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• A novel composite auxetic reentrant honeycomb structure is designed and fabricated. • The one-stage light gas gun and diffuser-type shock tube were utilized to generate and propagate exponential decaying shock wave. • The effect of gradient form on impact resistance performance was experimentally and numerically investigated. • The effect of relative density of composite reentrant honeycomb structure was analyzed and investigated. The researches on dynamic responses of underwater impulsive loading have been conducted. However, the previous study mainly concentrated on metal sandwich structure and fixed supported boundary. The relative research on composite auxetic re-entrant honeycomb structure and simply supported boundary are rarely. In this paper, the effect of the gradient form and relative density on impact resistance performance of composite auxetic re-entrant honeycomb structure was experimentally and numerically investigated. The one-stage light gas gun was applied to provide initial kinetic energy of the fly plate, and the diffuser-type shock tube was utilized to generate and propagate exponential decaying shock wave. The pressure–time curve was respectively amplified and recorded by the charge amplifier and oscilloscope. The response speed, final deflection of rear panel and failure mode of cores and panels were used to evaluate impact resistance of composite auxetic re-entrant honeycomb structures. Moreover, acoustic-structure interaction algorithm was applied to simulate impact course of specimens in Abaqus/Explicit. The results between experiment and numerical simulation exhibited good consistency. The results indicated that the positive gradient form could excessively slow down response speed of rear panel by dissipating energy of shock wave, and the average gradient demonstrated smaller final displacement of rear panel and less failure compared with graded structures. [ABSTRACT FROM AUTHOR]

• High-velocity impact performance of AA 7475-T7351 aluminum plates impacted by spherical and cubical projectiles. • Predicting impact velocity limits that lead to liquid (fuel) leaks from impacted aluminum plates. • Effect of different impact orientations of a cubical projectile on the ballistic and leakage velocity limits of aluminum plates. This paper presents numerical and experimental findings of high-velocity impact tests conducted on thin AA 7475-T7351 aluminum plates subjected to the impact of small cubical and spherical projectiles. The investigation includes an examination of the influence of different impact angles, namely edge-on, corner-on, and face-on orientations, on the target performance. Following each impact test, the damaged plates underwent a leakage test, to determine the leakage threshold caused by the impact event. To gain a deeper insight into the failure modes and penetration mechanisms of thin-walled aluminum plates, finite element models were developed for various impact scenarios. The results revealed that both the shape and orientation of the projectile significantly impact the ballistic and liquid leakage limit velocities of targets. Notably, the cubical projectile exhibited lower ballistic and leakage limits than the spherical projectile. In terms of the leakage limit, a clear correlation was identified between the sharpness of the projectile's nose and leakage limit velocity. As the projectile's nose became sharper, the consistent trend was a decrease in leakage limit velocity i.e. the corner-on impact orientation (having the sharpest nose) exhibited the lowest leakage limit velocity, while the face-on impact orientation (having a blunt nose) displayed the highest leakage limit velocity. However, in contrast to the leakage limit velocity, a definitive relationship between the projectile nose sharpness and ballistic limit velocities was not observed. This is evident as the corner-on impact orientation, associated with the sharpest nose, registered the highest ballistic limit velocity, while the edge-on impact orientation, with an intermediate nose sharpness, recorded the lowest ballistic limit velocity. [ABSTRACT FROM AUTHOR]

• This paper summarises the research carried out to date on the impact resistance of concrete subjected to different impact load regimes, with a focus on high-velocity projectile impact load. • An experimental database is compiled on the response of concrete elements to high-speed projectile impacts, which is used to identify the critical failure modes of concrete under impact loads (i.e. spalling, scabbing, penetration, and perforation of the targeted specimens) and the parameters influencing the impact resistance of concrete (i.e. velocity, mass and shape of the projectile, concrete compressive strength, type and size of aggregate, and type and ratio of reinforcement). • In addition, the adequacy of existing empirical formulas to predict the penetration depth is assessed by using the experimental database. • A critical discussion highlights the effect of various design parameters on the impact resistance of concrete and determines the key aspects that should be addressed in future research. This paper summarises the research carried out to date on the impact resistance of concrete subjected to different impact load regimes, with a focus on high-velocity projectile impact load. An experimental database is compiled on the response of concrete elements to high-speed projectile impacts, which is used to identify the critical failure modes of concrete under impact loads (i.e. spalling, scabbing, penetration, and perforation of the targeted specimens) and the parameters influencing the impact resistance of concrete (i.e. velocity, mass and shape of the projectile, concrete compressive strength, type and size of aggregate, and type and ratio of reinforcement). In addition, the adequacy of existing empirical formulas to predict the penetration depth is assessed by using the experimental database. A critical discussion highlights the effect of various design parameters on the impact resistance of concrete and determines the key aspects that should be addressed in future research. [ABSTRACT FROM AUTHOR]

