• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.734-739
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• 2008

In this study, the nonlinear mechanical behavior of flexible textile composites was predicted by two-step analyses: micromechanics and mesomechanics. The effective material properties for fiber tows of flexible textile composite lamina were calculated in micromechanics, which were then used to calculate the effective tensile stress-strain curve of flexible textile composites in mesomechanics. A user defined material algorithm was developed and inserted in ABAQUS to account for the geometric non-linearity due to the large rotation and shear deformation of fiber tows in mesomechanics. It was found that the stress-strain behavior of flexible textile composites exhibited significant non-linearity. The effective tensile modulus agreed well with the test result.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.91-94
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• 2003

Laminated composites are liable to fatal damage under impact load due to the fact that they have no reinforcement in the thickness direction. To overcome the inherent weakness, three dimensional (3D) textile reinforcements have drawn much interests. In this paper, impact performance of 2D and 3D textile composites has been characterized. For 2D composites, fiber bundle size and fiber pattern have been varied. For 3D composites, orthogonal woven preforms of different density and type of through-thickness fibers have been studied. To assess the damage after the impact loading, specimens were subjected to C-scan nondestuctive inspection. Compression after impact (CAI) were also conducted in order to evaluate residual compressive strength.

• Carbon letters
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• v.25
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• pp.43-49
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• 2018

This study suggests the novel thermoplastic toughening agent, which can be applied in the monomer forms without increasing the viscosity of the epoxy resin and polymerized during the resin curing. The diazide (p-BAB) and dialkyne (SPB) compounds are synthesized and mixed with the epoxy resin and the carbon fiber reinforced epoxy composites are prepared using vacuum infusion process (VIP). Then, flexural and drop weight tests are performed to evaluate the improvement in the toughness of the prepared composites to investigate the potential of the novel toughening agent. When 10 phr of p-BAB and SPB is added, the flexural properties are improved, maintaining the modulus as well as the toughness is improved. Even with a small amount of polytriazolesulfone polymerized, due to the filtering effect of the solid SPB by the layered carbon fabrics during the VIP, the toughening and strengthening effect were observed from the novel toughening agent, which could be added in monomer forms, p-BAB and SPB. This suggests that the novel toughening agent has a potential to be used for the composites prepared from viscosity sensitive process, such as resin transfer molding and VIP.

• Textile Coloration and Finishing
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• v.30 no.2
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• pp.77-89
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• 2018

In the case of fiber/rubber composites for tire applications, the interfacial adhesion between fiber and rubber significantly affects the physical properties of the finished products. Generally, organic synthetic fibers used for tire cords are treated with resorcinol formaldehyde latex(RFL) primer on the surface of the fiber to improve the adhesion to rubber. Changes of adhesion between rubber and tire cords might weaken as temperature rises due to overheating of car engine and friction with road. In this study, the effects of temperature on the primer treated polyketone cord/rubber composites and the changes in interfacial adhesion were investigated. Polyketone cord/rubber composites were prepared after RFL solution treatment on the surface of polyketone fibers. After that, composites was thermally aged at different temperature conditions(60, 80, 100, $120^{\circ}C$) and times(1, 5, 10, 15days). The adhesion strength of polyketone cord/rubber composite treated with RFL primer was higher than untreated composite by more than 3 times. After heat aging, the adhesion strength of untreated polyketone cord/rubber composites increased while the RFL treated polyketone cord/rubber composites decreased somewhat.

• Textile Coloration and Finishing
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• v.28 no.4
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• pp.239-245
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• 2016

In this study, carbon/phenol composites were prepared from carbon fiber preform and phenol resin by RTM(resin transfer molding) process. And changes in the properties of the composite according to the pre-treatment of phenol resin was mainly studied. RTM process conditions were deduced from viscosity and thermal analysis of phenol resin which were rheometer and thermogravimetric analyzer(TGA). RTM process was performed under various injection and molding temperature. Characterization of the prepared C/P composites were evaluated by various analysis. Morphology of composites was analyzed by Micro-CT(MCT), Mechanical properties of composites were measured through the flexural properties. As results, volatile impurities of phenol resin were effectively removed at resin pre-treatment temperature of $100^{\circ}C$ and composite was sufficiently cured at molding temperature of $180^{\circ}C$.

