Carbon Fiber Bar Research Articles

Cyclic thermoresistivity of resin-based carbon fiber bars modified with mixed carbon powder and nano-silica

The addition of conductive fillers to the carbon fiber bar reduces its resistivity and improves electrical stability. Unstable conductivity and susceptibility to ambient temperature change impede the application of this technique in engineering, unless such influence can be eliminated by technical means or precisely predict. In this paper, modified epoxy Resin based carbon fiber bars with 4 sets of different mixed fillers have been designed to evaluate the temperature-resistance effect under different temperature cycles. Results show that the initial volume resistivity reduces due to the incorporation of carbon powder(CP) and nano-silica(NS), and meets the lowest when the CP and NS mass ratio is 1:0.6. The volume resistivity increases linearly with the temperature rising, and reaches the maximum temperature sensitivity coefficient of 78.8%. During the temperature cycle process, the volume resistivity of all specimens first decreases and then increases with the increasing temperature uniformly. The three groups (CP/NS ratio 1:0.2, 1:0.6, and 1:0) share the same PTC effect transition temperature range, from 30 to 60 °C. And for the 1:1 group, the transition temperature is about 0 °C, which is the lowest. Altogether, these enhancements provide avenues for future self-sensing carbon fiber composites in engineering structures.

Bond Coefficient kb of Concrete Beams Reinforced with GFRP, CFRP, and Steel Bars

There are several reasons why civil and structural engineers should use Fiber Reinforced Polymer bars in concrete. The primary reason is durability, and other relevant parameters, high strength and, lightweight. Non-corrosive attributes make their use particularly suitable in different situations. Due to low elastic modulus and poor bonding, the use of Fiber Reinforced Polymer results in larger crack widths under serviceability limit state especially beams reinforced with glass fiber bars. The study purpose of this paper is to investigate the kb values. The methodology of this paper is comparing the analytical and experimental results. The investigation included 12 beams, using the four-point load test. The geometrical parameters of tested beams with dimensions: 130×220×2200 mm, reinforced with different diameters, helically-grooved glass fiber bars, and sand-coated carbon fiber bars. The measured cracks were used to assess the current kb values recommended in the design codes and guides. The findings did not support the use of the same kb value for different bars because, in addition to the type of bar, the value of kb is also affected by the type of surface and the diameter of the bar. What is observed based on results shows that CFRP bars have a more constant value depending on the diameter, while GFRP bars have large value changes depending on the diameter. Doi: 10.28991/cej-2021-03091722 Full Text: PDF

Study on short-term prestress loss of bridge reinforced with large diameter carbon fiber bars

At present, the technology of strengthening bridge with prestressed CFRP bars is gradually rising, so it is necessary to study the law of prestress loss. In order to evaluate the short-term prestress loss of prestressed carbon fiber reinforced (CFRP) bars, the prestress loss of CFRP bars used for reinforcement of reinforced concrete beams was studied by combining laboratory tests with practical reinforcement projects. The anchorage loss, concrete elastic compression loss of CFRP bars were obtained by measuring the prestressed loss data of CFRP bars used to strengthen retired old beams and corresponding theoretical calculation. Then, combined with the corresponding loss data of 6 prestressed CFRP bars in the actual strengthening project of Wenzhou Lijing Middle Bridge, the experimental investigation was carried out. The results show that the prestress loss of CFRP bars is between 4%∼8%, and develops rapidly in the early stage, among which the anchorage loss accounts for 45.90%. The anchorage retraction value is about 1.33mm, and the elastic compression loss of concrete is basically negligible.

