Foam-filled Tubes Research Articles

Crashworthiness design and enhanced energy absorption of multi-cell thin-walled circular tubes

In order to improve the crashworthiness and enhance the energy absorption capacity of thin-walled structures, a new multi-cell thin-walled circular tube was established by combining the advantages of type I (bending-dominant) and type II (tension-dominant) structures in this paper. The crush resistance and specific energy absorption (SEA) of multi-cell empty and multi-cell foam-filled tubes (MFTs) subjected to axial crushing loads were experimentally investigated. It was shown that due to the introduction of ribbed structures, the crush resistance and energy absorption efficiency of multi-cell empty tubes can be obviously enhanced. Filling the empty tube with foam, the peak force of foam filled thin-walled circular tube structure is improved distinctly. The MFTs have a higher crushing load efficiency and lower average loading fluctuation than the corresponding multi-cell empty tubes, which are mainly affected by the ribbed angles. With the increase in ribbed angles, the load-carrying capacity and the SEA of the MFTs can also be enhanced, but the undulation of the load-carrying capacity is simultaneously reduced. When the ribbed angle is more than 45°, the MFTs have better energy absorption and crushing load efficiency. Compared with a multi-cell empty tube, the SEA of the MFT increased by about 19%.

Compression behavior of ex-situ PVC foam-filled tubes

Abstract The present work investigates the mechanical characteristics of tubes filled with Polyvinyl chloride (PVC) foam. The tubes used are made of aluminum and were filled ex-situ. Static compression tests were performed on both axially (AL) and laterally (LL) loaded tubes. Comparisons between foam-filled (FFT) and empty (ET) tubes are presented, highlighting the foam-tube interaction effect. The emphasis is on elastic, strength and strain properties, but energy absorption performances are not neglected. Discussions regarding the failure mechanisms of ETs and FFTs are also presented. It was obtained that, regardless of the loading direction, FFTs show clearly superior mechanical properties to ETs. At the same weight, the specimens tested axially support higher loads than those tested laterally. This aspect is due to deformation mechanisms that take place in the samples during the tests. It was noted that the compressive strength is more affected by the filling than by the compressive modulus. Under lateral loads, the ETs samples fail quasi-brittle through complete failure of the tube, while in the case of FFTs, a ductile fracture with stable deformation of the sample is obtained.

Modeling the deformation of thin-walled circular tubes filled with metallic foam under two lateral loading patterns

Thin-walled circular tubes with metallic foam fillers are widely used in various engineering fields. This work examines the plastic behavior of thin-walled circular tubes filled with metallic foam under two different lateral loading patterns, by using both analytical and numerical methods. Two types of loading indenters, including a line load and a rigid plane, are considered. There have been very few studies on the lateral compression of foam-filled circular tubes crushed by a line load or a rigid plane. The analytical models assume that the tubular wall material is rigid and ideally plastic, and that the metallic foam fillers maintain a constant resistance known as plateau stress. Using the principle of virtual velocities, we derive succinct explicit solutions for the crushing forces as well as deformation characteristics in regard with the radius of the tubes, the flow stress of the tubular wall and the plateau stress of the filled foam under the two loading conditions. Finite element analysis is performed using the ABAQUS2023/Explicit code to model aluminum alloy circular tubes filled with aluminum foam. A comparison and analysis of the deformation characteristics of the tubular top generator and foam cross-sections are conducted. The proposed analytical crushing forces and deformation properties obtained herein agree well with the numerical simulation results and outperform previous theoretical models, which may serve as valuable formulations for the engineering application.

TIG welding of in-situ produced syntactic metal foam-filled tubes

Abstract Aluminium matrix double composites were produced via an in-situ pressure infiltration method. AlSi12 alloy matrix with densely packed lightweight expanded clay aggregate particle-filled foam was produced in-situ within AlMgSi0.5 alloy tubes. The attainable size of such double composites is limited; therefore, joining them is required to create larger parts. For the joining of these double composites, the applicability of tungsten inert gas (TIG) welding was tested. TIG welding was found to be applicable to join such composites. Metallurgically sound welded joints were produced. Nevertheless, the TIG welding of metal foam-filled tubes is very challenging and needs experienced welding personnel, and the weld bead was a bulk material, not a foam anymore.

