• Composites Research
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• v.37 no.3
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• pp.155-161
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• 2024

Boron nitride nanotubes and carbon nanotubes are the most representative one-dimensional nanostructures, and have received great attention as reinforcement for multifunctional composites for their excellent physical properties. The two nanotubes have similar excellent mechanical stiffness, strength, and heat conduction properties. Therefore, the reinforcing effect of these two nanotubes is greatly influenced by the properties of their interface with the polymer matrix. In this paper, recent comparative studies on the reinforcing effect of boron nitride nanotubes and carbon nanotubes through experimental pull-out test and in-silico simulation are summarized. In addition, the conflicting aspect of the two different nanotubes with structural defects in their side wall is discussed on the viscoelastic damping performance of nanocomposites.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.461-467
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• 1992

A fabrication process for SiC whisker preform reinforced AC4A Al composites is being developed. The Al alloy used as the matrix in this study is AC4A. SiC whisker preform made by Tokai Carbon Co. Ltd. Shizuoka, Japan were used. These consisted of $\beta$-type single crystals 0.1 ~ 10${\mu}$m in diameter and 20~10${\mu}$m in length. The most adequate fabrication condition was that whisker preform was preheated up to 750~80$0^{\circ}C$, set into a mould preheated to ~40$0^{\circ}C$, molten Al alloy heated to ~80$0^{\circ}C$ and applied pressure 75MPa. And Si$C_w$reinforced AC4A composite was advanced above twice than AC4AI/M. Also it was not large effect by pressure at Si$C_w$ 20v/o.

• Composites Research
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• v.30 no.6
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• pp.371-378
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• 2017

In this study, hygroelastic behavior of thermosetting epoxy is predicted by molecular dynamics simulations. Since consistent exposures to humid environments lead to macroscopic degradation of polymer composite, computational simulation study of the hygroscopically aged epoxy cell is essential for long-time durability. Therefore, we modeled amorphous epoxy molecular unit cell structures at a crosslinking ratio of 30, 90% and with the moisture weight fraction of 0, 4 wt% respectively. Diglycidyl ether of bisphenol F (EPON862) and triethylenetetramine (TETA) are chosen as resin and curing agent respectively. Incorporating equilibrium and non-equilibrium ensemble simulation with a classical interatomic potential, various hygroelastic properties including diffusion coefficient of water, coefficient of moisture expansion (CME), stress-strain curve and elastic modulus are predicted. To establish the structural property relationship of pure epoxy, free volume and internal non-bond potential energy of epoxy are examined.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.136-143
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• 2021

Polyurea has been investigated as a polymer matrix for composite materials because of its high mechanical strength. Although polyurea has a similar chemical structure to polyurethane, it has much higher strength and durability. In this study, the fabrication of polyurea composites reinforced with carbon nanotube (CNT) and graphene oxide (GO) is demonstrated to enhance the tensile strength of the glass fibers composite. Using FTIR and Raman spectroscopies, the chemical structures of polyurea, CNT, and GO are investigated. As a result, spectroscopy analysis reveals that the chemical structure of CNT, GO, and polyurea is maintained during the fabrication of the composite structure. Scanning electron microscopy reveals the uniform distribution of CNT and GO across the polyurea matrix. The reinforcement of 1 wt% CNT in polyurea enhances the tensile strength of CNT/polyurea composites. In contrast, the reinforcement of GO in polyurea induces the degradation of the tensile strength of GO/polyurea composites.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.141-148
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• 2012

In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hydrophobic silica aerogel. The surface modification of silica aerogel was performed to obtain UV curable urethane acrylate hybrid coating sols with good compatibility by using surfactant(Brij 56). The polycarbonate substrates were coated by the prepared composites and cured under UV radiation. The incorporation of aerogel with only 10 vol% of content resulted in remarkable improvement by about 28% in the thermal insulation property of the coated film, as compared with substrate. In addition, increasing aerogel content was found to give minor effect on the variation of optical transparency, adhesion, and surface hardness of the coated film.