The impact behavior of building and bridge structures is already a growing concern due to the frequent occurrence of vehicle collision accidents. Concrete-filled square steel tube stiffened with encased I-shaped carbon fiber reinforced plastic profile (CFST-CFRP) is suitable for building and bridge structures due to its high bearing capacity and small section size. Thus, this study experimentally and numerically presents the dynamic responses for CFST-CFRP columns under lateral impact to evaluate their impact resistance. Firstly, three CFST-CFRP columns and one CFST column were tested in a rigid vehicle impact device, with variations in impact velocity, impact type, impact impulse of the rigid vehicle, and CFRP profile. The impact force-displacement curve and failure mode of CFST-CFRP columns were obtained. Additionally, finite element analysis (FEA) models were built by ABAQUS and verified against tested results. Then, the working mechanisms of CSFT-CFRP columns under impact load were further revealed in-depth by analyzing displacement, impact force, inertia force, bending moment, shear force, and dissipated energy. Based on the working mechanisms, the effect of the CFRP profile on the dynamic response of CFST-CFRP member subject to different parameters was discussed. The results indicated that all the specimens fail at the support. With the additional CFRP profile in the CFST column, the failure pattern of the steel tube was transformed from fracture to local buckling. CFRP profiles enhance the impact resistance of CFST columns (incremented by 17%), and the increasing ratio rises with the decreasing steel ratio and steel strength of members. Steel tubes can share 72% and 78% of energy absorption and bending moment, which is the main impact-resistant component. For this study, valuable experimental data can be supplied for CFST-CFRP columns subjected to vehicle collision. Meanwhile, a theoretical reference for impact resistance design in the future is also provided. [ABSTRACT FROM AUTHOR]

• A new three-dimensional combined with hyperelastic, viscoelastic and elastoplastic mechanics is established for the analysis of impact response and fracture in polyurea coated aluminum plates with different coating methods. • The Ogden model and the generalized Maxwell model are established and fitted, which are suitable for characterizing the hyperelastic and viscoelastic response for polyurea under low and medium strain rates. • This study reveals the influence law of polyurea stiffness, aluminum strength, bonding strength, and polyurea thickness on impact resistance of polyurea coated aluminum plates. A novel three-dimensional model was established for analyzing the impact response and fracture of polyurea-coated aluminum plates using the LS-DYNA finite element code. Hyperelastic and viscoelastic constitutive models were established to characterize the impact response of polyurea, and a modified Johnson-Cook model was used to characterize the impact response of aluminum. The constitutive models of polyurea and aluminum were characterized and validated by comparing their results with those of tensile experiments under different strain rates. The simulation results of polyurea-coated aluminum plates were analyzed using the impact responses for different coating methods. Moreover, the effects of the polyurea stiffness, aluminum strength, bonding strength, and polyurea thickness on the impact resistance of polyurea-coated aluminum plates are discussed in detail. The impact peak force, energy absorption, and deformation results of the simulation of polyurea-coated aluminum plates for different coating methods were within 5% of the experimental results. Accordingly, the established model can accurately predict the fracture modes, thus demonstrating that the proposed methodology is more suitable for polyurea-coated aluminum plates under low-velocity impact than the existing methods. [ABSTRACT FROM AUTHOR]

