Foam-filled Tubes Research Articles

Can Plant-Based Natural Flax Replace Basalt and E-Glass for Fiber-Reinforced Polymer Tubular Energy Absorbers? A Comparative Study on Quasi-Static Axial Crushing

Using plant-based natural fibers to substitute glass fibers as reinforcement of composite materials is of particular interest due to their economic, technical, and environmental significance. One potential application of plant-based natural fiber reinforced polymer (FRP) composites is in automotive engineering as crushable energy absorbers. Current study experimentally investigated and compared the energy absorption efficiency of plant-based natural flax, mineral-based basalt, and glass FRP (GFRP) composite tubular energy absorbers subjected to quasi-static axial crushing. The effects of number of flax fabric layer, the use of foam filler and the type of fiber materials on the crashworthiness characteristics, and energy absorption capacities were discussed. In addition, the failure mechanisms of the hollow and foam-filled flax, basalt, and GFRP tubes in quasi-static axial crushing were analyzed and compared. The test results showed that the energy absorption capabilities of both hollow and foam-filled energy absorbers made of flax were superior to the corresponding energy absorbers made of basalt and were close to energy absorbers made of glass. This study, therefore, indicated that flax fiber has the great potential to be suitable replacement of basalt and glass fibers for crushable energy absorber application.

Evaluation of the Performance of Initiator on Energy Absorption of Foam-Filled Rectangular Tubes: Experimental and Numerical Assessment

In this paper, the effect of initiator on axial crushing response of partially foam-filled and foam-filled rectangular tubes was investigated. For this purpose, an initiator was placed at the top of the filling rectangular tube with rigid polyurethane foam to prevent a suddenly applied force to the main part of the structure when the accident occurs. In this new idea, the process of axial crushing was carried out in two steps. In the first step, the initiator crushed the foam core as much as the initiator length, and, the second step, the initiator simultaneously crushed the thin-walled rectangular tube and the foam core. In this research, a number of numerical simulations were performed to study the dissipated energy of the rectangular tubes with initiator. To verify these numerical findings, some quasi-static experimental tests were conducted to explain energy absorption, initial peak load and crush force efficiency. Moreover, load-displacement curves and deformation mechanism of this shock absorber with different length of initiators were described. The results showed that, in the considered material and geometry, the design with an initiator on partially foam-filled and foam filled rectangular tube have superior performance rather than the specimen without an initiator. In addition, selecting the appropriate length of initiator for the specimens of partially foam-filled and foam-filled resulted in an increase in the energy absorption. Besides, the results showed that the increase in the absorbed energy in the foam-filled specimen was more than that of the partially foam-filled specimens. Therefore, by applying the initiator on the top of the tube, it would be help to reduce the occupant injury and main structure in a collision.

Nosing process of empty and foam-filled circular metal tubes on semispherical die by theoretical and experimental investigations

Abstract Nosing process of circular metal tubes in empty and polyurethane foam-filled conditions on a semispherical rigid die was analyzed by theoretical and experimental methods. A new theoretical model of plastic deformation of circular metal tubes was demonstrated during the nosing process on a rigid semispherical die. Based on the analytical model, some theoretical relations were calculated to estimate instantaneous forming load and dissipated energy of empty and foam-filled circular metal tubes versus axial displacement. Some circular brazen and aluminum tubes were prepared and shaped into semispherical nosed nozzles to verify the present theory. Comparison of theoretical predictions and the corresponding experimental measurements reveals that predicted load-displacement and dissipated energy-displacement diagrams by theoretical formulas have a good correlation with the corresponding experimental curves and it proves verity of the theory. Also, the present theory shows that dissipated energy and axial load of empty tubes depend on material type, wall thickness and diameter of the tubes and they are independent of tube initial length. Furthermore, the experimental results show that the presence of polyethylene Teflon-constraints increases ultimate axial displacement of the forming process.

