• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.474-482
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• 2016

A Kelvin foam plate - widely used in the energy and transport industries as a lightweight structural material - was examined to estimate its Young's modulus using ultrasound. An isotropic tetrakaidecahedron foam structure was designed in SolidWorks and printed using 3D printer with an ABS plastic material. The 3D printed foam structure was used to build a foam plate with a 14 mm thickness ($50mm{\times}100mm$ in size) for the ultrasonic test. The Kelvin foam plate, a significantly porous medium, was completely filled with paraffin wax to enable the ultrasound to penetrate through the porous medium. The acoustic wave velocity of the wax-filled Kelvin foam was measured using the time of flight (TOF) method. Furthermore, the elastic modulus of the Kelvin foam was estimated based on an elastic structural model developed in this study. The Young's modulus of the produced Kelvin foam was observed to be approximately 3.4% of the bulk value of the constituent material (ABS plastic). This finding is consistent with experimental and theoretical results reported by previous studies.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.543-551
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• 2015

Polyurethane Foam(PUF), a outstanding thermal insulation material, is used for various structures as being composed with other materials. These days, PUF composed with glass fiber, Reinforced PUF(R-PUF), is used for a insulation system of LNG Carrier and performs function of not only the thermal insulation but also a structural member for compressive loads like a sloshing load. As PUF is a porous material made by mixing and foaming, mechanical properties depend on volume fraction of voids which is a dominant parameter on density. Thus, In this study, density is considered as the effect parameter on mechanical properties of Polyurethane Foam, and mechanical behavior for compression of the material is described by using modified Gurson damage model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.4
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• pp.191-197
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• 2018

This paper details the development of an isotropic elastic-damage constitutive model for polymeric foam based on irreversible thermodynamics to consider the growth and coalescence of voids. The constitutive equations describe the material behavior sustaining unilateral damage. To facilitate finite element analysis, the material properties for specific types of polymeric foams are applied to the developed model; the model is then implemented in ABAQUS as a user-defined material subroutine. To validate the developed damage model, the simulated results are compared to the results of a series of tensile tests on various polymeric foams. The proposed damage model can be utilized to further research on continuum damage mechanics and finite element analysis of polymeric foams in computational engineering.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.425-430
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• 2015

ZSM-5 crystals grew by hydrothermal synthesis method on the surface of foam type porous silicon carbide ceramics which fabricated by polymer replica method. Oxide layer was developed on the surface of the porous silicon carbide ceramics to induce growth of ZSM-5 from the surface. In this study, hydrothermal synthesis was carried out for 7 h at $150^{\circ}C$ using TEOS, $Al(NO_3){\cdot}9H_2O$ and TPAOH as raw materials in the presence of the porous silicon carbide ceramics. X-ray Powder Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses were confirmed $1{\sim}3{\mu}m$ sized ZSM-5 crystals have grown on the surface of porous silicon carbide ceramics. BET data shows that small pores about $10{\AA}$ size drastically enhanced and surface area increased from $0.83m^2/g$ to $30.75m^2/g$ after ZSM-5 synthesis on the surface of foam type porous silicon carbide ceramics.

• Composites Research
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• v.20 no.5
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• pp.20-25
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• 2007

Cyclic heating method is useful method for measuring the thermal diffusivity of porous materials. The main object of this paper is to develop and verify the thermal diffusivity measuring system of porous materials under vacuum condition. To verify this method, thermal diffusivities of the alumina ($Al_2O_3$) specimen and polystyrene foam were measured. Thermal diffusivities of these specimens were agreed with reference values. Thermal diffusivities of carbon/epoxy and porous insulation material were measured at atmospheric room temperature condition and vacuum condition respectively. Thermal diffusivities of carbon/epoxy and porous insulation material under vacuum are reduced by 66.4% and 64.9% compared to the thermal diffusivities under the atmospheric condition. These differences are considered the effect of the porous insulation material with an air.

• Composites Research
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• v.32 no.1
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• pp.56-64
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• 2019

In this paper, a model is developed to simulate carbon/carbon composite fabrication using chemical vapor infiltration, considering density and porosity change in the preform and multi-step hydrocarbons reactions. The model considers the preform as a porous medium whose diffusion and flow properties changes due to the porosity. To verify the theoretical model, two numerical analyses were performed for the case that the flow inside the preform is zero and the case that the flow inside the preform is calculated by fluid mechanics. The numerical results showed good agreement with the experimental data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.212-221
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• 2001

This paper deals with the design techniques for underwater acoustic basin. An underwater acoustic basin is needed for test and calibration of acoustic sensors, acoustic digital communication system, acoustic measurement system, and underwater image data telemetry system. KRISO(Korea Research Institute of Ships and Ocean Engineering) have planned the construction of an underwater acoustic tank from 1999 to 2001 through internal project. We studied about absorbtion characteristics of a porous re-cycled rubber which is selected as a absorption materials and designed absorption plate with wedge shape. The simulation of reflection analysis along the wedge angle for wedged type plate was presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.371-377
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• 2000

This paper deals with the design techniques for underwater acoustic basin. An underwater acoustic basin is needed for test and calibration of acoustic sensors, acoustic digital communication system, acoustic measurement system, and underwater image data telemetry system. KRISO(Korea Research Institute of Ships and Ocean Engineering) have planned the construction of an underwater acoustic tank from 1999 to 2001 through internal project. We studied about absorbtion characteristics of a porous re-cycled rubber which is selected as a absorption materials and designed absorption plate with wedge shape. The simulation of reflection analysis along the wedge angle for wedged type plate was presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.478-484
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• 2012

In this study, compression analyses of sandwich composites with porous core were carried out. Finite element models of aluminum foam and honeycomb core sandwich composite material were applied solid element. In the case of aluminum foam core, valid equivalence damage model was applied. In the in-plane compression analysis, the maximum load of aluminum foam core sandwich was similar with that of aluminum honeycomb core sandwich. But in case of aluminum honeycomb core sandwich, the load support region becomes longer in comparison with aluminum foam core sandwich. In the out-plane compression analysis, compression maximum load of aluminum honeycomb core sandwich was higher than that of aluminum foam core sandwich. Through these Simulation analysis, obtains the behavior of sandwich composites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.183-190
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• 2024

An environmentally-friendly nanocoating method that effectively adds flame retardant(FR) and gas shielding properties to combustible polymeric construction materials such as flexible polyurethane (PU) foam was studied. Naturally-driven two-dimensional(2D) nanomaterials such as graphene oxide (GO) can exhibit liquid crystalline (LC) properties in aqueous solutions, enabling uniform coatings on the various substrates including 3D-porous foams. LC phase-assisted coating serves as 3D-scaffold, facilitating the introduction of small molecules having antioxidant capabilities such as dopamine which is to form uniformly stacked FR coating. Additionally, the structural characteristics of the 2D-materials can effectively hinder the migration of toxic gases and flammable substances in the gas phase generated during combustion. This LC phase flame retardant coating technology could be a new approach to provide environmentally friendly and effective flame retardant and gas barrier properties to various types of polymeric materials.