• Textile Coloration and Finishing
• /
• v.27 no.1
• /
• pp.11-17
• /
• 2015

Recently, super fiber reinforced composite materials are widely used in many industries due to high mechanical properties. In this study, 2 different types of composite materials were manufactured in order to compare their mechanical properties. Carbon and Aramid fibers were used for reinforcement materials and Bisphenol-A type epoxy resin was for matrix. Two kinds of fiber-reinforced materials were manufactured by RIM(Resin Injection Molding) method. Before manufacturing composite materials, the optimal manufacturing and curing process condition were established and the ratio of reinforcement to epoxy resin was discussed. FT-IR analysis was conducted to clarify the structure of epoxy resin. Thermal and mechanical property test were also carried out. The cross-section of composite materials was observed using a scanning electron microscope(SEM).

• Tribology and Lubricants
• /
• v.24 no.4
• /
• pp.163-169
• /
• 2008

Tribological properties of ceramic brake discs were investigated using a commercial friction material. The discs were manufactured by liquid silicon infiltration (LSI) into a C-C preform. The disc surface was modified by two different methods, producing sliding surfaces with chopped carbon fibers and carbon felt. In addition, the composition of the surface was also changed. Friction characteristics of the discs were examined using a 1/5 scale dynamometer. Results showed that the type and composition of the disc surface significantly affected the level of braking effectiveness and high temperature brake performance. The discs with felt surfaces showed higher friction levels than those with chopped fiber surfaces and SiC tended to increase the friction level while C lowered the friction coefficient. The ceramic disc was more sensitive to the deceleration rate than gray iron, showing high speed sensitivity.

• Steel and Composite Structures
• /
• v.28 no.5
• /
• pp.541-557
• /
• 2018

This paper presents the influence of carbon nanotubes (CNTs) waviness and aspect ratio on the vibrational behavior of functionally graded nanocomposite sandwich annular sector plates resting on two-parameter elastic foundations. The carbon nanotube-reinforced (CNTR) sandwich plate has smooth variation of CNT fraction along the thickness direction. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. Effects of CNT distribution, volume fraction, aspect ratio and waviness, and also effects of Pasternak's elastic foundation coefficients, sandwich plate thickness, face sheets thickness and plate aspect ratio are investigated on the free vibration of the sandwich plates with wavy CNT-reinforced face sheets. The study is carried out based on three-dimensional theory of elasticity and in contrary to two-dimensional theories, such as classical, the first- and the higher-order shear deformation plate theories, this approach does not neglect transverse normal deformations. The sandwich annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free.

• Structural Engineering and Mechanics
• /
• v.67 no.4
• /
• pp.403-415
• /
• 2018

In the present study, nonlinear dynamic response of polymer-CNT-fiber multiscale nanocomposite plate resting on elastic foundations in thermal environments using the finite element method is performed. In this regard, the governing equations are derived based on Inverse Hyperbolic Shear Deformation Theory and von $K{\acute{a}}rm{\acute{a}}n$ geometrical nonlinearity. Three type of distribution of temperature through the thickness of the plate namely, uniform linear and nonlinear are considered. The considered element is C1-continuous with 15 DOF at each node. The effective material properties of the multiscale composite are calculated using Halpin-Tsai equations and fiber micromechanics in hierarchy. The carbon nanotubes are assumed to be uniformly distributed and randomly oriented through the epoxy resin matrix. Five types of impulsive loads are considered, namely the step, sudden, triangular, half-sine and exponential pulses. After examining the validity of the present work, the effects of the weight percentage of SWCNTs and MWCNTs, nanotube aspect ratio, volume fraction of fibers, plate aspect, temperature, elastic foundation parameters, distribution of temperature and shape of impulsive load on nonlinear dynamic response of CNT reinforced multi-phase laminated composite plate are studied in details.

• Journal of the Korean Applied Science and Technology
• /
• v.24 no.3
• /
• pp.264-271
• /
• 2007

Effect of dispersion methods for Vapor Grown Carbon Fibers (VGCF) in epoxy caused the change in mechanical properties of VGCF/epoxy nanocomposites, such as tensile modulus and tensile strength. The influence of VGCF types - atmospheric plasma treated (APT) VGCF and raw VGCF - and their contents was discussed in detail. Treating VGCF with atmospheric plasma enhanced the surface energy, therefore improved the bonding strength with epoxy matrix. Two different methods used to disperse VGCF were ultrasonic and mechanical homogenizer methods. When using dispersion solutions, the VGCF demonstrated good dispersion in ethanol in both homogenizer and ultrasonic method. The uniform dispersion of VGCF was investigated by scanning electron microscopy (SEM) which showed well-dispersion of VGCF in epoxy matrix. The tensile modulus of raw VGCF/epoxy nanocomposites obtained by ultrasonic method was higher than that of one obtained by homogenizer method. APT VGCF/epoxy nanocomposites showed higher tensile strength than that of raw VGCF/epoxy nanocomposites.

