PURPOSES : In this study, a fracture-based finite element (FE) model is proposed to evaluate the fracture behavior of fiber-reinforced asphalt (FRA) concrete under various interface conditions. METHODS: A fracture-based FE model was developed to simulate a double-edge notched tension (DENT) test. A cohesive zone model (CZM) and linear viscoelastic model were implemented to model the fracture behavior and viscous behavior of the FRA concrete, respectively. Three models were developed to characterize the behavior of interfacial bonding between the fiber reinforcement and surrounding materials. In the first model, the fracture property of the asphalt concrete was modified to study the effect of fiber reinforcement. In the second model, spring elements were used to simulated the fiber reinforcement. In the third method, bar and spring elements, based on a nonlinear bond-slip model, were used to simulate the fiber reinforcement and interfacial bonding conditions. The performance of the FRA in resisting crack development under various interfacial conditions was evaluated. RESULTS : The elastic modulus of the fibers was not sensitive to the behavior of the FRA in the DENT test before crack initiation. After crack development, the fracture resistance of the FRA was found to have enhanced considerably as the elastic modulus of the fibers increased from 450 MPa to 900 MPa. When the adhesion between the fibers and asphalt concrete was sufficiently high, the fiber reinforcement was effective. It means that the interfacial bonding conditions affect the fracture resistance of the FRA significantly. CONCLUSIONS: The bar/spring element models were more effective in representing the local behavior of the fibers and interfacial bonding than the fracture energy approach. The reinforcement effect is more significant after crack initiation, as the fibers can be pulled out sufficiently. Both the elastic modulus of the fiber reinforcement and the interfacial bonding were significant in controlling crack development in the FRA.

Carbon fibers (CFs) have a unique combination of properties which allow them to be widely used as reinforcing materials in advanced polymer composites. The mechanical properties of CF-reinforced polymer composites are governed mainly by the quality of interfacial adhesion between the CFs and the polymer matrix. Surface treatments of CFs are generally carried out to introduce chemical functional groups on the fiber surfaces, which provide the ability to control the surface characteristics of CFs. In this study, we review recent experimental studies concerning various surface treatment methods for CFs. In addition, direct examples of the preparation and properties of CF-reinforced thermosetting composites are discussed.

CFRP composites have high specific strength, specific stiffness, long fatigue life, light weight environmental safety characteristics. In this study, the mechanical properties are investigated through the compressive simulation analysis on the carbon fiber reinforced plastic sandwich. The experiment is carried out with the same condition as the analysis to verify the analysis result. One sandwich plate is composed with four layers. From the upper, this plate has the first, second, third and fourth layers due to the arrangement of angle direction. A plate has the symbol of [0/30/30/0] as the first, second, third and fourth layers due to the angle directions of 0°, 30°, 30° and 0°. There are the plates of [0/30/30/0], [0/60/60/0] and [0/90/90/0] in this study. The maximum compressive load becomes 53.139kN during the compression time of 12 sec in case of the plate of [0/30/30/0]. The maximum compressive load becomes 61.826kN during the compression time of 12 sec in case of the plate of [0/60/60/0]. The maximum compressive load becomes 53.002kN during the compression time of 12 sec in case of the plate of [0/90/90/0]. So, the plate of [0/60/60/0] endures the most load among three plates. The result of this study can be applied practically through the validation of experimental data on the simulation data. In this study, the mechanical characteristics are examined systematically through the impact analysis on the composite material of the carbon fiber reinforced plastic with aluminum foam by using the impact absorption due to CFRP plate.

In constructing the cast-in-place concrete track system, the installation of reinforcing bars to a TCL is one of the main causes of consuming construction time. In this study, to eliminate the reinforcing bar installation process, the applicability of the fiber reinforced concrete to the TCL is studied using the numerical analysis. The analysis is performed using the commercial finite element program, ABAQUS, and, in the analysis, the effect of the variations in fiber content rate and the surrounding temperature is considered. From the analysis, it is found that the fiber reinforced concrete has better applicability than the existing reinforced concrete with steel bar.

