• Composites Research
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• v.36 no.4
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• pp.270-274
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• 2023

The stacking configuration of fiber-reinforced polymer (FRP) composites, achieved via the filament winding process, exhibits distinct variations compared to conventional FRP composite stacking arrangements. Consequently, it becomes challenging to ascertain the influence of mechanical properties based on the typical stacking structures. Thus, it becomes imperative to enhance the mechanical behavior and optimize the interleaved structures to improve overall performance. Therefore, this study aims to investigate the impact of incorporating amorphous halloysite nanotubes (A-HNTs) within different layers of five unique layer arrangements on the low-velocity impact properties of interleaved carbon fiber-reinforced polymer (CFRP) structures. The low-velocity impact characteristics of the laminate were validated using a drop weight impact test, wherein the resulting impact damage modes and extent of damage were compared and evaluated under microscopic analysis. Each interleaved structure laminate according to whether nanoparticles are added was compared at impact energies of 10 J and 15 J. In the case of 10 J, the absorption energy showed a similar tendency in each structure. However, at 15 J, the absorption energy varies from structure to structure. Among them, a structure in which nanoparticles are not added exhibits the highest absorption energy. Additionally, various impact fracture modes were observed in each structure through optical microscopy.

• Composites Research
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• v.37 no.4
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• pp.343-349
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• 2024

The use of composite materials for structural fasteners is increasingly common, making it crucial to assess the deformation of these fasteners under fatigue behavior. In this study, clamp-type fasteners were manufactured using carbon fiber reinforced composites, and their structural stability and sectional damage rates were evaluated using electrical resistance measurement during fatigue behavior. While clamp-type composite fasteners exhibited minimal deformation in flat sections, significant deformation occurred in the bent sections due to fatigue. It was observed that insufficient angular stability led to concentrated damage in the bent sections. The dynamic fatigue behavior showed that the length change rate of the composite fasteners was within 0.6%, but the angular change rate reached up to 6%, indicating that the bent sections are the most critical areas. By utilizing the self-sensing capability of the composite fasteners, sectional damage behavior was assessed through electrical resistance measurement. Significant damage was noted in the bent sections due to fatigue, and 3D-CT results revealed substantial deformation and interfacial damage when the initial bend angle of the fasteners was less than 90 degrees. These findings highlight the importance of reinforcing the stiffness of the bent sections and establishing systematic angular standards in the development of composite fasteners.

• Composites Research
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• v.17 no.5
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• pp.54-60
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• 2004

A new three-dimensional model for predicting the relationship between the prestrain of the composite and the amount of phase transformation of shape memory alloy inducing shape memory effect has been proposed by using Eshelby's equivalent inclusion method with Mori-Tanaka's mean field theory. The model composite is aluminum matrix reinforced with short TiNi fiber shape memory alloy, where the matrix is work-hardening material of power-law type. The analytical results predicted by the current model show that most of the prestrain is induced by the plastic deformation of the matrix, except the small prestrain region. The strengthening mechanism of the composite by the shape memory effect should be explained by excluding its increase of yield stress due to the work-hardening effect of the matrix.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.90-97
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• 2009

Dispersion and self-sensing evaluation for single-carbon fiber reinforced in three different acid-treated CNT-epoxy nanocomposites were investigated by electro-micromechanical techniques and wettability tests. Self-sensing based on contact resistivity exhibited more noise for single carbon fiber/acid-treated CNT-epoxy composites than it did for untreated CNT. However, the apparent modulus was higher the acid treated case than the untreated case which is attributed to better stress transfer. The interfacial shear strength (IFSS) between carbon fibers and the CNT-epoxy was lower than that between carbon fiber and neat epoxy due to the increased viscosity associated with the addition of the CNT. The CNT-epoxy nanocomposite exhibited more hydrophobicity than did neat epoxy. Change in the thermodynamic work of adhesion was consistent with changes in the IFSS but disproportional to that of the apparent modulus. The optimum condition of acid treatment on the need can be obtained instead of the maximum condition.

• Composites Research
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• v.29 no.2
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• pp.73-78
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• 2016

In this paper, The concept of a wheel with carbon fiber composite is to replace the conventional material used for a wheel hub, such as plastic, with a disk-type hub made of carbon fabric and epoxy resin. The impact load from the ground under real conditions was considered; a low-velocity impact test was conducted to evaluate the impact performance of the carbon wheel and compare it with that of a conventional plastic wheel. This study applied a 70 J impact load as a test condition. The impact energy was controlled in the test by adjustment of height and weight of impactor. The use of a carbon disk wheel hub was confirmed to reduce weight and generate an excellent repulsive force at low energy under conditions similar to real driving conditions. The results showed that the maximum load increased proportionally depending on the impact load, but the growth of the maximum load was reduced at a 20 J impact load and tended to decrease at a 45 J impact load. The carbon wheel showed excellent properties ; the level of rebounding was 35.3% and 19.1% of the total impact energy at impact loads of 5 J and 10 J, respectively. On the other hand, the carbon disk wheel rebounded less than 5% of the total energy due to crack generation of the thin carbon hub for impact loads of more than 20 J.

