Carbon Fibre Reinforced Polymer Tubes Research Articles

Damage Detection of CFRP Filament Wound Tubes Using Electrical Resistance Measurement

The electrical resistance measurement method was used for damage detection of Carbon Fiber Reinforced Polymer (CFRP) tubes during torsion and flexural loading. The symmetrical convex octagon shape specimens were manufactured using a filament winding technology. The specimens were manufactured with Integrated Loop Technology (ILT) joints at the ends in a single production step. This configuration of tubes with ILT joints allows very effective load transfer and it is also efficient from the manufacturing point of view. This type of components could be used in construction of robotic arms for automated processes. Possible collisions and resulting overloading can cause damage to the composite tubes. Such damage could be overlook due to cabling, coating and casing covering the surface of the robotic arms. In addition to the above, the requirement for a smooth surface must also be met. Therefore, possible way how to easily detect serious damage of CFRP tubes was investigated, together with a testing of a novel approach to an electrical contact manufacturing. The electrical contacts for damage monitoring were made of carbon fiber tows with electrically connected endings. They were integrated to the composite structure during filament winding process. Four specimens were loaded by flexural loading and two specimens were loaded by torsional loading. All specimens were loaded by three cycles of operational loading and then loaded to final fracture. It was shown that the presented type of electrical connection to the structure is feasible, does not disturb the surface of the sample and does not affect the ultimate strength of the specimen. According to our measurements, operational loading could be monitored only to a limited extend using the electrical resistance measurement. This is because the fracture damage caused significant change in measured electrical resistance of the specimen for both torsional and flexural loading. The presented measurement configuration with electrodes made of integrated carbon fibers is suitable for further investigation in the field of fracture damage detection of carbon fiber wound profiles.

Behavior of CFRP-Confined Sand-Based Material Columns under Axial Compression.

This paper presents an innovative pumpable standing support designed for underground mines located in the arid and semi-arid deserts of the Gobi region with a shortage of water resources. The exterior shell of this pumpable standing support is made of carbon fiber-reinforced polymer (CFRP), while the infill material is a sand-based material (SBM). As the novel backfill material, SBM is the combination of high-water cementing material and desert sand. A series of experimental tests were conducted to obtain the mechanical response mechanism of this novel pumpable standing support under uniaxial compression. Test variables investigated in this research covered the water-to-powder ratio of the cementing material, the mixing amount of sand, and the thickness of the CFRP tube. Test results confirmed that the CFRP-confined SBM columns exhibited typical strain hardening behavior with the acceptable axial deformation. It was also demonstrated that using high-strength cementing material, a thicker CFRP tube, and a high mixing amount of sand effectively increased the bearing capacity of the CFRP-confined SBM column. Except for the exemplary structural behavior, the consumption of high-water cementing materials of the novel pumpable standing support is smaller than that of its counterparts made of pure cementing material, when specimens with the same mechanical performance are compared.

Post Tensioned CFRP tubes for improved energy absorption

Thin-walled tubes made of CFRP (Carbon fiber reinforced Polymer) are being increasingly used as CC (Crush Cans) due to their higher specific energy absorption capacity in the automotive domain for absorbing impact energy during a frontal crash. Finite element analysis (FEA) based computational methods have matured over the years with increased accuracy and acceptable correlation with experimental results. FEA-based computational studies when used appropriately can reduce the number of physical tests and prototypes required besides accelerating the overall cycle design time. The present work proposes an FEA based design validation approach for the evaluation of post-tensioned crush can design that can absorb more impact energy compared to a normal CFRP thin tube. The FEM based method uses a combination of multiple simulation techniques to predict the behavior of a post-tensioned tube. The post-tensioning in the present work has been proposed in the form of internal pressure for the thin tube. It was found that a safe value of pressure, when applied as a post-tensioning load, can improve the energy absorption capacity without increasing the weight of the tube.