This paper deals with the strengthening effect of reinforced concrete beams strengthened with carbon fiber sheets (CFSs). Fifteen strengthened reinforced concrete (RC) beams were experimentally evaluated to determine improvements in structural performance. Test parameters in this experimental study are strengthening ratios and strengthening methods of CFSs (I-S, I-W, U-S, U-W type). RC beams strengthened with CFSs were tested under sustaining load. Considering strengthening ratios and strengthening methods of carbon fiber sheets, structural performance and failure mode of test specimens were evaluated. The results show that maximum capacity of beams strengthened with CFSs is about 28.8% in I-S type, 20.5% in I-W type, 26.0% in U-S type, 28.7% in U-W type higher than that of control beam.

Shear wall systems behave as individual wall because of openings like window and elevator cage. When coupling beams are installed in shear walls, they will have high strength and stiffness so that be less damaged by lateral loads like earthquake. However, coupling beam is difficult construction method. And arranging reinforcement of slender coupling beams are especially hard. It is because the details of coupling beam provided by ACI 318 are complex. In this paper, experiments were conducted using coupling beams with 3.5 aspect ratio to improve the details of slender coupling beams provided by ACI 318. Two specimens were proposed for this study. One specimen applied with bundled diagonally reinforcement only. Another specimen applied both bundled diagonally reinforcement and High-Performance Fiber Reinforced Cementitious Composite (HPFRCC) so that coupling beams have half of transverse reinforcement. All specimen were compared with a coupling beam designed according to ACI 318 and were evaluated with hysteretic behaviors. Test results showed that the performance of two specimen suggested in this study were similar to that of coupling beam designed according to current criteria. And it was considered that simplification of the details of reinforcement would be available if transverse reinforcement was reduced by using bundled diagonally reinforcement and HPFRCC.

기계의 무게를 대폭 줄이는 것을 목적으로 복합재료에 대해서 많은 연구를 진행하고 있다. 본 연구에서 탄소 섬유 강화 플라스틱과 알루미늄 폼으로 조합해서 만든 샌드위치에 대해서 압축 시뮬레이션 해석을 하였다. 또한 탄소 섬유 강화 플라스틱의 섬유의 배열방식은 [0/90/90/0]이다. 시뮬레이션 해석 방법은 ANSYS를 이용하여 실제와 같은 경계조건을 주고 유한요소해석을 진행하였다. 시편을 압축하는 동안에 탄소 섬유 강화 플라스틱과 알루미늄 폼이 그 접착력보다 크게 발생되어 떨어지는 형상이 일어났다. 또한 2438.3MPa의 최대 등가응력이 발생된 것을 확인하였다. 본 연구에서 나온 해석결과는 안전설계 및 복합재료의 개발에 필요한 자료를 제공할 수 있을 것으로 사료된다.

The prime objective of this research was to study the influence of hot-pressing pressure and matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/carbon-composite. Secondary objectives included determination of the physical and mechanical properties of the resulting composite. The ‘hybrid carbon-fiberreinforced mesophase-pitch-derived carbon-matrix’ composite was fabricated by hot pressing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt% from 30 to 70. Densification of all the compacts was carried at low impregnation pressure with phenolic resin. The effect of the impregnation cycles was determined using measurements of microstructure and density. The results showed that effective densification strongly depended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showed that compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%, gained density gradually during three densification cycles and showed the symptoms of further gains with additional densification cycles. In contrast, samples that were hot-pressed at moderate pressure and at moderate reinforcement wt%, achieved maximum density within three densification cycles. Furthermore, examination of microstructure revealed the formation of cracks in samples processed at lower pressure and with low reinforcement wt%.

PURPOSES: To evaluate the feasibility of cut waste fishing net as a reinforced fiber for concrete. METHODS: Strength characteristics of fiber reinforced concrete using waste fishing net were investigated. The cut waste fishing nets with 4~5cm length were putted into the soil-cement and cement concrete for pavement slab. RESULTS: Compression and tensile strength of fiber reinforced concrete using waste fishing net were increased. CONCLUSIONS: It was concluded that cut waste fishing net can be used as a reinforced fiber for cement concrete. However, sometimes using cut waste fishing net leads to decrease the strength; therefore, further researches are needed for real project.

Recently, methods that usea carbon-based filler, a conductive nanomaterial, have been investigated to develop composite fillers containing dielectric materials. In this study, we added geometric changes to a carbon fiber, a typical carbon-based filler material, by differentiating the orientation angle and the number of plies of the fiber. We also studied the electrical and electromagnetic shield characteristics. Based on the orientation angle of 0˚, the orientation angle of the carbon fiber was changed between 0, 15, 30, 45, and 90˚, and 2, 4, and 6 plies were stacked for each orientation angle. The maximum effect was found when the orientation angle was 90˚, which was perpendicular to the electromagnetic wave flow, as compared to 0˚, in which case the electrical resistance was small. Therefore, it is verified that the orientation angle has more of an effect on the electromagnetic interference shield performance than the number of plies.

