Fiber Reinforced Polymer Composite Tubes Research Articles

Lateral compression behavior of expanded polypropylene foam-filled carbon fiber reinforced polymer and aluminum/carbon fiber reinforced polymer composite tubes: An experimental study

This study investigates the energy-absorbing capability of the circular cross-section carbon fiber reinforced polymer (CFRP) and Aluminum/CFRP (Al/CFRP) composite tubular structures under quasi-static lateral compression. The CFRP composite tubes were manufactured with the 6, 8, and 10 layers to observe the thickness effect. A specially designed and manufactured polymer mold was used to manufacture identical CFRP composite tubes. Expanded polypropylene (EPP) foam with densities of 30 kg/m3, 60 kg/m3, and 75 kg/m3 was chosen as a filler material to enhance the energy absorption and efficiency because of its superior properties of high strength-to-weight ratio. The experiments revealed that the carbon fiber layer number directly affected CFRP and Al/CFRP composite tubes' force and the absorbed energy values. The increase in the maximum and average force values is more evident than in the Al/CFRP tubes due to using aluminum tubes constraining the effect of the carbon woven part. Additionally, EPP foam filling significantly contributes to the tubes' absorbed energy. The absorbed energy increased proportional to the foam density, and the 10-layer Al/CFRP tube filled with 75 kg/m3 sample absorbed the highest energy value as 257 J. However, considering the crashworthiness parameters (i.e., specific energy absorption, crush force efficiency, and work effectiveness), the best sample combination did not absorb the highest energy. Although the 6-layer CFRP composite tube absorbed the lowest energy, it has higher specific energy absorption and work effectiveness. According to the crashworthiness parameters, the best efficiency was obtained in the 10-layer composite tubes filled with 75 kg/m3.

Investigation of Functionally Graded Adherents on Failure of Socket Joint of FRP Composite Tubes.

Fiber-reinforced polymer (FRP) matrix materials are quickly being investigated for application in concrete construction repair, reinforcement, and refurbishment. The technology has progressed to the point that its future acceptance is mainly reliant on the availability of established design guidelines based on recognized performance criteria, as well as the cost competitiveness of these technologies in contrast to conventional rehabilitation methods. The goal of this study is to evaluate the different functional grades of adhesives throughout bond length for bonded socket joints of laminated FRP composite pipes. Damage development resistance is high with a functionally graded FRP composite socket joint, as shown. To extend the service life of the structure, the joint designer should use an FRP composite socket joint with a functionally graded adhesive (FGA).

Design of a Lightweight Multifunctional Composite Railway Axle Utilising Coaxial Skins

The rising economic and environmental pressures associated with the generation and consumption of energy necessitates the need for lightweighting of railway vehicles. The railway axle is a prime candidate for lightweighting of the unsprung mass. The reduction of unsprung mass correlates to reduced track damage, energy consumption and total operating costs. This paper presents the design of a lightweight multifunctional hybrid metallic-composite railway axle utilising coaxial skins. The lightweight axle assembly comprises a carbon fibre reinforced polymer composite tube with steel stub axles bonded into either end. The structural hybrid metallic-composite railway axle is surrounded by coaxial skins each performing a specific function to meet the secondary requirements. A parametric sizing study is conducted to explore the sensitivity of the design parameters of the composite tube and the stub axle interaction through the adhesive joint. The optimised design parameters of the axle consist of a; composite tube outer diameter of 225 mm, composite tube thickness of 7 mm, steel stub axle extension thickness of 10 mm and a bond overlap length of 100 mm. The optimised hybrid metallic-composite railway axle design concept has a mass of 200 kg representing a reduction of 50% over the solid steel version.

Development of self-floating fibre reinforced polymer composite structures for photovoltaic energy harvesting

This paper presents an innovative self-floating fibre reinforced polymer (FRP) composite structure for photovoltaic energy harvesting through both experimental and numerical studies. The main structural components include the primary beams using FRP composite tube system and secondary beam using galvanized steel rectangular hollow sections to form the floating platform with the railless supporting frame on top. The mechanical performance of glass fibre fabrics with different fibre densities and orientations for the primary beams was investigated through experiments. The 0/90° glass fibre fabric in 170 g/m2 was used due to better structural performance and relatively low cost. Modelling approach considering two-way fluid–structure coupling was further developed to study the hydrodynamic characteristics of the self-floating FRP composite structure caused by wind, waves and flows. The functionality and structural safety can therefore be evaluated for the proposed FRP structure under certain aquatic environments, providing a solution to construct floating photovoltaic power stations with the unique advantage in corrosion resistance of the FRP composites.

