• Polymer(Korea)
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• v.39 no.2
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• pp.219-224
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• 2015

In this work, the effect of fiber array direction including $0^{\circ}$, $0^{\circ}/90^{\circ}$, $0^{\circ}/45^{\circ}/-45^{\circ}$ was investigated for mechanical properties of basalt fiber-reinforced composites. Mechanical properties of the composites were studied using interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$) measurements. The cross-section morphologies of basalt fiber-reinforced epoxy composites were observed by scanning electron microscope (SEM). Also, the surface properties of basalt fibers were determined by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). From the results, it was observed that acid treated basalt fiber-reinforced composites showed significantly higher mechanical interfacial properties than those of untreated basalt fiber-reinforced composites. These results indicated that the hydroxyl functional groups of basalt fibers lead to the improvement of the mechanical interfacial properties of basalt fibers/epoxy composites in the all array direction.

• Composites Research
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• v.16 no.6
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• pp.41-47
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• 2003

Composites are widely used for aircraft, satellite and other structures due to its good mechanical and thermal characteristics such as low coefficient of thermal expansion(CTE), heat-resistance, high specific stiffness and specific strength. In order to use composites under condition of high temperature, however, material properties of composites at high temperatures must be measured and verified. In this paper, material properties of T700/Epoxy were measured through tension tests of composite specimens with an embedded FBG sensor in the thermal chamber at the temperatures of RT, $100^{\circ}$, $200^{\circ}$, $300^{\circ}$, $300^{\circ}$. Through the pre-test of an embedded optical fiber, we confirmed the embedding effects of an optical fiber on material properties of the composites. Two kinds of specimens of which stacking sequences are [0/｛0｝/0]$_{T}$. and [$90_2$/｛0｝/$90_2$]. were fabricated. From the experimental results, material property changes of composites were successfully shown according to temperatures and we confirmed that fiber Bragg grating sensor is very appropriate to strain measurement of composites under high temperature.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.215-222
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• 1995

Anisotropic pitch-based C-type and hollow carbon fibers can obtain wider shear stresses during the spinning and induce higher molecular orientation than that of round along the fiber axis. These fibers reinforced unidirectional epoxy composites were prepared by hot-press moulding method and perpendicular and parallel thermal conductivities of the composites were measured by a steady-state meth od. In the case of round carbon fibers reinforced epoxy composites(H-CF/EP), thermal anisotropic factor showed nearly 50, while those of H-CF/EP and C-CF/EP showed about 130 and 118, respectively. As a result, both H-CF/EP and C-CF/EP had an excellent directional thermal conductivity to distribute heat, above 200 %.

• International Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.16-20
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• 2020

The recent trend is increasing towards the usage of polymer matrix composites since they have a wide variety of applications. They have applications in the field of aircraft and space industry, sporting goods, medical devices, marine and automotive applications and also in commercial usage. The most commonly used fibre-reinforced polymer matrix composite is Glass fibre reinforced epoxy (GFRE) composite which is used in aviation, sports and automotive industries. However, the strength of GFRE composites is not adequate for structural applications. Therefore, the current research focuses on increasing the strength of GFRE composites by reinforcing with micro Graphite (Gr) particulates. The Gr used is an ultra-fine powder with particle size 250 ㎛. Gr is known to have good wear resistance, thermal conductivity and can operate at high temperatures. Gr particulates are mixed with the epoxy matrix in various weight ratios. Hand-lay technique is used for fabricating the composites. Mechanical properties such as tensile strength, elongation, compressive strength and flexural strength are obtained experimentally to study the effect of change in Gr content (0-5 wt. %). The tests were done as per ASTM standards.

• Composites Research
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• v.16 no.3
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• pp.49-57
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• 2003

This paper presents the tensile characteristics for carbon/epoxy, carbon/phenolic and silica/phenolic composites under elevated temperature, which are considered for vehicle structure or thermal protection materials. The tensile test was conducted with servo-hydraulic testing machine and high temperature furnace, and the mechanical properties such as tensile strength, elastic modulus and Poisson's ratio were evaluated by using high temperature strain gages. Also, they were compared each other with respect to fiber orientation and temperature effect. These test results were used for designing and analyzing some airframe structures with these composites.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.918-923
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• 2008

