Fiber Composite Tubes Research Articles

Study on the bending mechanical properties of composite tube and metal joint bonding structure

Abstract The study of the mechanical properties of composite adhesively bonded joints is a very important issue, which directly affects the safety and reliability of the structure. This article studies the bending performance of carbon fiber composite tubes and metal joint bonding structures, as well as obtains the structural bearing capacity, influencing factors, and structural failure modes. Through mechanical analysis and static bending load tests, it is shown that the failure model of composite tube adhesively bonded metal joints under bending load is manifested as the first layer peeling or interlayer failure of the composite material in the bonding area between the tube and the joint, leading to local crushing at the end of the tube. There is no gap between the tube and the joint, which has little effect on the bending bearing capacity. The thickness gradient treatment at the end of the joint does not help improve the bending bearing capacity. The adhesive layer is at a 90 ° angle, which makes it easy for the first layer to peel off; it should be avoided. Other angle layers have little impact on load-bearing capacity. The longer the bonding length is, the stronger the bending capacity is. The adhesive J133 or 420 has a similar load-bearing. Wrapping a carbon fiber unidirectional layer around the ends of tubes and joints is helpful in improving their bending load-bearing capacity.

Lateral compression behavior of expanded polypropylene foam–filled carbon and glass fiber composite tubes

Abstract The crashworthiness and deformation behavior of circular composite tubes that were internally supported with expanded polypropylene (EPP) foams were investigated under lateral compression tests. Carbon woven (CFRP) and glass woven fiber/epoxy (GFRP) composites and EPP foam with densities of 30, 60, and 75 kg·m−3 were used. According to results, empty CFRP and GFRP tubes absorbed almost the same amount of energy; however, the GFRP tube had a higher specific energy absorption value due to its lower weight compared to the CFRP tube. EPP foam filling has a more significant effect on the crashworthiness of CFRP tubes compared to GFRP tubes. The best results in CFRP tubes, in terms of specific energy absorption, were obtained as 2.67 J g−1 at 75 kg·m−3 EPP foam-filled sample; however, 60 kg·m−3 EPP foam–filled sample exhibited the best configuration in terms of force efficiency. For the GFRP tubes, the best configuration was obtained at 60 kg·m−3 EPP foam–filled sample for all of the crashworthiness parameters. It is seen that the crushable length of composite tubes was shortened with the increase of EPP foam density. Lastly, the deformation behaviors of composite tubes showed that the CFRP tubes were more brittle than the GFRP tubes.

Dynamic response of composite tube reinforced porous polyurethane structures under underwater blast loading

The hyper-elastic porous structures show excellent acoustic stealth, impact isolation and underwater explosion protection properties when they are subjected to underwater blast loads. But the energy absorption ability of them needs to be improved, which is caused by premature densification. Therefore, the composite reinforced hyper-elastic porous polyurethane structure (CRHPP) filled with carbon fiber composite circular tubes are designed and fabricated in this paper. Based on quasi-static compression test results, it is shown that the CRHPPs has a 407% increase in energy absorption compared to the porous polyurethane structure. The dynamic responses and failure modes of the CRHPPs subjected to underwater blast loads are investigated by tests and simulations. The CEL (Coupled Eulerian-Lagrangian) method combined with the three-dimensional Hashin criterion are used to simulate the response process. In order to further improve the underwater explosion resistance of the CRHPPs, the effects of structural gradient on the responses are simulated and analyzed. The results show that the stiffness and energy absorption capacity of the hyper-elastic porous polyurethane structure can be significantly improved by adding composite tubes. There are no permanent damage and densification in the CRHPPs subjected to far-field underwater blast loads. Whether gradient or uniform in the other layers, these CRHPPs without reinforcement in the front first layer show better underwater explosion resistance and protection effect.

A novel post-processing method for progressive failure analysis of brittle composite compression

Finite element analysis of brittle materials in axial compression typically uses element deletion to allow continued global deformation post-element-failure. However, element deletion produces cyclic load-displacement curves that underestimate energy absorption and are not representative of a continuum system. Two key observations support the conclusion that results from an appropriately discretized model can be an adequate representation of a continuum system. Specifically, the frequency of the oscillations in the load-displacement curve is directly dependent upon element length in the loading direction, and the peak amplitudes of oscillations are mesh size independent. A method of post-processing the analysis results, by connecting the peak amplitudes of oscillations, is proposed and applied to a series of continuous carbon fiber composite crush tubes. The load-displacement curve, stable crushing load, and specific energy absorption of the post-processed results compare well to an experimental study of crush tubes with similar layups.

