• Title/Summary/Keyword: elastic composites

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Effects of Blowing and Nucleating Agents on the Foaming Properties of Nylon 6

  • Jung-soo Kim;Sung Yeol Kim
    • Elastomers and Composites
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    • v.58 no.2
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    • pp.65-69
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    • 2023
  • To reduce the weight of the engineering plastic Nylon 6 resin, two high-temperature foaming agents, p-toluenesulfonyl semicarbazide (PTSS) and 5-phenyltetrazole (5-PT) (0-10 phr), were added and foamed without other additives. We investigated the effects of the foaming agent type and content on the foam density (g/cm3) and percent weight reduction rate of the Nylon 6 foam, and 5-PT exhibited better foaming performance than PTSS. In the case of 5-PT, the weight reduction rate was above 36% when the blowing agent content was 1.5 phr or higher, indicating that 5-PT is an effective blowing agent for reducing the Nylon 6 foam weight. Additionally, we studied the effect of the nucleating agent Talc content (0-0.4 phr) on Nylon 6 foaming, and the nucleating agent Talc considerably reduced foaming.

Wave propagation in spherical and cylindrical panels reinforced with carbon nanotubes

  • Yi-Wen Zhang;Hao-Xuan Ding;Gui-Lin She
    • Steel and Composite Structures
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    • v.46 no.1
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    • pp.133-141
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    • 2023
  • Based on the third-order shear deformation theory, the wave propagations in doubly curved spherical- and cylindrical- panels reinforced by carbon nanotubes (CNTs) are firstly investigated in present work. The coupled equations of wave propagation for the carbon nanotubes reinforced composite (CNTRC) doubly curved panels are established. Then, combined with the harmonic balance method, the eigenvalue technique is adopted to simulate the velocity-wave number curves of the CNTRC doubly curved panels. In the end, numerical results are showed to discuss the effects of the impact of key parameters including the volume fraction, different shell types (including spherical (R1=R2=R) and cylindrical (R1=R, R2=→∞)), wave number as well as modal number on the sensitivity of elastic waves propagating in CNTRC doubly curved shells.

Intrinsic Properties and Potential Wide Uses of Polyrotaxane Derivatives in Relation to Slide Ring Cross-Links Architectures

  • Juho Yun;Namil Kim
    • Elastomers and Composites
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    • v.58 no.4
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    • pp.201-207
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    • 2023
  • Owing to their unique properties originating from slidable cross-links, polyrotaxane derivatives have potential applications as polymer electrolytes for lithium-ion batteries, lightweight polymer alloys for vehicular bodies and their glazing, elastic rubbers for tires, hydrogels for drug delivery. This article reviews the structures of polyrotaxanes comprising cyclic molecules threaded by a linear axle polymer. Next, the versatile characteristics of polyrotaxane gels, elastomers, and polymer alloys such as toughness, elasticity, and softness are discussed in relation to their supramolecular architectures. Finally, the mechanical behavior of solid ring cross-links are compared with that of conventional fixed cross-links for better understanding.

Thermal/Mechanical Properties of Hafnium Carbide Coatings on Carbon-Carbon Composites (탄소-탄소 복합재료의 하프늄 탄화물 코팅재의 열적/기계적 특성)

  • Choi, So-dam;Seo, Hyoung-IL;Lim, Byung-Joo;Sihn, Ihn Cheol;Lee, Jung Min;Park, Jong Kyoo;Lee, Kee Sung
    • Composites Research
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    • v.31 no.5
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    • pp.260-266
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    • 2018
  • This study investigates thermal and mechanical characterization of Hafnium carbide coating on the $C_f-C$ composites. The hafnium carbide coatings by vacuum plasma spray on the C/C-SiC composites are prepared to evaluate oxidation and wear resistance. We perform the thermal durability tests by thermal cycling at $1200^{\circ}C$ for 10cycles in air and investigates the weight change of each cycle. We also evaluate the wear and indentation behavior using tungsten carbide ball indenter as a mechanical evaluation. As a result, the HfC coating is beneficial to reduce of weight loss during thermal cycling test and improve the elastic property of C/C-SiC composite. Especially, the HfC coating improves the wear resistance of C/C-SiC composite.