The influence of gap size on the development of fracture union with a micro external fixator

Increasingly, the rat femoral fracture model is being used for preclinical investigations of fracture healing, however, the effect of gap size and its influence on mechanobiology is not well understood. We aimed to evaluate the influence of osteotomy gap on osteotomy healing between the previously published extremes of guaranteed union (0.5 mm) and non-union (3 mm) using this model.A femoral osteotomy in 12–14 week old female Wistar rats was stabilised with a micro fixator (titanium blocks, carbon fiber bars) with an osteotomy gap of 1.0 mm (n = 5), 1.5 mm (n = 7), 2.0 mm (n = 6). After five weeks, the left femur was retrieved. The osteotomy gap was scanned using X-ray microtomography and then histologically evaluated. The radiographic union rate (complete mineralised bone bridging across the osteotomy) was three times higher for the 1.0 mm than the 2.0 mm gap. The 1.0 mm gap had the largest callus (0.069μm3) and bone volume (0.035μm3). Callus and bone volume were approximately 50% smaller within the 2.0 mm gap.Using cadaveric rat femurs stabilised with the external fixator, day 0 mechanical assessment of construct stiffness was calculated on materials testing machine displacement vs load output. The construct stiffness for the 1.0, 1.5 and 2.0 mm gaps was 32.6 ± 5.4, 32.5 ± 2.4, and 32.4 ± 8.3 N/mm (p = 0.779). Interfragmentary strain (IFS) was calculated using the change in osteotomy gap displacement as measured using microstrain miniature differential reluctance transducer spanning the osteotomy gap. Increasing the gap size significantly reduced the IFS (p = 0.013). The mean ‘day 0’ IFS for the 1.0, 1.5 and 2.0 mm gaps were 11.2 ± 1.3, 8.4 ± 1.5 and 6.1 ± 1.2% respectively.A 1.5 mm gap resulted in a delayed fracture healing by 5 weeks and may represent a useful test environment for fracture healing therapy. Increasing gap size did not affect construct stiffness, but did reduce the ‘day 0’ IFS, with a doubling of non-union and halving of bone volume measured between 1.0 and 2.0 mm gaps.

Responsibility of NSM FRP Bars in Shear Fortifying of Strengthened R.C. Beams

Several R.C. (reinforced concrete) beams research have been surveyed in the shear area using fiber-reinforced polymer (FRP) composites and ended in collapse in the shear due to the separation of the FRP. The NSM method utilizing fiber fortified polymer (FRP) bars is currently an entrenched method for the reinforced concrete strengthening structures. The main proposal of this search is to look into experimentally for strengthening shear behavior with RC NSM carbon fiber reinforced polymer (CFRP) bars and exhibit the numerical outcomes for strengthened beams in shear with various FRP types; carbon fiber bar (CFRP), aramid fiber bar (AFRP), and glass fiber bar (GFRP) in shear. Three-dimensional beam models using finite element method are formed with software ANSYS-2013 to study the behavior of FRP in strengthening. Finally, a simply proposed equation is produced to estimate the shear strengthening capacity. The proposed equation affirms the exactness and viability of the experimental numerical result.

FEM performance of concrete beams reinforced by carbon fiber bars

Concrete structures may be vulnerable to harsh environment, reinforcement with Fiber Reinforced Polymer (FRP) bars have an increasing acceptance than normal steel. The nature of (FRP) bar is (non-corrosive) which is very beneficial for increased durability as well as the reinforcement of FRP bar has higher strength than steel bar. FRP usage are being specified more and more by public structural engineers and individual companies as main reinforcement and as strengthening of structures. Steel reinforcement as compared to (FRP) reinforcement are decreasingly acceptable for structural concrete reinforcement including precast concrete, cast in place concrete, columns, beams and other components. Carbon Fiber Reinforcement Polymer (CFRP) have a very high modulus of elasticity “high modulus” and very high tensile strength. In aerospace industry, CFRP with high modulus are popular among all FRPs because it has a high strength to weight ratio. In this research, a finite element models will be used to represent beams with Carbon Fiber Reinforcement and beams with steel reinforcement. The primary objective of the research is the evaluation of the effect of (CFR) on beam reinforcement.

