The corrugated steel plate (CSP) exhibits significant mechanical advantages over their flat counterpart, particularly in terms of the increased bending stiffness, improved load-bearing capacity, and enhanced buckling resistance. In this study, low-velocity impact tests were carried out on seven sinusoidal CSPs by a drop weight testing system, and a novel confinement device was developed to achieve fixed boundaries at both ends of the CSP. The design parameters which exhibited significant effects on out-of-plane impact responses of CSPs were considered, including impact velocity, steel plate thickness, and hammer shape. Increasing the thickness from 2.86 mm to 4.71 mm significantly improved the impact resistance of the CSP, leading to a 45.51% reduction in maximum displacement. Under low-velocity impact, although the impact velocity obviously influenced the CSP's deformation, causing a 40.78% increase in maximum displacement as the velocity rose from 5.26 m/s to 7.13 m/s, the impact force plateau remained nearly unchanged until evident membrane effect occurred. Additionally, the CSPs exhibited similar impact processes subjected to different hammer shapes, with the difference in impact force plateau less than 6%. Numerical studies on impact responses of the CSPs were conducted via the LS-DYNA program, and the internal force distributions, internal energy and stress contours of the CSPs, derived from finite element (FE) predictions, were discussed. The FE results revealed that the impact resistance of the CSP was primarily governed by the central three corrugations, whereas the central single corrugation under direct hammer impact absorbed most of the impact energy.

Buried structures exhibited favorable protective capacity subjected to airburst and surface explosion, but were threatened by the subsurface detonations from earth-penetration weapons. Different from the former, buried explosion could couple significant amounts of energy to the surrounding soil, leading to strong ground shocks and thus strong loads transmitted to the buried structure. In the current study, to protect a buried RC box structure subjected to ground shock, a novel buried hollow concrete cell array was proposed and applied near the sidewalls of the structure. This protection approach took advantage of reducing explosion energy coupling to mitigate the transmitted ground shock and reduce the response of the structures. With the numerical model verified with test data and design provisions, the mitigation effect of ground shock by the hollow cell array and its protection effect on buried RC box structures were investigated. It was found that the proposed approach exhibited favorable protection effects within the concerned distance for structural protection in terms of dynamic response. The ground shock peak pressure was reduced by approximately 64.1% at the scaled distance of 0.6m/kg1/3, while the corresponding sidewall center deflection and support rotation of the sidewall were remarkably reduced by 87.3%. Subsequently, major governing parameters on the protection effect were discussed, including the hollow component thickness, the concrete strength, the hollow cross-section configuration, the horizontal explosion location, the explosion burial depth, as well as the explosion equivalent. Increasing hollow component thickness or concrete strength would increase the damage of the buried structure. While the protection effect of the array was influenced by the detonation location and explosion equivalent, the protection effect of the array was generally favorable. Furthermore, some design recommendations for the array were provided to facilitate the application in engineering practice.

Advanced constitutive models have greatly improved the characterization of thermomechanical behaviors of materials affected by dynamic strain aging (DSA). However, the inherent complexity of these mechanical responses usually poses significant challenges for the numerical implementation of these models. Thus, within a small-strain elastoplastic framework, this study developed a novel hybrid explicit-implicit integration algorithm (HEI-IA) to enhance the accuracy and reliability of stress updating for the constitutive models considering DSA. This algorithm follows the traditional return mapping framework but employs a hybrid strategy in the plastic correction phase. Specifically, it first attempts an implicit solution. If convergence difficulties arise due to DSA-induced anomalous material responses, it automatically switches to an explicit scheme to ensure calculation continuity. The performance of the proposed algorithm was compared with that of the conventional implicit and explicit algorithms by conducting three numerical tests, including single element tests, split Hopkinson pressure bar loading simulations, and steel tube impact tests. The results demonstrated that the proposed HEI-IA achieved good robustness and accuracy across all numerical tests, effectively resolving the convergence issues of implicit methods and the accuracy limitations of explicit methods. In addition, the computational efficiency and time step sensitivity of HEI-IA were also discussed.