Blast responses of carbon-fiber reinforced polymer tubular columns filled with seawater sea-sand concrete

Concrete-filled fiber-reinforced polymer tubular (CFFT) columns are advanced structures in civil engineering due to their advantages of high strength, good corrosion resistance, and strong stability. In this study, four groups of columns were designed, with three groups of CFFT columns cast with carbon-fiber reinforced polymer (CFRP) tube and seawater sea-sand concrete (SSC) reinforced with glass fiber reinforced plastic (GFRP) bars and one group of reference SSC columns. Quasi-static compression and field explosion experiments were conducted to investigate their quasi-static and dynamics mechanical performances. The damage of exploded columns was evaluated by direct radiography (DR) inspection and residual bearing capacity testing. The quasi-static compression capacity of the CFFT column is about twice of the summation of the load bearings of the CFRP tube and the SSC column with the help of the constraint effect of the CFRP tube. An improved model was proposed to predict the compression capacity of the CFFT column considering the strength of the CFRP tube. The CFRP tube attenuates the spalling failure of SSC columns and transfers the damage to concrete tensile crack and CFRP damage. The innovative CFFT column filled with GFRP bars reinforced SSC exhibits immense potential in marine protective structures.

Confinement of Concrete by Fiber Reinforced Polymer Tube: A Review

Researchers studied a lot of strengthening techniques of concrete, one of which is the technology of concrete confinement. This technique is common to utilize fiber fabric impregnated with epoxy resin adhesive. Relevant applications mainly include strengthening the existing structure and new structural construction. This paper presents a review of previous studies on the confinement of concrete using fiber-reinforced polymer (FRP) tubes. Four main parameters were investigated in this study: the number of layers of FRP tubes, cross-sectional shape and slenderness ratio, material types of FRP tubes, and concrete types. The results of the investigation showed that increasing the number of FRP tubes resulting in a significant improvement in the behavior of confined specimens, circular cross-section specimens exhibited better behavior than square. Also, the behavior of confined square specimens improvement with increasing the angular radius. A carbon fiber reinforced polymer tube is better than (aramid, glass, and basalt) fibers. Finally, the concrete confining technique significantly improved the behavior of specimens regardless of the type of concrete confined, and the effect of confining decreases with the increase of compressive strength of the concrete confined.

Behavior of High Strength Concrete Filled Square Steel Tube Stub Columns with Inner CFRP Tube Under Biaxial Eccentric Compression

This paper studies the contribution of CFRP (carbon fiber-reinforced polymer) to the mechanical behavior of high strength concrete-filled square steel tube (HCFST) under biaxial eccentric compression. The new type of composite member is composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. The finite element analysis was made by ABAQUS on the behavior of high strength concrete filled square steel tubular columns with inner CFRP circular tube subjected to bi-axial eccentric loading. The results obtained from the finite element analysis were verified with the experimental results. In addition, the load-deflection curves in the whole process were calculated and analyzed, which can be divided into three segments: Elastic phase, plastic phase, descending phase. Based on the load-deflection curves, the stresses analysis on the core concrete, CFRP tube and steel tube were conducted. The confinement effect of the CFRP tube improves the ductility of HCFST-CFRP stub column. CFRP ratio and eccentricity affect the ultimate bearing capacity of HCFST stub column. Finally, a calculation formula of ultimate bearing capacity was proposed in the paper.

Effect of self-stressing on concrete-encased-steel filled circular CFRP tubes under axial compression

This paper presents the experimental results of concrete-encased-steel filled CFRP (carbon fiber reinforced polymer) tube (CSFCT) cylinders under monotonic axial compression. In this experiment, the prestress produced by the expansion agent was applied to the self-stressing concrete-encased-steel filled CFRP tube cylinders. The experimental parameters included the prestress, the layers of CFRP (1, 2, 3 layers) and the dimensions of section steel. It is aimed to investigate the influence of these parameters on the behavior of concrete-encased-steel filled CFRP tube cylinders under axial compression. Test results showed that compared with the non-prestressed test specimens, the application of prestress in self-stressing cylinders eliminates the stress lag of CFRP, makes the utilization ratio of CFRP higher, and improves the standard ultimate load, intercept load and inflection load. Meanwhile, the axial compression behavior of columns was improved with the increase of CFRP layers regardless of the prestress. The results also indicated that CFRP has more efficient confinement effect on small-cross sectional area section steel compared with large one. According to the test results, on the basis of the existing theoretical model, considering the influence of initial prestress and section steel, the calculation models of the inflection load and ultimate axial strain were modified. Finally, the stress-strain model of CSFCT cylinders with high accuracy was developed.