Soft body armors have been widely used by law-enforcement and military personnel. However, predictive capabilities on the critical conditions for the impact failure of these armors are still not well-developed. As part of a special issue, this article summarizes our recent experimental research efforts aiming at developing a better understanding of impact failure of soft body armors at several size scales, ranging from shoot packs, single-plies, yarns, and fibers. The experiments reveal that impact resistance of packets is dictated by axial properties and shear strength of the textile materials, as well as structural properties such as weave patterns. At the single-ply level, the critical impact velocity depends heavily on the nose shape of the projectiles, as well as the axial and transverse properties of the yarns. The failure of yarns and fibers depends on the stress state, as interpreted from the effects of nose shapes of the indenters and from the application of multi-axial stress states. The effects of aging on the impact resistance is also discussed. [ABSTRACT FROM AUTHOR]

• An improved co-simulation for the impact test of injection-molded composite wheel is proposed. • The composite wheels are injection molded and the impact test is conducted to verify the method. • Compared with the existing methods, the improved version gives much more accurate results. • Achieving the match state between the two types of mesh models improves the simulation results. • The wheel's impact resistance varies with tires used, but no consistent rules can be followed. The excellent mechanical properties, ease of processability and intrinsic recyclability drive the long-fiber-reinforced thermoplastic composite to be recognized as a potential alternative material. And combined with injection molding process, a new path to promote the lightweight design of automobile wheels may be opened up. At present, some numerical methods of 13-degree impact test have been proposed to evaluate the mechanical performance of such composite wheels, but the simulation accuracy is insufficient arising from the following drawbacks to provide a reliable basis for the optimal design. Specifically, the one is to use the simplified tire model to evaluate its effect on the impact resistance of wheel, and the other is that during establishing the anisotropic material model of composite wheel by using the mapped fiber orientation information, the finite element mesh model for injection molding analysis is not matched with the one for structural analysis. Aiming at these problems, an improved co-simulation method is proposed to more accurately predict the impact performance of such wheels. Then, the long-glass-fiber reinforced polyamide 66 composite wheels are fabricated through injection molding process and the corresponding impact test is performed to verify the validity of this approach. And compared with the existing co-simulation method, the calculation accuracy of this improved version is obviously increased. Besides, the effects of these improvements on the simulation results are comparatively analyzed, and the influence of different actual tires on the impact performance of wheel is also investigated by test. The results show that, whether or not to achieve the match state between the two types of mesh models significantly affects the final impact simulation results, and the impact performance of composite wheel varies obviously with different tires used but no consistent rule can be followed. [ABSTRACT FROM AUTHOR]

The impact resistance of concrete structures is of major importance in engineering application. Computational methods are increasingly used for such types of applications but face difficulties due to the complex physical behaviour involving large deformations and large strains. Meshfree methods seem ideally suited to deal with these types of problems. In this manuscript, we present stochastic simulations based on the element-free Galerkin method to predict upper and lower bounds of the impact resistance of concrete structures. We account for stochastic distribution of material parameters and validate our results with benchmark experiments conducted by the group of Hanchak. [ABSTRACT FROM AUTHOR]

• New partially-infused Kevlar/Polycarbonate laminate to improve impact resistance. • This partially-infused structure is inexpensive and simple to manufacture. • Fiber yarns in this structure contain fully infused exterior and dry fiber core. • The fully infused exterior provides good stiffness and interlaminar toughness. • The dry fiber core provides high energy dissipating during impact. High toughness Kevlar fiber reinforced polymer composites are adopted for applications such as bulletproof shields, helmets and hard body armor that require high impact resistance as well as sufficient structural stiffness and strength. However, the impact energy absorption of fully-infused stiff composites made of Kevlar fibers and matrix is not as good as that of dry Kevlar fabrics. This study proposes a partially-infused Kevlar fiber reinforced thermoplastic laminate with significantly improved impact resistance. Unlike conventional Kevlar fiber reinforced laminates where the resin is fully infused into the fiber yarns, the fabrication process of partially-infused laminates is controlled such that only the exterior of the Kevlar fiber yarns is infused with thermoplastic resin. Consequently, the Kevlar fibers at the core of each fiber yarn are unrestricted during impact, thus, dissipating more energy. The infused exterior of Kevlar fiber yarns forms tough interlaminar interfaces that resist delamination during out-of-plane loading. The partially-infused laminate has similar static indentation resistance and slightly lower bending resistance when compared to conventional fully-infused Kevlar reinforced thermoplastic laminate, but dissipated 318% more energy in ballistic penetration tests performed with a 12 mm diameter steel spherical projectile. [ABSTRACT FROM AUTHOR]