A novel efficient energy absorber: circular metal foam-filled tube under external inversion over a die

A novel efficient energy absorber: circular metal foam-filled tube under external inversion over a die

Crashworthiness analysis and multi-objective optimization design for foam-filled spiral tube

Thin-walled structures, due to their favorable mechanical properties and exceptional energy absorption capabilities, find extensive applications across various engineering fields. This study, drawing inspiration from natural spiral structures, introduces a novel foam-filled spiral tube (FFST) to further enhance the crashworthiness of thin-walled structures. The spiral tubes (STs) and random foam are additively manufactured. Quasi-static compression tests are undertaken to investigate the energy absorption properties of STs, foam and FFSTs. Unlike conventional methods, this study adopts micro-computed tomography (micro-CT) technology to understand the mechanisms of interaction between the foam and ST. The parametric study is performed based on the finite element model to evaluate the influence of meso‑structure properties of tubes and foam fillers on the crashworthiness and deformation modes. The experimental results indicate that an increase in the wall thickness of both the ST and foam leads to a simultaneous increase in specific energy absorption (SEA) and initial peak crushing force (IPCF). Conversely, a decrease in the wavelength and an increase in the amplitude of waves results in the reduction of both SEA and IPCF, along with an enhancement of crushing force efficiency (CFE). Micro-CT images indicate mutual extrusion between the foam and ST and with a reduction in wavelength, the number of folds in the samples increased, thus enhancing the energy-dissipation capacity. The numerical results reveal a strengthening of interaction between the foam and ST with decreasing wavelength and increasing foam cell wall thickness. A theoretical model is proposed for predicting the plateau stress of FFSTs based on the energy conservation principle and the plastic hinge theory. Comparisons between theoretical and test results exhibit good agreement. Comparing the FFST obtained through multi-objective optimization design with an ST featuring same structural parameters, it is observed that the IPCF increases by 8.00 %, SEA increases by 18.10 %, and the undulation of load-carrying capacity (ULC) decreases by 31.96 %. Finally, through a comparative analysis with other energy-absorbing structures, the outstanding performance of this structure is established. This study offers a new approach for investigating interaction effects and provides useful guidelines for the design of future high-performance light-weight materials and structures.

Novel interaction effects enhance specific energy absorption in foam-filled CFRP tapered tubes

This study unveils a novel interaction effect in the foam-filled CFRP tapered tubes that enhances their specific energy absorption (SEA), challenging the conventional understanding that foam fillers decrease the SEA of structures like foam-filled CFRP straight tubes and foam-filled metal tapered tubes. Quasi-static axial compression tests were conducted on foam-filled CFRP tubes with varying taper angles (0°, 5°, 10°, 15°) to confirm and quantify this newfound interaction effect. The energy absorption characteristics and interaction effect due to the foam filler in the foam-filled CFRP tapered tubes were thoroughly evaluated and compared to 3D-printed 316L stainless steel tubes and unfilled CFRP counterparts. Contrary to expectations, our results indicate that the foam-filled CFRP tubes consistently outperform both steel and unfilled CFRP tubes in energy absorption. Intriguingly, the CFRP foam-filled tapered tubes in this study demonstrated higher SEA compared to CFRP tubes without foam filler, underscoring the remarkable effectiveness of CFRP materials in foam-filled tapered tube applications. Our comprehensive interaction effect analysis highlights the substantial contribution of the unique synergy between the foam filler and the debris of the CFRP tapered tube to this increased SEA. Additionally, we propose a novel hybrid design that integrates straight and tapered CFRP tubes with foam fillers, leveraging the newfound interaction effect to further enhance the energy absorption of tapered tubes. This research not only emphasizes the advantages of foam fillers in enhancing CFRP tapered structures but also introduces innovative possibilities for energy absorption applications across various industries.

Investigation and optimization of energy absorption performance of axially joined metal and composite foam-filled hybrid tubes

Investigation and optimization of energy absorption performance of axially joined metal and composite foam-filled hybrid tubes

Experimental and numerical study on the energy absorption performance of aluminum foam-filled multi-cell square tubes

When rockbursts occur, the unloading rate of the relief valve of the hydraulic support is less than the loading rate of the impact load, which leads to a continuous increase in the hydraulic column pressure or even failure. To improve the service life of hydraulic support structures under impact loading, an aluminum foam-filled multi-cell square tube is designed and investigated as an energy absorption component to prevent support column failure. In this study, the energy absorption performance of the multi-cell square tube during buckling deformation is investigated via simulation and quasi-static compression tests considering the cross-sectional shape and aluminum foam filling rate. The equivalent crushing load of the tube is calculated by analyzing the impact of the basic deformation unit. The results show that the corner-to-corner (C2C) multi-cell square tube exhibits the best energy absorption performance among six kinds of cross sections. In addition, the interaction between aluminum foam and a multi-cell square tube can improve the performance of the multi-cell square tube. Furthermore, after the C2C component is installed in the support column, the load on the column is significantly reduced, and most of the impact energy is absorbed. These results are expected to improve the performance of hydraulic supports and can be used to prevent rockbursts, which is highly important for practical engineering.