Energy-absorption characteristics of tube-reinforced absorbent honeycomb sandwich structure

Nomex honeycombs are widely used in lightweight structures due to their unique porous structure. By adding an absorbent agent to Nomex honeycomb wall and filling carbon fiber reinforced polymer (CFRP) tube, a novel tube-reinforced absorbent honeycomb sandwich structure was proposed. Its compressive properties and energy absorption characteristics were studied experimentally and numerically. Compared with empty absorbent honeycomb, the normalized elastic modulus E, peak stress and energy absorption of tube-reinforced absorbent honeycomb can be increased by 55.74%, 621.69% and 327.86% respectively. Moreover, the energy absorption of the tube-reinforced absorbent honeycomb was increased by 30.34%, compared with the sum of empty absorbent honeycomb and CFRP tube tested separately. The interaction effects and enhancement mechanism between absorbent honeycomb and CFRP tube were also discussed. The excellent electromagnetic absorption and mechanical properties make this novel honeycomb sandwich structure much more competitive not only in electromagnetic wave stealth application but also in load-carry structures.

Behavior of FRP-confined sea-sand concrete columns with a prefabricated concrete-filled FRP-steel core

Adopting fiber-reinforced polymer (FRP) composites as a confining device and a protective skin not only allows usage of sea-sand concrete which is generally forbidden in conventional steel reinforced concrete structures, but also leads to enhancement of concrete strength and deformation capacity. This paper presents a pilot study on axial compression tests on hybrid FRP-confined sea-sand concrete columns with a prefabricated concrete-filled FRP-steel tube core (simply referred to as FRP-Confined Sea-sand Concrete-Prefabricated Core Columns or FCSC-PCCs). The prefabricated concrete-filled glass FRP (GFRP)-steel core, serving as reinforcing core in FRP-confined concrete columns, is expected to enhance the FRP-confined concrete columns and enable to make use of sea-sand in the concrete between the two tubes. Effects of the steel tube diameter, the GFRP tube thickness and the thickness of the external Carbon FRP (CFRP) tube are carefully investigated. The axial load–axial strain curve of FCSC-PCCs as well as the confined concrete in FCSC-PCCs generally exhibit a monotonically ascending behavior owning to the confinement from the external CFRP tube and the internal FRP-steel composite tube. A new model for average ultimate axial stress and axial strain of confined concrete in FCSC-PCCs is established and the comparisons demonstrate that the proposed model is of satisfactory accuracy.

Following the effect of braid architecture on performance and damage of carbon fibre/epoxy composite tubes during torsional straining

The torsional performance of bi-axially braided carbon fibre reinforced polymer (CFRP) tubes as a function of braid architecture is investigated. It is found that for a given braid pattern, the 45° braided CFRP tubes have higher shear moduli and lower shear strength than the 35° braids. In general, 2/2 (regular) braided CFRP tubes exhibit both higher shear strength and higher shear modulus than 1/1 (diamond) braids. However, beyond the peak load, the shear strength of 2/2 braided CFRPs exhibits sudden and steep drops, resulting in a lower remnant shear strength than 1/1 structures after the shear strain exceeds 4.5%. Moreover, the damage evolution is monitored in-situ by synchrotron X-ray computed tomography during torsional straining. It shows that for a 2/2 structure, inter-tow debonded regions are vertically interconnected allowing rapid crack propagation and strength drops, whereas for the 1/1 braid they are distributed in a chequer board pattern causing a more gradual loss of strength. The fibre/matrix interfacial strength and tow cross-over density play key roles in the torsional failure of 1/1 and 2/2 braided CFRP tubes, as the former controls damage initiation and the latter controls damage propagation.