Since crack detection for laminated composites in-service is effective to improve the structural reliability of laminated composites, it have been tried to detect cracks of laminated composites by various nondestructive methods. An electric potential method is one of the widely used approaches for detection of cracks for carbon fiber composites, since the electric potential method adopts the electric conductive carbon fibers as reinforcements and sensors and the adoption of carbon fibers as sensors does not bring strength reduction induced by embedding sensors into the structures such as optical fibers. However, the application of the electric method is limited only to electrically conductive composite materials. Recently, a piezoelectric method using piezoelectric characteristics of epoxy adhesives has been successfully developed for the adhesive joints because it can monitor continuously the damage of adhesively bonded structures without producing any defects. Polymeric materials for the matrix of composite materials have piezoelectric characteristics similarly to adhesive materials, and the fracture of composite materials should lead to the fracture of polymeric matrix. Therefore, it seems to be valid that the piezoelectric method can be applied to monitoring the damage of composite materials. In this research, therefore, the feasibility study of the damage monitoring for composite materials by piezoelectric method was conducted. Using carbon fiber epoxy composite and glass fiber composite, charge output signals were measured and analyzed during the static and fatigue tests, and the effect of fiber materials on the damage monitoring of composite materials by the piezoelectric method was investigated.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.100-107
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• 2006

The objective of this research is to investigate the electromagnetic interference(EMI) shielding characteristics of fiber reinforced composites. We fabricated glass and carbon fiber reinforced composites filled with metal powder and nano carbon black. The measurements of shielding effectiveness(SE) were carried out frequency range 300MHz - 1GHz for commercial purposes such as electric or telecommunication devices. The return loss and loss due to absorption were also measured as a function of frequency in the micro wave(300MHz-1GHz) region. It is observed that the SE of the composites is the frequency dependent, increase with the increases in filler loading. The Mg metal powder filled composite showed higher SE compared to that of carbon black. The Mg metal powder/epoxy composite was shown to exhibit up to 40dB of SE. The results indicates that the composite having higher filler loading can be used for the purpose of EMI shielding as well as for some microwave applications.

• Journal of Drive and Control
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• v.13 no.1
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• pp.43-48
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• 2016

This paper presents a preliminary study on the pressure sensing characteristics of smart nano composites made of MWCNT (multi-walled carbon nanotube) to develop a novel pressure sensor. We fabricated the composite pressure sensor by using a solution casting process. Made of carbon smart nano composites, the sensor works by means of piezoresistivity under pressure. We built a signal processing system similar to a conventional strain gage system. The sensor voltage outputs during the experiment for the pressure sensor and the resistance changes of the MWCNT as well as the epoxy based on the smart nano composite under static pressure were fairly stable and showed quite consistent responses under lab level tests. We confirmed that the response time characteristics of MWCNT nano composites with epoxy were faster than the MWCNT/EPDM sensor under static loads.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.233-243
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• 2019

This paper depicts the development and characterizations of laminated composites made with cellulosic giant cane (Arundinaria gigantea) fiber mats and epoxy resin. Zirconia-toughened mullite (ZTM) is used as a filler material in the laminated composite which was prepared from sillimanite through plasma processing technique. The mechanical characterizations of this composite have been carried out as per ASTM standards to evaluate its usability as a structural material. The effects of varying weight percentages of the filler and two different fiber orientations namely, angle-ply [$+45^{\circ}/-45^{\circ}/+45^{\circ}$] and balanced cross-ply [$0^{\circ}/90^{\circ}/0^{\circ}$] on the physical and mechanical properties such as density, microhardness, impact strength, tensile strength and interlaminar shear strength of the layered composite specimens have been investigated. The study indicates that the inclusion of zirconia-toughened mullite in the composite laminate as filler improves its mechanical properties. Moreover, the use of giant cane fiber mat in the laminate is more eco-friendly than the synthetic fibers. This research also helps in generating additional data to enrich the repository of natural fiber reinforced laminated composites.

• Composites Research
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• v.22 no.1
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• pp.15-21
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• 2009

In this paper, static compressive test and compression-compression fatigue test of carbon/epoxy composites which have different micro-structures were carried out with respect to the bias angle. In order to find out the effect of the micro-structure of the fabric composite on compressive characteristics the specimens made of UD carbon/epoxy composite comprising the same fiber and matrix system as the fabric composite were also prepared. The compressive strength and modulus were measured and these values were used to develop a semi-empirical formula for predicting compressive strength of the fabric composite with bias angles. The fatigue behavior of the fabric composite with respect to the bias angle variation was also investigated.