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In this paper, low-velocity impact of square columns filled with density-graded foam (DGF) is investigated experimentally, numerically and analytically. The low-velocity impact experiments are carried out to study the effect of density gradient on the deformation patterns and energy absorption of the DGF-filled columns. Numerical calculations are performed to study the effects of density distribution mode, density difference, average density of DGF and wall thickness of square column on the energy absorption. According to the energy method and basic folding element theory, the instantaneous dynamic crushing force is predicted analytically. The analytical predications are in good agreement with experimental results. It is found that the DGF-filled columns have excellent energy absorption capacity and low initial peak force compared to the uniform-filled columns with the same weight. [ABSTRACT FROM AUTHOR]

Axial splitting and curling behaviour of circular sandwich metal tubes with metal foam core is investigated analytically and experimentally. The sandwich tubes split axially and the strips curl outward by prefabricated cracks at the distal end of the specimens. Axial compression experiments of circular sandwich metal tubes are carried out and deformation modes are found. A theoretical model is developed to predict the axial splitting and curling behaviour of the circular sandwich metal tubes including effects of the tearing of the cracks, plastic bending, curling, foam compression and friction. It is shown that the analytical predictions capture the experimental results reasonably. Effects of the tube thickness, foam strength, foam thickness, the number of the prefabricated cracks, and the semi-angle of the die are of vital important in energy absorption devices by the axial splitting and curling of circular sandwich tubes. [ABSTRACT FROM AUTHOR]

The paper used the analytical and numerical methods to analyze large deflection of multilayer sandwich beams with foam-filled trapezoidal corrugated and foam cores. Considering both the strength of metal foam and corrugated core, we obtained a yield criterion for the multilayer sandwich structure foam-filled trapezoidal corrugated and foam cores. Based on proposed yield criterion, we further presented an analytical solution for large deflection of such multilayer sandwich beam under transverse loading. Well agreement is achieved between analytical and numerical results. What is more, we discussed the effects of foam strength, punch size, face-sheet thickness and middle foam thickness on the plastic behaviors. • Large deflection of multilayer sandwich beams with foam-filled trapezoidal corrugated and foam cores is studied. • The yield criterion for multilayer sandwich structures with foam-filled trapezoidal corrugated and foam cores is obtained. • Analytical solutions are derived for large deflection of multilayer sandwich beams under transverse loading. • Good agreement is achieved between analytical and numerical results. • Foam strength, punch size and face-sheet thickness have significant effects on plastic behavior of sandwich beams. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic response of multilayer curved aluminum honeycomb sandwich beams under low-velocity impact is investigated experimentally. The deformation process and final failure modes of multilayer curved aluminum honeycomb sandwich beams are observed and analyzed. The numerical calculation is conducted, and the numerical results are in good agreement with experimental ones. The effects of core thickness, core-thickness gradient, and gradient of inscribed circle diameters in upper and lower honeycombs on the load-carrying capacity and energy absorption of multilayer curved aluminum honeycomb sandwich beams are explored. It is shown that the multilayer curved sandwich beam has the best energy absorption capacity when the thicknesses of upper and lower cores are same. The total energy absorption of the specimen with the lower layer of 30 mm and the upper layer of 10 mm is 63.7% of that of the specimen with upper and lower layers of same thickness, and the total energy absorption of the specimen with the lower layer of 10 mm and the upper layer of 30 mm is 53.5% of that of the specimen with upper and lower layers of same thickness, respectively, under 40 J impact energy. In the range of curvature angle from 20°to 60°, the energy absorption capacity and mitigation ability of the multilayer curved sandwich beam can be effectively improved. Also, increasing the face-sheet thickness can effectively improve the energy absorption capability of multilayer curved sandwich beams. • Low-velocity impact of multilayer curved sandwich beams is investigated experimentally and numerically. • Deformation process of multilayer curved aluminum honeycomb sandwich beams is analyzed. • Numerical results are in good agreement with experimental ones. • For curvature angles from 20° to 60°, energy absorption of curved sandwich beams can be improved. [ABSTRACT FROM AUTHOR]