Experimental and numerical study on the impact response of the steel-concrete-steel-foam-filled-tube energy absorbing structure

A novel energy absorbing structure is proposed and can be fixed on the front of protected structures to reduce the impact-induced damage. This energy absorbing structure consists of nine polyurethane foam-filled steel tubes (PUFFSTs) and a steel-concrete-steel sandwich panel (SCSSP) and is named steel-concrete-steel-foam-filled-tube energy absorbing structure (SSEAS). The present study investigates the energy dissipation characteristics and dynamic responses of SSEAS through both experimental and numerical analyses. All specimens exhibited the same failure mode, including the collapse of the centre PUFFST and the local indentation of the SCSSP. The investigated parameters contain the thickness and width of the steel tube, thickness of concrete core and the initial momentum of the drop weight. A comprehensive discussion is presented on the impact response and energy dissipation performance. The results indicate that the thinner concrete core would result in larger deformation but shallower local indentation. Additionally, raising the width and thickness of the steel tube would result in higher energy absorbing capacity and larger proportion of energy dissipation of PUFFSTs. The numerical studies also show that higher initial momentum of the drop weight would induce a longer duration and larger energy dissipation of PUFFSTs.

Crashworthiness analysis of empty and foam-filled circular tubes with functionally graded thickness

Crashworthiness analysis of empty and foam-filled circular tubes with functionally graded thickness

Numerical crashworthiness analysis of 2014 Aluminium-Silicon Carbide Particle (SiCp) foam filled Carbon Fiber-Reinforced Plastic (CFRP) tube under impact loading

Aluminium foam and Carbon Fiber Reinforced Plastic (CFRP) are widely used composite materials in automobile industries due to the benefits of lightweight and energy absorption capacity. Therefore, in this study, the numerical crashworthiness analysis of 2014 Aluminium-SiCp (2014AA-SiCp) foam filled in CFRP tube has been performed under impact loading. Quasi-static compression tests have been conducted on 2014AA-SiCp foam to extract the mechanical parameters required for numerical simulations. To understand the crushing behavior under the axial impact loading, 2014AA-SiCp foam-filled CFRP tube has been numerically modelled using ABAQUS® software. The parametric study was carried out to explore the effects of filler material, foam densities, and impact velocities on crushing behavior. It was found that load increases with the rise in foam density and impact velocity. Moreover, the deformation increases with the increase in impact velocity. Results showed that the load carrying capacity of foam filled CFRP tubes was significantly improved compared to that of empty CFRP tubes. The foam filled CFRP specimens exhibited peak load of 122 kN and an energy absorption capacity of 3012 J, showcasing an approximate improvement of 43% and 11% respectively, over the values obtained for empty CFRP tubes.

Elastic-plastic response for the foam-filled sandwich circular tube under internal blast loading

The dynamic response and the blast resistance of an aluminum foam-filled sandwich circular tube under internal blast loading was investigated theoretically. The deformation of the structure is decoupled into three phases corresponding to blast loading interacting with the internal tube, foam core crushing and external tube deformation. During the process, the theoretical model includes both the circumferential membrane forces and the axial moment components and considers an elastic-plastic strengthening model for internal/external tubes. The proposed model is tested against the experimental results for the mid-point deflection of the external/internal tubes. The influence of the physical and geometrical parameters of the structure on their deformation is investigated. It is shown that the dimensionless mid-point deflection of the external tube decreases as the tangent modulus of the internal/external tube increases, while the tangent modulus of the internal tube has a larger effect on the mid-point deflection of the external tube. The minimum mass of a sandwich circular tube can be found when the deformation of the external tube is specified. The research results can provide theoretical basis for lightweight structure design.