This study investigated the lateral impact behaviour of partially encased steel-concrete composite (PEC) members through finite element (FE) simulation and analytical modelling. A detailed FE model was developed and validated against available experimental data. The mean predicted-to-tested ratios of the peak impact force, mean impact force and maximum mid-span displacement were 1.01, 1.01 and 0.99, respectively, indicating accuracy of the FE model. Based on the validated FE model, the dynamic response characteristics, energy dissipation and internal force evolution of PEC members were analysed. Parametric studies were conducted to obtain the effects of axial force, flange thickness, web thickness and flange-to-web area ratio. The results showed that the presence of axial force increased the initial peak impact force but reduced the impact resistance owing to the second-order effect. Increasing the flange and web thicknesses improved impact resistance and reduced maximum displacement, whereas the flange-to-web area ratio had a non-monotonic influence owing to the competing effects of bending and shear resistance. Moreover, a two-degrees-of-freedom model considering second-order and strain-rate effects was proposed. The analytical predictions showed well agreement with FE results.

Aluminum alloy circular tubular members in building structures may be subjected to accidental lateral impacts during service, experiencing coupled effects of axial static loading and lateral impact during the damage process. This study presents an experimental and numerical investigation into the dynamic behavior of 6082-T6 aluminum alloy circular tubes and aluminum foam-filled composite tubes under combined static axial loading and lateral impact. A test setup incorporating a self-compensating axial force device was developed to maintain stable axial loading during impact events. Twenty-one specimens were tested under varying axial compression ratios (mu ranging from-0.6 to +0.6) and impact energies (625-5625 J), revealing three distinct failure modes: local dent deformation with overall bending, three-hinge plastic deformation, and cracking near the end. Results demonstrate that axial tension enhances impact resistance, increasing peak impact force and reducing maximum displacement, whereas axial compression exhibits the opposite effect. An implicit-explicit approach (using ANSYS/Implicit and ANSYS/LS-DYNA) was employed and verified against the test data to accurately capture the dynamic responses of both empty tubes and aluminum foam-filled tubes. Parametric studies were also conducted to investigate the influence of filling aluminum foam into empty tubes under various loading conditions. A dimensionless empirical formula was derived to predict the maximum displacements of the tubes subjected to lateral impact (without axial force and under axial compression with mu =-0.4). The findings provide guidelines for the design of aluminum foam-filled composite tubes under combined axial static loading and lateral impact.

The impact resistant performance of a novel steel-concrete-steel (SCS) panel with energy absorber (SPEA) was investigated by performing impact tests, from which two types of failure modes were categorized based on the crushing magnitudes of energy absorber. The sandwich panel subjected to impact load exhibits both global and local deformation. During the crushing process of energy absorber, the rotation of plastic hinges of steel plate and the compression of aluminum foam blocks were observed. Additionally, the influences of steel plate thickness of energy absorber and impact momentum on the dynamic responses of SPEA were investigated. The results indicated that there was an optimum steel plate thickness of energy absorber resulting in improved impact resistance of SPEA. The SPEA exhibited better impact resistant performance under higher impact momentum. Based on the experimentally obtained dynamic response characteristics of SPEA, an equivalent 3DOF model was developed to predict the impact responses of SPEA, and the accuracy of the model was validated via comparing the predictions with impact test results.