• At relative bond lengths of 20/L and 25/L, it is safer to use CFRTP as the impact surface than Al as the impact surface. • At relative bond lengths of 35/L and 45/L, high and stable residual strengths are guaranteed for both CFRTP and Al as impact surfaces. However, in terms of cost savings, 35/L is a better choice. • The thermoplastic Al/PEEK/CFRTP has better impact resistance than the thermosetting FM94/Al joints. Due to their excellent impact resistance, high toughness, short forming time, and recyclability, carbon fiber-reinforced thermoplastic (CFRTP) composite materials can be blended and bonded with aluminum alloys (Al) to produce lighter structures with better impact resistance. In this study, the effects of impact energy (5, 10, 15, 20 J) and impact surface (CFRTP and Al) on Al/PEEK/CFRTP joints with different relative bond lengths (20/L, 25/L, 35/L, 45/L, where L is the length of the adherend) were explored through a combination of joint impact damage modes, energy absorption rates, residual strengths, and tensile fracture surfaces. The results showed that when the relative bond lengths were 20/L and 25/L, using CFRTP as the impact surface significantly reduced the residual strength loss of the joint. When the relative bond lengths were 35/L and 45/L, the influence of the impact surface on the joint was significantly reduced. A relative bond length of 35/L was the ideal choice for structural safety and cost savings. [ABSTRACT FROM AUTHOR]

High impact resistance and greater energy absorption capacity are desirable properties for concrete. Innovative and sustainable materials may be used to improve these properties. In the present study, the effect of replacement of fine aggregates by waste rubber fibers on the impact resistance of concrete has been assessed. Silica fume has also been considered as replacement of cement. Six replacement levels of rubber fiber (0%, 5%, 10%, 15%, 20% and 25%) and three replacement levels of silica fume (0%, 5% and 10%) have been considered for three different water cement ratios. Impact tests on concrete have been conducted by three different techniques; drop weight test, flexural loading test and rebound test. Relationships between impact test results of drop weight test, flexural loading test and rebound test have also been established. In view of large variation of impact values, a two-parameter Weibull distribution is adopted to analyze the experimental data of drop weight test. The study demonstrates that the waste rubber fiber can be used as a sustainable material to improve the impact resistance and ductility of concrete. The study also demonstrates that the silica fume improves the impact resistance and reduces the ductility of rubber fiber concrete. [ABSTRACT FROM AUTHOR]

• High-velocity impact resistance of doubly curved CFRP sandwich panels is presented. • Impact tests are carried out by using a single-stage air gas gun test machine. • An analytical model is developed to describe the ballistic limit velocity. • Parametric analyses are carried out for various radius of curvature of the panels. This work describes the high-velocity impact behavior of doubly curved sandwich panels. The sandwich panels are manufactured using carbon/fiber epoxy composite face sheets, polyurethane foam core and 3D-printed PLA plastic cellular auxetic (re-entrant) honeycombs. High-velocity impact tests are carried out by using a single-stage air gas gun test machine. A spherical steel projectile with the radius of 5 mm is impacted to the center of the specimens with the speed of 100 m/s. The experimental data are used to validate explicit finite element models of the doubly curved structures. An analytical model is also developed for the ballistic limit of the flat and doubly curved sandwich panels, and the analytical results are compared to those obtained from the numerical ones. Parametric numerical analyses of the high-speed impact of the curved sandwich panels are then carried out considering various radii of curvature of the panels. The results show that the energy absorption is increased as the curvature is decreased for the panels with both foam and re-entrant core. In addition, the core configuration provides a key role in the impact resistance of the sandwich panels. Re -entrant models show an increase in specific energy absorption (SEA) compared to the foam core types. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this paper, impact loading results from numerical simulations of plain concrete (PC) and fiber-reinforced concrete (FRC) are compared with experimental testing data, which were based on a testing procedure recommended by ACI committee 544. Concrete specimens were prepared with two water–cement ratios 0.36 and 0.46. Hooked-end steel fibers with an aspect ratio equal of 80 at 0.5% and 1% volume fractions and polypropylene fibers at 0.2%, 0.3% and 0.5% volume fractions were used. Both the numerical and experimental analysis results indicated that increasing the fiber volume fraction increased the impact resistance of the concrete specimens. The impact resistance increase was greater for normal-strength than that for high-strength concrete. The results also demonstrated that steel fibers are more effective at increasing impact resistance than polypropylene fibers. [Copyright &y& Elsevier]