Improving the energy absorption capacity of square CFRP tubes with cutout by introducing chamfer

Carbon fiber reinforced polymer (CFRP) tubes have been widely used as energy absorption devices. Because it is inclined to deform in progressive crushing mode (PCM) with low initial peak force Fp and high specific energy absorption SEA (the energy absorption per unit mass). In many cases, cutouts are introduced into these tubes to meet engineering requirements. However, the cutouts can cause a collapse in the middle height (i.e., mid-height collapse mode), and thus the SEA of the CFRP tubes is even reduced by 56%. Therefore, in this research, a chamfer is introduced into the CFRP tubes with cutout to trigger the PCM, thereby increasing the energy absorption capacity. A series of validation experiments show that the chamfer can trigger the PCM with about 64% decrease of Fp and 52% increase of SEA. The parameter study is conducted to investigate the effect of size and position of the cutout on the energy absorption of CFRP tubes with a 45-degree chamfer. The result indicates that the chamfer can eliminate the negative effects of cutouts and improve the energy absorption capacity in most cases. Furthermore, the contrastive analysis between CFRP and metal tubes reveals the difference in energy absorption characteristics of these two types of tubes and further explains the advantages of energy absorption of the CFRP tubes with a 45-degree chamfer and a cutout.

High strength expansive concrete-encased-steel filled carbon fiber reinforced polymer tubes under axial monotonic and cyclic load

High-strength concrete-encased-steel filled CFRP (carbon fiber reinforced polymer) tube (HCSFC) takes advantages of high strength of concrete, steel and confinement of FRP, resulting in enhanced structural load carrying capacity and deformability. In this study, expansive high-strength concrete is filled between CFRP tube and sectional steel to study the mechanical properties of high-strength expansive concrete-encased-steel filled CFRP tube (HECSFC) under monotonic and cyclic axial compression. Twenty-four specimens were fabricated in this study. The variables included the number of CFRP layers (0, 1, 2 layers), cross-sectional shape (circular and square), self-stress level (with or without self-stress) and loading mode (monotonic and cyclic). Test results show that the peak load of HCSFC specimen is greater than their nominal load-carrying capacity, which indicates that CFRP plays a confinement role on the internal core concrete-encased-steel. As the number of layers increases, both the normalized peak load and the ultimate axial strain increase. For specimens under the same number of layers, cross sectional shape and loading mode, the ultimate axial strain and strain reduction factor of self-stressing specimens are higher than those of nonprestressed specimens. At the same time, it is found that the confinement efficiency of CFRP on circular specimen is higher than that of square specimen. Analytical results show that the modified existing stress-strain models of CFRP confined concrete predict well with the experimental results.

Effect of initiator geometry on energy absorption of CFRP tubes under dynamic crushing

This study investigates the effect of initiator geometry, i.e. an inward-triggering cap (ITC), an outward-triggering plug (OTP) and a flat-surface plate (FSP), on the failure mechanisms and energy absorption of two carbon fibre reinforced polymer (CFRP) tubes, [03/45/−45/90/−45/45/03] (type U) and [03/902/03/(0/90)] (type W), under dynamic and quasi-static crushing in the axial direction. Under both dynamic and quasi-static crushing, the ITC induced massive transversely fractured fronds with enormous fragments, leading to high specific energy absorption, whereas the OTP produced the lowest specific energy absorption. The specific energy absorption of CFRP tubes under dynamic crushing were 32–40% and 12–69% lower than those under quasi-static crushing for the U-type tube and W-type tube, respectively. With the FSP, as compared to the U-type tube, the W-type tube had a higher specific energy absorption, though the wall thickness of the W-type tube was about 0.15 mm less than that of the U-type tube. Comparative analysis of the specific energy absorption indicated that the CFRP tubes were advantageous with the FSP when subjected to dynamic crushing, but they performed better with the ITC under quasi-static crushing.