The failure behavior and energy absorption performance of aluminum honeycomb sandwich beams with glass fiber-reinforced epoxy/aluminum laminates (GLARE) face-sheets under three-point bending are experimentally and numerically studied. The experimental specimens consists of 2/1 (2 aluminum sheets and 1 glass fiber/epoxy laminates) GLARE and aluminum honeycomb core. The effects of core height (8 mm, 20 mm, 40 mm) and indenter shape (cylindrical indenter and flat indenter) on bending failure behavior are tested in quasi-static three-point bending. Six sandwich beam specimens (300 mm-long and 40 mm-wide) were prepared. The initial failure modes of GLARE sandwich beams are observed, i.e. core shear and indentation. The numerical model considering geometric nonlinearity is established by ABAQUS/Explicit software and its effectiveness is verified by the experimental results of specimens with the same size and loading conditions. The effects of geometric and material parameters on the load-carrying capacity and energy absorption of the GLARE sandwich beams are discussed in details. It is shown that increasing the face-sheet thickness, honeycomb wall-thickness, the ratio of the core height to span length and the elasticity effect of metal materials or reducing the side length of the honeycomb cell can improve the load-carrying capacity and energy absorption of GLARE sandwich beams. The work can provide the guidance for the design of the GLARE sandwich structure with honeycomb core. • Bending failure behavior and energy absorption of sandwich beams with GLARE face-sheets are studied. • The initial failure modes of GLARE sandwich beams are observed. • Numerical results are in good agreement with experimental ones. • Increasing face-sheet thickness, honeycomb wall-thickness can improve the load-carrying capacity and energy absorption. [ABSTRACT FROM AUTHOR]

In this paper, the plastic behavior of a clamped rectangular sandwich tube with metal foam core is studied by analytical and numerical methods. Using the yield criterion, the analytical solution for plastic behavior of a rectangular metal foam core sandwich tube under transverse loading is derived. The numerical calculation is conducted, analytical results are compared with numerical ones. Analytical and numerical results are verified by each other. Finally, the influences of the punch width, loading position, foam strength, and tube-wall thickness on large deflection of the sandwich tubes are discussed based on the analytical model. It is shown the load and plastic energy increase with the increase of punch width, the metal-foam strength and tube-wall thickness, loading position moving from the center to the sides. [ABSTRACT FROM AUTHOR]

• Dynamic response of sandwich plates with GLARE face-sheets under metal foam projectile impact is studied. • Effects of impulse and thickness on dynamic response are studied by single impact experiments. • The ability of resisting multiple impacts and the ultimate failure mode are measured. • The numerical results are in good agreement with experimental ones. Aluminum honeycomb sandwich plate with fiber metal laminate (FML) as panel can combine the advantages of FML face-sheet and honeycomb core, and has advantages of high specific strength / specific stiffness, lightweight and good energy absorption performance. In this paper, the dynamic response of aluminum honeycomb sandwich plates with Glass Laminate Aluminum Reinforced Epoxy (GLARE) face-sheets under metal foam projectile impact is studied. The single foam projectile impact test is conducted to study the dynamic response of honeycomb sandwich plates with GLARE face-sheets. The debonding between metal and composite layers of the front face-sheet, the fiber fracture, buckling, shear and fracture of core are observed. Also, the multiple foam projectile impact test is carried out to study the impact resistance of the sandwich plate. The numerical calculation is conducted, numerical results are compared with experimental ones. Influences of the impulse, face-sheet thickness, fiber laying angle, honeycomb height, wall thickness of core and cell length of honeycomb on impact resistance and energy absorption of sandwich plates are discussed. It is found that the improvement range of the maximum deflection of back face-sheet gradually decreases with the increase of face-sheet thickness. In addition, by increasing the impulse, decreasing the face-sheet thickness and decreasing the core stiffness, the energy absorption of sandwich plates under metal foam projectile impact can be enhanced. These findings can be used to guide the optimal design of FML sandwich structures under metal foam projectile impact. [ABSTRACT FROM AUTHOR]