Abstract: This study investigated the impact resistance and mechanical properties of steel fiber-reinforced concrete with water–cement ratios of 0.46 and 0.36, with and without the addition of silica fume. Hooked steel fibers with 60-mm length and an aspect ratio of 80, with three volume fractions of 0%, 0.5%, and 1% were used as the reinforcing material. In pre-determined mixtures, silica fume is used as a cement replacement material at 8% weight of cement. The experimental results show that incorporation steel fibers improve the strength performance of concrete, particularly the splitting tensile and the flexural strengths. A remarkable improvement was observed in impact resistance of the fibrous concretes, as compared with the reference materials. The results demonstrate that when steel fiber is introduced into the specimens including silica fume, the impact resistance and the ductility of the resulting concrete are considerably increased. [Copyright &y& Elsevier]

Abstract: The impact resistance of polypropylene fibre-reinforced concrete (FRC) was investigated using the repeated drop-weight impact test recommended by ACI Committee 544. The results were analysed based on a statistical approach. The variation in results was examined within the same batch and between different batches. Statistical parameters were compared with reported variations in impact resistance of concrete composites reinforced with other types of fibres such as carbon and steel fibres. Statistical analysis indicated that the results obtained from this test had large variations and it is necessary to increase the number of replications to at least 40 specimens per concrete mix to assure an error below 10%. It is concluded that this test with its current procedures and recommendations should not be considered as a reliable impact test. This study has highlighted the need for modifying this test in such a way as to increase its accuracy and reduce the large variation in results. [Copyright &y& Elsevier]

This paper concerns the protective structures against rock fall. We propose a new concept of rock-shed protection. The proposed rock-shed protection is made of reinforced concrete slabs held up by specially designed supports that act as a type of expendable fuse to absorb high rock-fall energy especially when shock occurs on the side of the slab. Thus, by a simple change of damaged supports and local restoration of concrete in the impact area, the structure can continue to be used. We present also an experimental method to characterize and analyze shock absorption effected by this type of reinforced concrete slab. The analyzed slab is a 1/3 scale reproduction of an actual structure. [Copyright &y& Elsevier]

To confirm the ultimate impact-resistant capacity of Prestressed Concrete (PC) rock-sheds constructed over the highways in Japan, prototype impact tests are conducted by using two types of PC rock-shed frames: inverted L frame and fully rigid frame. The two types are of equal dimensions: span length=10.1 m, upper flange width=150 cm, column height=4.65 m. The impact tests are performed by iteratively and freely dropping a 3000/5000 kg steel weight onto the center of each frame covered with a 90 cm thick sand cushion. The results obtained from this study are as follows: (1) the fully rigid frame has more than 1.7 times the impact-resistant capacity of the inverted L frame with reference to input impact energy; (2) the fully rigid frame can effectively disperse the sectional forces over the whole structure; (3) the inverted L frame and fully rigid frame PC rock-sheds designed based on allowable stress design procedure have more than three and five times the margin against collapse, respectively. [Copyright &y& Elsevier]

