Three deformation modes of foam material under different loading rates [41]. In the process of rapid deformation, there is not enough time to redistribute the stress, which causes a significant vibration phenomenon. The curve shows a long stress plateau that corresponds to the high energy absorption under compression, then the stress rises sharply when entering the densification stage. Deformation response of EPS foam under combined compression-shear loading. Moreover, energy absorption capabilities of PE foams were assessed under both quasi-static and high strain rate loading conditions. The third group of tests were conducted at high strain rates using a double diaphragm aerodynamic shock tube. The deformation and the strain of the foam were studied by a high-speed camera and, moreover, the energy absorption of the foam under different loading rates is discussed. It can be argued that this figure does not present the stressstrain curve for the specimen, because that the specimen deformation behavior at such a high strain rate is not uniform and the strain is preferentially localized close to the specimen front surface. These kind of injurieslead to a revolutionary kind of solution to minimise the damage of theseaccidents by using a material which can absorb the energy of the impact. During the shock mode compression process, the energy absorption in the specimen varies linearly. Based on the test method, the failure progress and final failure modes of PE foams are discussed. Consequently, the stressstrain curve is shown in Figure 7b, and its strain rate was calculated over the proportional region of the specimen displacementtime relationship. Representative forcetime and stressstrain curves under QSST loading are shown in Figure 6. Refer to the Energy Absorption page for more technical information. If the internal strain of the specimen is assumed to be uniform during the compression process, the strain rate of the specimen should be 6100 s1. The novel test method based on a shock tube has advantages of long loading time and high loading rates, which are useful in investigating the impact properties of foams at high strain rates. The results showed that the foam exhibited a nonuniform deformation along the specimen length under high strain rates. The high-speed camera images, shown in Figure 10, also provide further evidence. However, because of factors such as the cellular structure and viscoelastic nature of the polymer, the evaluation of elevated strain rate properties of foams is challenging [20,21,22]. Zhang H., Zhou Y., Zhang F., Gong W., He L. Studies on Foaming Properties and Mechanical Properties of Polypropylene /beta-Cyclodextrin Foamed Composite. Characterization of cork and cork agglomerates under compressive loads by means of energy absorption diagrams. Therefore, the forcetime curve can be converted to obtain the stressstrain curve of the specimen, as shown in Figure 6b. Bosi F., Pellegrino S. Nonlinear thermomechanical response and constitutive modeling of viscoelastic polyethylene membranes. Thespecific properties of aluminium provides unique characteristics to thealuminium metal foam like it is very light in weight as compared to other metalfoam. Polymeric foams are widely used in protective applications due to their high energy absorption capability [1,2,3], and the properties of a variety of open-cell and closed-cell foams have been widely studied under quasi-static compression [4,5,6], impact, and high strain rate loading conditions [7,8]. When the inequality above is equal, the second critical velocity is obtained, that is, the critical velocity for the shock mode to transitional mode: Therefore, when the deformation velocity of the specimen is less than Vc1, the specimen is in homogeneous mode. This demonstrates that the energy density value is greatly affected by velocity under the shock mode. Therefore, we have to find another way to calculate the energy absorption. Flexural deformation behavior of carbon fiber reinforced aluminium hybrid foam sandwich structure. sharing sensitive information, make sure youre on a federal In the shock mode, the stress in the specimen is not uniform. The gas, pockets make foam very light weight and at the time of impact most of the, energy is absorbed by the material and hence it helps in minimising the damage. The energy density is greatly affected by velocity under the shock mode. However, under a high strain rate, the energy density value varies in a wide range. Here, v represents the velocity of the compression deformation, and c represents the impact velocity in the foam. An Experimental and Computational Study of the High-Velocity Impact of Low-Density Aluminum Foam. This research was supported by the Fundamental Research Funds for the Central Universities (grant number 31020200503003), Basic Research Project of Natural Science of Shaanxi Province (grant number 2019JQ-032), National Natural Science Foundation of China (grant number 51905443), and Aviation Science Foundation (grant number ASFC-20191605300). A representative set of specimens failed under quasi-static, intermediate, and high strain rate compression are shown in Figure 9ac, respectively. National Library of Medicine The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. The, material which was introduced for this purpose was later known as foam. The pressures behind the shock wave, p2, ps, and p5, all maintain a stable pressure value (see Figure 8b). The magnitude of the vibration is determined by the number of stomatal units that collapse due to this initial cascade effect. The stress transfer within the specimen from the proximal to distal end depends on the strain rate and total applied strain. Zhao Z., Jing L. The response of clamped sandwich panels with layered-gradient aluminum foam cores to foam projectile impact. This kind of testing allows for observing the extent of damage in the foam with respect to the distance from the impact location [14]. The results from impact tests are augmented with high strain rate loading results obtained from a shock tube-based test method [35,36,37]. The dynamic crushing stress A can be calculated by Equation (6), where 0 can be obtained from the quasi-static tests and Vs can be obtained from Figure 8a. ; Writingreview & editing, validation, Y.Z. Fan Z., Zhang B., Liu Y., Suo T., Xu P., Zhang J. Interpenetrating phase composite foam based on porous aluminum skeleton for high energy absorption. all are the result ofadvancements made in technology after Industrial Revolution. Aluminium metalfoam is used in many sectors like : +7 (343) 344 44 11 info@alupor.com, Simple experiment shows low deflection of impact with ALUPOR. The specimen deformation varies as the strain rate changes. These observations show that the specimen failure behavior transitions from uniform to nonuniform compression and the transition zone is greater than the strain rate of 40 s1 tested in this work. Diagram of the stress of foam materials as a function of the strain , the green line is R-P-P-L model and the red line is R-LHP-L model [42]. Cao S.Z., Liu T., Jones A., Tizani W. Particle reinforced thermoplastic foams under quasi-static compression. about navigating our updated article layout. Johnsen J., Grytten F., Hopperstad O.S., Clausen A.H. The deformation localization in the center is likely due to the area that triggered the initial failure of a few cells that led to preferential compression. For example, when polymer foam material is used as the core of sandwich composite [12,13,14], its impact resistance and energy absorption effect are significantly improved compared with similar materials [15,16]. The specimen deformation becomes progressively more localized as the compressive strain rate is increased and the deformation mode changes from homogeneous to transitional to shock mode, as shown in Figure 1 [41]. The pressure curve was obtained by the two pressure sensors mounted in the shock tube. When the deformation velocity of the specimen is greater than Vc2, the specimen is in shock mode [41]. Thematerial which was introduced for this purpose was later known as foam. Experiments on the foams show that the strain in the foam is not uniform along the specimen length at high strain rates. Here, both a modified drop weight impact method and the shock tube test method were used for foam shock testing at high strain rates. Ramirez B.J., Misra U., Gupta V. Viscoelastic foam-filled lattice for high energy absorption. Learn more It is found that the tup velocity did not reach the condition of transition mode, while the velocity of shock wave reached the condition of shock mode. A transparent specimen chamber is constructed to allow for capturing the specimen deformation using a high-speed camera. However, since the loading time and loading strain displacement of the split Hopkinson pressure bar have certain limitations, the condition of high strain rate loading for closed cell polymer foam of large thickness cannot be achieved. In homogeneous mode, the energy absorption of foam under plastic deformation can be calculated according to the stressstrain curve under quasi-static loading [45,46,47]: where Eq is the energy absorption of foam under quasi-static loading, L is the strain entering the densification phase, is the stress of the foam, D is the volume of the specimen. Such an effect combines the elastic, plateau, and densification effects in a small zone and does not lead to the appearance of individual zones in the energy density curve for the entire specimen. This effect becomes more pronounced as the compressive strain rate is increased. The main reason of most of the injuries is impact. The experimental deformation of the shock tube belongs to the shock mode deformation. The