Design optimization of the bamboo-inspired foam-filled tube for high-speed train collision energy absorption

This study first developed a novel bamboo-inspired foam-filled tube (BFFT) for potential application in high-speed trains, considering the practical use conditions. The BFFT was initially designed by mimicking the macro and micro characteristics of bamboo culms and understanding their axial crushing mechanical behavior. The key bionic parameters are drawn based on the crashworthiness indices of natural bamboos with various geometric sizes and growth ages. The numerical simulation model of the BFFT under axial impact load was established and verified using simplified super folding element (SSFE) theory and drop-weight experiments. A multi-objective optimization on the BFFT was conducted to find the optimal parameter alternative, integrating experimental design method of the optimal Latin hypercube, the response surface agent model and the non-dominated sorting genetic algorithm (NSGA-II). The crashworthiness performance of the optimized BFFT was compared with the initial design scheme, a conventional circular tube and other existing energy absorbers of rail vehicles. The results indicated that the EA, SEA and IPCF values of the optimized BFFT can be improved by 150.2 %, 63.3 %, and 48.5 %, respectively, when considering the single target requirement. In comparison to the initial design scheme and conventional circular tube, the SEA value of the final optimized BFFT increased by 44.7 % and 53.0 %, respectively. The proposed novel BFFT demonstrated a superior crashworthiness, providing inspiration for enhancing and optimizing passive safety performance of high-speed trains.

Experimental Investigation of the Dynamic Responses of Thin-Walled and Foam-Filled Steel Tubes Subjected to Repeated Impacts.

In this study, a horizontal impact setup was used to measure the dynamic responses of specimens fixed on a reaction wall and subjected to repeated impacts generated by a large-tonnage impactor. The contact force, deformation process, energy absorption, and other properties of two specimens (a thin-walled steel tube and foam-filled steel tube) were thoroughly investigated. The results demonstrated that the thin-walled tube's properties were consistent with the four-phase and six-phase deformation models and that the foam-filled tube's properties were consistent with the two-phase deformation model. In the early stages of the experiment, the foam-filled and thin-walled tubes were similar in terms of the contact force and energy absorption. However, when the polyurethane (PU) strain reached 0.8, the PU significantly increased the support of the tubes, reduced the contact force (by extending the contact time), and increased the energy absorption capacity by 33.6-43.5%. The crush curves of the specimens were in agreement for cases involving multiple impacts, as well as for one impact with the same impact of kinetic energy. The crush curves can be used to assess the actual performance of crashworthy devices. Furthermore, after repeated impacts, the foam-filled tube exhibited a pseudo-shakedown behavior.

Investigation of the Bending Properties of Ex situ Functional Metal Foams

In each industry, compromises have to be made when choosing materials. Lower-density materials have a significant advantage in the automotive sector, especially due to rising fuel prices, since weight reduction can lower overall fuel consumption. The advantageous properties of metal foams, such as low density, high specific strength, and excellent energy absorption, should be researched and exploited in as many areas and ways as possible. This research aims to perform and evaluate the bending tests of ex situ functional metal foams: aluminum alloy matrix (AlSi7Mg) was used, which was filled with Ø2.5–3.0 mm lightweight expanded clay aggregate particles and surrounded by thin-walled aluminum tubes (AlMgSi0.5) with a wall thickness of 2 mm and an outer diameter of Ø32 mm. Empty tubes, foam-filled tubes (with and without structural epoxy adhesive) and metal matrix syntactic foams were compared based on their flexural strength and energy absorption capacity. Quasi-static three-point bend tests were carried out up to 25 mm deflection. The foam-filled tubes with epoxy adhesive showed an average of 6% increase in flexural strength compared to the foam-filled tubes without adhesive and a 145% increase compared to the metal matrix syntactic foams.

Investigation on quasi-static axial crushing of Al/PVC foam-filled Al6063-T5 tubes

Abstract This study experimentally investigated the energy-absorbing capability of foam-filled 6063-T5 aluminum tubes. Thus, different sample combinations were created with two different foams, PVC (80 kg m−3) and aluminum (200, 350 kg m−3), which were used as filling materials. The first group of samples consisted of uniform foam-filled aluminum tubes. In contrast, tubes were filled with radially graded foams in the second group, which included a ring PVC foam and a cylindrical aluminum foam in the center. Empty tube absorbed 329 J, while it reached the values of 384, 488, and 606 J by using PVC and low- and high-density aluminum foams, respectively. The specific energy absorption value of the empty tube was obtained as 23.2 J g−1. In comparison, it was 19.3 J g−1 in the high-density aluminum foam-filled sample, although it absorbed the highest energy value. This shows that high-density aluminum foam was inefficient in terms of the crashworthiness of the structure. Finally, the best sample regarding the specific energy absorption and crush force efficiency was obtained in the sample where the PVC foam ring and high-density aluminum tube were used together. This sample had 7 % higher specific energy absorption and 34 % higher crush force efficiency than the empty tube.

