Foam-filled Tubes Research Articles

Manufacturing, Heat Treatment and Investigation of Foam-Filled Tubes

Abstract Composite metal foams are hybrid structures with the main advantages of high specific strength and mechanical energy absorption associated with low density. In the course of our research, we successfully manufactured functional metal foams of EN AC-44200 matrix filled with lightweight expanded clay aggregate particles (LECAPs) in EN AW-6060 alloy tubes with a diameter of 50 mm and a wall thickness of 5 mm. Manufacturing was performed by low-pressure infiltration directly into the aluminium tube. Six different types of samples were examined: metal matrix syntactic foam, in-situ metal foam, ex-situ metal foam, and their heat-treated pairs. In the compression tests, the heat treatment provided a visible improvement in the results of the ex-situ metal foams.

Energy Absorption Characteristics of Foam Filled Tri Circular Tube under Bending Loads

In this study, the researcher carried out a comparative investigation of the crashworthy features of different tubular structures with a quasi-static three bending point, like the foam-filled two and tri circular tube structures. Energy absorption capacities and failure modes of different structures are also studied. Furthermore, the general characteristics are investigated and compared for instance the energy absorption, specific energy absorption and energy-absorbing effectiveness for determining the potential structural components that can be used in the field of vehicle engineering. Experimental results indicated that under the bending conditions, the tri foam-filled structures were higher crashworthiness behaviour than the two foam-filled circular structures. Therefore, this study recommended the use of crashworthy structures, such as foam-filled tri circular tubes due to the increased bending resistance and energy-absorbing effectiveness.

Radial crushing response of ex-situ foam-filled tubes at elevated temperatures

The current research investigates the mechanical properties and deformation mechanisms of foam-based composites under radial compressive loadings at different temperatures between 25 to 450 °C. The radial compression tests are performed at 10 mm·min−1 on aluminum foams (AFs), empty tubes (ETs) and foam-filled tubes (FFTs) within a heating chamber. The obtained force–displacement curves are analyzed to investigate the main mechanical properties of the samples such as yield, plateau and densification forces. The deformation mechanism of each individual component is studied at room temperatures. According to obtained results, the radial compression of AFs does not show any shear failure in the early stages of their deformation at room temperature. Instead, the shearing delays at higher displacement during the radial loading of AFs. In addition, unlike axial loadings, the radial compression of the ETs does not progress through successive folding at all tested temperatures. The interaction effect between tubes and foams is observed at all testing temperatures, highlighting a maximum at temperatures close to room temperature. The mechanical properties of FFTs outperform the AFs and ETs. However, at temperatures close to melting point of AF, there is no significant difference in energy absorption capacity of the FFTs and ETs.

Energy absorption behaviour of an aluminium foam-filled circular-triangular nested tube energy absorber under impact loading

A novel aluminium foam-filled circular-triangular nested tube (AFCTNT) energy absorber was developed in this study, and its energy absorption behaviour under impact loading was experimentally and numerically studied. Drop-weight impact tests on the AFCTNT energy absorbers with different volumes of aluminium foam filler were first conducted to obtain their energy absorption parameters, force–displacement responses, and deformation modes. In addition, numerical studies on AFCTNT energy absorbers were also carried out, and the specific energy absorption of nested tubes and aluminium foam were obtained to further reveal their energy absorption performances. Experimental results indicated that the deformation modes of AFCTNT energy absorbers were evidently affected by the volume of aluminium foam filler. Moreover, the energy absorption performances of AFCTNT energy absorbers were found to be significantly improved by filling aluminium foam in terms of higher energy absorption, specific energy absorption, mean crushing force, and crushing force efficiency. Both experimental and numerical results demonstrated that the AFCTNT energy absorber with fully-filled aluminium foam outperformed the other AFCTNT energy absorbers owing to more significant interaction effect between the nested tubes and aluminium foam.