Eco-marathon racing car casing and frame structure design

In addition to the Pneumobil competition, our team will also participate in the Shell Eco-marathon with an electric-powered prototype category car. Based on our results so far, we are in the midfield of European competitions. After several modifications to our current car, we will be building a new car again in 2022. The goal of building eco-marathon racing cars is to achieve the lowest possible energy consumption, and accordingly, great emphasis should be placed on reducing weight and drag coefficient.Our previous cars used a welded aluminum frame and fiberglass. One of the best ways of weight reduction would be a self-supporting, carbon-fiber composite frame structure; however, the team does not currently have the technology to produce this. The frame structure of the new car consists of carbon fiber composite tubes, the nodes are 3D printed, fiber-reinforced composite elements. The streamlined casing of the vehicle consists of vacuum formed PETG elements. By using this structure, the total weight can be radically reduced at minimal cost. In our publication, we describe the main steps in the design of the casing and frame structure, finite element analysis of air resistance and deformations, and the drive chain.

Experimental investigation on multi-layered filament wound basalt/E-glass hybrid fiber composite tubes

In this study, the mechanical damage of Basalt/E-glass hybrid fiber-reinforced polymer composite tubes was evaluated experimentally using Micro hardness on transverse direction, uni-directional static tensile loading, and Quasi-static compressive loading. The Burn-off test method has been studied for the volumetric fraction of hybrid composite tubes. The multi-layer hybrid composite tubes composed of eight layers of plies at constant fiber tension of 20N, a constant mandrel rotation speed of 45 RPM and constant winding angle of ±55° for basalt fiber and ±90° for E-glass fiber were fabricated through a 3-axis filament winding machine with a seamless amalgamation of the stage by stage curing in the furnace. Eleven tube arrangements with fiber content proportion of {100%, 25:75%, 50:50% and 75:25%} with various stacking sequence were studied. The test results provide that these mechanical property’s behavior was moderately affected by the proportion of fiber content and most of the time affected by the variation of layer stacking sequence. Adding 50% of basalt and 50% E-glass fiber sharing of BGH7 hybrid combination of basalt laminate placed in the outer side increases the mechanical characterization compared to the 25% and 75% sharing of basalt and E-glass fiber. The fractured fibrous matrix of the tensile specimens and compressive specimens was assessed using a scanning electron microscope (SEM).

Chiral-Lattice-Filled Composite Tubes under Uniaxial and Lateral Quasi-Static Load: Experimental Studies

Our research investigated the energy absorption characteristics of chiral auxetic lattices filled cylindrical composite tubes subjected to a uniaxial and lateral quasi-static load. The lattice structures were manufactured using a 3D printing technique. Carbon fiber composite tubes without filler material were initially subjected to uniaxial and lateral quasi-static crushing load. The same types of experiment were then performed on chiral lattices and chiral lattices filled composite tubes. For the different cases, the load–displacements curves were analyzed and the specific energy absorption (SEA) values were compared. The SEA capability for the axial quasi-static crushing of the chiral lattices filled composite tubes decreased in comparison with the hollow composite design. However, the most significant result was that the average SEA value in the case of lateral loading increased dramatically in comparison with the hollow composite configuration.

Evaluation of Bonding Gap Control Methods for an Epoxy Adhesive Joint of Carbon Fiber Tubes and Aluminum Alloy Inserts.

The aim of this paper is to compare two methods of epoxy adhesive bond gap control: one with a geometrical (mechanical) solution and the other with glass beads, which have the diameter of the desired bond gap and are mixed with an epoxy adhesive. The adhered materials were carbon fiber composite tubes and aluminum alloy inserts, which were used as wishbones in a suspension system of a motorsport vehicle. It was assumed that the gap thickness would be equal to 0.2 mm and the length of a bond would be 30 mm. The internal diameter of the tubes was 14 mm and 18 mm, whereas the inserts’ external diameter was 13.6 mm and 17.6 mm. Their surface has been subjected to mechanical treatment with sand paper starting from 240 grit up to 400. The adhesives used were EA 3425 and EA 9466 cured at 80 °C for 2 h. The results showed that the glass beads method provides more consistent and better results as compared to the geometrical (mechanical) method. Further study in the area of fatigue and interfacial failure modes could be useful.

