• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.520-525
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• 2016

In this study, a mixture of polypropylene fibers and glass fibers were used to weave polypropylene/glass fiber-reinforced composite panels with characteristics such as highly elongated short fibers, high ductility, anti-fouling, and hydrophobicity as a result of a directional property. Mechanical and environmental tests were carried out with specimens fabricated with this composite panel, and its applicability to shipbuilding and ocean leisure industries was evaluated through a comparison with existing glass fiber-reinforced composite materials. The results of this experiment verified the excellence of the polypropylene/glass-mixed woven fiber-reinforced composite material compared to the existing glass fiber-reinforced composite material. However, the forming process needs to be changed to improve the weak interfacial bonding, and the properties of the composite material itself could be improved through mixed weaving with other fibers after development. Maximizing of the advantages of the polypropylene fibers and overcoming their shortcomings will improve their applicability to the shipbuilding, ocean leisure, and other industries, and increase the value of polypropylene fibers in the composite material market.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.497-502
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• 2013

In this study, the interlaminar fracture toughness in mode I of a hybrid composite inserted with different types of non-woven tissues was determined. The interlaminar fracture toughness in mode I is obtained by a double cantilever beam test. The experiment is performed using three types of non-woven tissues: 8 $g/m^2$ of carbon tissue, 10 $g/m^2$ of glass tissue, and 8 $g/m^2$ of polyester tissue. Considering a specimen with no non-woven tissue as a reference, the interlaminar fracture toughness in mode I of specimens inserted with non-woven carbon and glass tissues decreases by as much as 6.3% and 11.4%, respectively. However, the fracture toughness of a hybrid composite specimen inserted with non-woven polyester tissue increases by as much as 69.4%. It is considered that the specimen inserted with non-woven polyester tissue becomes cheaper, and lighter, and the value of the fracture toughness becomes much greater than that of the non-woven carbon tissue.

• Journal of Wind Energy
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• v.14 no.3
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• pp.83-90
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• 2023

The purpose of this study is to evaluate the inter-laminar fracture toughness characteristics of CFRP pultrusion spar cap materials reinforced with non-woven glass fabric. Test specimens were fabricated by the infusion technique. A non-woven glass fabric and artificial defects were embedded on the middle surface between two pultruded CFRP panels. Double cantilever beam (DCB) and End Notched Flexure (ENF) tests were performed according to ASTM standards. Fracture toughness and crack propagation characteristics were evaluated with load-displacement curves and delamination resistance curves (R-Curve). The fracture toughness results were calculated by compliance calibration (CC) method. The initiation and propagation values of Mode-I critical strain energy release rate value G_Ic were 1.357 kJ/m2 and 1.397 kJ/m2, respectively, and Mode-II critical strain energy release rate values G_IIc were 4.053 kJ/m2 for non-precracked test and 4.547 kJ/m2 for precracked test. It was found that the fracture toughness properties of the CFRP pultrusion spar-cap are influenced by the interface between the layers of CFRP and glass fiber non-woven.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1681-1690
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• 1992

The effects of the stress ratio and the fiber orientation(0.deg./90.deg. and .+-.45.deg.) to the load direction on the fracture behavior of the glass/epoxy plain woven composites were studied. The tests were carried out using compact tension specimens under both static and fatigue loading. The values of $k_{a}$ obtained from the energy release rate are independent of notch depth(a/w=0.2~0.6) for the 0.deg./90.deg. specimens, but decreases with an increase in a/w for the .+-.45.deg. specimens. And $k_{q}$ has higher values than $k_{ASTM}$ has been evaluated by the ASTM E399 test procedure. It is shown in the relation between fatigue crack growth rate da/dN and stress intensity factor range .DELTA.K using modified shape correction factor that da/dN decreases with a decrease in stress ratio and is lower for .+-..deg. specimens than for 0.deg./90.deg. These phenomena can be explained by the crack deflection to the load direction.n.n.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.405-411
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• 2011

Using combinations of carbon and glass fiber composites normally used for strengthening of concrete structures, the hybrid effect from strengthening concrete structures using the composite is studied. To produce the hybrid effects, the specimens were made with optimum proportions of carbon fibers with glass fibers. Then, direct tensile tests were conducted on the hybrid FRP (fiber reinforced polymer) specimens. Unlike the woven fiber sheet currently used in construction sites, the FRP specimens have to be directly combined with the fibers, which make the work very complicated. Therefore, direct tensile test specimens manufacturing method based on the combination of high-tension carbon fibers and E-type glass fibers was proposed and the effects of hybridization is studied through the direct tensile test. By comparing the ductility index, the modulus of elasticity, and the stress-strain curves of the specimens, the most optimum glass to carbon fiber combination ratio for the hybrid FRP was found to be 9 to 1 with ductile K-type epoxy. The study results are discussed in detail in the paper.

