• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.3
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• pp.85-94
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• 2006

Practially useful method of steel fiber for construction work is presented in this study. The most important purpose of this study is to develop a model which can predict mechanical behavior of the structure according to aspect ratio and volume fraction of steel fiber. Experiments on compressive strength, elastic modulus, and splitting strength were performed with self-made cylindrical specimens of variable aspect ratios and volume fractions. The experiment showed that compressive strength was not in direct proportion to volume fraction which doesn't seem to have great influence over compressive strength. However, splitting strength showed almost direct proportion to aspect ratio and volume fraction. Improvement of optimal efficiency was confirmed when the aspect ratio was 70. Experiments on flexural strength, fracture energy, and characteristic length were carried out with self-manufactured beams with notch. As a result, increases of flexural strength, fracture energy, and characteristic length according to increase of volume fraction tend to be prominent when aspect ratio is 70. The steel fiber improves concrete to be more ductile and tough. Moreover, regression analysis was the performed and predictable model was developed after determining variables. With comparison and analysis of suggested estimated values and measured data, reliance of the model was verified.

• Computers and Concrete
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• v.26 no.3
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• pp.275-283
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• 2020

Reinforced concrete (RC) does not provide sufficient resistance against impacts and blast loads, and the brittle structure of RC fails to protect against fractures due to the lack of shock absorption. Investigations on improving its resistance against explosion and impact have been actively conducted on high-performance fiber-reinforced cementitious composites (HPFRCCs), such as fiber-reinforced concrete and ultra-high-performance concrete. For these HPFRCCs, however, tensile strength and toughness are still significantly lower compared to compressive strength due to their limited fiber volume fraction. Therefore, in this study, the tensile behavior of slurry-infiltrated fiber-reinforced cementitious composites (SIFRCCs), which can accommodate a large number of steel fibers, was analyzed under static and dynamic loading to improve the shortcomings of RC and to enhance its explosion and impact resistance. The fiber volume fractions of SIFRCCs were set to 4%, 5%, and 6%, and three strain rate levels (maximum strain rate: 250 s^-1) were applied. As a result, the tensile strength exceeded 15 MPa under static load, and the dynamic tensile strength reached a maximum of 40 MPa. In addition, tensile characteristics, such as tensile strength, deformation capacity, and energy absorption capacity, were improved as the fiber volume fraction and strain rate increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.251-260
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• 2011

In this study, the effect of natural jute fiber volume fraction on the bond characteristics of polyolefin based macro fiber in natural jute fiber reinforced cement composites, including bond strength, interface toughness, and microstructure analysis are presented. The experimental results on polyolefin based macro fiber pullout test of different conditions are reported. Natural jute fiber volume fractions ranging from 0.1% to 0.2% are used in the mix proportions. Pullout tests are conducted to measure the bond characteristics of polyolefin based macro fiber from natural jute fiber reinforced cement composites. Test results are found that the incorporation of natural jute fiber can effectively enhance the polyolefin based macro fiber-cement matrix interfacial properties. The bond strength and interface toughness between polyolefin based macro fiber and natural jute fiber reinforced cement composites increases with the volume fraction of natural jute fiber. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results.

• Steel and Composite Structures
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• v.50 no.2
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• pp.183-199
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• 2024

In this paper, a closed-form rigorous solution for interfacial stress in continuous steel beam with variable section strengthened with bonded prestressed FRP plates and subjected to a uniformly distributed load is developed using linear elastic theory and including the variation of fiber volume fractions with a longitudinal orientation of the fibers of the FRP plates. The results show that there exists a high concentration of both shear and normal stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. The theoretical predictions are compared with other existing solutions. Overall, the predictions of the different solutions agree closely with each other. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate and the fiber volume fractions where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This research gives a numerical precision in relating to the others studies which neglect the effect of prestressed plate and the shear lag impact. The physical and geometric properties of materials are taken into account, and that may play an important role in reducing the interfacial stresses magnitude.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.373-380
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• 2017

Concrete structures are often subjected to long-term static and short-term dynamic loads. Due to a relatively low tensile strength and energy dissipating characteristics, the impact resistance of concrete is considered poor. This study investigates the feasibility of using polypropylene fibers to improve the impact resistance of reinforced concrete slabs. Fourteen polypropylene fiber reinforced concrete slabs were fabricated and tested using a drop weight test. The effects of slab thickness, fiber volume fractions, and impact energy on the dynamic behaviors were evaluated mainly in terms of impact resistant, crack patterns, and failure modes. The post impact induced strains versus time responses were obtained for all slabs. The results showed that adding the polypropylene fiber at a dosage of 0.90% by volume of concrete leads to significant improvement in the overall structural behavior of the slabs and their resistance to impact loading. Interestingly, the enhancement in the behavior of the slabs using a higher fiber dosage of 1.2% was not as good as achieved with 0.90%.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.5
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• pp.56-62
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• 2002

