• Geomechanics and Engineering
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• v.18 no.5
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• pp.555-566
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• 2019

The purpose of this paper is to investigate the thermal effects on the behaviour reinforced-concrete beams strengthened by bonded angle-ply laminated composites laminates plate $[{\pm}{\theta}n/90m]_S$. Effects of number of $90^{\circ}$ layers and number of ${\pm}{\theta}$ layers on the distributions of interfacial stress in concrete beams reinforced with composite plates have also been studied. The present results represent a simple theoretical model to estimate shear and normal stresses. The effects the temperature, mechanical properties of the fibre orientation angle of the outer layers, the number of cross-ply layers, plate length of the strengthened beam region and adhesive layer thickness on the interfacial shear and normal stresses are investigated and discussed.

• Steel and Composite Structures
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• v.46 no.4
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• pp.471-483
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• 2023

This paper presents an analytical hyperbolic theory based on the refined shear deformation theory for mechanical stability analysis of the simply supported advanced composites plates (exponentially, sigmoidal and power-law graded) under triangular, trapezoidal and uniform uniaxial and biaxial loading. The developed model ensures the boundary condition of the zero transverse stresses at the top and bottom surfaces without using the correction factor as first order shear deformation theory. The mathematical formulation of displacement contains only four unknowns in which the transverse deflection is divided to shear and bending components. The current study includes the effect of the geometric imperfection of the material. The modeling of the micro-void presence in the structure is based on the both true and apparent density formulas in which the porosity will be dense in the mid-plane and zero in the upper and lower surfaces (free surface) according to a logarithmic function. The analytical solutions of the uniaxial and biaxial critical buckling load are determined by solving the differential equilibrium equations of the system with the help of the Navier's method. The correctness and the effectiveness of the proposed HyRPT is confirmed by comparing the results with those found in the open literature which shows the high performance of this model to predict the stability characteristics of the FG structures employed in various fields. Several parametric analyses are performed to extract the most influenced parameters on the mechanical stability of this type of advanced composites plates.

• Steel and Composite Structures
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• v.48 no.2
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• pp.191-206
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• 2023

The present research investigates how micromechanical models affect the behavior of Functionally Graded (FG) plates under different boundary conditions. The study employs diverse micromechanical models to assess the effective material properties of a two-phase particle composite featuring a volume fraction of particles that continuously varies throughout the thickness of the plate. Specifically, the research examines the vibrational response of the plate on a Winkler-Pasternak elastic foundation, considering different boundary conditions. To achieve this, the governing differential equations and boundary conditions are derived using Hamilton's principle, which is based on a four-variable shear deformation refined plate theory. Additionally, the Galerkin method is utilized to compute the plate's natural frequencies. The study explores how the plate's natural frequencies are influenced by various micromechanical models, such as Voigt, Reuss, Hashin-Shtrikman bounds, and Tamura, as well as factors such as boundary conditions, elastic foundation parameters, length-to-thickness ratio, and aspect ratio. The research results can provide valuable insights for future analyses of FG plates with different boundaries, utilizing different micromechanical models.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.198-205
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• 2017

Thermal dissipation was investigated for poly methyl methacrylate (PMMA) composite films containing graphite and multi wall carbon nanotube(CNT) powders as filler materials. After mixing PMMA with fillers, solvent, and dispersant, the pastes were prepared by passing through a three roll mill for three times. The prepared pastes were coated $15{\sim}40{\mu}m$ thick on a side of 0.4 mm thick aluminium alloy plate and dried for 30 min at $150^{\circ}C$ in an oven. The content of fillers in dried films was varied as 1, 2, and 5 weight % maintaining the ratio of graphite and CNT as 1:1. Raman spectra from three different samples exhibited D, G and 2D peaks, as commonly observed in graphite and multi wall CNT. Among those peaks, D peak was prominent, which manifested the presence of defects in carbon materials. Thermal emissivity values of three samples were measured as 0.916, 0.934, and 0.930 with increasing filler content, which were the highest ever reported for the similar composite films. The thermal conductivities of three films were measured as 0.461, 0.523, and $0.852W/m{\cdot}K$, respectively. After placing bare Al plate and film coated samples over an opening of a polystyrene box maintained for 1 h at $92^{\circ}C$, the temperatures inside and outside of the box were measured. Outside temperatures were lower by $5.4^{\circ}C$ in the case of film coated plates than the bare one, and inside temperatures of the former were lower by $3.6^{\circ}C$ than the latter. It can be interpreted that the PMMA composite film coated Al plates dissipate heat quicker than the bare Al plate.