Crashworthiness study and optimisation of free inversion foam-filled tubes under dynamic loading

ABSTRACTThe inversion processes of the proposed tubes under axial impact are simulated to investigate the detailed features of crushing process by using the explicit finite element FE code LS-DYNA. To validate the FE results, a new theoretical relation is developed . The validated FE model was then used for the parametric studies, to investigate the maximum crush distance and the effect of impact mass and the geometry parameters (i.e. wall thickness, foam density) on response of free inversion tubes under different strain rate loadings. Finally, a search algorithm combining Latin hypercube design (LHD) points and genetic algorithm is developed to carry out the multiobjective optimisation through the geometrical average method. The optimal design of the foam-filled free inversion tube demonstrates a significant improvement in the crashworthiness over the benchmark designs with the same loading conditions.

The temperature effect on the axial quasi-static compressive behavior of ex-situ aluminum foam-filled tubes

This study focuses on the effect of temperature on the mechanical behavior of closed-cell aluminum-alloy foam filled tubes (FFTs) under quasi-static compressive loads. The results of the compressive testing indicated that at each tested temperature the closed-cell aluminum foam improves the mechanical properties of the empty steel tubes. This behavior is related to the interaction effect between the aluminum foam as filler material and the empty tubes. Also, it was observed that the deformation mechanism of FFTs at all tested temperatures is axisymmetric concertina mode with formation of two folds. Due to the softening phenomenon of the steel tube matrix with increasing of temperature the distribution and size of propagated micro-cracks on both loading surfaces and peripheral folds decreased significantly from the order of millimeters up to micrometers. Finally, it was observed that the increasing of the working temperature reduces the ability FFTs to absorb energy during compression test.

Foam-Filled Grooved Tubes with Circular Cross Section Under Axial Compression: An Experimental Study

In this article, absorbed energy per unit of initial tube length, initial peak force and mean folding force in empty and polyurethane foam-filled simple and grooved specimens with circular cross section are investigated, experimentally. Results demonstrate that in the empty and foam-filled simple specimens, absorbed energy per unit of initial tube length, initial peak force and mean folding force are larger than the corresponding values of the empty and foam-filled grooved specimens, respectively. But, increment of absorbed energy due to the foam-filler in the grooved tubes is more than the corresponding value in the simple specimens. Also, diagrams of absorbed energy and folding force versus the grooves distance have the minimum value. Therefore, there is a critical value for the grooves distance and according to the application viewpoint, to produce a good energy absorber, the grooves distance is selected far from the critical grooves distance. The experimental results show that when the grooves distance (λ) decreases, deformation mode inclines to the concertina (regular) mode and when λ increases, the deformation mode inclines to the diamond mode. Finally, a semiempirical relation is derived to predict the initial peak force of empty and foam-filled grooved tubes.

Quasi-static compressive behavior of the ex-situ aluminum-alloy foam-filled tubes under elevated temperature conditions

This manuscript focuses on the uniaxial compressive performance of thin walled steel tubes filled with closed-cell aluminum-alloy foam (ex-situ FFTs) at high temperature. For this purpose, the axial compressive behavior of empty tubes, closed-cell aluminum foam, and ex situ FFTs was evaluated under quasi-static loading conditions at 300°C. The FFTs were compressed according to the concertina mode with the formation of two folds at the tested temperature. Also it was concluded that inserting closed-cell aluminum foam as a filler material inside the empty steel tube improved its energy absorption by 23% at 300°C, as well as reducing crack initiation and propagation in the steel tube.

Energy absorption characteristics of a foam-filled tri-tube under axial quasi-static loading: experiment and numerical simulation

ABSTRACTThe circular tube is one of the most widely used energy absorbers in structure crashworthiness. To improve the energy absorption performance of the said tube, a foam-filled tri-tube is proposed. Axial quasi-static crushing experiments are conducted to investigate the energy absorption characteristics of the foam-filled tri-tube. Other tube configurations, such as empty single tubes, foam-filled single tubes, empty double tubes, foam-filled double tubes and empty tri-tubes, are also tested for comparison with the foam-filled tri-tube. Results show that the foam-filled tri-tube has better energy absorption performance than other tubes. A finite element model is developed to perform a parametric study on the effect of tube diameter, wall thickness and foam density on the energy absorption characteristics of the foam-filled tri-tube. The results show that parameters, such as outer tube diameter, wall thickness and foam density, have significant influence on the energy absorption characteristics of the foam-filled tri-tube, whereas the inner tube diameter has less influence.