density is 27.2 kg/m3, the average diameter and the wall thickness of the cell are 1.49 mm and about 0.017 mm, respectively. Dynamic response of foam core sandwich panel with composite facesheets during low-velocity impact and penetration. Cetin E., Baykasoglu C. Energy absorption of thin-walled tubes enhanced by lattice structures. Impact of an individual in many, conditions cause severe brain injury, broken limb etc. HHS Vulnerability Disclosure, Help In order to study the energy absorption characteristics of polymer foam under high strain loading, a new method to obtain the energy absorption was found through theoretical derivation. It provides a new calculation method for obtaining the energy absorption value of foam material. In the transitional and shock modes, the strain in the foam is not uniform along the specimen length at high strain rates, which makes the calculation of the foam material unreliable. Henriques I.R., Rouleau L., Castello D.A., Borges L.A., Deu J.F. When the specimen is opened, it can be seen that the changes in internal and external appearance are consistent. In order to improve the impact resistance of aircraft, it is of great significance to study the energy absorption characteristics of polymer foam material. Effect of microstructure on the properties of polystyrene microporous foaming material. The impact test of foam with intermediate strain rate loading was explored. Based on the test method, the failure progress and final failure modes of PE foams are discussed and, moreover, energy absorption capabilities of PE foams are assessed under both quasi-static and high strain rate loading conditions in this paper. In this figure, the specimen length steadily decreased at a constant rate while the compressive load increased moderately, and its rate turned to zero at the moment the compressive load reached the maximum value. Miltz J., Ramon O. These kind of injuries, lead to a revolutionary kind of solution to minimise the damage of these, accidents by using a material which can absorb the energy of the impact. When the incident wave hits the specimen, the first reflected wave ps is generated. In addition, the results obtained from this kind of impact cannot be compared to those obtained from compression tests due to the difference in the specimen loading configuration. However, when the compression velocity is large enough, the impacted foam will rapidly collapse and densify close to the proximal end. Therefore, we cannot get the strainstress curve. According to [41], the impact energy can be divided into deformation energy and other energy loss, and can be given by: where Es and Ew are the energy absorption of foam under the high strain rate loading and the other energy loss, respectively. Some benefits of a Duocel Energy Absorber include: Duocel foam is used as an energy absorber in various industries and applications, including: 55 Greg Street, Sparks, NV 89431 | sales@ergaerospace.com | (510) 658-9785, Pyrotechnic hardware containment (e.g., explosive bolts), Adjust relative density to control stress-strain behavior Larger ligament cross section results in a stronger structure, Open celled structure significantly reduces unwanted rebound, Easily integrates into an assembly/system. However, in the shock wave deformation process, the energy absorption capacity of the foam maintained a good stability and exhibited the best energy absorption state when the speed was higher than 26 m/s. Energy absorption characteristics of polymeric foams used as cushioning materials. Guo Y., Yang H., Liu X., Zheng Z., Wang J. Compressive mechanical behavior of closed cell Aluminum foam under dynamic loading. The experimental results showed that the stress of the material increases with the increase in strain rate. Krundaeva A., De Bruyne G., Gagliardi F., Van Paepegem W. Dynamic compressive strength and crushing properties of expanded polystyrene foam for different strain rates and different temperatures. The diameters of the driver and driven chambers were 50.8 mm and 25.4 mm, respectively. High energy absorption efficiency of thin-walled conical corrugation tubes mimicking coconut tree configuration. Moreover, the whole deformation process of foam exhibited the linear phase, the plateau phase, and the density phase, respectively; (b) the diagram of the stress of the foam as a function of the strain, the yield stress 0 is 0.00998 MPa, the locking stress L is 0.27 MPa, and the locking strain L is 0.78. Le Barbenchon L., Kopp J.B., Girardot J., Viot P. Reinforcement of cellular materials with short fibres: Application to a bio-based cork multi-scale foam. The test was conducted at a strain rate of 103 s1 calculated from Figure 6a, allowing uniform compression of the foam specimen, as the length L of the specimen and the strain rate of the compression specimen were known. Careers. and Z.C. The deformation at an