• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.93-107
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• 2017

The article presents the vibration and acoustic responses of un-baffled doubly curved laminated composite panel structure under the excitation of a harmonic point load. The structural responses are obtained using a simulation model via ANSYS including the effect various geometries (cylindrical, elliptical, spherical and hyperboloid). Initially, the model has been established by solving adequate number of available examples to show the convergence and comparison behaviour of the natural frequencies. Further, the acoustic responses are obtained using an indirect boundary element approach for the coupled fluid-structure analysis in LMS Virtual.lab by importing the natural frequency values. Subsequently, the values for the sound power level are computed using the present numerical model and compared with that of the available published results and in-house experimentally obtained data. Further, the acoustic responses (mean-square velocity, radiation efficiency and sound power level) of the doubly curved layered structures are evaluated using the current simulation model via several numerical experimentations for different structural parameters and corresponding discussions are provided in detail.

• Steel and Composite Structures
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• v.16 no.4
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• pp.389-415
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• 2014

This study deals with dynamic model of composite sandwich panels with functionally graded flexible cores under low velocity impacts of multiple large or small masses using a new improved higher order sandwich panel theory (IHSAPT). In-plane stresses were considered for the functionally graded core and face sheets. The formulation was based on the first order shear deformation theory for the composite face sheets and polynomial description of the displacement fields in the core that was based on the second Frostig's model. Fully dynamic effects of the functionally graded core and face-sheets were considered in this study. Impacts were assumed to occur simultaneously and normally over the top and/or bottom of the face-sheets with arbitrary different masses and initial velocities. The contact forces between the panel and impactors were treated as internal forces of the system. Nonlinear contact stiffness was linearized with a newly presented improved analytical method in this paper. The results were validated by comparing the analytical, numerical and experimental results published in the latest literature.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.272-281
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• 1999

Cylindrical panels are widely used as aircraft fuselages and rocket etc, and the cutouts for weight reduction or wiring at such structures tend to cause the stress concentration and the local radial displacement so that seriously effect the stability of structures. In this paper, for the cylindrical composite panel with coutout at the center, the buckling and postbuckling behaviour regarding the shape and size of cutout is analyzed by finite element method. Also the lamination mechanism , changing bending stiffness and fiber orientation angle variation are researched to be regarded in studying the laminated composite materials.

• Journal of the Korean Society for Railway
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• v.7 no.1
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• pp.55-59
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• 2004

Composite materials were used widely due to merit of light weight, low maintenance cost and easy installation. But it is the cause of enormous casualties to men and properties because of weak about the fire. Particularly, it is more serious in case of subway train installed composite materials. For this reason, experimental comparison has been done fur measuring heat release rate(H.R.R) and smoke production rate(S.P.R) of interior panels of electric motor car using cone calorimeter. A high radiative heat flux of 50kW/㎡ was used to bum out all materials and to simulate the condition of fully developed fire case in the tests. It was observed that Heat Release Rate and Smoke Production Rate curves were dependent on the kinds of the interior materials. From the heat release rate curves, the sustained ignition time, peak heat release rate and total heat release rate were deduced, These data are useful in classifying the materials by calculating two parameters describing the possibility to flashover.

• Steel and Composite Structures
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• v.52 no.5
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• pp.595-608
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• 2024

This study presents a static analysis of thin shallow cylindrical and spherical panels, as well as plates (which are a special case of shells), under Levy-type mixed boundary conditions and various loading conditions. The study utilizes the boundary discontinuous double Fourier series method, where displacements are expressed as trigonometric functions, to analyze the system of partial differential equations. The panels are subjected to a simply supported type 3 (SS3) boundary condition on two opposite edges, while the remaining two edges are subjected to clamped type 3 (C3) boundary conditions. The study presents comprehensive tabular and graphical results that demonstrate the effects of curvature on the deflections and moments of thin shallow shells made from symmetric and antisymmetric cross-ply laminated composites, as well as isotropic steel materials. The proposed model is validated through comparison with existing literature, and the convergence characteristics are demonstrated. The changing trends of displacements and moments are explained in detail by investigating the effect of various parameters, such as stacking lamination, material types, curvature, and loading conditions.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.187-190
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• 2001

Response surface method is applied to evaluate the reliability of laminated composite panels. Since the linear and nonlinear first-ply failure load are computed using deterministic finite element analysis, new probabilistic finite element analysis is not necessary. Tsai-Wu criterion is used to construct the limit state suface. Material properties, layer thickness and lamina strengths of laminated composite panel are treated as random design variables. feasibility and accuracy of current method is validated using Monte-Carlo method Which perform thousand times of finite element analysis directly.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.46-51
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• 2015

Since it is impossible to predict earthquakes, they involve more casualties and property damage compared to meteorological disasters such as heavy snow and heat waves, which can be predicted through weather forecasts. This has highlighted the need for seismic design and reinforcement. Recently, the use of composite materials as reinforcement has surged because steel plate reinforcement and section enlargement are likely to result in increased weight and physical damage to structures. This study evaluates the seismic performance of panels created from composite materials, and their guide systems. The specimens were miniature versions of actual steel structures, and displacement loads were applied in the transverse direction. Seismic performance was found to improve when structures were reinforced with seismic panels.