Strain Rate Effect on the Compressive and Tensile Strength of Hooked Steel Fiber and Polyamide Fiber Reinforced Cement Composite (변형 속도에 따른 후크형 강섬유 및 폴리아미드섬유보강 시멘트 복합체의 압축 및 인장강도 특성)

  • Kim, Hong-Seop;Kim, Gyu-Yong;Lee, Sang-Kyu;Son, Min-Jae;Nam, Jeong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.3
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    • pp.76-85
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    • 2017
  • In this study, to evaluate the mechanical properties of fiber-reinforced cement composites by strain rate, hydraulic rapid loading test system was developed. And compressive and tensile strength of the hooked steel fiber and polyamide fiber reinforced cement composite were evaluated. As a result, the compressive strength, strain capacity and elastic modulus were increased with increasing strain rate. The effect of compressive strength by type and volume fraction of fibers was not significant. The dynamic increase factor(DIF) of the compressive strength was higher than that of the CEB-FIP model code 2010 and showed a trend similar to that of ACI-349. The tensile strength and strain capacity were increased with increasing strain rate. The hooked steel fibers were drawn from the matrix. The tensile strength and strain capacity of hooked steel fiber reinforced cement composites were increased as the strain rate increased. The tensile strength and deformation capacity of the fiber reinforced cement composites were increased. And, hooked steel fibers were drawn from the matrix. On the other hand, because the bonding properties of polyamide fiber and matrix is large, polyamide fiber was cut-off with out pullout from matrix. The strain rate effect on the tensile properties of polyamide fiber reinforced cement composites was found to be strongly affected by the tensile strength of the fibers.

Study on the Coefficient of Thermal Expansion for Composites Containing 2-Dimensional Ellipsoidal Inclusions (2차원 타원형의 충전제를 함유하는 복합재료의 열팽창 계수 연구)

  • Lee, Kee-Yoon;Kim, Kyung-Hwan;Jeoung, Sun-Kyoung;Jeon, Hyoung-Jin;Joo, Sang-Il
    • Polymer(Korea)
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    • v.31 no.2
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    • pp.160-167
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    • 2007
  • This paper proposes a model for the solutions predicting the coefficient of thermal expansion of composites including fiber-like shaped$(a_1>a_2=a_3)$ and disk-like shaped$(a_1=a_2>a_3)$ inclusions like two dimensional geometries, which was analyzed by one axis and a single aspect ratio, $(\rho_\alpha=a_1/a_3)$. The analysis follows the procedure developed for elastic moduli by using the Lee and Paul's approach. The effects of the aspect ratio on the coefficient of thermal expansion of composites containing aligned isotropic inclusions are examined. This model should be limited to analyze the composites with unidirectionally aligned inclusions and with complete binding to each other of both matrix and inclusions having homogeneous properties. The longitudinal coefficients of thermal expansion $\alpha_{11}$ decrease and approach the coefficient of thermal expansion of filler, as the aspect ratios increase. However, the transverse coefficients of thermal expansion $\alpha_{33}$ increase or decrease with the aspect ratios.

Properties on the Strength of Polymer Concrete Using Nano MMT-UP Composite (나노 MMT-폴리머 복합체를 이용한 폴리머 콘크리트의 강도 특성)

  • Jo, Byung-Wan;Moon, Rin-Gon;Park, Seung-Kook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.761-766
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    • 2006
  • Polymer composite are increasingly considered as structural components for use in civil engineering, on account of their enhanced strength-to-weight ratios. Unsaturated polyester (UP) resin have been widely used for the matrix of composites such as FRP and polymer composite, due to its excellent adhesive. Polymer nanocomposites are new class of composites derived from the nano scale inorganic particles with dimensions typically in the range of 1 to 1000 nm that are dispersed in the polymer matrix homogeneously. Owing to the high aspect ratio of the fillers, mechanical, thermal, flame, retardant and barrier properties are enhanced without significant loss of clarity, toughness or impact strength. To prepare the MMT (Montmorillonite)-UP exfoliated nanocomposites, UP was mixed with MMT at $60^{\circ}C$ for 3 hours by using pan mixer. XRD (X-ray diffraction) pattern of the composites and TEM (Transmission Electron Micrographs) showed that the interlayer spacing of the modified MMT were exfoliated in polymer matrix. The mechanical properties also supported these findings, since in general, tensile strength, modulus with modified MMT were higher than those of the composites with unmodified MMT. The thermal stability of MMT-UP nanocomposite is better than that of pure UP, and its glass transition temperature is higher than that of pure UP. The polymer concrete made with MMT-UP nanocomposite has better mechanical properties than of pure UP. Therefore, it is suggested that strength and elastic modulus of polymer concrete was found to be positively tensile strength and tensile modulus of the MMT-UP nanocomposites.