intermediate strain rate is not expected to be uniform along the specimen length. This is also a key factor in the foams ability to absorb energy. Zheng Z., Liu Y., Yu J., Reid S.R. Luong et al. A split Hopkinson pressure bar is the most popular experimental method in the study of metal high strain loading. Firsttechnique is known as Open Cell manufacturing while the other is called Closedcell manufacturing. When the specimen is completely compressed and hits the rigid body, a second reflection wave (p5) is generated. The signal of the load cell was amplified and transmitted to an oscilloscope (Tektronix TDS 2014B, Tektronix, Inc., Beaverton, OR, USA) before being captured by a computer. In some foams, there is a wide range of stomatal sizes and stomatal wall thicknesses. Here, 0 is the yield stress of the material, L is the locking strain of the material, E1 is the hardening modulus of the material, and pl is the plateau stress. Hohe J., Beckmann C., Bohme W., Weise J., Reinfried M., Luthardt F., Rapp F., Diemert J. The specimen did not show any densification effect and the energy density was linear in the entire deformation range. Quasi-static compressive behavior and constitutive model of graded foams. The impact test of foam with high strain rate loading was also explored. Li Z.J., Chen W.S., Hao H. Mechanical properties of carbon foams under quasi-static and dynamic loading. This means that the specimen deformed at a constant strain rate in the elastic and plateau regions. PMC legacy view This incident shock wave traveled through the driven chamber and interacted with the specimen placed in a transparent acrylic test chamber. Jahnke D., Azadeh-Ranjbar V., Yildiz S., Andreopoulos Y. Five specimens were tested, and their deformation was also captured by the high-speed camera with a frame rate at 100,000 Hz. With the development of the aviation industry, more and more aircraft structures have used polymer foam core sandwich composites. Ouellet S., Frost D., Bouamoul A. Shock tubes have also been used to study the effect of the shock wave on the deformation behavior of foams [40]. Khosroshahi S.F., Olsson R., Wysocki M., Zaccariotto M., Galvanetto U. According to reference [42], 0, L, and E1 can be obtained from the stressstrain curves. In the absence of complete fracture, there may be vibrations in the specimen and multiple impacts due to rebound (although air brakes and other methods can be used to minimize such effects). The .gov means its official. Through theoretical derivation, the calculation method of the energy absorption of foam material under shock mode deformation is solved. The typical deformation progress of the foam in drop weight impact test and shock tube test: (a) drop weight impact test; (b) shock tube experiment. All authors have read and agreed to the published version of the manuscript. Part II: High strain rate dynamic tests. However, the previous shock tube-based studies were focused on the post-mortem of foams to observe the deformation and failure mechanisms. Between 1750 and 1850, a new kind of revolution startedfrom England which was later knows as Industrial Revolution by thehistorians. The results compared the energy absorption results with the values obtained under quasi-static compression tests. Inertia effects in uniaxial dynamic compression of a closed cell aluminium alloy foam. Influence of strain rate and temperature on the mechanical behaviour of rubber-modified polypropylene and cross-linked polyethylene. Received 2021 Mar 19; Accepted 2021 May 25. Reid S.R., Peng C. Dynamic uniaxial crushing of wood. The specimen energy absorption varied linearly in the early stage and then increased rapidly, corresponding to a uniform compression process. Although the quasi-static (103 s1) and intermediate (40 s1) tests were conducted at four orders of magnitude of strain rate, the failure features of specimens are similar, which show that some plastic deformation is not recovered and densified cells scattered in the specimen. Here, a plateau region is followed by a densification stage. Munoz-Pascual S., Saiz-Arroyo C., Vuluga Z., Corobea M.C., Rodriguez-Perez M.A. Ha N.S., Lu G.X., Xiang X.M. The new PMC design is here! Response of anisotropic polyurethane foam to compression at different loading angles and strain rates. The energy density increases rapidly in the densification region after the compression ratio of the specimen reaches 0.7. When the deformation velocity of the specimen is greater than Vc1 and less than Vc2, the specimen is in the transitional mode. Tan P.J., Harrigan J.J., Reid S.R. Once a stomatal unit collapses, the stress is redistributed in the surrounding area and a new equilibrium is reached. During the shock wave compression of the specimen, the specimen was subjected to a constant pressure of ps. Zou Z., Reid S.R., Tan P.J., Li S., Harrigan J.J. The diagram shows a