다.