• Composites Research
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• v.36 no.5
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• pp.369-376
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• 2023

This study focuses on investigating the influence of epoxy polymer crosslinking density, a crucial aspect in composite material matrices, on the yield surface using molecular dynamics simulations. Our approach involved generating epoxy models with diverse crosslinking densities and subjecting them to both uniaxial and multiaxial deformation simulations, accounting for the elasto-plastic deformation behaviors. Through this, we obtained key mechanical parameters including elastic modulus, yield point, and strain hardening coefficient, all correlated with crosslinking conversion ratios. A particularly noteworthy finding is the rapid expansion of the yield surface in the biaxial compression region with increasing crosslinking ratios, compared to the uniaxial tensile region. This unique behavior led to observable yield surface variations, indicating a significant pressure-dependent relationship of the yield surface considering plastic strain and crosslinking conversion ratio. These results contribute to a deeper understanding of the complex interplay between crosslinking density and plastic mechanical response, especially in the aspect of multiaxial deformation behaviors.

• Composites Research
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• v.14 no.3
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• pp.51-56
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• 2001

It is known that the elastic modulus, maximum stress, and maximum strain of fiber-reinforced polymer composites are affected by high pressure. Fracture behavior is also known to be affected by high pressure. In this work, the pressure effect on the compressive fracture toughness of thick quasi-isotropic composites was investigated. Dog-bone type specimens of stacking sequence, [0$^{\circ}$/$\pm$45$^{\circ}$/90$^{\circ}$]$_{11s}$ were used. Compressive fracture tests were conducted under four pressure levels. The pressure levels applied were 0.1 MPa, 100 MPa, 200 MPa, and 300 MPa. Fracture toughness for each pressure level was determined from the compliance method. The results show that the compressive fracture toughness increases with increasing pressure. Specifically, fracture toughness increases 44% as the pressure increases from 0.1 MPa to 300 MPa.

• Polymer(Korea)
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• v.24 no.4
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• pp.564-570
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• 2000

The waste FRP occured in the fabrication of SMC (sheet molding compound) bathtubs and the waste polyurethane foam occured in electronic manufacture and waste insulator were applied as a soundproof and light weight pannel in the waste FRP unsaturated polyester matrix resin composites to recycle. The effect of filler contents on the mechanical properties and interfacial phenomena of the filler and matrix on the composites was evaluated. The tensile strength of composites reached its maximum value of 82.34 MPa when the filler content was 70 wt%, and the more content of reinforcement is increased, the more tensile modulus was decreased. The flexural strength and modulus of composites, reinforced 70 wt% with filler content, were dominant compared to the other samples to 72.5 MPa, 958.4 MPa respectively. When composite of reinforced 70 wt% with filler content, it was confirmed that pull out phenomena and cracks did not occur in the interface of reinforcement and matrix resin through the SEM observation. Also, waste FRP and urethane foam were dispersed well into matrix resin as filler.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.4
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• pp.191-195
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• 2004

This study investigated the effect of deep-sea environment on the compressive characteristics of polymer matrix composite. The specimens used in the experiment were thick Carbon-Epoxy composites that were made from Carbon-Epoxy prepregs. The specimens were immersed into seawater for thirteen months. The seawater content at saturation was about 1.2% of the specimen weight. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. It was found that the compressive elastic modulus increased about 10% as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased additional 2.3％ as the pressure increased to 270 MPa. It was also found that compressive fracture strength and compressive fracture strain increased with pressure in a linear behavior. Compressive fracture strength increased 28％ and compressive fracture strain increased 8.5％ as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.363-371
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• 2003

This study is mainly concerned with phenomenon of cavitation-erosion on the several materials and corrosive liquids which were applied with vibrator(suggested by ASTM G 32, 20KHz, 50$mu extrm{m}$). The maximum erosion rate by cavitation erosion in both of distilled water and sea water appeared to be proportioned to their hardness and tensile strength. Cavitation weight loss and rate of cast iron in sea water condition were greater(approximately 3 times) than that in distilled water condition, however in case of stainless steel and brass the cavitation weight loss of composite materials were not so different in both of their conditions. Cavitation weight loss of composite materials were shown as below on this test, Duratough DL : Weight loss in sea-water condition were greater (approximately 2.3 times) than it's distilled water condition. The main tendency of cavitation erosion for metals appeared that small damaged holes causing by cavitation erosion was observed with radial pattern. On the other hand, the tendency for composites appeared that small damaged holes were observed randomly.