Study on Axial Compression Properties of Aluminum Foam-filled Steel Tube Members After High Temperature

Study on Axial Compression Properties of Aluminum Foam-filled Steel Tube Members After High Temperature

Bending behavior of cenosphere aluminum matrix syntactic foam-filled circular tubes

Thin-walled tubes filled with aluminum foam have been widely studied in the field of energy absorption. Embedding fly ash cenospheres into aluminum matrix provides a low-cost, yet effective solution to enhance its strength and energy absorption capability significantly, as shown in the authors’ previous study. In this paper, the bending performance of the developed cenosphere Al matrix syntactic foam (SF) is further investigated, and its dependence on geometrical features, including thickness of tube and diameter of cenospheres, as well as filled ratios is established. The result that bending resistance and energy absorption performance of the tubes are mainly governed by wall thickness and filled ratios is acknowledged. In parallel, numerical models were developed in LS-DYNA, and the simulation results were in good agreement with the test results, which suggest that such developed SF potentially will have extensive practical applications.

Manufacturing and Investigation of In Situ and Ex Situ Produced Aluminum Matrix Foam‐Filled Tubes

Composite metal foams (CMFs) are hybrid structures, which are usually produced from separate parts, and not in one step as functional, structural elements. Functional CMFs are characterized by high strength, high stiffness, and extreme energy absorbing properties compared with conventional metallic foams, which allow them to be used as load‐bearing and energy absorbing elements. Test specimens are made in AlMgSi0.5 tubes with the wall thickness of 5 mm. AlSi12 casting alloy is used as matrix material. To ensure the foam structure porosity, lightweight expanded clay aggregate particles (LECAPs) are used with unimodal and bimodal size distribution. The results show that low‐cost unimodal and bimodal foam‐filled tubes (FFTs) can be produced in situ by inert gas pressure infiltration. Besides their low density, these CMFs achieve high strength, high toughness, and special, functional properties compared with simple metallic foams. After heat treatment, in situ produced bimodal FFTs have the highest energy absorption capacity of an average of 67.2 J cm−3, which is 9% higher than the average value of the ex situ FFTs. Therefore, it is advantageous to produce in situ FFTs, because with proper manufacturing, it requires less machining, making the production easier, while achieving better compressive properties.

Crashworthiness design of car threshold based on aluminium foam sandwich structure

During a side impact accident of an automobile, the automobile threshold plays an important role in maintaining the living space of passengers, and thus the crashworthiness design of thresholds may effectively improve the crash safety of the car. Inspired by the excellent load carrying and energy absorption capacity of foam-filled double tubes, a sandwich threshold which is composed of an original threshold, an aluminium foam and a square tube was proposed. Finite element simulation was carried out to study the three-point bending behaviour of sandwich thresholds and the influence of the tube shape on the bending resistance of sandwich thresholds. The results show that the bending capacity of sandwich thresholds first increases and then decreases with the increase of the outer length of the square tube. The average bending capacity of the sandwich threshold can be increased by 185%, while the filling mass is only 17.2% of the original threshold. Besides, the filling scheme of foam in corners was introduced to realise the lightweight design, which not only ensures the improvement of the bending resistance of the filled threshold but also greatly reduces the mass of the filling structure. The three-point bending experiments were also performed to test the foam corner-filled threshold. Finally, through the vehicle side pole impact simulation using the component modelling method, it is verified that the sandwich and foam corner-filled threshold can effectively improve the crashworthiness of the car.

Simulation of thin-walled double hexagonal aluminium 5754 alloy foam-filled section subjected to direct and oblique loading

This paper presents the numerical study of the dynamic loading on the thin-walled tube made of aluminium alloy. The non-linear finite element was used to simulate and to predict the crushing phenomenon of the structure subjected to dynamic loading. The study deals with the energy absorption of empty and aluminium foam-filled double thin-walled hexagonal tubes under axial crushing load. The specimen is a regular hexagonal tube which consists of an outer and inner tube. The outer tube was fixed at a perimeter of 360 mm with a side of 60 mm each. While different inner perimeters were used. The paper studied two types of structures, the empty double hexagonal tubes and foam-filled tubes. The multi-criteria decision making (MCDM) process, the complex proportional assessment method (COPRAS) was used to select the best specimen. Although it has 17% lower specific energy absorption, the specimen of inner side tube of 45 mm with foam (H-D-F) was the best crashworthiness performance was selected as the best one since it has 64% lower peal force, 33% higher in CFE and reduction in specimen mass by 30%.