Flexural Strengthening of RC Beams with Lap Splices

This paper presents results from an experimental study on the external strengthening of reinforced concrete beams having lap splice length less than that recommended by codes of practice for flexural tensile reinforcement. Six reinforced concrete beams having the same dimensions and reinforcement were considered in the experimental program. Firstly, two control beams were tested. The first control beam was made without any splice in the flexural tensile reinforcement whereas the second one had a mid span lap splice with a length of 240 mm which represents20 times the bar diameter. The other four beams had splices with length as that provided for the second control beam. These four beams were considered in order to investigate four different external strengthening techniques for beams having insufficient lap splice length compared as recommended by codes of practice. The external strengthening techniques included the use of near-surface mounted (NSM) bars or external bonding plates. Both carbon fiber bars and deformed steel bars were considered for the NSM technique. The external bonding plates included the use of carbon fiber laminate and anchored steel plate. The experimental results showed that all the techniques considered successfully restored more than the flexural capacity of the control beam without splice but with different ductility levels and different modes of failure. Also, an improvement in the beams stiffness was observed

External Fixator Kickstands for Free Soft Tissue Flap Protection

Protected elevation represents a critical component of postoperative care, particularly in posteriorly located flaps, to prevent pressure on the flap's vascular pedicle and ensure a successful skin graft. Although several short case series and technique papers have described kickstand placement to prevent heel ulcers as an adjuvant to fixator placement for fracture management, there remains a paucity of reports describing external fixator placement solely for extremity elevation and pressure alleviation in the postoperative care of flap coverage procedures. Patients who underwent lower extremity free flap coverage procedures requiring temporary elevation were included. Age, diagnosis, soft tissue procedures performed, type of external fixator placed, duration of frame placement, mode of removal, and complications related to external fixator placement were documented. Patients requiring external fixator placement for fracture management were excluded. Twelve patients with 13 lower limb soft tissue defects were included in our case series. A thin-wire ring external fixator kickstand was applied in 5 limbs while the rest underwent placement of a uniplanar carbon fiber bar type external fixator kickstands. The average time for removal of the frames was 4 weeks. No complications were reported from kickstand placement. The use of external fixator kickstands is an effective and safe adjuvant to soft tissue flap procedures for the lower extremity. Our case series is the largest in the literature and first to address the technical considerations for frame placement, positioning, and removal for external fixator kickstands placed solely for flap coverage procedures. Level IV, retrospective case series.

Numerical evaluation of bond–slip relations for near-surface mounted carbon fiber bars embedded in concrete

The present study deals with obtaining the bond relations for near surface mounted (NSM) CFRP bars embedded in concrete. The procedure for numerical simulation of pull-out tests with displacement control loading on NSM CFRP bars embedded in concrete has been presented to establish the bond relations. Parametric studies are performed considering various factors affecting the bonding of CFRP bar with concrete. Effect of tensile strength of epoxy adhesive filled in the groove to hold the CFRP bar and the influence of presence of ribs by varying the ribs diameter and ribs spacing are studied in the present investigations. Non-linear finite element models are developed by considering the parameters. It is found from the present study that as the ribs spacing decreases there is an increase in the bond strength, as the CFRP bar is more intact and uniform in the embedded system. But there is a drop in the bond strength when the ribs spacing is decreased beyond 0.8times the diameter of the CFRP bar. Further, with the increase in epoxy strength there is a decrease in the bond strength as the ultimate failure takes place in concrete. It is worth mentioning that with the increase in ribs diameter, there is an increase in the bond strength but decrease in the corresponding slip. The numerical models proposed and the relations obtained are very helpful in developing the bond–slip models and would be useful in designing the CFRP based strengthening schemes.