Owing to its relatively high thermal stability compared with other fibers, basalt fiber could sustain an effective bridging effect at elevated temperatures, showing great potential for enhancing the elevated temperature performance of grouting material. To this end, the influence of basalt fiber length and volume fraction on the thermal performance of grouting material was further explored by experimental investigation and numerical simulation. Firstly, specimens of basalt fiber-reinforced grouting material (BFRGM) with different fiber lengths and volume fractions were prepared for the elevated temperature test. The test results demonstrated that specimens incorporating basalt fibers exhibited superior thermal resistance, as evidenced by a slower central temperature rise compared to the specimen without fiber. Subsequently, based on a validated numerical model, the specific heat and thermal conductivity of BFRGM were identified with a genetic algorithm by minimizing the difference between measured and computed central temperature rise curves of the specimens. The identified results demonstrated that the specific heat of BFRGM exhibited five distinct temperature-dependent stages, while its thermal conductivity gradually decreased as temperature increased. Compared with the fiber-free specimen, BFRGM containing basalt fibers with a length of 9 mm and a volume fraction of 0.5 % exhibited a 5.22-7.73 % reduction in thermal conductivity as the temperature rose from ambient to 800 degrees C. Based on experimental and numerical results, a piecewise temperature-dependent formula was proposed to predict the specific heat of BFRGM, while a modified Maxwell model, accounting for fiber length and volume fraction, was developed by introducing an interfacial resistance coefficient and a fiber correction factor, enabling more accurate prediction of its thermal conductivity. These findings contributed to a more accurate prediction of the thermal behavior of BFRGM, providing a reliable basis for investigating the post-high-temperature mechanical properties of BFRGM and BFRGM-filled grouted sleeves, thereby facilitating its broader application in grouted sleeve connections.

This study employed experimental and theoretical approaches to examine the lateral impact response of axially loaded concrete-filled double-skin steel tubular (CFDST) members with local corrosion. Experimental tests were carried out to systematically investigate the influences of the corrosion area, corrosion depth ratio, and axial compression ratio on the failure mechanisms and impact response of the corroded CFDST members. The results indicated that more severe corrosion would significantly weaken the structural impact resistance, characterized by decreased impact force and increased displacements. A higher axial compression ratio was also found to reduce the impact resistance of the corroded CFDST member. A global bending deformation was observed for the corroded CFDST member, together with the presence of slight local indentation. Furthermore, a theoretical model based on a two-degree-of-freedom (TDOF) system was developed to calculate the time histories of impact force and displacement for the corroded CFDST members. The predicted results showed good agreement with the experimental data, verifying the accuracy and reliability of the proposed model for assessing the impact responses of corroded CFDST members.

Auxetic structures have attracted increasing attention as energy absorbers owing to their unique deformation mechanisms, and foam filling provides an effective strategy to further enhance their energy absorption performance. However, most existing studies have focused on foam-filled 2D auxetic structures, leaving the performance enhancement of foam filling in 3D auxetic structures rarely explored. To address this limitation, this study proposed a novel foam-filled auxetic metamaterial (FFAM) by filling the polyurethane foam into an origami-inspired 3D auxetic metamaterial. Quasi-static compression tests and numerical simulations were carried out to investigate the mechanical behaviour of the FFAM along three orthogonal directions. The results demonstrated that the FFAM exhibited a 3D negative Poisson’s ratio (NPR) effect in all compression directions. The energy absorption of FFAM was significantly higher than the sum of those from individual foam and empty auxetic metamaterial due to the interaction effect between auxetic frame and foam filler. Compared with the empty auxetic metamaterial, the FFAM achieved much higher specific energy absorption (SEA), with improvements of 29.16%, 52.75%, and 44.74% under compression along the x-, y-, and z-directions, respectively. The parametric study revealed that increasing folding angle weakened the in-plane energy absorption performance but improved it in the out-of-plane direction. The foam filled in the 3D auxetic metamaterial generally demonstrated superior SEA than that filled in the re-entrant double-arrow honeycomb with a 2D NPR effect, due to the enhanced auxetic behaviour. Additionally, increasing wall thickness improved the energy absorption performance of the FFAM.