Efficient energy absorption of functionally-graded metallic foam-filled tubes under impact loading

Abstract The deformation behavior and crashworthiness of functionally-graded foam-filled tubes (FGFTs) under drop-weight impact loading were investigated. Closed cell aluminum, A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations. The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components, and then propagates in the high-strength components through the gradual increment of stress. The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption (SEA) for the graded structures, whereas the high-strength zinc foam has no positive effect on the crash performance. The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions. However, the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition. The Al−A356 foam-filled tubes with a combination of the highest SEA (10 J/g) and the lowest initial peak stress (σmax of 10.2 MPa) are considered as the best lightweight crashworthy structures.

Mechanical investigation of in-situ produced aluminium matrix syntactic foam-filled tubes

This research focuses on the mechanical investigations of in-situ produced AlSi12 aluminium alloy matrix syntactic foam-filled tubes. The samples were manufactured by low-pressure infiltration in a tube made from AlMgSi0.5. As second phase 3.5–4 mm average diameter lightweight expanded clay aggregate particles were used. The mechanical analysis extends to compressive tests of three different type of samples: empty tubes, metal matrix syntactic foams, and foam-filled tubes. The results show the best specific mechanical energy absorbing capacity in the case of foam-filled tubes, since the matrix creates a durable boundary layer with the tube wall.

Crashworthiness enhancement of thin-walled hexagonal tubes under flexural loads by using different stiffener geometries

Thin-walled structure tubes have been widely used in automotive applications as energy absorber members due to the excellent energy absorption ratio to the weights. The purpose of this study is to enhance the energy absorption of the thin-walled hexagonal tube by using different stiffeners geometries under the flexural impact. The structure has been subjected to an impact velocity of 50 km/h with a striker mass of 1500 kg at a 90-degree angle as recommended by the technical protocol section of the Insurance Institute for Highway Safety (IIHS) side-impact crash test. Besides the empty tube and the foam-filled tube, nineteen stiffeners were used in this study. A comparison between the reinforced and non-reinforced structure was made in terms of the specific energy absorption (SEA) and the crushing force efficiency (CFE). The numerical results have shown that stiffeners have improved the crashworthiness parameters when compared with the conventional empty tube. The numerical results have revealed that the introducing stiffeners to the structure have enhanced the structure performance since the stiffeners restrict the flattening of the upper side when subjected to compressive loadings and the SEA was improved for different wall thickness used. The results have shown that the H-5 stiffener was chosen as the best geometry since the SEA was increased up to 114%, the CFE was enhanced by 27% and the bending resistance was also improved.

Preparation and properties of rigid polyurethane foams added with graphene oxide-hollow glass microspheres hybrid

ABSTRACT Rigid polyurethane foam (RPUF) as a filling material that can enhance the crashworthiness of thin-walled tubes. GO-HGMS hybrid was prepared by solution blending of graphene oxide (GO) and hollow glass microspheres (HGMS). The effect of the composite on the compression properties of RPUF was investigated. The GO-HGMS hybrid was characterized by fourier transform infrared spectroscopy (FTIR), x-ray diffraction(XRD), and scanning electron microscopy (SEM). The compression test and microstructure results show that the best compression performance and the largest apparent density of the composite foam were obtained when the hybrid content was 4 wt %. In addition, the compression test results of empty tubes (ET) and foam-filled tubes (FFT) under lateral load indicate that the combination of lightweight foamed material and thin-walled tube improves the stability of thin-walled tube deformation and the ability of the structure to resist deformation. GO-HGMS/RPUF as the filling material of thin-walled tube structure greatly improves the bearing capacity and energy absorption level of ET.