• Textile Coloration and Finishing
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• v.29 no.2
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• pp.77-85
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• 2017

The interfacial adhesion between fiber and matrix affects the physical properties of fiber reinforced composites. In this study, 3-(Methacryloyloxy)propyltrimethoxy silane(MPS) coupling agent was used to increase the interfacial adhesion between polyketone fiber and epoxy resin. The change of surface chemical composition of polyketone fiber treated with MPS was analyzed using a FTIR-ATR. The interfacial bonding between fiber and resin increased with silane coupling agent largely. Consequently, interfacial shear strength(IFSS) was enhanced with increasing concentration of MPS coupling agent and thus, the physical properties of the composites such as flexural properties and dynamic mechanical properties were changed. Flexural strength and modulus increased when the MPS concentration was higher than 0.5wt%. The dynamic storage modulus of Polyketone/Epoxy composites treated with MPS was higher than that of the untreated one. When the MPS concentration of 3wt%, the highest storage modulus was obtained.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.3-6
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• 2003

In this work, poly(ethylene oxide) nanofibers were fabricated by electrospinning to prepare nanofibers-reinforced composites. And the PEO powders-impregnated composites were also prepared to compare with physicochemical properties of nanofibers-reinforced composites. Morphology and fiber diameter of PEO nanofibers were determined by SEM observation. Mechanical interfacial properties of the composites were investigated in fracture toughness tests and interlaminar shear strength (ILSS) test. As a result, the fiber diameter decreased in increasing applied voltage. However the optimum condition for the fiber formation was 15 ㎸, resulting from increasing of jet instability at high voltage and the prepared PEO nanofibers were useful in fiber reinforced composites. The PEO-based nanofibers-reinforced composites showed an improvement of fracture toughness factors ($K_{IC} and G_{ IC}$) and ILSS, compared to the composites impregnated with PEO powders. These results were noted that the nanofibers had higher specific surface area and larger aspect ratio than those of the powder, which played an important role in improving the mechanical interfacial properties of the composites.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.38-41
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• 2001

A new 2-D braided textile metal matrix composite was developed and characterized. The constituent materials consist of PAN type carbon fiber as reinforcements and pure aluminum as matrices. The braided preforms of different braider yarn angles were fabricated. For a fixed bundle size of 12K, three braider yarn angles was selected: $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$. The braided preforms were infiltrated with pure Al by vacuum assisted squeeze casting. Through the investigation of melt pressing methods and the effects of process parameters such as applied pressure, and pouring temperature, the optimal process conditions were identified as follows: applied pressure of 60MPa, pouring temperature of $800^{\circ}C$. Using the measured geometric parameters, 3-D engineering constants of metal matrix composites have been determined from the elastic model, which utilizes the coordinate transformation and the averaging of stiffened and compliance constants based upon the volume of each reinforcement and matrix material.

• Composites Research
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• v.13 no.2
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• pp.8-21
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• 2000

In th is paper. the low degree of homogeneity issue in the effective modulus was studied for plain weave textile composites. Unit cell analyses were performed using multi-field macroelements. The effective moduli were calculated for finite and infinite configurations and the statistics assessment of the results was presented. Results indicated that the effective modulus of plain weave textile composites depended strongly on the fiber tow phase shift angles and the number of layers. As the number of layers increased, however, the distribution of the modulus showed concentration and higher degrees of homogeneity was attained.

• Advanced Composite Materials
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• v.17 no.3
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• pp.247-258
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• 2008

This paper is concerned with the long-term performance of geo-textile (GT) composites in terms of creep deformation and frictional properties. Composites of PVA GT and HDPE GM were made to investigate the advanced properties of long-term performance related to waste landfill applications. The same experiments were also performed for typical polypropylene and polyester GT and compared to PVA GT/HDPE GM composites. We also develop high performance GT composites with GM by using PVA GT, which is capable of improving the frictional properties and thus enhances long-term performance of GT composites. Experimental study reveals that the friction coefficient of GT composites is relatively large compared with those of polyester and polypropylene non-woven GT as long as the friction media has similar size to the particles of domestic standard earth. In addition, the geo-composites bonded with geo-grid by a chemical process were investigated experimentally in terms of strain evaluation and creep response values. Geo-grid plays an important role as a reinforcing material. Three kinds of geo-grid were prepared as strong yarn polyester and they were woven type, non-woven type, and wrap knitted type. The sample geo-grids were then coated with PVC. The rib tensile strength tests were conducted to evaluate geo-grid products in terms of tensile strength with regard to single rib. The test was performed according to GRI-GGI. It was concluded again from the experiments that the tensile and creep strains of the geo-grid showed such stable values that the geo-grid prepared in this study could protect geo-textile partially in practical structures.