Detailed investigation of adhesive fillet tubular T-joint of laminated FRP composite tube under axial compressive load

Composite structures have wide applications in mechanical fields. Such structures consist of several joints, which may run a risk of eventually weakening a structure in case of excessive weight. It is, therefore, necessary to strengthen a structure so as to reduce the chance of failure. The present study was undertaken with a model of tubular T-joint having adhesive fillet. It also focussed on three-dimensional stress analysis on adhesive fillet. The model was made of laminated fibre-reinforced polymer (FRP) composite tubes with adhesive triangular fillet, subjected to axial compressive loading. The modelling and analysis were carried out by using finite element method (FEM) for three different joints with different geometrical parameters. The model was validated by using the available finite element model results. Based on the present finite element model results, the axial stress (σz) at brace-fillet intersection, circumferential stress (σφ) and circumferential-axial stress (τφr) at chord-fillet intersection were found to have greater effect as compared with other stress components. The maximum value of stress component could be noticed in between the brace and the chord joint region, which could eventually cause failures. The effect of adhesive fillet on deflection was studied in details by using ANSYS 18.1, and results showed that deflection of adhesive fillet model could be reduced by 12.36% as compared with non-fillet condition. Based on the present research findings, the presence of adhesive fillet was found to significantly reduce deflection effect as well as improve joint strength and stability of the structure.

Detection of bending direction and amplitude by electrical resistance measurement of axial carbon fibers in braided composite tube

In this paper, electrical resistance measurement (ERM) was used to detect the direction and amplitude of the bending force on fiber-reinforced polymer composite (FRPC) tubes. The method was based on research into the influence of position on the sensing behaviors of carbon fibers (CFs) as separated resistive elements under flexural tests. CFs were inserted into the fabric reinforcement fabricated by a circular braiding machine as axial tows that are separated by bias tows (Kevlar fibers) to serve as sensors. In experiments, samples of FRPC tubes with four axial tows were fabricated and bent at two different angles relative to the distribution of CFs while deformation was maintained in the elastic zone. The resistance change ratios of the CFs varies from −1.5% to 0.3% and the zero-crossing point on the tube is at 105°. The results showed that CF resistances would change in a particular pattern as the tube was being bent, and the bending direction and force amplitude could be derived from this pattern.

Progressive failure prediction of FRP tubes by modified damage model

ABSTRACTAn accurate material model plays a significant role in predicting the progressive damage of fibre-reinforced polymer (FRP) structures. A modified bilinear constitutive model is proposed to describe the stiffness degradation caused by the progressive intra-lamina damage, and has been embedded into the commercial software ABAQUS through the subroutine VUMAT. All coefficients, corresponding to various damage mechanisms, could be identified by specimen tests under typical loading conditions. As a case study, the compression test of a FRP composite tube is carried out and compared with the simulation results obtained by this model to verify the accuracy and versatility in predicting impact energy absorption and peak force as well as failure modes. Compared with other published simulation methods, the proposed model has better versatility, in which the progressive damage control coefficients are stable and insensitive to different types of FRPs.

Fabrication and characterisation of carbon fibre reinforced polymer rods with aluminium foam core

Carbon fibre reinforced polymer composites are high-performance materials that have become the dominant advanced composite materials used for aerospace, automobile, sporting goods and other applications owing to their high strength, high modulus and low density. In this study, a new fabrication technique of aluminium foam was employed where NaCl was used as the space holder and argon gas was injected into the aluminium molten metal. The NaCl particles were then removed by dissolution process. The aluminium foam specimens were then wrapped with carbon fibre pre-preg and cured in a vacuum oven. The compressive properties such as compressive strength, elastic modulus and failure strain were obtained from the analysis of stress-strain curves. The results showed that carbon fibre reinforced polymer composite tubes with aluminium foam core exhibited higher compressive strength and elastic modulus compared with neat aluminium foam rods and neat carbon fibre reinforced polymer rods.