Experimental and theoretical investigations on lateral crushing of aluminum foam-filled circular tubes

Mechanical response and energy absorption of aluminum foam-filled and empty circular tubes with different geometries were investigated experimentally and theoretically. All specimens including foam-filled circular and empty circular tubes were compressed laterally by two rigid plates. Effects of the geometrical characteristics of specimens and densities of aluminum foam on deformation and energy absorption of the foam-filled and empty circular tubes were considered. Experimental results show that the presence of aluminum foam filled in the circular tubes changes the deformation modes and increases the energy absorption of the foam-filled circular tubes. An analytical model for the plastic deformation of the foam-filled circular tubes under the lateral loading was proposed. The relations of lateral loading and energy absorption of the foam-filled circular tubes were obtained. Comparisons between the analytical predictions and the experimental results were performed and good agreement was achieved.

Blast response of cladding sandwich panels with tubular cores

This paper reports on the response of cladding sandwich panels with tubular cores to uniform blast load. The core of the cladding sandwich panels consisted of empty or foam-filled thin-walled circular tubes (38mm in diameter) made from either aluminium 6063-T6 or mild steel riveted laterally between the skin plates at varying spacing arrangements. The tubular cores were arranged to provide four different types of panels. The front plate skin of the panel, exposed to the blast load, was made from DOMEX 700 Steel while the back plate skin was made from mild steel. Three types of polymeric cellular foams, namely self-raising polyurethane, expanded polystyrene and cross-linked polyethylene, were used to fill the circular tubes. The “uniform” blast load was achieved by detonating varying charge masses of explosive (ranging from 6g to 50g) with a prescribed load diameter of 40mm at a stand-off distance of 200mm down a square tube. Energy was dissipated mostly through the plastic deformation of the tubular cores. The foam added extra energy absorbing capacity. The results showed an increase in average deflection with an increase in charge mass/impulse for the different types of panels. The cladding panels with the least interaction between the tubular cores were observed to have the highest energy absorption capabilities for a given charge mass.

Aluminum alloy foam-filled aluminum tube fabricated by friction stir back extrusion and its compression properties

Al tubes filled with Al foam were fabricated by friction stir back extrusion (FSBE), which can realize metal bonding between the foam and tube. In this process, an Al tube was first fabricated from bulk Al. Next, foamable precursor was coated on the surface of the inner wall of the fabricated tube. Thereafter, the tube coated with the precursor was heat-treated to foam the precursor, thus obtaining a tube filled with foam. In the tube fabrication process, it was found that a tube can be fabricated from a block with no defects and similar compression responses to that of a tube fabricated by a machining process. For the foaming process, it was found that the bonding of the precursor and tube induces strong bonding between the foam and tube. Regarding the compression properties of the tube, it was found that the foam-filled tube exhibited superior compression properties to empty tubes and foams. In particular, during compression tests, a decrease in the stress in stress–strain curves for an empty tube due to the generation of a fold can be avoided by filling the tube with foam filler with metal bonding between the foam and tube.

Large-Deflection Bending of Clamped Metal Foam-Filled Rectangular Tubes

Large-deflection bending of fully clamped slender metal foam-filled rectangular tubes is investigated theoretically, experimentally and numerically. A plastic yield criterion for the foam-filled rectangular tube is proposed. Considering the filled foam strength effect and the interaction of bending and stretching, an analytical solution is proposed to predict the structural response of the foam-filled rectangular tubes transversely loaded by a flat punch. Clamped bending tests of aluminium alloy foam-filled rectangular tubes are conducted. The analytical model captures experimental results reasonably. Numerical calculations are carried out to predict the large-deflection behavior of the foam-filled tubes, and good agreement is achieved between the analytical solutions and numerical results. The effects of wall thickness of tube, punch size and filled foam strength are discussed in detail. It is demonstrated that the present analytical model can reasonably predict the post-yield behavior of the foam-filled rectangular tube.