Comparative study on aluminum/GFRP/CFRP tubes for oblique lateral crushing

Thin-walled composite structures are increasingly used in vehicles attributed to their lightweight and high energy-absorbing capacity. However, understanding crushing behavior of tubal structures made of different materials for lateral impact loading from different directions is fairly limited, which restricts their further applications. This study aimed to investigate the oblique lateral crashworthy characteristics of thin-walled circular tubes with aluminum, glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) materials by experimental, numerical and analytical methods. Thin-walled tubes were considered to bear the combined lateral compression and shear loading radially through two parallel rigid platens from the oblique angles of 0°, 10°, 20° and 30° to the horizontal direction, respectively. The effects of loading angles on crushing process, failure modes and crashworthiness indicators were quantified. Similar deformation patterns of each type of the tubes can be observed under these different loading angles, where frictional shear was found to be of limited effect on the deformation mode. With increase in loading angle, initial crushing force decreased, also the energy absorption of GFRP tube decreased whilst those of aluminum and CFRP tubes increased as seen from a prolonged process in the energy absorption-displacement curve. The specific energy absorption ( S E A ) of the aluminum, GFRP and CFRP tubes ranged from 2.36 to 2.62 J/g, 1.1 to 0.88 J/g and 0.79–0.96 J/g, respectively; and their corresponding crushing force efficiencies ( C F E ) ranged from 1.18 to 1.49, 0.74 to 0.59 and 0.6 to 0.65, respectively. To further explore the crushing behavior, finite element models were established and validated against the experiments. Finally, an analytical model was derived to predict the crashworthiness of thin-walled tubes under oblique lateral crushing. The study is expected to provide insights and guide to design of crashworthy structures for oblique lateral loading. • The oblique lateral crushing behavior of thin-walled aluminum, GFRP and CFRP tubes. • The FE and theoretical models of aluminum, GFRP and CFRP tubes under oblique lateral crushing. • The oblique lateral crushing performance and energy absorption mechanism of thin-walled aluminum, GFRP and CFRP tubes.

Performance and damage of carbon fibre reinforced polymer tubes under low-velocity transverse impact

Abstract The performance and damage of carbon fibre reinforced polymer (CFRP) tubes under low-velocity transverse impact are investigated. Drop hammer tests were performed to determine the mechanical behaviour and failure modes of different specimens. Further, numerical simulations were performed to analyse the damage evolution during the impact process, and the effect of lamination sequence on the transverse impact performance was analysed. The results show that under impact energies of 5 and 10 J, the tubes tend to generate circumferential cracks. When the impact energy is between 15 and 30 J, the tubes absorb energy by generating circumferential and longitudinal cracks. The damage evolution of the tubes can be better understood through the simulation results. When the ply angle increases from 0° to 75°, the fracture mode of the tube changes from a longitudinal to a circumferential crack. Tubes with complex ply angles have better energy absorption performance.

Experimental results of circular FRP tube confined concrete (CFFT) and comparison with analytical models

This study experimentally investigates the axial compressive behavior of Carbon Fiber Reinforced Polymer Tube Confined Concrete (CFRP CFFT) and Glass Fiber Reinforced Polymer Tube Confined Concrete (GFRP CFFT) specimens. The experimental results demonstrate significant improvement in the axial stress-strain behavior of CFRP CFFT and GFRP CFFT specimens with an increase in thicknesses of CFRP tubes and GFRP tubes, respectively. The axial stress-strain (fc−εc) curves of CFRP CFFT and GFRP CFFT specimens were constructed using well-known stress-strain models for Fiber Reinforced Polymer confined concrete. The fc−εc curves of CFRP CFFT and GFRP CFFT specimens constructed using the Samaan et al. [1] model mapped well with the corresponding experimental fc−εc curves, whereas fc−εc curves constructed as per the Lam and Teng [2] model exhibited a reasonable match with the corresponding experimental fc−εc curves. The fc−εc curves of CFRP CFFT and GFRP CFFT specimens constructed based on ACI 440.2R-08 [3] considerably underestimated the experimental axial stresses and axial strains. A parametric study was carried out to examine the effects of actual confinement ratio and type of FRP tube confinement on the fc−εc curves of CFFT specimens. It was found that actual confinement ratio and type of FRP tube confinement significantly influence the axial stress versus axial strain curves of CFFT specimens.