Alternative way of shaping fibers suitable for papermaking was introduced. Impact refining, which was done simply by hitting wet fibers with a metal weight vertically, was intended to keep the fibers from shortening and to cause mostly internal fibrillation. Virgin chemical pulp, its recycled one and OCC were used in the experiment. It was noticed from the experiment that impact refining on virgin chemical pulp kept the fiber length and increased bonding properties greatly. However, in the recycled fibers from the chemical pulp, fiber length and bonding properties were decreased. In OCC, which seems to contain fractions of semi-chemical pulp and mechanical pulp (GP), and which is recycled pulp from corrugated boxes, fiber length and bonding properties were decreased disastrously. We believe recycled cellulosic fibers (recycled chemical pulp and OCC in this case), which went through hornification, were less resistant to the mechanical impact than virgin chemical pulp. For virgin chemical pulp, impact refining allowed no significant fiber length shortening, high WRV, and high mechanical strength.

• Animal Bioscience
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• v.36 no.7
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• pp.1044-1058
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• 2023

Objective: The objective of this study was to characterize physiochemical and nutrient profiles of feedstock and co-products from canola bio-oil processing that were impacted by source origin. The feedstocks and co-products (mash, pellet) were randomly collected from five different bio-oil processing plants with five different batches of samples in each bio-processing plant in Canada (CA) and China (CH). Methods: The detailed chemical composition, energy profile, total digestible nutrient (TDN), protein and carbohydrate subfractions, and their degradation and digestion (CNCPS6.5) were determined. Results: The results showed that TDN_1x was similar in meals between CA and CH. CH meals and feedstock had higher, truly digestible crude protein (tdCP) and neutral detergent fiber (tdNDF) than CA while CA had higher truly digestible non-fiber carbohydrate (tdNFC). The metabolizable energy (ME_3x), net energy (NE_Lp3x, NE_m3x, and NE_g3x) were similar in meals between CA and CH. No differences were observed in energy profile of seeds between CA and CH. The protein and carbohydrate subfractions of seeds within CH were similar. The results also showed that pelleting of meals affected protein sub-fractionation of CA meals, except rapidly degradable fractions (PB1), rumen degradable (RDPB1) and undegrdable PB1 (RUPB1), and intestinal digestible PB1 (DIGPB1). Canola meals were different in the soluble (PA2) and slowly degradable fractions (PB2) between CA and CH. The carbohydrate fractions of intermediately degradable fraction (CB2), slowly degradable fraction (CB3), and undegradable fraction (CC) were different among CH meals. CH presented higher soluble carbohydrate (CA4) and lower CB2, and CC than CA meals. Conclusion: The results indicated that although the seeds were similar within and between CA and CH, either oil-extraction process or meal pelleting seemed to have generated significantly different aspects in physiochemical and nutrient profiles in the meals. Nutritionists and producers need to regularly check nutritional value of meal mash and pellets for precision feeding.

• Fibers and Polymers
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• v.7 no.4
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• pp.432-435
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• 2006

High Modulus and high tenacity polypropylene fibers have been prepared by drawing on a gradient heater. Results show that fiber properties are significantly affected by temperature profiles of final stage drawing on a gradient heater. The gradient drawn filaments showed superior mechanical properties when compared to filaments drawn over a constant temperature heater. Fibers with initial modulus of 16.4 GPa and tenacity of 670 MPa have been manufactured in the process. The nature of the gradient drawing had a significant effect on end properties. The superior mechanical properties are attributed to the high crystal perfection and crystallinity and low void fractions obtained at high draw ratios when drawn over a gradient heater.

• Structural Engineering and Mechanics
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• v.54 no.1
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• pp.1-17
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• 2015

An experimental investigation is conducted to examine the behavior and cracking of steel fiberre-inforced concrete spandrel L-shaped beams subjected to combined torsion, bending, and shear. The experimental program includes 12 medium-sized L-shaped spandrel beams organized into two groups, namely, specimens with longitudinal reinforcing bars, and specimens with bars and stirrups. All cases are examined with 0%, 1%, and 1.5% steel fiber volume fractions and tested under two different loading eccentricities. Test results indicate that the torque to shear ratio has a significant effect on the crack pattern developed in the beams. The strain on concrete surface follows the crack width value, and the addition of steel fibers reduces the strain. Fibrous concrete beams exhibited improved overall torsional performance compared with the corresponding non-fibrous control beams, particularly the beams tested under high eccentricity.

• Carbon letters
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• v.3 no.2
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• pp.85-92
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• 2002

4D carbon fiber preforms were manufactured by weaving method and their carbon fiber volume fractions were 50% and 60%. In order to form carbon matrix on the preform, coal tar pitch was used for matrix precursor and high density carbon/carbon composites were obtained by high densification process. In this process, manufacture of high density composites was more effective according to pressure increasement. When densificating the preform of 60% fiber volume fraction with 900 bar, density of the composites reached at 1.90 $g/cm^3$ after three times processing. Degree of pressure in the densification process controls macro pore but it can not affect micro pore. During the carbonization process, micro pore of the preform were filled fully by once or twice densification processing. But micro pore were not filled easily in the repeating process. Therefore, over three times densification processing is the filling micro pore.