The impact responses of circular steel tubes at elevated temperatures were experimentally and numerically explored in this paper. A drop weight impact loading system was employed to apply the impact forces to the specimens after they were heated to the target temperature by employing an assembled furnace. All specimens presented a failure mode of three plastic hinges. The impact resistance of specimens exhibited an initial decrease, later increase and eventual decrease as the temperature increased. This phenomenon was caused by the negative temperature sensitivity of steel strength (i.e., strength increases with temperature) induced by dynamic strain aging (DSA). Moreover, the impact force and displacement of specimens significantly increased with impact velocity. Corresponding finite element (FE) models were established and verified with experimental results. The model was employed to investigate the bending moment distribution and energy absorption of the steel tubes subjected to impact at elevated temperatures. The FE results showed that steel tubes first experienced a bending-dominated phase, followed by a tensile-dominated phase during impact. In addition, the majority of impact energy was absorbed by the steel tubes at the plastic hinge zones when the temperature was less than 400 ℃. However, the energy dissipation became more uniform across the specimen at higher temperatures, especially at 700 ℃. These findings firstly provided the comprehensive demonstration of the influence of the temperature on impact responses of steel tubes, particularly clarifying the anomalous behavior characteristics caused by DSA effect.

A novel impact-resistant panel comprising dual steel-concrete-steel panels and infilled gradient aluminum foam (named as DSCS-GAF panel) was firstly proposed. The impact behavior of DSCS-GAF panel was studied by conducting drop hammer impact tests. The failure mode of DSCS-GAF panel showed global bending and local indentation, while distinct punching shear failure was observed for the impact-resistant panel with absence of upper SCS panel. The influences of thickness ratio of concrete in upper layer to lower layer on the impact responses of DSCS-GAF panel were investigated. The Finite Element (FE) models of DSCS-GAF panel under impact loading were established and validated against the test results. The numerical simulation results showed that the gradient aluminum foam panels and upper SCS panel in DSCS-GAF panel absorbed the majority of the impact energy. Furthermore, the parametric analysis was conducted based on the validated FE model to investigate variables including the thickness of steel faceplate and gradient aluminum foam panels.

Steel-lightweight aggregate concrete-steel (SLCS) panels have potential applications in protecting critical infrastructure against impacts from unmanned aerial vehicles, aircraft engines, and other large-mass debris. Therefore, in the present study, gas gun tests and numerical analyses were conducted to investigate their projectile impact resistance. The deformation development, damage characteristics, and energy dissipation of the panel during and after the impact were examined. Furthermore, the influence of important factors such as impact velocity, stud spacing, concrete core thickness, faceplate thickness, rear plate thickness, and number of impacts on the panel response was then discussed in detail. The results showed that the response of the SLCS panel was governed by the coupling of faceplate indentation or penetration, punching damage of the concrete core, and rear plate deformation. With increasing impact energy, the response mode transformed from relatively localized damage to pronounced local penetration and eventually perforation failure. An appropriate reduction in stud spacing enhanced the composite panel resistance and the overall energy dissipation capacity. However, an excessively small stud spacing intensified response localization and reduced the impact resistance. Moreover, for the same mass increment, increasing the rear plate thickness led to the greatest improvement in impact resistance. In addition, repeated impacts enlarged the response region and made the cumulative damage effect more evident, whereas a single impact was more likely to produce deeper local penetration. Comparisons under equal total kinetic energy and equal cumulative incident momentum showed that kinetic energy primarily governed damage and deformation. This study provided a reference for the impact-resistant design of the SLCS panels.

Ceramic–fiber composite armor systems are widely employed to resist high-velocity projectiles. However, analytical models that can accurately capture the complex interaction mechanisms between the projectile, ceramic fragmentation, and the laminate backing remain scarce. This study develops a mechanism-based analytical model to characterize the penetration of high-velocity projectiles into ceramic–fiber composite armor. The model is established based on damage morphologies observed in ballistic experiments and interaction mechanisms revealed by finite element (FE) simulations. The penetration process incorporates stress wave propagation in the ceramic, progressive projectile erosion, and membrane-dominated deformation of the fiber backing, enabling the prediction of the ballistic limit (V50) and projectile mass loss during penetration. The predictions show good agreement with experimental and numerical results, with deviations in V50 remaining below 3.6% for different projectile types and ceramic materials. Furthermore, parametric analyses indicate that increasing projectile aspect ratio enhances penetration efficiency by reducing resistance and erosion, whereas increasing projectile radius significantly lowers V50 while increasing the required penetration energy due to higher initial mass. Finally, the model is applied to armor design for NIJ RF3 compliance. A ballistic limit map is established as a function of ceramic and UHMWPE thickness, from which a configuration with 12 mm ceramic and 9 mm UHMWPE is identified as optimal, achieving minimum structural thickness with relatively low areal density. This analytical model provides a practical and efficient tool for the design and optimization of lightweight ceramic–fiber composite armor systems.