Damage modelling of repeatedly impacted square fibre-reinforced polymer composite tube

This paper proposed a lifetime prediction model to characterise the damage response of square fibre-reinforced polymer (FRP) composite tubes under repeated axial impact. The model, which is a function of damage parameter D and normalised impact number Nf, used an energy-based approach. Series of impact and quasi-static compressive tests on composite tubes were undertaken to determine the required parametric values and to validate the reliability of the proposed model. Testing was performed by axially impacting 100mm FRP pultruded tubes to 130 repeated impacts or up to collapse using a drop-mass type impact apparatus. The quasi-static compressive test was conducted using a 2000kN capacity servo-hydraulic compressive testing machine. Results showed that the impact fatigue curve of the composite tubes follows a power function relationship. The variation of incident energies Ein between the fitting curve and experimental data is less than 3%. A good agreement is observed between the experimental data points and the prediction model.

Experimental investigation on the behaviour of square FRP composite tubes under repeated axial impact

Series of impact tests were conducted to investigate the behaviour of fibre reinforced polymer (FRP) composite tubes under axial impact. The effects of damage parameters such as the mass of the impactor, incident energy and number of impacts on their behaviour were studied. The tests were performed by axially impacting 100mm square FRP pultruded tubes to 130 repeated impacts or up to collapse using a drop-weight type impact apparatus. Impact masses and drop heights were varied to produce incident energies ranging from 158 to 635J. The results showed that the peak load degradation of collapsed tubes is more rapid when it is impacted by higher incident energy. Heavier impactors caused more damage to the tubes at lower incident energies as reflected by their lower number of impacts to collapse, however, its effect gradually decreases at relatively higher energies. The incident energy is a major damage factor in the collapse of the tubes for lower number of impacts. However, the number of impacts becomes the key factor when the value of the incident energy decreases.

Load and resistance factor design of fiber reinforced polymer composite bridge deck

The majority of our bridges were constructed with conventional civil engineering materials of steel and concrete in a typical slab on girder or truss construction. Reinforced concrete bridge decks have approximately 40% life of the steel girders that support these structures. In order to support the use of alternative materials to replace deteriorating concrete decks, this paper outlines the Load and Resistance Factor Design (LRFD) of Fiber Reinforced Polymer composite (FRP) panel highway bridge deck. The deck would be of a sandwich construction where 152.4mm×152.4mm×9.5mm square pultruded glass FRP (GFRP) tubes are joined and sandwiched between two 9.5mm GFRP plates. The deck would be designed by Allowable Stress Design (ASD) and LRFD to support AASHTO design truckload HL-93. There are currently no US standards and specifications for the design of FRP pultruded shapes including a deck panel therefore international codes and references related to FRP profiles will be examined and AASHTO-LRFD specifications will be used as the basis for the final design. Overall, years of research and laboratory and field tests have proven FRP decks to be a viable alternative to conventional concrete deck. Therefore, conceptualizing the design of FRP bridge decks using basic structural analysis and mechanics would increase awareness and engineering confidence in the use of this innovative material.

Durability studies on concrete columns encased in PVC–FRP composite tubes

A new hybrid concrete column was developed for new construction. The proposed hybrid column, cast in place, consists of an exterior PVC–fiber reinforced polymer (FRP) shell with a concrete core. The exterior shell is commercially available cylindrical PVC pipe externally reinforced with impregnated continuous fiber in the form of hoops at different spacing. The proposed system (PVC–FRP) uses less fibers than current FRP confining methods but has similar strength and toughness characteristics. This paper present the results of an experimental study on the performance of hybrid concrete columns subjected to different environmental conditions such as room temperature, freeze and thaw, wet and dry conditions. Test variables included the type of fiber (carbon, aramid and glass), the spacing between the FRP hoops and the environmental exposure conditions. The specimens were subjected to 200 and 400 freeze/thaw and wet/dry cycles. At the end of each exposure, the specimens were instrumented and tested under a uniaxial compressive test load. The stress–strain behavior was used to evaluate the effect of exposure conditions on the strength, stress–strain behavior and ductility of the confined specimens. Test results show that the external confinement of concrete columns by PVC–FRP tubes results in enhancing compressive strength, ductility and energy absorption capacity. Durability tests show that the PVC–CFRP confined specimens performed quite well under the severe exposures used in this study, whereas the PVC–GFRP and PVC–AFRP confined specimens experienced reductions in both strength and ductility.