In this study, carbon fiber reinforced plastic and aluminum foam used in impact absorber are assembled and modelled. These models are investigated by impact simulation and verified by experimental data. Impact energies of 30 J, 60 J and 100 J are applied on these specimens by striker. For example the experiment for impact energy of 30 J is done and verified by referring to analysis result. As the structural safeties of these assembled composite materials can be anticipated through this study result, these simulation analysis results can be applied into real field.

An orthotropic plastic constitutive model for fiber-reinforced composite material, is developed, which is simple and efficient to be implemented into computer program for a predictive analysis procedure of composite laminates. An orthotropic initial yield criterion, as well as work-hardening model and subsequent yield surface are established that includes the effects of different yield strengths in each material direction, and between tension and compression. The current model is implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS). The accuracy and efficiency of the anisotropic plastic constitutive model and the computer program PACS are verified by solving a number of various fiber-reinforced composite laminates. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

본 논문에서는 탄소 섬유 강화 플라스틱 샌드위치 복합재료의 시뮬레이션 해석을 통해 기계적 충격특 성에 대해 연구를 하였다. 스트라이커에 30 J, 60 J, 100 J의 충격에너지를 부여하여 고정 된 시험편에 충격을 가했다. 시뮬레이션 해석 방법은 ANSYS를 이용하여 실제와 같은 경계조건을 주며 유한요소해 석을 진행하였다. 그 결과는 100J의 충격에 에너지를 가해졌을 때 스트라이커가 시험편을 완전히 관통하는 모습이 보이고 충격에너지 30J과 60J일 때는 스트라이커가 시험편을 관통하지 않았다. 본 연구의 결과로 탄소 섬유 강화 플라스틱과 알루미늄 폼으로 조립한 복합재료의 구조적 안전성을 예측과 구조적 안전성이 높이는 사료가 된다.

For the artistic column used by Glass Fiber Reinforced Plastic(GFRP), the connection of steel with GFRP were needed. Due to the fabricating characteristics of hand laminating, GFRP surfaces had to be connected. Because there were no existed data of these connection, experimental study has to be followed so that the structural strength and buckling mode could be investigated. In this paper, therefore, the axial tests of steel with GFRP were performed. The connection of GFRP's surfaces could be also tested as well. As a result, it could be figured out that the strength of these connections were determined by the adhesive strength.

The hysteretic behavior of diagonal reinforced coupling beams is excellent during earthquakes. However, construction of the diagonal reinforced coupling beams is difficult due to complex reinforcement details required by current code procedures (ACI 318-11). Due to the detail requirement, reinforcement congestion and interference among transverse reinforcement always occur during construction field. When the aspect ratio of the beam is large, the interference of reinforcement becomes more serious. The objective of this paper is to simplify the reinforcement details of slender coupling beams by reducing transverse reinforcement around the beam perimeter. For this purpose, high- performance fiber reinforced cementitious composites are used for making coupling beams. Experiments were conducted using three specimens having aspect ratio 3.5. Test results showed that HPFRCC coupling beams with half the transverse reinforcement required by ACI 318-11 provided identical seismic capacities to the corresponding coupling beams having requirement satisfying the requirement specified in ACI 318-11.

Ultra high performance concrete which has recently been studied was developed to complement the brittle behaviour and dynamic uppermost limit of high strength concrete. Fiber reinforced concrete which mixed steel fiber is receiving attention as an alternative about this and is being developed to complement the disadvantages of high strength concrete including lower toughness coefficients and crack resistance and spalling in fires. Review about fiber reinforced ultra high strength concrete that this study tries to treat includes reduction of self shrinkage generated by high cement content per unit volume of concrete, evaluation of compression and tension strength to lower internal and external spalling resistance and fragility factors of member of framework, and flow characteristics of concrete which doesn't harden according to steel fiber amounts and used materials. As the result, the more fiber reinforcement increases, the more compression and tensile strength increase and deformation control of cement matrix and improvement of energy absorption ability showed the great effect in shrinkage reduction.