Reinforced concrete (RC) slabs are highly susceptible to severe failure modes such as spalling and penetration when subjected to blast loading, which significantly compromises structural integrity and safety. As most existing building structures are constructed with RC, enhancing the blast resistance of important ones is a crucial issue in structural protection. Engineered cementitious composites (ECC), characterized by high tensile strength, strain-hardening behavior, and excellent ductility, have demonstrated substantial potential for improving blast mitigation performance. In the present study, both experimental testing and numerical simulations were conducted to investigate the response and damage of ECC panels with varying thicknesses subjected to projectile impact of different velocities. Numerical models were developed which enable high-fidelity analyses of the influence of major governing parameters such as velocity, mass, and projectile shape on the damage response of the ECC plates. Furthermore, a prediction formula for penetration depth under different impact conditions was proposed. The findings provide references for the application of ECC in protective structures and facilitate the design of blast-resistant structures with ECC in engineering practice.

Metallic tubular components in weapon and protective systems are often subjected to extreme internal explosions and fragment impacts, resulting in severe plastic deformation and structural failure. Previous studies have mainly examined pure metallic or glass fiber-reinforced metal tubes under internal shock-wave loading, with limited attention to fiber-metal hybrid structures. This study investigates the dynamic response and failure mechanisms of carbon fiber-reinforced stainless steel tubes (CFR-SST) under internal combined loading of explosion shock wave and fragments through controlled experiments and validated finite element simulations. Explosion experiments with and without fragment loading evaluated the circumferential expansion rate (CER) and fragment residual velocity (FRV). The finite element model, calibrated against experimental data, was employed to analyze the influence of fiber winding angle and layer number. Based on the simulation results, a multi-angle hybrid winding strategy was developed. Dynamic experiments show that aligning the fiber orientation with the load direction markedly enhances blast mitigation performance. The 90 degrees winding structure, in which the fibers align with the radial stress direction, reduces CER by 39.2 % and FRV by 54.6 % compared to pure metal tubes. Furthermore, a multi-angle hybrid strategy was proposed in which 90 degrees layers (>= 50 %) provided the main stiffness, +70 degrees layers reduced shear slip, and +45 degrees layers improved toughness and energy absorption. The optimized laminate design achieved a 15.3 % lower CER than the uniform 90 degrees winding structure. This study provides quantitative guidance for the structural design and optimization of CFR-SSTs under various explosive conditions.

The lateral impact responses of partially-encased composite (PEC) members were investigated via both experimental and analytical approaches. The impact experiments were conducted on PEC members to obtain their deformation process, failure mode, impact force-time and displacement-time responses. The effects of the initial velocity, clear span, impact direction and types of transverse reinforcements (i.e., links and stirrup) on impact responses of PEC members were experimentally investigated. The results indicated that the higher impact velocity would result in higher impact force, larger specimen deformation and energy dissipation. The PEC member with larger span exhibited smaller impact resistance, inducing larger specimen deformation. The impact direction had significant influence on the impact response of PEC members due to the differences in bending resistance. While the types of the transverse reinforcements employed in this study had negligible effect on the impact behaviours. Moreover, a two degrees-of-freedom (2-DOFs) model was developed to calculate the responses of the PEC members under the lateral impact. The developed 2-DOFs model demonstrated its applicability by accurately predicting the test results.