• Hybrid plate-lattices exhibit higher energy absorption capacity and progressive failure compared to elementary ones. • The effectiveness of hybrid plate-lattices are more significant at higher impact energies (> 40 J). • The relative density decides the best balance between stiffness and unstable damage growth. • The hybrid plate-lattices achieve a direction-independent impact response • The hybrid plate-lattices exhibit higher specific energy absorption than that of the conventional aluminum lattices and other practical metamaterials. This study is focused on the low-velocity impact response of 3D plate-lattices fabricated via stereolithography additive manufacturing (AM). Elementary (SC, BCC and FCC) and hybrid (SC-BCC, SC-FCC and SC-BCC-FCC) configurations were tested and the effects of impact energy, relative density, plate-thickness, multiple impacts and impact angle on the dynamic crushing behavior and energy absorption characteristics were analyzed. The experimental results reveal that the hybrid lattices, due to the existence of larger number of open and closed sub-cells, were able to attenuate the peak impact stress transmitted to the structure and extend the duration of the load pulse (high toughness). A significant energy dependency of contact force-displacement characteristics of hybrid structures was noticed with increase in impact energy. The SC-BCC-FCC hybrid plate-lattices depicted a 70% increase in toughness and their specific energy absorption capacity is higher than the conventional aluminum lattices and other practical metamaterials. Experimental observations also revealed that the distribution of plates in each elementary structure in hybrid configuration plays an important role in mitigating the deleterious failure mode by transforming the brittle mode fracture into progressive damage of the plate-lattices. This paper, believed to be the first comprehensive experimental study, discusses the role of relative density, plate-thickness, multiple impacts, impact energy and oblique impact on the low velocity impact response of geometrically hybridized plate-lattice structures. The results of this investigation suggest that the concept of hybridization of plate-lattice architectures in conjunction with AM will enable development of lightweight high impact energy absorbing structures for a wide variety of applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• The effect of reinforcing bars on the impact resistance of RC panel was investigated. • Hard-projectile impact testing for RC panel and numerical analysis were conducted. • Reinforcing bars afforded a confining force to concrete, and entrapped fragments. • Narrowing the rebar spacing enhanced the impact resistance. • Rebar diameter and yield strength barely affected impact resistance. Experimental and numerical studies were conducted to investigate the effect of reinforcing steel on the impact resistance of reinforced concrete structures and to reveal its mechanism. Hard-projectile impact tests using a single-stage gas gun were performed with reinforced concrete panels to simulate a nuclear power plant structure. Parametric analysis was conducted with a numerical model that applied a finite element method coupled with smoothed particle hydrodynamics using the following four variables: the impact velocity of the projectile as well as yield strength, spacing and diameter of the reinforcing steel. The experimental and numerical analysis results indicated that the impact resistance was significantly affected by the spacing of the reinforcing steel, but not by the yield strength or the diameter of the reinforcing steel. Narrower rebar spacing improved the impact resistance due to the enhanced confining and fragment trapping effects. [ABSTRACT FROM AUTHOR]

• The deformation response of sandwich plates with composite foam core subjected to high velocity impact of foam projectile was investigated by using experimental method. • The failure modes of the sandwich plates subjected to impact loading was concluded. • Effect of impact loading intensity, core thickness and core density on the damage of plates was evaluated. • The energy absorption of sandwich plates with different configuration was studied. In this study, the deformation and damage behaviors of sandwich plates with composite foam core subjected to high velocity impact of metallic foam projectile are investigated. A series of experiments was conducted to address the dynamic response, failure modes and energy absorption characteristics of the sandwich plates with different configurations. The dynamic behavior of the sandwich plates was analyzed by using 3D-DIC technique with high speed cameras. The failure modes of the sandwich plates as well as front face sheet, foam core and rear face sheet were identified and discussed. The results indicate that the symmetric deformation of rear face sheet increased with the impact loading increasing, and the core with greater thickness lengthen the responding time of the structures effectively. Compared with the thickness of core, core density played the more important role on improving the impact resistance of the sandwich plates at same areal mass. The effect of sequence of core layers on the impact resistance can be neglected in this study. Additionally, the energy absorption analysis of the six different configurations exhibited that the plates with high density core provided more stable and superior energy absorption efficiency. The study could provide a valuable reference for designing more efficient light weight protective structures. [ABSTRACT FROM AUTHOR]