Behaviour of short CFRP-steel composite tubed reinforced normal and high strength concrete columns under eccentric compression

The use of steel tubed reinforced concrete (STRC) column maximizes the confinement effectiveness of steel tube as the steel tube is disconnected at the beam-column joint. However, for high-strength and high performance concrete, the confinement from the steel tube would be limited. Also, certain measures need to be implemented to prevent the corrosion of steel tube. Carbon fibre reinforced polymer (CFRP) has the advantages of high strength-to-weight ratio and good corrosion resistance. However, the complicated construction procedures and relatively brittle post-peak behaviour limit its application to new concrete buildings. The combination of CFRP and STRC column is a good alternative to solve the concerning problems. This study experimentally investigated the behaviour of CFRP-steel composite tubed reinforced concrete (C-STRC) columns under eccentric compression. The observed failure modes, load-deformation curves, and load-stress curves of the steel tube and longitudinal reinforcing bars are presented. The test results show that the load capacity and deformability of the C-STRC columns with normal concrete strength are enhanced due to the use of CFRP and steel tube. The plastic stress distribution method was employed to analyse the axial load versus moment interaction curves and the results were found to be generally in good agreement with the test ones.

Effect of winding angle on the quasi-static crushing behaviour of thin-walled carbon fibre-reinforced polymer tubes

Carbon fibre-reinforced polymer (CFRP) tubes have been increasingly used in various structural applications due to its lightweight and attractive crashworthiness performance. The key parameter of the winding angle plays an important role in the energy-absorbing performance of CFRP tubes. In order to understand the relationship between the compressive performance and winding angle, this article is aimed to study the effect of winding angle with ±45°, ±60° and ±75° of CFRP tubes. The thin-walled CFRP tubes were performed by the quasi-static compression test, which were fabricated using the wet winding technique. The result was concluded that as the winding angle increased, the compressive modulus showed the decreasing trend. In the view of energy absorption (EA) and specific energy absorption (SEA), it was exhibited the decreasing trend as the winding angle increased. It was noted that CFRP tubes with ±45° winding angle recorded the average maximum SEA of 24.67 kJ kg−1. Moreover, the crushing behaviour of thin-walled CFRP tubes were involved and studied.

Aluminium to Carbon Fibre Reinforced Polymer tubes joints produced by magnetic pulse welding

In this work, Aluminium AA7075-T6 to Carbon Fibre Reinforced Polymer (CFRP) tube joints using magnetic pulse welding technology were performed. The process was found suitable for joining this material combination when a rigid support is used to constrain the CFRP wall displacement. A minimum discharge energy of 2.5 kJ was seen to produce tight interfaces in tubular geometry for 1 mm of stand-off distance. A larger number of turns in the coil was found to reduce both the damages caused by the impact forces and to increase the joint axial resistance. To protect the CFRP tube from impacts and achieve a weld, an electrolytic Nickel coating was deposited over the CFRP tube. Welding was produced between the coating and the aluminium tube with no intermetallic compounds observed on the interface for the energies tested.

Experimental investigation on vibration characteristics of shear thickening fluid filled CFRP tubes

Vibration attenuation performance of structures is significantly important in aerospace, automotive, sport and medical equipment applications. In order to enhance the vibration absorption properties, shear thickening fluid (STF) is a candidate component in the structures due to its viscoelastic behavior. In this study, the vibration characteristics of carbon fiber reinforced polymer (CFRP) tubes were investigated. To compensate the lack of vibration isolation behavior of CFRP tubes, a natural STF was filled into the tubes and thus, the thickening rheology of this smart fluid was benefited in the STF/CFRP structures. The vibrational properties of the structures were investigated with modal analysis and the natural frequencies and damping ratios were calculated for two different boundary conditions (single and double-fixed ends). The results showed that the STF integration into the CFRP tubes significantly enhances the natural frequency of the structures as well as providing higher damping ratio in the STF/CFRP systems.