• Steel and Composite Structures
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• v.12 no.1
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• pp.53-72
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• 2012

In this study, the physically-based failure models for matrix and fibers in compression and tension loading are introduced. For the 3D stress based fiber kinking model a modification is proposed for calculation of the fiber misalignment angle. All of these models are implemented into the finite element code by using the advantage of damage variable and the numerical results are discussed. To investigate the matrix failure model, purely in-plane transverse compression experiments are carried out on the specimens made by Glass/Epoxy to obtain the fracture surface angle and then a comparison is made with the calculated numerical results. Furthermore, shear failure of $({\pm}45)_s$ model is investigated and the obtained numerical results are discussed and compared with available experimental results. Some experiments are also carried out on the woven laminated composites to investigate the fracture pattern in the matrix failure mode and shown that the presented matrix failure model can be used for the woven composites. Finally, the obtained numerical results for stress based fiber kinking model and improved ones (strain based model) are discussed and compared with each other and with the available results. The results show that these models can predict the kink band angle approximately.

• Advanced Composite Materials
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• v.17 no.2
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• pp.177-190
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• 2008

As the first step in discussing the reliability of composite structures, a fundamental study was performed to obtain the scattering characteristics of glass-fiber reinforced plastics (GFRP) and woven carbon fiber reinforced plastics (WCFRP) as well as a reference metal. The Euler buckling load was obtained experimentally for each material. The experiments were conducted for specified rectangular specimens with simply supported edges. A new attachment to realize the simply support boundary conditions for composite materials have been prepared before these experiments. The scattering data in the results for GFRP and WCFRP composites were compared with those of a typical metal of aluminum alloy. The experimental data were also compared with numerical simulations including the uncertainties.

• Coupled systems mechanics
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• v.12 no.5
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• pp.445-459
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• 2023

In this study, a cyclic tensile test on a notched butterfly specimen made of woven glass fiber composite was performed on a modified Arcan fixture. During the mechanical test, the sample was monitored with a hybrid stereoscopic system comprised of two visible lights and one infrared camera. The visible light cameras were employed for kinematic measurements using a finite-element-based multiview correlation technique. A semi-hybrid correlation approach was followed, providing Lagrangian temperature fields of the Region of Interest. Due to the complex composite architecture and specimen shape, localized shearing was observed during the tensile loading. Furthermore, asymmetrical damage developed around the notches as revealed by localized strains and thermal hot spots.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.426-434
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• 2010

This study is experimentally performed to evaluate the strength reduction behavior and its statistical properties of plain woven glass/epoxy composites. The results indicate that the major impact damage of plain woven glass/epoxy composites is the fiber breakage and matrix crack, whereas the dominant impact damage of unidirectional carbon/epoxy laminates is the delamination, which depends on the stacking sequence. The residual strength prediction models, previously proposed on unidirectional laminates, are applied to evaluate the residual strength of plain woven glass/epoxy composites with impact damage. Among these models, the results by Caprino and Avva's model have a good agreement with the experimental results. To investigate the variability of residual strength of the impacted composite materials, a statistical model was proposed and its results were in conformance with the experimental results regardless of their thickness.

• Macromolecular Research
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• v.12 no.1
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• pp.119-126
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• 2004

In this study, the influence of silane coupling agents, featuring different organo-functional groups on the interlaminar and thermal properties of woven glass fabric-reinforced nylon 6 composites, has been by means of short-beam shear tests, dynamic mechanical analysis, scanning electron microscopy, and thermogravimetric analysis. The results indicate that the fiber-matrix interfacial characteristics obtained using the different analytical methods agree well with each other. The interlaminar shear strengths (ILSS) of glass fabric/nylon 6 composites sized with various silane coupling agents are significantly improved in comparison with that of the composite sized commercially. ILSS of the composites increases in the order: Z-6076 with chloropropyl groups in the silanes > Z-6030 with methacrylate groups> Z-6020 with diamine groups; this trend is similar to that of results found in an earlier study of interfacial shear strength. The dynamic mechanical properties, the fracture surface observations, and the thermal stability also support the interfacial results. The improvement of the interfacial properties may be ascribed to the different chemical reactivities of the reactive amino end groups of nylon 6 and the organo-functional groups located at the ends of the silane chains, which results from the increased chemical reactivity in order chloropropyl > methacrylate > diamine.