Quasi static axial compression of empty and PU foam filled circular aluminium and light gauge square steel tubes

Abstract For structural applications, Concrete Filled Steel Tubes (CFST) proved as efficient building material. Further study on composite filled tubes to increase strength to weight ratio is evident to improve material efficiency and reduce load on structure. In the recent years, investigations on impact resistance and energy absorption of foam filled thin walled Aluminium and Steel composite tubes have gained importance for mechanical and aerospace applications and also as crash barriers to improve its dynamic characteristics. These are made by metal tube envelopes filled with Polyurethane foam infill material. Present study is carried out to understand the strength and behaviour of PU Foam Filled Tubes for structural applications. This paper presents experimental work on Quasi Static Axial Compression Tests on Empty and PU Foam filled Circular Aluminium and Light Gauge Square Steel Tubes. For Aluminium Tubes, D/t of 40.20 and 30.15 and L/D of 3.32 and for Steel Tubes, b/t of 125, 100 and 83.33 and L/b of 2, 3 and 4 were considered. High density PU foam (of density 150 kg/m3) alone, Empty tubes and Polyurethane foam-filled tubes are tested for quasi-static axial compression experimentally and validated the results with numerical simulation using ABAQUS 6.14–3 software. The mean crushing loads of hollow and polyurethane foam-filled circular Aluminium and Square Steel tubes were calculated from FEM and experimental results. The experimental and numerical values are in agreement. This study reveals that due to composite action between tube and foam, the resistance to buckling has improved significantly when compared to empty tubes even for high L/D & L/b ratios.

On energy-absorbing mechanisms and structural crashworthiness of laterally crushed thin-walled structures filled with aluminum foam and CFRP skeleton

In the present study, thin-walled tubes filled with aluminum foam and CFRP skeleton (FCFTs) are developed and manufactured based on a multiple material system. The structural crashworthiness of the proposed design is investigated under quasi-static lateral loading. Further, the aluminum tube, the foam-filled tube and the tubes filled with CFRP skeleton are also designed and tested to perform a comparative study. It is found that the FCFT-1 (the tube filled with foam and CFRP skeleton with square cells) exhibits superior SEA (specific energy absorption), which is almost five times that of the individual aluminum tube, and almost 10% higher than that of the foam-filled tube. However, FCFT-2 (the tube filled with foam and CFRP skeleton with triangular cells) provides relatively lower energy-absorbing capacity, as its aluminum tube generates several axial cracks during crushing process leading to low deformation level of the foams. Furthermore, crush simulations are conducted to better understand the energy-absorbing mechanisms of the FCFT-1. The numerical results demonstrate that the plastic deformation of the separated foams makes up the major part of the total energy absorption. Besides, the performance improvement of FCFT-1 can be partly attributed to the fact that the separated foams generate larger plastic deformation during crushing process. Apart from this, the increased interaction effects between the separated foams and the CFRP skeleton lead to a higher FE (frictional energy), which also makes a slight contribution to the performance improvement of FCFT-1. Finally, parametric studies are performed to explore the influences of design parameters on the crashworthiness characteristics of FCFT-1. It is indicated that the energy-absorbing capacity can be slightly improved by raising cell number, proportion of 45° layer or foam density. The present work is expected to provide some insights for researchers and engineers to design such structures for energy absorption applications.

Deformation and energy absorption properties of cenosphere-aluminum syntactic foam-filled tubes under axial compression

The cenosphere-aluminum syntactic foam-filled tubes were prepared by inserting aluminum matrix syntactic foam which is reinforced with cenospheres whose average particle sizes are different (150 μm, 200 μm and 300 μm) into empty steel tubes. Quasi-static axial compression tests were conducted on empty steel tubes, cenosphere-aluminum syntactic foam filler and cenosphere-aluminum syntactic foam-filled tubes. Based on the experimental results, numerical simulation was carried out to investigate the effects of the thickness of the tube wall and the type of filler on crushing behaviour of cenosphere-aluminum syntactic foam-filled tubes. It has been shown that the tube wall can effectively restrain the syntactic foam filler and improve the plastic deformation ability of the specimen. In addition, the interaction between the two can significantly improve the bearing capacity of the foam-filled tube. The height of the specimen has little effect on its peak stress, while a large height-to-diameter ratio may cause instability, which is not conducive to the energy absorption of the specimen. The increase of the tube wall thickness is beneficial to increase the specific energy absorption of the foam-filled tube.