Micro-XCT Characterization and Numerical Analysis of Bending Damage Mechanism in Carbon Fiber Plain, Twill and Winding Composite Tubes

Transverse bending damage morphologies of carbon fiber composite tubes with different ply structures were investigated by the micro-XCT characterization. Structural effects of the plain, twill and winding on the damage mechanism were analyzed. The experimental results present fiber-resin cracking, interlayer delamination and fiber tows breakage with structural deformation from the peak load to final catastrophic failure. Woven fabric plies in the plain and twill composite tubes cannot be effectively slipped because of their tight interlaced structures, which makes the load propagate along the warp and weft fiber tows, resulting in more fiber tows breakage under bending-induced stretching. There is no interlaced effect on the failure mechanism for the winding tubes, resulting in a fact that the bending load can only be transferred from the fiber-resin or the layer-to-layer interface, with more interlaminar slippage and obvious springback behaviors under in-plane shear. For investigating the interlaced effect on failure mechanism, plain and winding models under transverse bending were established using continuous shell elements, and different constitutive description were used to simulate interlayer failure and intra-layer failure behaviors. By comparing the numerical results with the experimental ones, the influence of the fabric structure on the failure behavior of the tube were analyzed.

Mechanical Characterization of Basalt and Glass Fiber Epoxy Composite Tube

The application of basalt fibers are possible in many areas thanks to its multiple and good properties. It exhibits excellent resistance to alkalis, similar to glass fiber, at a much lower cost than carbon and aramid fibers. In the present paper, a comparative study on mechanical properties of basalt and E-glass fiber composites was performed. Results of apparent hoop tensile strength test of ring specimens cut from tubes and the interlaminar shear stress (ILSS) test are presented. Tensile tests using split disk method provide reasonably accurate properties with regard to the apparent hoop tensile strength of polymer reinforced composites. Comparison between the two tubes showed higher basalt fiber composite performance on apparent hoop tensile strength (45% higher) and on the interfacial property interlaminar shear stress (ILSS) (11% higher). New data obtained in this work on basalt fiber composite tubes confirm the literature for basalt fiber composite with other geometries, where it overcomes mechanical properties of the widely used glass fiber composites.

Dynamic compressive strength and mechanism of failure of Al-W fiber composite tubes with ordered mesostructure

The split Hopkinson pressure bar was used to investigate the dynamic behavior of high density aluminum alloy (Al 6061-T6) – tungsten (W) fibers composite tubes with periodic arrangements of W fibers in axial and hoop directions processed by using the combination of Cold Isostatic Pressing (CIPing) and Hot Isostatic Pressing (HIPing). Additional heat treatment of some samples allowed them to regain the original strength of Al 6061-T6, which was annealed during HIPing. The high-strain-rate deformation resulted in the strength increase for both types of samples (with and without the heat treatment) compared to quasi-static deformation. Samples after additional heat treatment exhibited higher dynamic strength. We consider that the strain rate sensitivity of the composite samples is caused by W fibers, which are responsible for the high strength of the samples and mechanism of their fracture.After dynamic tests, the Al matrix was chemically removed from the heavily deformed samples to reveal the mode of deformation of the W fibers: microbuckling and kinking in the axial direction. These mechanisms initiated the fracture of the composite samples followed by sample bulging due to plastic flow of the Al matrix and the subsequent fracture of W fibers in the hoop direction.

Ultra-efficient wound composite truss structures

This paper presents the design, analysis, manufacturing, experimental testing, and multiobjective optimization of a new family of ultra-efficient composite truss structures. The continuously wound truss concept introduced here is a versatile, low cost and scalable method of manufacturing truss structures based on a simple winding process. A prototype truss configuration is shown and experimentally characterized under torsion and three point bending loads. A large deformation implementation of the direct stiffness method is shown to provide good prediction of the stiffness properties of the prototype truss. This model is extended to include strength prediction with multiple failure modes. The design space achievable with these truss structures is then explored through multiobjective optimization using the NSGA II genetic algorithm. These continuously wound truss structures have the potential to provide between one and two orders of magnitude increase in structural efficiency compared to existing carbon fiber composite tubes.