An experimental investigation on energy absorption of thin-walled bitubal structures by inversion and axial collapse

This paper investigate a new design model for energy absorption of empty and polyurethane foam-filled circular bitubal tubes. In this study, an experimental technique is used to evaluate crashworthiness parameters and crushing behavior of the bitubal energy absorbers under compressive quasi-static loading. One of the aims of this new and innovative design is to increase the energy dissipation maximally through the tube inversion and the axial collapse, simultaneously. To do so, the inner tube with inversion and the outer tube with the collapse leads to a dissipation of energy in the deformation process. However, the stable collapse in the outer tube is required for a complete inversion of the inner tube. Therefore, by creating outer grooves at some determined areas along tube length, a long tube is divided into small parts to prevent asymmetric folding. In the present work, the effects of shrink-fitting and polyurethane foam are studied to control the sudden force applied to the main part of the structure when the accident occurs The results of experimental tests show that the energy absorption capacity of bitubal specimens are greater than that of monotubal ones. Also, the foam-filled in the bitubal structures and the shrink-fitting of tube leads to increase the energy absorption and the specific energy absorption in comparison with the simple ones. The proposed method would help to reach the improved crashworthiness structure in the hope of reducing the occupant injury in a collision.

Theoretical study of absorbed energy by empty and foam-filled composite tubes under lateral compression

This paper is an attempt for introduction of new theoretical relations in order to predict energy absorption behavior of empty and polyurethane foam-filled composite tubes, which are made of woven fiber fabrics, during lateral compression between two rigid plates. Such theoretical relations can be used to specify portion of different deformations that are happened during crushing process in total energy absorption of the structures. Knowing these data may help the designers to reinforce the energy absorbers more effectively. Also, several experiments are conducted on empty and polyurethane foam-filled circular E-glass/Vinylester composite tubes in order to validate the theoretical relations. The specimens are laterally compressed between two rigid plates during a quasi-static process. According to experimental studies, the composite tubes collapse with different modes of deformation during lateral flattening. Different relations are introduced for prediction of the absorbed energy of tubes with different deformation modes. The theoretical and experimental energy-displacement diagrams and total absorbed energy by the composite tubes are compared and good agreements are found. Finally, theoretical relations are compared with each other and effects of different energy absorption mechanisms on total energy absorption are discussed based on the presented relations.

Optimization and Crashworthiness Investigation of Empty and Aluminium Foam Filled Square Tubes

Foam-filled thin-walled structures have drawn considerable attention and been widely applied in automotive and aerospace industries for their significant advantages in a high energy absorption and light weight. Recently the application of foam filled square tube in automobile industries has taken hike because of crashworthiness characteristic of foams. In the present study, energy absorption capacity of the empty (aluminum and mild steel) and foam in-filled (various aluminum alloys) square tubes have been numerically evaluated under car hitting condition. The finite element method (FEM) is applied in modeling the empty and foam-filled square tubes. The results show that the foam-filled square tubes have outstanding energy absorption characteristics under all the conditions considered. Based on the study results, best combination of materials in shell column wall and in-filled foam has been recommended.

Collapse behavior of thin-walled conical tube clamped at both ends subjected to axial and oblique loads

The structures of the vehicles during the crushing processes or accidents not only experience direct or axial collisions but sometime these structures are crushed off-axially. Therefore, it is very crucial to study whether or not a foam-filled tube is capable of supporting the oblique compression forces efficiently and effectively. In this paper, investigation of the axial and oblique loading collapse behavior of thin-walled conical tube clamped at both ends is presented. Several numerical simulations using ABAQUS finite element explicit code are carried out to study crashworthiness characteristics of empty and foam-filled thin-walled conical tubes clamped at both ends. In order to verify these numerical results, a series of quasi-static axial and oblique compression tests are performed. The validated finite element model was then used for the parametric studies, in order to determine the effect of the empty and filler tube geometry parameters (i.e. semi-apical angle) and loading parameters (i.e. load angle) on the energy absorption and mean crushing load. The primary outcome of this study is to provide information for the use of foam-filled conical tubes as energy absorbers where oblique loading is expected.