Bending Characteristics of Polymethylmethacrylate Columns, Connecting Bars of Carbon Fiber, Titanium, and Stainless Steel Used in External Skeletal Fixation and an Acrylic Interface

To (1) mechanically evaluate polymethylmethacrylate (PMMA) columns of various sizes and compare them to connecting bar materials (carbon fiber composite, titanium, stainless steel) and (2) compare the properties of an intact PMMA column to those of an acrylic interface. Experimental mechanical study. Experiment 1: 6 groups of 6 specimens each; experiment 2: 2 groups of 12 specimens each. All specimens were tested in 3-point bending. Stiffness, yield strength, and ultimate strength values were calculated for each specimen. PMMA 1 columns (23.25 mm) compared favorably to titanium or stainless-steel bars. PMMA 3 columns (30.15 mm) and carbon fiber bars had similar yield strength but PMMA 3 columns were less stiff than carbon fiber bars. PMMA 3 columns had lower bending modulus and a higher variability in their mechanical properties than PMMA 1 or PMMA 2 (25.64 mm) columns. Acrylic interface specimens were less strong but as stiff as intact specimens. An acrylic interface was easily created and had acceptable biomechanical characteristics. PMMA 2 and PMMA 3 columns are not recommended for clinical use at this time. Further tests are needed to analyze an acrylic patch in a more clinically relevant loading model.

구조적 손상을 입은 철근콘크리트 보의 전단보강 효과에 관한 연구

This study examines shear capacity performance and structural characteristics of reinforced concrete beam using carbon fiber sheet(CFS), g)ass fiber sheet(GFS), glass fiber steel plate(GSP) and carbon fiber bar CB) which are reinforcing materials for reinforced concrete beam in order to produce similar condition to repair and reinforce actual structure and aims to provide data available In designing and constructing reinforced concrete structures under the structural damage. This study obtains the following conclusions. After considering the shear experiment results. it was indicated that the CB reinforced test object was the best in the shear capacity improvement and ductility capacity as it was contained in the concrete and was all operated, Also, GFS reinforced test object indicated the reduced flexural capacity but good shear capacity. GSP reinforced test object had bigger reinforcing strength than other reinforcing test objects. On the other hand, it showed the lowest reinforcement effect as compared section thickness of reinforced material because it showed the bigger relativity a section thickness of reinforced material. If the adherence to the concrete is improved, it will seem to show bigger reinforcement effect.

The Economic Impact of Reprocessing External Fixation Components

The trend toward temporizing external fixation of complex fractures has resulted in increased expenditures for these devices. Increasing pressure to reduce health-care expenditures has led to exploration of reuse of equipment intended for single use. Devices must be tested and recertified prior to redeployment in hospital stock. We report the rate of manufacturer recertification and institutional cost savings associated with a reuse program approved by the United States Food and Drug Administration. All Hoffmann-II external fixation components that had been removed at our institution during the study period were submitted to the manufacturer for visual inspection and mechanical testing. Pass rates for original components and previously recycled components were determined. With use of a conservative pass rate and the assumption of a maximum of three recertifications of each component, the total potential hospital savings on external fixation were calculated. The first pass rate was 76%. The second pass rate (i.e., the rate for components that had already been recertified once and had been sent for a second recertification) was 83%, but that rate was derived from a limited sample. On the basis of a conservative pass-rate estimate of 75%, the predicted average number of uses of a recyclable component was 2.7. The recertified components were sold back to our hospital at 50% of the original price. Because carbon-fiber bars and half-pins are not recycled, 85% of the charges expended on a new external fixation component are spent on portions of the system that are recyclable. The potential total savings on reusable components was found to be 32%, with a total savings of 27% for the whole external fixation system. No recertified components failed in clinical use over the course of the study. With the expansion of cost-control efforts, the recycling of medical devices appears inevitable. Previous data have demonstrated the safety of reuse of external fixation devices, and this study confirms that finding. Our paper demonstrates the real cost savings associated with a manufacturer-based testing and recertification program. Issues of voluntary participation in reuse programs, component ownership, and the impact of savings on patient charges are yet to be worked out by individual institutions.