• Composites Research
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• v.29 no.3
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• pp.111-116
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• 2016

The tilting pad journal bearing for the turbo compressor application has a role to support high speed and heavy loading rotor. White metal has been widely used for the bearing material but the conventional bearing is immediately suspended and induces serious serious damage to the rotor under the unexpected oil cut situation or the insufficient oil film formation. The carbon fiber reinforced composite having high specific stiffness, specific strength and excellent tribological characteristics can solve these seizure problems. In this work, the study on the durability of high thermal resistance carbon fiber/epoxy composite tilting pad journal bearing under oil cut situation was conducted. The material properties of the composite materials including tensile, compressive and interlaminar properties were measured at room and high temperature of oil cut situation. To investigate the possibility of failure of composite tilting pad journal bearing under oil cut situation, the stress distribution of the composite bearing was analyzed via finite element analysis and the Tsai-Wu Failure index was calculated. To verify the failure analysis results, the oil cut tests for the composite tilting pad journal bearing were conducted using industrial test bench.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.194-205
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• 1994

In this research, we attempt to fabricate an excellent CFRC(Carbon Fiber Reinforced Carbon), which has good thermal and mechanical properties, with 8H/satin woven fabric prepreg, high modulus and high strength type continuous carbon fiber and raw coal tar pitch(RCTP) matrix or THF soluble fraction(THFSP) matrix which has good graphitizability. Green bodies were fabricated with hot press molding technique and CFRC samples were made after carbonization, impregnation, recarbonization and graphitization steps. For the purpose of characterization of the physical properties, SEM, polarized light microscope, TGA were observed, and tested flexural strength, modulus and ILSS. After heat treating the THFSP matrix up to $2300^{\circ}C$, the value of $C_0$/2 was 3.380$\AA$, which is analogous to the structure of natural graphite and the value of 2$\theta$ is $26.276^{\circ}$ approached to the Bragg's angle of natural graphite. As a result of TGA to test the high temperature air oxidation, the THFSP matrix, graphitized up to $2300^{\circ}C$, exhibited the best air oxidation resistance. And mechanical properties were increased up to 65~70% as fiber volume fraction increased. Because of the good orientation graphitizability, the fracture surface of THFSP matrix CFRC is very good.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.84-91
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• 2017

Fiber reinforced plastic (FRP) is a typical plastic composite which is fabricated using fiber reinforcement with resin to represent the high strength properties. The mechanical properties of FRP should be determined by a fibrous material, and the studies about the role of fiber as a reinforcement has been an interested subject, whereas a study along the effect of filler is not so big. However, the filler effect must be considered on the properties of the composite, because the filler influence on the plastic or resin compound which reacts as a matrix material of the composite. Thus, in this work, we studied the filler effect with size and content using $3-6{\mu}m$ of ground calcium carbonate. The specimen was prepared by sheet molding compound (SMC) method, and the mechanical properties were compared with bending strength and tensile strength. As a result, it was confirmed that the size and contents of calcium carbonate affected the strength of composites, and the condition of $2.8{\mu}m$ which was the smallest size condition showed the highest strength.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.2
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• pp.89-99
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• 1997

Although discontinuously reinforced metal matrix composite(MMC) is one of the most promising materials for applications of aerospace, automotive industries, the thermal residual stresses developed in the MMC due to the mismatch in coefficients of thermal expansion between the matrix and the fiber under a temperature change has been pointed out as one of the serious problem in practical applications. There are very limited nondestructive techniques to measure the residual stress of composite materials. However, many difficulties have been reported in their applications. Therefore it is important to establish analytical model to evaluate the thermal residual stress of MMC for practical engineering application. In this study, an elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two-dimensional in-plane fiber misorientation. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. This model is more general than past models to investigate the effect of parameters which might influence thermal residual stress in composites. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for in-plane fiber misorientation. Fiber volume fraction, aspect ratio, and distribution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distribution type for in-plane misorientation.

• Composites Research
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• v.35 no.2
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• pp.115-119
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• 2022

The performance of carbon fiber is important for the production of these high-quality polymer composite materials such as CFRP (Carbon Fiber Reinforced Plastic). For this purpose, it is essential to use an optimized spinning process for improving the mechanical, physical, and structural properties of the precursor fiber, which greatly affects the properties of the carbon fiber, and the use of a suitable precursor polymer. In this study, the content of MAA (Methacrylic Acid), MAA injection time, and concentration of AIBN (2,2'-Azobis(2-methylpropionitrile)) were set as parameters for the polymer synthesis process, and Poly(AN-co-MAA) (poly(acrylonitrile-co-methacrylic acid)) was polymerized by solution polymerization. Poly(AN-co-MAA) with a molecular weight of 305,138 g/mol and an MAA ratio of 4.2% was dissolved in DMF (N,N-dimethylformamide) at a concentration of 16.0 wt%, and then a precursor fiber was prepared through dry-jet-wet spinning. The precursor fiber had a tensile strength of ~1.06 GPa and a tensile modulus of ~22.01 GPa, and no voids and structural defects were observed on the fiber.