• Blast resistance of fluid-filled corrugated sandwich beams was investigated experimentally and numerically. • Fluid filling could effectively reduce mid-span deflection of the face sheet and enhance the plastic buckling/progressive folding resistance of the corrugated core. • A combined SPH-FE model of fluid-filled sandwich beams was established to characterize the overall structural response of fluid-filled sandwich beams. • Dependence of permanent mid-span deflection upon fluid filling and sealing material was quantified numerically. The effect of fluid filling on the dynamic response of corrugated sandwich beams under simulated blast loading with close-celled metallic foam projectile was systematically investigated. Deformation and failure modes as well as displacement/contact force/energy absorption histories of water-filled sandwich beams were obtained at different impact levels and compared with those of empty sandwich beams. Subsequently, a combined smoothed particle hydrodynamics-finite element (SPH-FE) model was employed to simulate the dynamic responses of water-filled sandwich beams, explore the underlying mechanisms, and assess the influence of fluid-filling and sealing material on permanent beam deflection. Good agreement was achieved between numerical simulations and experimental measurements. Under impact loading, the filled liquid provides strong interaction between fluid and sandwich components owing to its inertia and incompressibility. Fluid-filling led to not only significantly reduced permanent deflection of both face sheets but also considerably enhanced resistance of the corrugated core against plastic buckling and progressive folding [ABSTRACT FROM AUTHOR]

• Tests of 18 HSCFST members subjected to transverse impact loadings were conducted. • Impact force, deformation and energy absorption of HSCFST were investigated. • Influence of material strengths on the impact resistance was discussed in detail. • A FE model was developed, performing good prediction for impact responses of HSCFST. High strength materials and dynamic loadings are two important research topics for building structures. In this study, high-strength concrete filled square steel tube columns (HSCFST) using S690 along with Q355 structural steel subjected to transverse impact loadings were experimentally tested by a drop hammer tester, and the impact force, deformation, and energy absorption of such specimens were obtained. Results showed that HSCFST has great impact resistance, showing high impact force plateau value and small deflection. The influence of steel strength, concrete strength, steel ratio, and impact energy on impact resistance was deeply analyzed. Compared with normal-strength materials, using high strength steel can improve its impact resistance but the contribution is not as great as the increment of yield stress, whilst using the high-strength concrete has limited effect. Besides, a refined finite element (FE) method by ABAQUS/Explicit employing the rate-dependent constitutive model for S690 was adopted to simulate the dynamic responses of HSCFST under impact loadings, performing a good agreement with tests. This study provides the basic experimental data of HSCFST subjected to transverse impact and develops a reasonable FE model to predict its impact resistant performance, contributing to the related studies of HSCFST components. [ABSTRACT FROM AUTHOR]

• Impact resistance of polyurea-steel composite plates to low velocity impact is researched experimentally and numerically. • A numerical simulation method for the simulation of the impact processes is introduced. • The mechanisms of the polyurea layers on the improvements of impact resistance of the composite plates are investigated and presented. • The relationships of the thicknesses of polyurea layers and the impact resistances of the composite plates are presented and discussed. • A parameter was introduced to characterize the energy absorption efficiency of the composite plates. Experimental and numerical studies on the response of polyurea coated steel plates to low velocity impact of a cylindrical hammer are presented in this paper. Low carbon steel plates were made and coated with polyurea layers to enhance their impact resistances. The polyurea-steel composite plates were constrained by a test rig and impacted by a blunt cylinder hammer using a drop weight machine. Numerical simulations of the impact processes were performed using the finite element code LS-DYNA. The numerical simulation method was validated by comparing its results with the experiments'. The experimental results showed that the polyurea coatings can effectively improve the ultimate energy absorption capacity of the steel plates. The decreasing order of the ultimate energy absorption capacity of the composite plates when coated with same thickness of polyurea layers was: the upper-side-coated plates, the double-side coated plates and the lower-side-coated plates. In order to quantify the energy absorption efficiency of the composite plates, a parameter E d was proposed, and it was found that the composite plate coated with 4 mm polyurea on its upper side had the greatest value of E d among all the plates. [ABSTRACT FROM AUTHOR]