A Study on the Development of Multiscale Bridging Method Considering the Particle Size and Concentration Effect of Nanocomposites (나노입자의 크기효과와 체적분율 효과를 동시 고려한 나노복합재의 멀티스케일 브리징 해석기법에 관한 연구)

  • Yang, Seung-Hwa;Yu, Su-Young;Cho, Maeng-Hyo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.4
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    • pp.343-348
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    • 2009
  • In this study, an efficient sequential bridging method to characterize both the particle size effect and concentration effect on the mechanical properties of nanocomposites at high volume fraction is suggested through a molecular dynamics(MD) simulations and micromechanics of composites materials. The Young's modulus and the shear modulus of the nanocomposites at various particle radius and at 12% volume fraction were obtained from MD simulations and multi-inclusion model was adopted to describe both modulus in continuum model. In order to describe the particle size effect, an additional phase, effective interface, was adopted as characteristic phase and the non-dilute concentration effect which appears at 12% volume fraction was describe via the variation of the elastic modulus of the infinite medium. Both the elastic modulus of the interface and infinite medium were fitted into functions of particle radius for the applicability of the present bridging method at various particle radii. Using the present bridging method the elastic modulus of the nanocomposites was efficiently obtained with accuracy. In addition, the effect of the interface thickness and modulus on the elastic modulus of the nanocomposite was investigated.

Polymerization Shrinkage Behavior Measured by Digital Image Correlation for Methacrylate-based and Silorane-based Composites During Dental Restoration (디지털 이미지 상관법을 이용한 Methacrylate기질과 Silorane기질 복합레진의 치아 수복 시 중합수축거동)

  • Park, Jung-Hoon;Choi, Nak-Sam
    • Composites Research
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    • v.33 no.3
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    • pp.125-132
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    • 2020
  • The polymerization shrinkage behavior of dimethacrylate-based composite (Clearfil AP-X, Kuraray) and silorane-based composite (Filtek P90, 3M ESPE) used for dental composite restorations was measured using digital image correlation method. The stress distribution on the surface of specimen was calculated by finite element analysis with equivalent elastic modulus and was compared with the measured shrinkage distribution. Camera images were monitored by a CCD camera during and after the irradiation of light. As a result of the DIC analysis, a non-uniform shrinkage distribution was observed in both composite resins, and the resin core inside the ring specimen had free flowability, leading to in greater shrinkage strain than the resin/ring interfacial region. It was observed that as the distance from the center of the resin increased, the radial average shrinkage strain decreased. The radial average shrinkage strain during light irradiation occurred to be 33% for P90 and 57% for AP-X of the entire strain at the end of the test. The shrinkage behavior of P90 and AP-X was measured to be significantly different from each other during light irradiation. In the resin near the resin/ring interface, it was confirmed that the tensile strain rapidly formed to increase after light irradiation, causing a tensile stressed, interface weak.

Sliding Wear Properties of Carbon Fiber Reinforced $Si_3N_4$ Ceramics (탄소섬유강화 질화규소 세라믹스의 마찰마모 특성)

  • Park Yi-Hyun;Yoon Han-Ki;Kim Bu-Ahn;Park Won-Jo
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.05a
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    • pp.347-351
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    • 2004
  • [ $Si_3N_4$ ] composites have been extensively studied for engineering ceramics, because it has excellent room and high temperature strength, wear resistance properties, good resistance to oxidation, and good thermal and chemical stability. In the present work, carbon short fiber reinforced $Si_3N_4$ ceramics were fabricated by hot press method in $N_2$ atmosphere at $1800^{\circ}C$ using $Al_2O_3\;and\;Y_2O_3$ as sintering additives. Content of carbon short fiber was $0\%,\;0.1\%\;and\;0.3\%$. The composites were evaluated in terms of density, flexural strength and elastic modulus through the 3-point bending test at room temperature. Also, The wear behavior was determined by the pin on disk wear tester using silicon nitride ball. Experimental density and flexural strength decreased with increasing content of carbon fiber. But specific modulus increased with increasing content of carbon fiber. In addition, friction coefficient and specific wear loss decreased with increasing content of carbon short fiber by reason of interfacial defects between matrix and fiber.

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