In this study, the crashworthiness performance of triangular Kirigami (TK) structures with various geometric configurations is systematically investigated. Quasi-static crushing experiments are first conducted to provide reference data for the calibration and validation of the numerical models. Subsequently, extensive finite element (FE) models are developed in LS-DYNA to examine the influence of geometric parameters on the crashworthiness behavior of the proposed structures. Three key geometric parameters, namely the inclined sidewall length, model height, and model length, are used to describe the structural configurations, and their effects are evaluated in terms of energy absorption and specific energy absorption. The results indicate that the sidewall inclination angle, jointly controlled by the inclined sidewall length a and the model height h, plays a critical role in governing crashworthiness performance, and an optimal range of 40 degrees to 60 degrees is recommended. In addition, the model length must be carefully selected, as inappropriate values may lead to inefficient energy absorption and an undesirably high initial peak crushing force.

In this study, the dynamic behaviour of the partially-encased composite (PEC) structural member under soft-impact loading was experimentally, numerically and analytically investigated. Drop-weight impact tests were conducted to obtain the impact force and deformation responses of PEC members. In the test, the steel tube served as the deformable impactor to apply the soft-impact loading at the mid-span of the specimen. Six identical specimens were tested, and the varying parameters comprised the impact velocity, impactor stiffness, and impact direction. A consistent flexural failure mode was observed across all tested specimens. The finite element (FE) model was developed to further investigate the energy dissipation responses of both the deformable impactor and the specimen. The reasonableness of the established FE model was confirmed by comparing the failure modes, impact force histories, and displacement responses obtained from experimental and numerical results. Furthermore, an analytical model was developed based on the two degree-of-freedom (TDOF) spring-mass system, aiming to predict the impact force and displacement histories of the PEC member under soft-impact loading. The accuracy of the TDOF model was verified through the comparison with experimental data.

In this study, three triangular Kirigami-inspired corrugated designs (TKD1, TKD2, and TKD3) are proposed as energy-absorbing cores for sandwich structures. Kirigami-inspired modifications were introduced into conventional triangular corrugated sheets to enable controlled deformation and enhance its energy absorption capacity. Quasi-static crushing tests were conducted to characterise the deformation and energy-absorption behaviour of the proposed designs and to validate the finite element (FE) models developed in LS-DYNA. The validated models were subsequently employed to investigate the crushing performance of the structures over a range of relative densities and crushing velocities, encompassing both quasi-static and dynamic loading conditions. The crashworthiness of the proposed configurations was evaluated in terms of peak and average crushing forces, crushing force efficiency, energy absorption, and specific energy absorption, and the results were benchmarked against conventional cellular cores reported in the literature. The triangular Kirigami designs exhibited stable, progressive crushing behaviour, characterised by the absence of a pronounced initial force spike and a well-developed plateau region up to densification. Increasing the relative density of the models enhanced the energy absorption capability of all configurations, while dynamic analyses revealed an evident influence of crushing velocity on both the initial peak force and the overall energy absorption response. Among the proposed designs, TKD2 configuration demonstrated a particularly favourable balance between energy absorption capacity and crushing force efficiency across a wide range of loading rates. The results demonstrated the potential of triangular Kirigami corrugated core designs as lightweight, high-performance energy absorbers for applications involving impact and dynamic loading.

The Dynamic response of two cavities, an elliptical inclusion and a linear crack near anisotropic bi-material interface, was explored analytically by incident out-plane waves in the current work. Firstly, the media is divided into two half spaces (an elastic anisotropic half space with a circular cavity and a linear crack, and an elastic isotropic half space containing an elliptical cavity and an elliptical inclusion). With the help of the image principle, the complex function method is then used to derive the wave fields in each half space. Combined with Green’s functions approach, the relevant Green’s functions developed in the “crack creation” and “conjunction of two half spaces” procedures are derived sequentially. Subsequently, based on the “conjunction” technique, undetermined anti-plane forces are applied to the horizontal surfaces of two half spaces to maintain the continuity criteria of the interface. A series of Fredholm integral equations isobtained and then solved by utilizing the direct discrete technique. Dynamic stress concentration of two elliptical cavities and an elliptical inclusion is mainly considered graphically to discuss the interaction between two half spaces. Finally, a parametric study on the dynamic stress concentration factor (DSCF) was given to show the influence of different parameters on the interaction.