Elastic response of water-filled fiber composite tubes under shock wave loading

We experimentally and numerically investigate the response of fluid-filled filament-wound composite tubes subjected to axial shock wave loading in water. Our study focuses on the fluid–structure interaction occurring when the shock wave in the fluid propagates parallel to the axis of the tube, creating pressure waves in the fluid coupled to flexural waves in the shell. The in-house-developed computational scheme couples an Eulerian fluid solver with a Lagrangian shell solver, which includes a new and simple material model to capture the response of fiber composites in finite kinematics. In the experiments and simulations we examine tubes with fiber winding angles equal to 45° and 60°, and we measure the precursor and primary wave speeds, hoop and longitudinal strains, and pressure. The experimental and computational results are in agreement, showing the validity of the computational scheme in complex fluid–structure interaction problems involving fiber composite materials subjected to shock waves. The analyses of the measured quantities show the strong coupling of axial and hoop deformations and the significant effect of fiber winding angle on the composite tube response, which differs substantially from that of a metal tube in the same configuration.

Experimental and Theoretical Analysis of Carbon Fiber Filament Wound Tubes with Symmetric Winding Angle under Tensional Loading

Carbon fiber composite tubes with symmetric winding angles were experimented under tensional loading and theoretically calculated using classical laminate theory. The experimental result showed that the axial stiffness of filament wound tubes without woven fiber was a little higher than that of filament wound tubes with woven fibers. In addition, the theoretical calculation results of axial stiffness had a good agreement with the experimental results of filament wound tubes without woven fiber.

Finite element modeling of hollow and concrete-filled fiber composite tubes in flexure: Optimization of partial filling and a design method for poles

In this paper, the nonlinear finite element model developed and verified in the companion paper [Son J, Fam A. Finite element modeling of hollow and concrete-filled fiber composite tubes: Part 1 — model development and verification in flexure. Engineering Structures 2008;30(10):2656–66] has been used to study fiber-reinforced polymer (FRP) tubular poles partially filled with concrete in flexure. Partial filling is proposed as a low-cost alternative to using thicker-walled tubes, to enhance flexural strength and stability. The partial concrete fill length is optimized in cantilever-type mono-poles for tubes with different diameter-to-thickness ( D / t ) ratios and different laminate structures. It was found that this optimum length is reduced in any one of the following conditions: as D / t ratio becomes smaller, when fiber angles relative to the longitudinal axis in angle-ply tubes increases, when longitudinal fiber fraction in cross-ply tubes reduces, and when a laterally distributed load is applied instead of a point load at the tip. Simple expressions were established to calculate moment capacities of hollow and concrete-filled FRP tubes. They were then incorporated into a simple design approach developed to predict the optimum concrete fill length, on the basis of that failure occurs in the concrete-filled and hollow parts simultaneously. A procedure to account for tapered poles is also presented.

Finite element modeling of hollow and concrete-filled fiber composite tubes in flexure: Model development, verification and investigation of tube parameters

A nonlinear finite element model is developed to study the flexural behavior of hollow and concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs). It accounts for material and geometric nonlinearities and is capable of detecting local buckling in thin-walled hollow tubes. In thick-walled hollow tubes and CFFTs, FRP material failure is detected through the Tsai–Wu failure criteria. The model has been successfully verified using experimental results. It was then used in a parametric study to examine hollow tubes and CFFTs of different diameter-to-thickness ( D / t ) ratios of 40–125. Two different FRP laminates were considered; angle-ply of 10–75 deg angle measured to the longitudinal axis, and crossply with 25%–75% longitudinal fiber fraction. It was shown that the flexural strength increases as the angle of fibers is reduced or the longitudinal fiber fraction increased, particularly for small D / t ratios. The angle, however, has no effect on the strength of hollow tubes with large D / t ratios. The effectiveness of concrete-fill is reduced as the angle increases, up to 35–45 deg, and then stabilizes. It is not affected, however, by the fraction of longitudinal fibers. In a companion paper [Fam A, Son Je-Kuk. Finite element modeling of hollow and concrete-filled fiber composite tubes: Part 2–Optimization of partial filling and a design method of poles. Engineering Structures 2008;30(10):2667–76. [9]], the model is used to study and optimize partial concrete filling of FRP tubular mono-poles, and develop a design method.