• Fibers and Polymers
• /
• v.1 no.1
• /
• pp.32-36
• /
• 2000

An alternative strategy to .educe the percolation threshold of carbon black (CB) in polymer blends was investigated using random copolymer ternary blends of polystyrene (PS), poly(methyl methacrylate)(PMMA), and a styrene-methyl methacrylate random copolymer (SMMA). The target morphology was to selectively locate CB particles in the encapsulating layer of SMMA during melt mixing. The CB used in this study is BP-2000 from Cabot and has a strong selective affinity to PS. Even when the CB was premixed with SMMA, it moves to the PS phase during the melt mixing. However, we also observed the CB particles located at the interface between SMMA and PS phases. Through this study it is found that the interaction between polymers and CB particles is critical for selectively localizing CB particles in multi-component polymer blends. Although appropriate processing condition may retard the movement of CB particles to the polymer phase with affinity, it cannot prevent it completely and locate them to the SMMA phase, which is not thermodynamically favored. To locate CB particles in an encapsulating layer of ternary polymer blends, first of all, polymers forming it should have selective affinity to CB.

• Magazine of the Korea Concrete Institute
• /
• v.2 no.3
• /
• pp.55-64
• /
• 1990

With the increasing use of Fiber Reinforced Concrete as a structural material. More information on its mechanical properties is needed. This paper reports the results of experiments on the behavior of Carbon Fiber Reinforced Concrete under monotonic and cyclic compressive loading. The results are that (1) CFRC does improve its compressive strength by adding fibers to a concrete matrix. (2) Adding any fiber to a concrete matrix produced a substaintial change in its stress-strain response. This change is characterized by a significant increase in ductility as described by the descending portion of the stress-strain curve. (3) As compare with plain concrete, the normalized cyclic behavior of CFRC has a much stability. A higher fiber"" content produes a lesser steep descending portion, which results in a higher ductlity of the material.

• Advanced Composite Materials
• /
• v.16 no.1
• /
• pp.1-10
• /
• 2007

Composite materials consisting of crushed carbon fiber reinforced plastics (CFRP) pieces and acrylonitrile-butadiene-styrene (ABS) resin were prepared by an injection mold method to solve the problem of recycling of CFRP. The electrical properties, such as electrical resistivity, alternating current impedance and electromagnetic interference (EMI) shielding effect, were measured for the composites. The electrical resistivity of the composites showed a percolation type of conduction behavior and no difference between parallel and perpendicular to the injection direction was observed for CFRP content higher than the critical value. Measurement of alternating current impedance revealed that the conduction mechanism is attributed to the direct conductive paths generated by distributed carbon fibers; however, strong frequency dependence of the impedance was observed for the CFRP content near the critical one. The frequency dependence of the impedance is caused by the inter-fiber connection and can be expressed as a simple equivalent circuit. The absorption component of shielding effect (SE) was smaller than the expected value estimated from its resistivity. The decline of SE is thought to be caused by the decrease in effective thickness due to fiber orientation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.4
• /
• pp.564-573
• /
• 2001

The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.

• Journal of the Semiconductor & Display Technology
• /
• v.14 no.2
• /
• pp.61-65
• /
• 2015

SiC composite materials are usually used to very high temperature condition such as thermal protection system materials at space vehicles, combustion chambers or engine nozzles because they have high specific strength and good thermal properties at high temperature. One of the most widely used fabrication methods of SiC composites is the chemical vapor infiltration (CVI) process. During the process, chemical gases including Si are introduced into porous preform which is made by carbon fibers for infiltration. Since the processes take a very long time, it is important to reduce the process time in designing the reactors and processes. In this study, both the gas flow and heat transfer in the reactors during the processes are analyzed using a computational fluid dynamics method in order to design reactors and processes for uniform, high quality SiC composites. Effects of flow rate and heater temperature as process parameters to the infiltration process were examined.