steady increase in the energy density in the elastic and plateau region. Cylindrical specimens of 25.4 mm in diameter and height were used for testing. Ling C., Ivens J., Cardiff P., Gilchrist M.D. Part IIshock theory and comparison with experimental data and numerical models. The difference in PE foam material behavior in homogeneous mode and shock mode was observed through experiments. Rusch K.C. Pei L., Guo Y.B., Zhou M.W., Shim V.P.W. The structure of the PE foam specimen. The stresscompression ratio curve of the specimen front during the whole compression is presented in Figure 8c. The representative shock test results of foam specimens are presented in Figure 8. The basic characteristics of the specimen deformation are similar to those at quasi-static loading. The present work involved a modified drop weight impact instrumentation, where a standard hemispherical impact tup was replaced with a 25 mm diameter flat face tup to load a cylindrical specimen of the same diameter. The experiment allowed for developing the stressstrain diagram for the specimen and computing the energy absorption for comparison with those obtained from quasi-static and high strain rate loading conditions [29,30]. However, the shock tested (greater than 6100 s1) partially melts and resolidifies the specimen surface during the high strain rate deformation. Zheng Z.J., Yu J.L., Li J.R. The intermediate strain rate for this experiment was in the range of 40 s1. The pressure in the shock tube was measured by two pressure sensors (PCB 101A06, PCB, Depew, NY, USA) before being recorded by an oscilloscope (Tektronix TDS 2014B, Tektronix, Inc., Beaverton, OR, USA). https://creativecommons.org/licenses/by/4.0/. The shock tube developed in this work provides loaddisplacement data from the load cell, pressure transducers, and a high-speed camera and allows for comparing the energy absorption capability in other loading conditions. The results of the theoretical model agree with the experimental results, which verifies the theory. The rigidlinearly hardening plasticlocking (R-LHP-L) model is adopted to judge the three modes [42]. Industrial Revolution not only increased the rate of production but the rate ofaccidents and injuries while working were also greatly increased. When the impact stress of A inside the specimen is greater than the compaction stress of the specimen (L), the shock mode appears [41,42,43,44]: where Vs is the compression velocity of the foam, L is the densification strain of the foam. The drop weight impact test has been widely used for characterizing the intermediate strain rate impact properties of foams [26,27], where a plate-like specimen is loaded under mid-point impact conditions [28]. Therefore, the experimental results agree with the theoretical expectation. Aluminium metal foam has vast range of applications. Rc represents the compressed part. Energy Absorption Behavior of Al-SiC-Graphene Composite Foam under a High Strain Rate. The stainless-steel shock tube had two driver chambers and one driven chamber, as shown in Figure 5. The strain rates of these QSSTs were set at 103 s1, 102 s1, and 101 s1. carried out the Hopkinson pressure bar test on a very thin polyvinyl chloride (PVC) foam. official website and that any information you provide is encrypted This stable energy absorption state disappeared until the speed was lower than 1.3 m/s. Shock tubes, having a single or a double diaphragm fracture mechanism to generate shock waves, have been widely used in aerodynamics research [38,39]. Youssef G., Reed N., Huynh N.U., Rosenow B., Manlulu K. Experimentally-validated predictions of impact response of polyurea foams using viscoelasticity based on bulk properties. The impact energies were 4 J and 3 J, respectively. The energy density at a high strain rate was higher than that for the quasi-static or intermediate strain rate range at any strain level. This convex shape of the specimen is also visible in Figure 10b for the shock loaded specimen, while the quasi-static and intermediate strain rate tested specimens show a flat front. Dynamic compressive behavior of rigid polyurethane foam with various densities under different temperatures. El-Qoubaa Z., Othman R. Strain rate sensitivity of polyetheretherketones compressive yield stress at low and high temperatures. SHPB experiment research on dynamic property of expanded polystyrene foam. Combining the specimen velocity curve with Equation (7), the energy absorption of the specimen can be calculated under the shock mode. Using a shock tube as a controlled experimental platform is very helpful for determining the high strain rate properties of materials. When the speed is less than 1.3 m/s, this stable energy absorption state disappears. An official website of the United States government. It can be seen from the references that the energy density curves obtained are the same as