• Steel and Composite Structures
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• v.18 no.1
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• pp.1-28
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• 2015

In this paper, the dynamic response of functionally gradient steel (FGS) composite cylindrical panels in steady-state thermal environments subjected to impulsive loads is investigated for the first time. FGSs composed of graded ferritic and austenitic regions together with bainite and martensite intermediate layers are analyzed. Thermo-mechanical material properties of FGS composites are predicted according to the microhardness profile of FGS composites and approximated with appropriate functions. Based on the three-dimensional theory of thermo-elasticity, the governing equations of motionare derived in spatial and time domains. These equations are solved using the hybrid Fourier series expansion-Galerkin finite element method-Newmark approach for simply supported boundary conditions. The present solution is then applied to the thermo-elastic dynamic analysis of cylindrical panels with three different arrangements of material compositions of FGSs including ${\alpha}{\beta}{\gamma}M{\gamma}$, ${\alpha}{\beta}{\gamma}{\beta}{\alpha}$ and ${\gamma}{\beta}{\alpha}{\beta}{\gamma}$ composites. Benchmark results on the displacement and stress time-histories of FGS cylindrical panels in thermal environments under various pulse loads are presented and discussed in detail. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of FGS structures under time-dependent mechanical loadings.

• Journal of the Korean Wood Science and Technology
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• v.44 no.4
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• pp.600-606
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• 2016

Wood-based composite panels such as plywood, particleboard (PB), or medium density fiberboard (MDF) are mostly used in the lamination on their surface for the manufacturing of furniture, or interior building products, the concern on the formaldehyde emission (FE) from the surface laminated wood panels is increasingly attracting attentions from the public. Thus, this study was conducted to understand influence of surface laminating materials to the FE from PB and MDF with or without edge sealing, using 24-hour desiccator method. Both PB samples that had been laminated on their surface with low-pressure laminate (LPL) or polypropylene (PP) film and MDF that had been treated with poly(vinyl chloride) (PVC) or coating were tested for the FE with or without edge sealing. As expected, the FE of PB with the sealed edges decreased to 37.4% and 80.7% with the LPL and PP lamination, respectively. The surface laminated MDF with the sealed edges also showed a decrease in the emission up to 57.8% and 54.3%, with the PVC lamination and coating, respectively. However, the coated MDF samples showed 5.3% increase in the emission when their edges were not sealed, indicating a FE form the solvent used for coating. These results showed that the type of surface lamination materials on wood-based composite panels has a great impact on their resultant FE, indicating that the influence of surface laminating materials should be taken into consideration for the formaldehyde mission measurement.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.29-38
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• 1997

The effect and control of wood property of reconstituted composite panels for improved board properties by wood-waste materials and development of combination method for heterogeneous materials have been of interest to the wood science researchers. The purpose of this study is to consider the properties in relation to hot pressing conditions and to develope the optimum hot pressing condition with waste wood and waste tire for the manufacturing of composite boards. The study of composite boards for recycling of wood and waste tire is nothing up to the present. Physical and mechanical properties such as specific gravity, moisture content, swelling coefficient, modulus of rupture and modulus of elasticity in bending test were studied. The condition of 3-stage press time for the lowest moisture content of composite board was $4{\rightarrow}3{\rightarrow}3$ minutes. Specific gravity of composite panels was affected mainly by the amount of rubber chip. Because of the low rigidity and high elasticity in rubber chip, it is considered the composite panel was adequate material in the place of compression load, but not bending load. Therefore, it was concluded that a use of rubber-based wood composite panel is proper to the interior materials such as floor a room than exterior materials. From the test results, the most optimum hot pressing conditions were $4{\rightarrow}3{\rightarrow}3$ minutes for 3-stage press time and $45{\rightarrow}20{\rightarrow}5kg/cm^2$ for 3-stage press pressure. The rubber-based wood composite panel was very excellent in elasticity by combination of rubber chip in comparison with existing other wood-based materials. Therefore, it was considered that rubber-based wood composites can be applicable to every interior materials such as floor a room and will be expected to effective reuse and recycle of waste tires and wood-waste materials, and will be contribute to protection of environment pollution in earth.