In this paper, the large deflection of the slender circular metal foam-filled tube (FFT) under transverse loading is studied theoretically and numerically. The yield criterion of the circular foam-filled tube is proposed. Using the yield criterion, the analytical solution for the plastic behavior of slender circular metal foam-filled tube under transverse loading is obtained considering the interaction between bending and stretching and foam strength. Large deflection of the circular metal foam-filled tube is numerically calculated. The analytical model captures numerical results. Influences of tube-wall thickness, punch width, foam strength, loading position and the radius of filled foam on the load-carrying capacity and energy absorption (EA) of foam-filled tubes are discussed in detail. The results show the load-carrying capacity and energy absorption of the foam-filled tubes increase with the increase of tube-wall thickness, foam strength, punch width and the radius of filled foam. • Large deflection of the slender circular metal foam-filled tube under transverse loading is studied. • The analytical solution of the plastic behavior of the circular foam-filled tube is obtained considering foam strength. • The analytical model captures the numerical results reasonably. • Load-carrying capacity and energy absorption increase with increase of tube-wall thickness, foam strength and radius of foam. [ABSTRACT FROM AUTHOR]

Axial splitting and curling collapse of square sandwich metal tubes with metal foam core is investigated analytically and experimentally. The square sandwich metal tube split axially and curl outward along prefabricated cracks. Axial compressive tests of square sandwich metal tubes with prefabricated cracks are conducted and deformation modes are observed. An analytical model for axial splitting and curling behavior of square sandwich metal tube considering plastic bending, crack tearing, curling, foam compression, friction is proposed. It is demonstrated the analytical predictions are in good agreement with experimental results. Influences of foam thickness, tube thickness, die angle, prefabricated crack length, and foam strength are of vital importance to axial splitting and curling of square sandwich metal tube. • A theoretical model is proposed to predict splitting and curling of sandwich tubes. • Axial compression experiments are carried out and deformation modes are found. • Analytical solution captures the experimental results reasonably. • Effects of foam thickness, die angle are of importance to splitting and curling. • The specific energy absorption of the sandwich tube is higher than single tube. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic collapse of circular metal foam core sandwich tubes in splitting and curling mode subjected to low-velocity impact. The splitting and curling modes occur along the prefabricated cracks on sandwich tubes. The deformation modes, i.e. crack propagation along the prefabricated crack, new crack initiation, merging old cracks are observed in experiments. It is found that the number of strips in the sandwich tube tends to develop from the number of prefabricated cracks to the number of steady strips. Based on the principle of minimum energy, the method for predicting the number of steady cracks in the inner and outer tubes of the sandwich tubes is established. The quasi-static analytical model is approximately used to predict experimental results, and analytical results capture experimental ones reasonably. It is demonstrated the better energy absorption characteristics can be obtained by the proper thickness of metal foam core. • Dynamic collapse of circular sandwich tubes in splitting and curling mode subjected to low-velocity impact is investigated. • The method for predicting the number of steady cracks in inner and outer tubes is established. • Analytical predictions capture the experimental results reasonably. • The analytical solutions can be used to predict the average force of the sandwich tubes. [ABSTRACT FROM AUTHOR]

