• Composites Research
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• v.16 no.1
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• pp.42-49
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• 2003

Brittle matrix composites often have interfacial debonding between the fiber and matrix which may lead to strength and stiffness degradation. The effect of interfacial debonding and fiber volume fraction on the mechanical properties of composite material were studied by using finite element method. Firstly, the modelling of fiber and matrix constituting the composite material was simplified under some assumptions. Traction and displacement continuity conditions were imposed along the boundary of adjacent representative volume elements. In order to obtain the effective material properties of composite material, stiffness constants were inverted. Numerical values of longitudinal moduli in case of perfect bonding were compared with theoretical values obtained by rule of mixtures and yielded consistency. Material properties of composite with large debonding an81e were found to decrease even though the fiber volume fraction increased.

• Transactions of Materials Processing
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• v.25 no.6
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• pp.402-408
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• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.105-115
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• 2015

In this study, to understand mechanical characteristic of hybrid reinforced concrete by PVA-fiber 6 mm and PP-fiber 50 mm, which are organic fiber replaced macro-fiber with PP-fiber, four mixed Hybrid Organic Fibers Reinforced Concrete (HFRC) is compared with one mixed plain concrete without fiber reinforcement. Volume portion of the fibers are limited under one percent. The result presents that hybrid reinforcement of the organic fibers cannot maximize stiffness and ductility behavior of the steel fiber reinforcement. however, in comparison to plain concrete, it is confirmed that meaningful relation between toughness index and equivalent flexural strength with advanced ductility behavior. Also, in the case of concrete hybrid reinforced by organic fiber, when the volume portion of the fiber increases, ductility also increases. PP-fiber, which is macro fiber, has more effect on the flexural behavior of concrete than PVA-fiber, which is micro fiber, does. The result also shows that it decrease chloride penetration in chloride penetration test.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.743-748
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• 2006

This paper presents results of an experimental study conducted to investigate the effect of volume fraction of fibers on the mechanical properties of a fiber-reinforced, lightweight aggregate concrete(FRLAC) that was produced without an autoclave process. The FRLAC enhanced the strength of lightweight, cellular concrete by adding polypropylene fibers and lightweight aggregates. To investigate the effect of volume fraction of fibers on the mechanical behavior of FRLAC and to determine the optimal volume fraction of fibers, a series of compression and flexural strength tests on FRLAC specimens with various fiber volume fractions(0%, 0.10%, 0.25%, 0.50%) were conducted. It was observed from the tests that a 0.25% volume fraction of fibers maximized the increase in the strength of FRLAC and the fibers controlled cracking in FRLAC.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.5-10
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• 1990

There are two main methods in reinforcing cements with glass fibers : spray-suction and premixing method. But GRC have been mostly studied by spray technique. In order to develop GRC made by premixing method, in this paper, the influence of glass fiber length, volume content and curing conditions upon the compressive, direct tensile and bending strengths of composites fabricated by a premixing method, were investigated. According to the test results, although it was difficult to obtain perfectly uniform distribution of fibers in GRC Pannel, it was found that tensile strength of cements with glass fiber was improved 2~5 times and flexural strength 4 times compared to conventional cement mortar upto fiber length 35 mm, volume content 4%.

• Journal of Power System Engineering
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• v.15 no.6
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• pp.47-52
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• 2011

In this study, an accurate 2-noded hybrid-mixed element for continuous fiber-reinforced laminated beams is newly proposed. The present element including the effect of shear deformation is based on Hellinger-Reissner variational principle, and introduces additional consistent node less degrees for displacement field interpolation in order to enhance the numerical performance. The micromechanical and lamination theory are employed in the finite element description to consider the effects of the laminate stacking sequences, material orthotropy, and fiber volume fraction, etc. The element stiffness matrix can be explicitly derived through the stationary condition and static condensation using Mathematica program. Several numerical examples confirm the accuracy of the present hybrid-mixed element and also show in detail the effects of the continuous fiber volume fraction, stacking sequences and boundary condition on the bending behavior of laminated beams.

• Computers and Concrete
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• v.19 no.4
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• pp.375-385
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• 2017

In the present paper experimental and numerical analysis of hook-ended steel fiber reinforced concrete is carried out. The experimental tests are performed on notched beams loaded in 3-point bending using fiber volume fractions up to 1.5%. The numerical analysis of fiber reinforced concrete beams is performed at meso scale. The concrete is discretized with 3D solid finite elements and microplane model is used as a constitutive law. The fibers are modelled by randomly generated 1D truss finite elements, which are connected with concrete matrix by discrete bond-slip relationship. It is demonstrated that the presented approach, which is based on the modelling of concrete matrix using microplane model, able to realistically replicate experimental results. In all investigated cases failure is due to the pull-out of fibers. It is shown that with increase of volume content of fibers the effective bond strength and slip capacity of fibers decreases.

• Journal of Sensor Science and Technology
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• v.16 no.4
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• pp.254-258
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• 2007

A novel cure sensor based on the side-polished single mode fiber has been proposed and demonstrated. Two different UV curable epoxies were used to verify the feasibility of the side-polished single mode fiber as a high sensitivity cure sensor. The volume change of the epoxy by UV curing results in a corresponding change of the refractive index. The sensor can be used to monitor the curing process, the refractive index variation and the volume change of epoxy in real time during the UV curing process. In addition, small birefringence of the epoxy film can be detected using the sensor.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.121-124
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• 2004

In this paper, a series of fracture tests are performed for the chemically prestressed steel fiber reinforced concrete (SFRC) manufactured with addition of expansive additives for the study of fracture behavior and characteristics. Cracking loads of the chemically prestressed SFRC are greater than that of normal concrete and those are also increased by increasing of steel fiber volume. Thus, it is necessary to obtain optimum steel fiber volume to induce chemically prestressing effectively to concrete members. The result of three-points bending tests shows that early-cracking resistance of the chemically prestressed SFRC is increased without increase of fracture energy. From the test, the tension softening curves are also obtained by poly-linear approximation method and simulated behaviors by using the determined tension softening curves agree with experimental results. And it is confirmed that cracking and ultimate behaviors of chemically prestressed SFRC can be predicted by using obtained fracture characteristics.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.253-256
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• 2006

The HPFRCCs show the multiple crack and damage tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For practical application, it is needed to investigate the fractural behavior and of HPFRCCs and understand the micro-mechanism of cement matrix with reinforcing fiber. The objectives of this paper are to examine the compressive behavior, fracture and damage process of HPFRCC by acoustic emission technique. Total four series were tested, and the main variables were the hybrid type, polyethylene (PE) and steel cord (SC), and fiber volume fraction. The damage progress by compressive behavior of the HPFRCCs is characteristic for the hybrid fiber type and volume fraction. And from acoustic emission (AE) parameter value, it is found that the second and third compressive load cycles resulted in successive decrease of the ring-down count rate as compared with the first compressive load cycle.