those obtained in [52,53]. Chapter 15.2Shock Wave Propagation in Multi-Phase Media: 15.2 Weak Shock Wave Interaction with Inert Granular Media. Tang N.H., Lei D., Huang D.W., Xiao R. Mechanical performance of polystyrene foam (EPS): Experimental and numerical analysis. Xu P.B., Yu Y., Li K., Wu X.T. Drozdov A.D., Christiansen J.D. Liu Y.D., Yu J.L., Zheng Z.J., Li J.R. A numerical study on the rate sensitivity of cellular metals. Zhang Y., Jin T., Li S., Ruan D., Wang Z., Lu G. Sample size effect on the mechanical behavior of aluminum foam. The observations of drop weight impact in Figure 10a show that the center of the specimen has deformed preferentially, not the top part close to the impact. FOIA The energy absorption of the foam under the different strain rates: (a) the diagram of the energy absorption as a function of the compression ratio, the red line (Eq) represents the energy absorption of the foam in the hydraulic test, the blue line (Ed) represents the energy absorption of the foam in the drop weight test, and the orange line (Es) represents the energy absorption of foam in the shock tube test; (b) the energy absorptions of the foam under the different strain rates, here, the energy absorption value was greatly affected by velocity under the shock mode. Writingoriginal draft, formal analysis, B.Y. The strain rates of these drop weight tests were set at 40 s1 and 36 s1, respectively. The trends of energy density under high strain rate deformation in previous studies are similar to the results obtained in this test, as the energy density changed linearly with the increase in strain rate [54,55]. The impact mass was 4 kg. An experimental and numerical survey into the potential of hybrid foams. However, in fact, the internal stress of the specimen was not uniform (this phenomenon will be shown in the next section), so it can be judged that the strain rate of the specimen was greater than 6100 s1, which is a high strain rate deformation. The following conclusions can be drawn from this study: The above conclusion shows that the PE foam as a protective material for aircraft has good energy absorption characteristics. Kesavan A., Madhavan V.R.B., Chinnadurai E. Mechanical and thermal properties of PVC and polyurethane foam hybrid composites. Response of a helmet liner under biaxial loading. The end of the stress plateau and onset of densification stage means the cell wall ruptured and the foam microstructure was permanently damaged. The result is a smooth plateau with slow deformation. The final energy density with the high strain rate is 0.34 MJ/m3. A new method for obtaining the stressstrain curve of foams under intermediate strain rate deformation is provided by modifying a drop weight test machine. The authors declare no conflict of interest. Foam materials and other materials can be combined into composite materials with excellent properties as needed [9,10,11]. It can be seen from the picturesthat the overall deformation of the specimen is not uniform from the beginning of the test. Duan Y., Zhao X.H., Du B., Shi X.P., Zhao H., Hou B., Li Y.L. This test can provide the necessary data for material design. Accessibility Figure 11b shows the energy density for all the specimens. The final deformation of the foam under different loading rates, the bottom figures are the cross section of the specimens cut along the section marked in the top figures: (a) specimen failed under the quasi-static loading; (b) specimen failed under intermediate strain rate loading; (c) specimens failed under high strain rate loading. The Open cell manufacturing is a very high endmanufacturing technique used for manufacture metal foam for aerospaceindustries; on the other hand, closed cell manufacturing techniques is used formanufacturing impact absorbing materials. Federal government websites often end in .gov or .mil. The experimental results of dynamic mechanical tests on foam materials showed that the density and temperature of the material will have a great influence on the mechanical properties and energy absorption effect of foam materials [31,32,33,34]. Here, the test theory is presented, and the test platform is designed with a special foam fixture and a visualization of the end of the tube, which is able to test foam impact properties and monitor the foam failure progress. The stressstrain curve of the foam at an intermediate strain rate was obtained. Ld is the distance between two pressure sensors, and Lb is the distance between the second sensor and rigid plate. According to the rigidplasticlocking (R-P-P-L) model, the dynamic crushing stress A at the proximal end is derived as [43,48,49,50]: The foam energy absorption is calculated by: The impact energy of the incident wave in the shock tube can be calculated by [51]: where Ei is the impact energy of the incident wave.
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