• Composites Research
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• v.20 no.1
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• pp.1-7
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• 2007

This study presents a methodology for optimization of static characteristics of golf club shafts. Stacking sequence for the optimal composite shaft performance is searched. A new objective function is defined for the simultaneous optimization of flexural and torsional stiffnesses. Classical lamination theory is used for the static analysis. As the optimization tool, genetic algorithm is applied with the stacking sequence as design. variables. With the optimal stacking sequence, dynamic characteristics of the shaft is also studied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.409-415
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• 2011

Optimization Analysis of angle-ply laminated shells, having one pair of opposite edges supported, are investigated on the basis of the first-order shear deformation theory. The equations of motion of the shell are solved by the use of ritz method. A range of results are presented for composite shells to show the effects of lamination angle and number of layers on natural frequency. In addition, an analysis of the strain energy distributions is used as an aid for the better understanding of the vibration characteristics of the shells.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.420-424
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• 2003

Stacking sequence optimization needs discrete programming techniques because ply angles are limited to a fixed set of angles such as $0^{\circ},\;{\pm}45^{\circ},\;90^{\circ}$. Two typical methods are genetic algorithm and branch and bound method. The goal of this paper is to compare the methods in the light of their efficiency and performance in handling the constraints and finding the global optimum. For numerical examples, maximization of buckling load is used as objective and optimization results from each method are compared.

• Composites Research
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• v.33 no.5
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• pp.288-295
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• 2020

Fiber-reinforced composite laminates have high specific stiffness and strength and are expected to be useful for weight reduction in weight-sensitive industries, such as automotive and aerospace. However, designing composite laminates is often dependent on designer's experience and intuition because of difficulties in determining the number of plies and stacking sequence, which tends to lead to over-design. In this study, optimal design of composite laminates was performed to minimize weight, while withstanding the given load. Based on the enumeration method, all combinations of stacking sequence satisfying the design guideline for composite laminates were considered. Composite laminates were discretized into panels. Optimal number of plies and stacking sequence for each panel were determined considering local load on each panel and contiguity across adjacent panels. Failure index from Tsai-Wu criteria was optimized for strength and buckling analysis was performed for compressive load. Stacking angles of 0, ±45 and 90° were used.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.734-739
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• 2001

In this paper, an algorithm for stacking sequence optimization which deals with discrete ply angles is used for optimization of composite laminated plates. To handle discrete ply angles, the branch and bound method is modified. Numerical results show that the optimal stacking sequence is found with fewer evaluations of objective function than expected with the size of feasible region, which shows the algorithm can be effectively used for layup optimization of composite laminates..

• Composites Research
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• v.12 no.1
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• pp.1-10
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• 1999

In order to predict the dynamic behavior of composite laminated plate accurately, the parametric identification is performed using its mechanical properties- $E_1,\;E_2,\;V_{12},\;G_{12}$ as design parameters. After natural frequencies are measured through simple vibration test, the objective function consists of the sum of errors between experimental and numerical frequencies of a structure. As optimization algorithm, conjugate gradient method is used to minimize the objective function. Sensitivity Analysis is performed to update design parameters during this process and can explain the result of parametric identification. In order to check the propriety of result, mode shapes are compared before and after identification. The improved prediction of natural frequencies of composite laminated plate is obtained with updated properties. For the application of result, updated properties is applied to the composite laminated plate that has different stacking sequence.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1239-1243
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• 2014

This paper presents the application of carbon-fiber-reinforced polymer (CFRP) for the damage absorption and optimal design of portable smart devices to close in life. CFRP specimens are subjected to a tensile test to estimate their mechanical properties in terms of the stacking angles. Further, the screw reverse torque and screw torque at each stacking angle are determined using a torque tester after tapping holes on the CFRP specimens. Two experiments are performed for comparing their results in order to determine optimal conditions. In the tensile test, a woven specimen is found to have the highest strength and stiffness. In the case of the woven specimen, no difference is observed even when it is applied to prevent loosening of the coating. And average result value was excellent.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.369-380
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• 2001

Although extensive efforts have been devoted to the optimal design of composite laminated plates in recent years, some practical issues still need further research. Two of them are: the handling of the ply angle as either continuous or discrete; and that of the uncertainties in material properties, which were treated as continuous and ignored respectively in most researches in the past. In this paper, an algorithm for stacking sequence optimization which deals with discrete ply angles and that for thickness optimization which considers uncertainties in material properties are used for a two step optimization of composite laminated plates. In the stacking sequence optimization, the branch and bound method is modified to handle discrete variables; and in the thickness optimization, the convex modeling is used in calculating the failure criterion, given as constraint, to consider the uncertain material properties. Numerical results show that the optimal stacking sequence is found with fewer evaluations of objective function than expected with the size of feasible region taken into consideration; and the optimal thickness increases when the uncertainties of elastic moduli considered, which shows such uncertainties should not be ignored for safe and reliable designs.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.233-236
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• 2002

An efficient method was developed in this study to obtain optimal stacking sequences, thicknesses, and minimum weights of stiffened laminated composite shells under combined loading conditions and stiffener layouts using genetic algorithms (GAs) and finite element analyses. Among many parameters in designing composite laminates determining a optimal stacking sequence that may be formulated as an integer programming problem is a primary concern. Of many optimization algorithms, GAs are powerful methodology for the problem with discrete variables. In this paper the optimal stacking sequence was determined, which gives the maximum critical buckling load factor and the minimum weight as well. To solve this problem, both the finite element analysis by ABAQUS and the GA-based optimization procedure have been implemented together with an interface code. Throughout many parametric studies using this analysis tool, the influences of stiffener sizes and three different types of stiffener layouts on the stacking sequence changes were throughly investigated subjected to various combined loading conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.330-335
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• 2003

Analysis and experiment on dynamic characteristics of automotive roof have been carried out experimentally and numerically to design a lightweight roof. Finite element analysis of a conventional steel automotive roof was verified by experiments on vibration characteristics. The dynamic analysis of carbon fiber reinforced composite automotive roof shows that the roof stiffness changes as the fiber orientation of the laminated panel changes. Optimization results yielded a composite roof, which was 52% lighter, than the steel conventional steel automotive roof. This paper addresses a design strategy of composite roof for weight reduction.