• This paper reviews investigations on energy absorption and dynamic response of sandwich structures over the past few decades. • The impact loading includes low-velocity impact, explosive loading as well as ballistic impact. • Core configurations of sandwich structures include metal foam and polymer foam, ungraded and graded honeycomb, auxetic honeycomb and foam inserted honeycomb, corrugated core and foam inserted corrugated core, truss core, undrilled and drilled I-core, and Y-shaped core. • The excellent characteristics concerning load resistance and energy absorption of sandwich structures can guide their application in engineering practice. With the swift advancement of aerospace, shipbuilding and engineering, the significance of sandwich structures with cellular cores is becoming increasingly prominent due to their multi-functional and lightweight attributes. In addition, impact loadings are very common in the engineering practice and may potentially cause significant adverse impact on products and equipment. Emerging manufacturing technologies facilitate the fabrication of high quality sandwich plates with improved stiffness and strength to withstand impact loadings. Therefore, extensive investigations have been conducted on sandwich structures under various impact loadings. This paper provides a comprehensive review of the valuable experimental, analytical, and numerical investigations conducted on the dynamic response of sandwich structures spanning several decades. The paper aims to reveal the underlying deformation mechanisms governing the response of sandwich structures subject to impact loadings. The focus is primarily on popular sandwich structures, such as beams, plates, and curved plates, under low-velocity impact, blast loading, and ballistic impact. Various core configurations of sandwich structures are explored, including metal and polymer foams, uniform and graded honeycombs, auxetic honeycombs, foam inserted honeycombs, corrugated core and foam inserted corrugated core, truss core, undrilled and drilled I-core, chiral core, star-shaped core and Y-shaped core. Current challenges and recommendations for future work have also been articulated. [ABSTRACT FROM AUTHOR]

The static axial crushing and energy absorption of density-graded aluminum foam-filled square metal columns are experimentally and theoretically investigated. Typical deformation modes are observed in experiments, such as symmetric, asymmetric, extension and rupture modes. Theoretical analysis is carried out and the predictions are in good agreement with the experimental results. The effects of gradient pattern, density difference, average density of foam, and wall thickness on the crushing of foam-filled columns are discussed. It is shown that the density-graded aluminum foam-filled square metal column is a novel topological structure with higher energy absorption, higher load-carrying capacity and much higher crushing force efficiency. [ABSTRACT FROM AUTHOR]

Dynamic response of sandwich plates with a metal honeycomb core under low-velocity impact has been investigated. Experiments of the fully clamped sandwich plates subjected to low-velocity impact of the drop-hammer with a hemispherical nose have been conducted and plastic failure modes have been measured. Structural damage mechanism of sandwich plates has been identified and explored. It is found that finite element simulations of these experiments are in good agreement with the experimental measurements. Analytical solutions for permanent deflections and peak impact forces are derived and capture the experimental results with reasonable accuracy. It is shown that the impact positions have important influence on the dynamic response of sandwich plates subjected to low-velocity impact. The impact resistance of sandwich plate decreases from the central position to the non-central positions. [ABSTRACT FROM AUTHOR]

• Experiments on the dynamic crushing of metal honeycomb-like hierarchical structures with perforated walls are carried out. • New failure modes of dynamic crushing of metal honeycomb-like hierarchical structures with perforated walls are obtained. • Specific energy absorption of structures of perforations on double walls are larger than those on single walls. • Compared with the uniform perforation design, the perforation gradient designs increase the mean crushing stress. Hierarchical structures have the potential advantage of enhancing their energy absorption capabilities. Honeycomb-like hierarchical structures are developed and manufactured by perforating on the cell walls consisting of single thickness inclined walls and double thickness vertical walls. The out-of-plane dynamic crushing experiments on metal honeycomb-like hierarchical structures with perforated walls are carried out to explore the failure modes and energy absorption mechanism. The impact failure modes of honeycomb-like hierarchical structures under different impact velocities are obtained. The corresponding numerical simulations are also performed. It is shown that the numerical results are in good agreement with experimental data. The dynamic mean crushing stress of the honeycomb-like hierarchical structures is larger than the quasi-static mean crushing stress. The mean crushing stress, total energy absorption, specific energy absorption of honeycomb-like hierarchical structures of perforations on double walls are larger than those of perforations on single walls with the same mass. Results from parametric study of factors that influence the dynamic crushing response of honeycomb-like hierarchical structures are presented. Compared with the uniform perforation design, the perforation gradient designs increase the mean crushing stress. [ABSTRACT FROM AUTHOR]