Seismic Performance of Reinforced Concrete Bridge Substructure Encased in Fiber Composite Tubes

Recent cyclic tests in the United States, China, and Japan have shown that fiber-reinforced polymer (FRP) tubes can effectively replace spiral reinforcement in reinforced concrete (RC) columns. This study was undertaken to advance the current state of the art for concrete-filled FRP tubes (CFFTs) by comparing their seismic performance with that of conventional RC bridge pier columns at the sectional, member, and bridge system levels. A nonlinear finite element model was developed for a bridge case study. Because FRP has a lower rupture strain than steel spiral and because of its linear elastic response, a CFFT section shows less ductility than an RC section. However, at the member level, a CFFT column distinctly outperforms its RC counterpart, with almost twice the base shear capacity and more than three times the lateral drift capacity. This phenomenon was attributed to the effective role of the FRP tube in extending the plastic hinge zone of the column well beyond its typical range in conventional RC columns. The implication of this behavior was shown through a seismic simulation of the entire bridge under a major historical shake with varying levels of magnified ground acceleration. The simulation showed the CFFT substructure to suffer moderate damage while maintaining structural integrity compared with the RC substructure, which suffered severe and irreparable damage.

Seismic Performance of Reinforced Concrete Bridge Substructure Encased in Fiber Composite Tubes

Recent cyclic tests in the United States, China, and Japan have shown that fiber-reinforced polymer (FRP) tubes can effectively replace spiral reinforcement in reinforced concrete (RC) columns. This study was undertaken to advance the current state of the art for concrete-filled FRP tubes (CFFTs) by comparing their seismic performance with that of conventional RC bridge pier columns at the sectional, member, and bridge system levels. A nonlinear finite element model was developed for a bridge case study. Because FRP has a lower rupture strain than steel spiral and because of its linear elastic response, a CFFT section shows less ductility than an RC section. However, at the member level, a CFFT column distinctly outperforms its RC counterpart, with almost twice the base shear capacity and more than three times the lateral drift capacity. This phenomenon was attributed to the effective role of the FRP tube in extending the plastic hinge zone of the column well beyond its typical range in conventional RC columns. The implication of this behavior was shown through a seismic simulation of the entire bridge under a major historical shake with varying levels of magnified ground acceleration. The simulation showed the CFFT substructure to suffer moderate damage while maintaining structural integrity compared with the RC substructure, which suffered severe and irreparable damage.

The Effect of Matrix Microcracks on the Stress-Strain Relationship in Fiber Composite Tubes

A model for the stress-strain behavior of fiber composites with matrix cracks is presented and applied to the deformation of fiber reinforced composite pipes under different combinations of hoop and axial stress. The model provides a good description of the nonlinear stress-strain relationship that develops in composites when the matrix is damaged by the progressive nucleation of microcracks during loading. Ply properties are expressed as a function of crack density, calculated as a function of increasing stress using the shear-lag approximation. The predictions are in very good agreement with data from multiaxial tests on ±55° filament wound glass-reinforced epoxy pipes.

The crushing response of braided and CSM glass reinforced composite tubes

Results from an experimental and analytical study on the behavior of braided and continuous strand mat (CSM) glass fiber composite tubes under quasi-static crush conditions are presented. The composite tubes have an initiator plug introduced at one open end (chamfered) while the other end is clamped. This procedure causes the tube to `flare' outwards into fronds and results in the progressive failure of the tube in the axial and hoop directions without global tube buckling. Axial force and axial displacements are measured during these tests in order to assess energy absorption. In addition, readings from strain gages that are placed at critical locations on the tube walls are used to understand the state of strain and stress on the tube walls away from the crush end. During a crush test, the axial load ascended to a maximum value and subsequently settled to a plateau value about which the load oscillated during the progressive crushing of the tube. Oscillations remained small for CSM tubes while the braided ones had larger and more distinct periodicity. Results from an analytical model that best simulates the failure of these tubes are presented. The model is based on an axisymmetric formulation of the cylindrical shell equations in conjunction with ideas from classical fracture mechanics and continuum damage mechanics.