• Elastomers and Composites
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• v.37 no.1
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• pp.21-30
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• 2002

Core-shell polymers of methyl methacrylate/styrene pair were prepared by sequential emulsion polymerization in the presence of sodium dodecyl benzene sulfonate(SDBS) as an emulsifier using ammonium persulfate(APS) as an initiator. The characteristics of these core-shell polymers were evaluated. Core-shell composite latex has the both properties of core and shell components in a particle, where as polymer blonds or copolymers show a combined properties from the physical properties or two homopolymers. This unique behavior of core-shell composite latex can be used in many industrial fields. However, in preparation of core-shell composite latex, several unexpected phenomina are observed, such as, particle coagulation, low degree of polymerization, and formation of new particles during shell polymerization. To solve the disadvantages, we studied the effects of surfactant concentrations, initiator concentrations, and reaction temperature on the tore-shell structure or PMMA/PSt and PSt/PMMA. Particle size and particle size distribution were measured by using particle size analyzer, and the morphology of the core-shell composite latex was observed by using transmission electron microscope. Glass transition temperature($T_g$) was also measured by using differential scanning calorimeter. To identify the core-shell structure, pH of the composite latex solutions were measured.

• Composites Research
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• v.32 no.5
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• pp.229-236
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• 2019

In this study, the effects of the additional processing parameters on the mechanical properties of thermoplastic composites fabricated with automated fiber placement (AFP) were evaluated. Annealing and vacuum bag only processes were then performed on the manufactured thermoplastic composites, respectively. For verification, the crystallinity was measured by differential scanning calorimetry (DSC), confirming the variation of semi-crystalline thermoplastic composite according to the process conditions. The void content of thermoplastic composites was evaluated by matrix digestion method while microscopic examination confirmed the porosity distribution. The interlaminar shear strength test was conducted for three different process parameters (VBO, annealing, and no treatment). A comparison of the three tested strengths was made, revealing that the porosity value had larger effect on the mechanical properties of the thermoplastic composite compared to the degree of crystallinity. Additionally, when thermoplastic composite melted up, the pores were continuously removed under vacuum process; the removal of the pores resulted in an increase of the interlaminar shear strength.

• Applied Chemistry for Engineering
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• v.16 no.5
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• pp.672-676
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• 2005

To improve the application of polymeric dental restorative composite (PDRC) for the posterior and anterior restoration, silica bridged with siloxane unit was firstly prepared by heat-treating a silica filler at various temperatures. Degree of conversion (DC), depth of cure, and dynamic volumetric polymerization shrinkage values of PDRC filled with silica bridged with siloxane unit were investigated to study the effect of heat-treated silica on the polymerization behavior of PDRC. From the experimental result, it was found that depth of cure was decreased with an increase of heat treatment temperature. on the other hand, both DC and polymerization shrinkage values were uniformly enhanced with increasing the heat treatment temperature. This phenomenon can be explained from the study that showed decrease of average particle size of silica resulted in the increase of relative amount of resin matrix in PDRC.

• Structural Engineering and Mechanics
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• v.22 no.3
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• pp.263-278
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• 2006

Starting with the geometrically non-linear formulation and the subsequent linearization, this paper presents a consistent formulation of the exact mechanical analysis of geometrically and materially linear three-layer continuous planar beams. Each layer of the beam is described by the geometrically linear beam theory. Constitutive laws of layer materials and relationships between interlayer slips and shear stresses at the interface are assumed to be linear elastic. The formulation is first applied in the analysis of a three-layer simply supported beam. The results are compared to those of Goodman and Popov (1968) and to those obtained from the formulation of the European code for timber structures, Eurocode 5 (1993). Comparisons show that the present and the Goodman and Popov (1968) results agree completely, while the Eurocode 5 (1993) results differ to a certain degree. Next, the analytical solution is used in formulating a general procedure for the analysis of layered continuous beams. The applications show the qualitative and quantitative effects of the layer and the interlayer slip stiffnesses on internal forces, stresses and deflections of composite continuous beams.