OPTIMIZATION DESIGN OF ALU FOAM-FILLED S-SHAPE SQUARE TUBE UNDER AXIAL DYNAMIC LOADING

This paper presents finite element simulation of the crash behavior and the energy absorption characteristics of S-shape square tubes which were fully or partially filled with aluminum foams. Base on the numerical results, it is found that, the density, the length of the filled foam and the thickness of tube directly affect the specific energy absorption (SEA) and peak crushing force (PCF) of the S-shape tubes. In this paper, the multi-objective particle swarm optimization (MOPSO) algorithm is employed to seek for optimal designs for the partial foam-filled S-shape tubes (PFSTs) and the full foam-filled S-shape tubes (FFSTs) with various design parameters such as the density, the length of filled foam and the thickness of tube, where response surface models are established to formulation SEA and PCF. The optimization results showed the energy absorption capability per unit mass of the PFSTs is more powerful than that of the FFSTs while the PCF constrained under the same level.

Crashworthiness of circular fiber reinforced plastic tubes filled with composite skeletons/aluminum foam under drop-weight impact loading

Carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP) have shown great promise in the design of light-weight thin-walled energy absorbers. Herein, circular CFRP/GFRP hybrid tubes and tubes, reinforced with internal composite skeletons (XS and OS), were fabricated to further enhance the energy absorption capacities. The crashworthiness and failure pattern of reinforced structures were compared with the hollow and aluminum foam-filled composite tubes. Moreover, low-velocity drop-weight impact tests were carried out to investigate the effect of hybridization design and filler types on the energy dissipation mechanism under axial compression. The experimental results revealed that the hollow composite tubes collapsed in progressive and the impact energy was absorbed by the generation of cracks, fiber fracture and friction. Also, the GFRP tubes exhibited better crashworthiness than CFRP tubes under low velocity impact, which was different from the quasi-static compression conditions. In contrast to hollow counterparts, the mean crushing force (MCF) of foam-filled tubes was improved by approximately 40%, whereas the specific energy absorption (SEA) was reduced by 30% due to the low weight efficiency of the aluminum foam. The filling of XS-skeleton divided the tube into four cells and improved the MCF by more than 10%. However, it reduced the SEA by around 8% due to unstable and inefficient deformation of XS-skeleton during crushing. By contrast, the OS-skeleton divided the hollow tube into more cells and collapsed progressively, resulting in superior energy absorption characteristics. Herein, the OS-filled GFRP tube was found to be the most crashworthy structure that improved the crushing force efficiency (CFE) and SEA by 50% and 7%, respectively.

Energy Absorption of Different Cell Structures for Closed-Cell Foam-Filled Tubes Subject to Uniaxial Compression

The energy absorption of different cell structures for closed-cell aluminum foam-filled Al tubes are investigated through quasi-static compression testing. Aluminum foams are fabricated under different pressures, obtaining aluminum foams with different cell sizes. It is found that the deformation of the foam core is close to the overall deformation, and the deformation band is seriously expanded when the cell size is fined, which leads to the increase of interaction. Results confirm that the foam-filled tubes absorb more energy due to the increase of interaction between the foam core and tube wall when the foaming pressure increases. The energy absorption efficiency of foam-filled tubes can reach a maximum value of 90% when the foam core is fabricated under 0.30 MPa, which demonstrates that aluminum foams fabricated under increased pressure give a new way for the applications of foam-filled tubes in the automotive industry.

Study on the Composite Structure of Aluminum Foam-Filled Thin-Walled Metal Tube to Reduce the Charge Overload inside the Projectile during the Penetration Process

When a projectile penetrates a target at high speed, the charge loaded inside the projectile usually bears a high overload, which will consequently severely affect its performance. In order to reduce the overload of the charge during the penetration process, the structure of the projectile was improved by adding two buffers at both ends of the charge. In this study, the mathematical expressions were first gained about the axial buffering force generated by the thin-walled metal tube, aluminum foam, and the composite structure of aluminum foam-filled thin-walled metal tube when they were impacted by the high-speed mass block through reasonable assumptions and stress analysis. During the experiment on the high-speed projectile penetrating reinforced concrete target, the acceleration curve of the charge and the projectile body were obtained. The results show that the maximum overload that the charge was subjected to during the launch and penetration process was significantly reduced, and the change in overload, which the charge was subjected to during the penetration process, was also less obvious.