Crashworthiness efficiency optimisation for two-directional functionally graded foam-filled tubes under axial crushing impacts

ABSTRACTRecent advancements in crashworthiness analysis of functionally graded foam-filled tubes are achieved by studying the energy absorption characteristics in lateral or axial directions, separately. In this paper, for the first time, two-directional (lateral and axial directions together) functionally graded foams (TDFGFs) under axial crushing loads are considered. The effect of variations of foam density on the specific energy absorption (SEA) and peak crushing force (PCF) is studied by controlling the gradient exponential parameters which give rise to significant effects on the crashworthiness of TDFGFs. Also, it is further analysed that how the mass of the TDFGF tube changes values of SEA in crushing process. In addition, as the result of performing multi-objective particle swarm optimisations, it is seen that the energy absorption characteristics of TDFGFs for higher values of gradient exponential parameters are improved significantly. The crashworthiness properties of optimum configurations for TDFGF are compared with the extreme cases of minimum, maximum densities and uniform foam-filled tubes with the same weight as the corresponding TDFGF tubes. Finally, a global sensitivity analysis is carried out. The results of this analysis reveal that the SEA and PCF functions are generally sensitive to the variations of the gradient exponential parameters.

Crushing response of square aluminium tubes filled with polyurethane foam and aluminium honeycomb

Experimental investigations were conducted to study the axial crushing behaviour of square aluminium tubes with different configurations. Quasi-static compressive loads were applied to square hollow aluminium tubes, aluminium honeycomb-filled tubes, polyurethane foam-filled tubes and aluminium tubes filled with both polyurethane foam and aluminium honeycomb at constant velocities of 0.15mm/s, 1.5mm/s and 15mm/s, respectively. The effects of honeycomb core, polyurethane foam, combined polyurethane foam and honeycomb on the axial crushing behaviour of square aluminium tubes were discussed. The influence of crushing velocity on these different tubular structures was also studied. Experimental results showed that the deformation mode was a progressive folding mode for square hollow aluminium tubes, while it was a splitting mode for square tubes filled with both polyurethane foam and aluminium honeycomb. The fold wavelengths of some typical cases were measured. The most crashworthy combination was found to be square aluminium tubes filled with both polyurethane foam and aluminium honeycomb, where the maximum increases of mean crushing force, energy absorption and specific energy absorption were up to 349%, 334% and 109% respectively, compared with those of hollow tubes.

Influence of auxetic foam in quasi-static axial crushing

Abstract This paper treats the influence of auxetic foam on the crush response and energy absorption response of square-section tubes when subjected to uniaxial quasi-static loading. The study aims at quantifying the energy absorption capability of auxetic foam-filled square tubes for variations in wall thickness, initial height, aspect ratio and slenderness ratio of the tube. The capability of simulating the crush response of auxetic foam-filled tubes using the validated numerical models is also presented. Based on the experimental results, the influence of the auxetic foam in the thin-walled square tubes was quantified in terms of energy absorption capacity, specific energy absorption and crush force efficiency. It is evident that a thicker tube filled with auxetic foam is preferable if the energy absorption level is the primary goal, yet this compromises the crush force efficiency. The outcome of this present study is the establishment of empirical models for estimating the quasi-static crushing response of auxetic foam-filled tubes with varying slenderness ratio and aspect ratio.

Finite Element Analysis and Crashworthiness Optimization of Foam-filled Double Circular under Oblique Loading

Finite element analysis and optimization design carry out for the quasi static responses of foam-filled double circular tube is presented in this paper. In the investigation of the crashworthiness capability, some aspects were considered for variations in geometry parameters of tubes and the loading condition to investigate the crashworthiness capability. Empty, foam-filled, and full foam-filled double tubes of thin walled structures were observed subjected to oblique impact (0˚ - 40˚). The numerical solution was used to determine the crashworthiness parameters. In addition, NSGA II and Radial Basis Function were used to optimize the crashworthiness capability of tubes. In conclution, the crash performaces of foam-filled double tube is better than the other structures in this work. The outcome that expected is the new design information of various kinds of cylindrical tubes for energy absorber application.