• Elastomers and Composites
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• v.52 no.3
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• pp.201-210
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• 2017

We studied the antibacterial effect and mechanical properties of PLA composites with in organic porous zeolite-type bacteriocides. The specimens were prepared by an intermeshing co-rotating twin screw extruder using different contents of inorganic bacteriocide. The degree of dispersion of the in organic bacteriocide in the PLA composite was confirmed by FE-SEM. The contents of Ag and Zn in the composite were also investigated by energy dispersive spectroscopy at different concentrations of the inorganic bacteriocide. The antibacterial effects were analyzed by turbidity analysis, shaking culture, and drop-test. The mechanical properties, such as the tensile and flexural properties, impact strength, and physical properties, were also investigated. As the content of inorganic bacteriocide increased, the antibacterial activity was increased, especially against Staphylococcus aureus. Mechanical properties, namely, tensile strength, elongation, flexural strength, and impact strength, tended to decrease with an increase in inorganic bacteriocide content, but the tensile and flexural modulus increased.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.393-400
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• 1996

The conducting polymer composites were prepared by imbibing the porous particle with an $FeCl_3$ oxidant solution, drying the imbibed porous particle, and imbibing again with pyrrole solution for polymerization to take place in the pore. The conductivity of the porous composite particles, was higher than that of nonporous particles. Also, the conductivity of composite was increased with increasing specific surface area and pore specific volume of the host porous particles since the degree of formation of conducting polymer in the pore increased.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.771-776
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• 1997

The various shape of calcium carbonate were prepared. For the preparation of the PP/$CaCO_3$ composite, these synthetic calcium carbonate(cubic, spheric and neddle type) and PP were mixed on a two roll mill and the mixture were pressed into plate. The effect of particle shape in the prepared composite on the crystallization temperature, heat of fusion, size of spherulite and mechanical properities were investigated. It was found that the former four were strongly influenced by that. When, especially, vaterite was mixed with PP, the size of spherulite was smaller and the degree of crystallinity was higher than others. Therefore, the tensile strength and Young's modulus were higher.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.154-157
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• 2000

Distributed piezoelectric sensor and actuator system has been designed for the active vibration control of shell structure. PVDF is used for the materials of sensor/actuator. To prevent the adverse effect of spillover, distributed modal sensor/actuator system is established. Although shell structure is three-dimensional structure, the PVDF sensor/actuator system can be treated as two-dimensional Finite element programs are developed to consider curved structures having PVDF modal sensor/actuator. The nine-node Mindlin shell element with five nodal degree of freedoms is used for finite element discretization. The electrode patterns and lamination angle of PVDF sensor/actuator are optimized to design the modal sensor/actuator system Genetic algorithm is used for optimization. Sensor is designed to minimize the observation spillover, and actuator is designed to minimize the system energy of the control modes under a given initial condition. Modal sensor/actuator for the first and second modes of singly curved cantilevered shell structure are designed using mentioned methods. Discrete LQG method is used as a control law. Experimental demonstrations of the active vibration control with designed sensor/actuator system have been performed successfully.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.650-655
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• 1993

Carbon/epoxy composite(CFRP) coupons previously damaged by low velocity impact were tested under static tensile loading and microscope progress of damage was characterized by ultrasonic C-scan, Scanning Acoustic Microscopy (SAM) and Acoustic Emission(AE) techniques which were based on the application of elastic waves. The degress of impact damage has been correlated with the AE activity during monotonic or loading/unloading tensile testing as well as the result of ultrasonic test. The coupons were subjected to impact velocities ranged from 0.71 to 2.17 m/sec, which introduced the amount of damage rated as 0%, 10%, 30%, and 50% with reference to the total absorbed energy at fracture. Special attention was paid to determine optimal AE parameters to characterize the microscopic fracture process and to predict the residual strength of composite laminates. AE RMS voltage during the early stage of tensile loading was found an effective parameter to quantify the degree of impact damage. It was also found that the Felicity ratio is closely related to the stacking sequence and the residual strength of the CFRP laminates.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.238-241
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• 2003

Recently, construction companies is briskly doing brand marketing investment through the housing brand development. The importance of brand asset is increasing, the brand management is time to set for strong brand. But brand asset management so far has been done in manufacturing and service industry, there is no discussion about housing brand asset management of construction companies. It is aware that how important brand is, but we can't present data for brand marketing investment owing to absence of brand asset management method. Therefore, the purpose of this paper is trying to deduce importance degree of brand asset composite factor through the brand power research. Also it is to present guideline about brand management strategy.