Transverse impact response of GFRP tubes filled with MWCNT-reinforced syntactic foam

Tubular composites made of glass fiber reinforced polymer (GFRP) have been widely used in the fields of infrastructure and automobile engineering. However, such composites are vulnerable to transverse loading occurrences and their effect on structural integrity. This paper focuses on investigating the response of hollow GFRP tubes and GFRP tubes filled with syntactic foam under transverse impacts. To enhance the stiffness of GFRP tube and improve the brittleness of syntactic foams, ribs were added to strengthen the tube wall, and multiwalled carbon nanotubes (MWCNTs) were used to reinforce the syntactic foam core. The impact response of the tubes was examined by considering the influence of ribs, MWCNTs, and the impact location. Experimental results revealed that the ribs contributed to enhancing the impact resistance of both hollow and filled tubes. However, the impact of ribs on energy absorption was less noticeable for the filled tubes. Incorporating 1.2 wt.% MWCNTs in the foam resulted in significant improvements of 25 % in peak impact force and 43 % in energy absorption for the filled tubes. Changing the impact location from the tube wall to the rib led to a significant increase of 33 % in peak impact force and 18 % in energy absorption for the hollow tubes. In contrast, the impact location had a minimal effect on the overall impact responses of the filled tubes. An analytical model was developed to predict the energy absorption capability of the composite tubes. This model accurately determined the energy absorption contribution of each component within the composite tube. The predicted results demonstrated good agreement with the experimental findings, validating the predictive capability of the model. Furthermore, multiscale finite-element (FE) models were developed to simulate the impact characteristics of foam-filled composite tube specimens. The validated FE model was subsequently utilized to conduct parametric study.

A novel efficient energy absorber with free inversion of a metal foam-filled circular tube

In this paper, a novel efficient energy absorber with free inversion of a metal foam-filled circular tube (MFFCT) is designed, and the axial compressive behavior of the MFFCT under free inversion is studied analytically and numerically. The theoretical analysis reveals that the energy is mainly dissipated through the radial bending of the metal circular tube, the circumferential expansion of the metal circular tube, and the metal filled-foam compression. The principle of energy conservation is used to derive the theoretical formula for the minimum compressive force of the MFFCT over free inversion under axial loading. Furthermore, the free inversion deformation characteristics of the MFFCT are analyzed numerically. The theoretical steady values are found to be in good agreement with results of the finite element (FE) analysis. The effects of the average diameter of the metal tube, the wall thickness of the metal tube, and the filled-foam strength on the free inversion deformation of the MFFCT are considered. It is observed that in the steady deformation stage, the load-carrying and energy-absorbing capacities of the MFFCT increase with the increase in the average diameter of the metal tube, the wall thickness of the metal tube, or the filled-foam strength. The specific energy absorption (SEA) of free inversion of the MFFCT is significantly higher than that of the metal tube alone.

Impact responses of the steel-PU foam-concrete-tube multilayer energy absorbing panel: Numerical and analytical studies

The enhancement of structural protection can be achieved by using energy absorbing structures as sacrificial layers. In this study, a new steel-PU foam-concrete-tube multilayer energy absorbing panel (SFCTMEAP) is developed to improve the impact resistance of buildings and infrastructures, and its behaviour under impact loading is numerically and analytically studied. A Finite Element (FE) model is established using LS-DYNA to further study the behaviours of SFCTMEAP, and its results (including the failure mode, displacement–time and impact force–time curves) agree well with the test data. The SFCTMEAP presents a deformation mode of local indentation of the front energy absorbing layer, flexure of the steel-concrete-steel panel and collapse of PU foam-filled steel tubes (PUFSTs). The energy dissipations of variant components of the SFCTMEAP are obtained through the FE model and the PUFSTs is the main energy absorbing component. In addition, parametric studies are performed to obtain the influences of the impact location, initial momentum of impactor and thickness of PU foam panel on the response of SFCTMEAP. The results indicates that the specimen with larger impact eccentric distance dissipates less impact energy, and raising the initial momentum of the impactor is benefit to the energy dissipation by the PUFSTs. Moreover, an analytical model is developed to calculate the displacement history of SFCTMEAP under the impact loading. The displacement responses predicted by the analytical model are found to be in good agreement with the test results.