• Journal of Korean Society of Steel Construction
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• v.23 no.5
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• pp.607-614
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• 2011

This study deals with thegeometrical nonlinear dynamic behavior of laminated plates made of advanced composite materials (ACMs), which contain central cutouts. Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration wereused for the nonlinear dynamic solution. The effects of the cutout sizes and lay-up sequences on the nonlinear dynamic response for various parameters werestudied using a nonlinear dynamic finite element program that was developed for this study. The several numerical results agreed well with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper showed significant interactions between the cutout and the layup sequence in the laminate. Key observation points are discussed and a brief design guide for laminates with central cutouts is given.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.1
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• pp.1-8
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• 2010

The dynamic instability analysis of delaminated composite structures subjected to in-plane pulsating forces is carried out based on the higher order shell theory of Sanders. In the finite element (FE) formulation, the seven degrees of freedom per each node are used with transformations in order to fit the displacement continuity conditions at the delamination region. The boundaries of the instability regions are determined using the method proposed by Bolotin. The numerical results obtained for skew plates and shells are in good agreement with those reported by other investigators. The new results for delaminated skew plate and shell structures in this study mainly show the effect of the interactions between the radius-length ratio and other various parameters, for example, skew angles, delamination size, the fiber angle of layer and location of delamination in the layer direction. The effect of the magnitude of the periodic in-plane load on the instability regions is also investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.73-76
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• 2008

Bipolar Plates for PEMFC have been a key component of fuel cells with MEA, thus in this research they have been fabricated by a compression molding technique after mixing graphite powder with phenol resin. The results have shown the prominent properties compared with those by foreign advanced company with respect to the electrical conductivity and flexural strength. In addition, it has been carried out that the Voltage-Current characteristics comparison according to the unit cell experiments of bipolar plates. As a result, we have obtained good performances and we are going to research the molding feasibility of bipolar plate's flow channel.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.369-383
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• 2018

In this work, a novel hyperbolic shear deformation theory is developed for free vibration analysis of the simply supported functionally graded plates in thermal environment and the FGM having temperature dependent material properties. This theory has only four unknowns, which is even less than the other shear deformation theories. The theory presented is variationally consistent, without the shear correction factor. The present one has a new displacement field which introduces undetermined integral variables. Equations of motion are obtained by utilizing the Hamilton's principles and solved via Navier's procedure. The convergence and the validation of the proposed theoretical model are performed to demonstrate the efficacy of the model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.77-83
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• 1998

The most of the design engineers for construction has academic background of bachelors degree. Theories for advanced composite structures are too difficult for such engineers and some simple but accurate enough methods are necessary. The senior author has reported that some laminate orientations have decreasing values of B$_{16}$, B$_{26}$, D$_{26}$, and D$_{26}$ stiffnesses as the ply number increases. Such plates above behave as special orthotropic plates and simple formulas developed by the senior author［1, 3］ can be used. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms(M$_{x}$) on the relevant partial differential equations of equilibrium. In this paper, the result of the study on the subject problem is presented.ted.d.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.223-230
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• 1998

The most of the design engineers for construction has academic background of bachelors degree. Theories for advanced composite structures are too difficult for such engineers and some simple but accurate enough methods are necessary. The senior author has reported that some laminate orientations have decreasing values of D$_{16}$, B$_{16}$, D$_{26}$ and B$_{26}$ stiffnesses as the ply number increases. Such plates behave as special orthotropic plates and simple formulas developed by the author can be used. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms(M$_{x}$) on the relevant partial differential equations of equilibrium. In this paper, the result of the study on the subject problem is presented.ented.d.