• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.919-927
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• 2002

In order to fabricate double-layered porous materials powders of different particle sizes were pressed stepwise. Ford＇s equation which predicts the fired density with the change in pressed density was employed in order to adjust the difference in sintering shrinkage of the green body with double-layered porous structure. Double-layered porous materials were characterized by investigating microstructures and permeability. SEM micrographs showed the distinct difference in pore sizes of double-layered porous material. Permeability of single-layered porous material increased by increasing the starting particle sizes and porosity as well. Permeability of the double-layered porous material depends largely on the layer of small pore diameter.

• Korea-Australia Rheology Journal
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• v.18 no.4
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• pp.217-224
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• 2006

Rapid flow advancement without void formation is essential in the liquid composite molding (LCM) such as resin transfer molding (RTM) and vacuum assisted resin transfer molding (VARTM). A highly permeable layer in multi-layered preform has an important role in improvement of the flow advancement. In this study, a multi-layered preform which consists of three layers is employed. Radial flow experiment is carried out for the multi-layered preform. A new analytic model for advancement of flow front is proposed and effective permeability is defined. The effective permeability for the multi-layered preform is obtained analytically and compared with experimental results. Compaction test is performed to determine the exact fiber volume traction of each layer in the multi-layered preform. Transverse permeability employed in modeling is measured experimentally unlike the previous studies. Accurate prediction of flow advancement is of great use for saving the processing time and enhancing product properties of the final part.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1149-1152
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• 2007

Many kind of damping materials are generally used on concrete slab in apartment building to reduce floor impact noise level. Lately, multi-layered damping material that is consist of several materials are used to improve the effect of floor impact noise insulation. In this study, dynamic stiffness of multi-layered damping material that is consist of common materials such as expanded polystyrene(EPS), expended polyethylene(EPE), ethylene vinyl acetate(EVA) and polyester was investigated. It was found that dynamic stiffness of multi-layered damping material could be estimated if know value of each layer that compose whole structure. And it was found that dynamic stiffness of whole structure did not change even if change order that build layer.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.41-46
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• 2007

Lightweight multi-layered boards with high stiffness for the automotive interior trims were developed, which were composed of a single material. The boards were constructed in the form of substrate/core/substrate with newly developed materials. The materials which have high tensile strength and elongation were selected for the substrate materials, and those which have high compressive strength and low density were selected for the core materials. 25 types of multi-layered boards were fabricated using the selected substrate and core materials. The compatibility with the skin materials, the formability and the tensile strength and flexural strength of the specimens were evaluated. The results show that three types of multi-layered boards(Kenboard/EPP foam/Kenboard, Twintex/PP honeycomb/Twintex, Curv sheet/EPP foam/Curv sheet) are appropriate for the automotive interior trims. Considering the ease of materials supply and the economical aspect, Kenboard/EPP foam/Kenboard is thought to be the most realistic alternative.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.183-190
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• 2007

It is well known that abrasive waterjet(AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain the better cutting quality of various materials such as metals, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, AWJ device still has some problems to obtain the high quality of thin workpiece. In this paper, we investigated the optimal microcutting conditions of AWJ, such as maximum pressure, cutting speed and standoff distance of thin multi-layered materials. The experimental results show that AWJ has possibilities and potential to apply to the microcutting of thin multi-layered materials for IT industrial applications.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.97-103
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• 2012

This study investigates thermal insulation properties of multi layer materials depending on thickness of air layers. Numerical analysis on the heat flow of different insulating materials was conducted to identify whether their temperature distributions demonstrate the reduced rate of heat transfer conclusively or not. Analytical model is divided into two categories. One is to distinguish temperature distribution of the air-layer materials from the non-air layer ones. The other is to compare the efficacy between eight-layered insulating materials with no air-layer contained and three-layered insulating materials which include an air-layer definitely. In the latter case, the identical thickness is assigned to each material. The effect of thermal insulation by including an air-layer is verified in the first analytical model. The result of the second model shows that the insulation of the eight-layered materials is coterminous at the three-layered ones with an air-layer and the thermal insulation of the two materials is imperceptible. The benefits of cost and energy saving are anticipated if air-layers are efficiently incorporated in multi layer insulating materials in a greenhouse.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.176-179
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• 2001

When the preform is composed of more than two layers with different in-plane permeability in resin transfer molding, effective average permeability should be determined for the flow analysis in the mold. The most frequently used averaging scheme is the weighted average scheme, but it does not account for the transverse flow between adjacent layers. A new averaging scheme is proposed predicting the effective permeability of the multi-layered preform, which accounts for the transverse flow effect. The new scheme is verified by measuring the effective permeability of the multi-layered preforms and the difference in each flow front position.

• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.758-766
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• 1997

Non-brittle fracture behaviour of the two composite structures made of two different brittle materials was investigated using 3-point bending test. First, the layered and fibrous macro-composites were fabricated using the material easily formed, yet showing a brittle fracture behaviour similar to ceramics. The layered and fibrous Al2O3 /Al2O3 composites with weak interface were also fabricated using plate of 2 mm thickness and rod of 3 mm diameter respectively. Comparison of the mechanical properties between these two structures was performed in the lights of flexural strength and work of fracture for the composites consisting of Al2O3 and simulated materials respectively. The strength ratio of layered structure to the monolith of same volume was 0.6 and the ratio of fibrous one was about 0.2 for the composites made of simulated brittle material. The ratio of the work of fracture of the fibrous to the layered was 0.47. For Al2O3/Al2O3 composites, the strength ratio of layered and fibrous structures to the monolith with same volume were about 0.6 and 0.2 respectively. The ratio of work of fracture of the fibrous to the layered was 0.6. These confirmed that the layered structure was superior to the fibrous one in terms of flexural strength and work of fracture.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.195-198
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• 2005

The role of elastic/plastic mismatch on the contact crack initiation is investigated for designing desirable surface-coated asymmetric layered composites. Various layered composites such as $Si_3N_4$ ceramics on $Si_3N_4+BN$ composite, soda-lime glass on various substrates with different elastic modulus for the analysis. Spherical indentation is conducted for producing contact cracks from the surface or interface between the coating and the substrate layer. A finite element analysis of the stress fields in the loaded layer composites enables a direct correlation between the damage patterns and the stress distributions. Implications of these conclusions concerning the design of asymmetric layered composites indicate that the elastic modulus mismatch is one of the important parameter for designing layered composite to prevent the initiation of contact cracks.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.137-140
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• 2005

Exfoliated nanocomposites of polypropylene/layered silicate were prepared by a melt compounding process using maleic anhydride modified polypropylene (PP-g-MAH) and organoclay. It was found that polypropylene/layered silicate nanocomposites exhibited remarkable reinforcement compared with the pure polypropylene or conventional composite filled with agglomerated organoclay. The polypropylene /layered silicate nanocomposites showed stronger and earlier shear thinning behaviors and outstanding strain hardening behavior than pure polypropylene or other conventional composites in shear and uniaxial elongational flows, respectively. We simulated rheological modeling for the pure polymer matrix and polypropylene/layered silicate nanocomposite in shear and elongational flows using K-BKZ integral constitutive equation. The two types of K-BKZequations have been examined to describe experimental results of shear and uniaxial elongational viscosities of pure polypropylene and polypropylene/layered silicate nanocomposite.