This paper proposes a double-layer foam-filled double-arrow negative Poisson’s ratio core sandwich (FDNPS) beam that combines the high static load-bearing capacity of corrugated panels with the energy-absorption capabilities of metal foam. In this paper, the yield criterion for the double-layer FDNPS beam’s cross-section is proposed, and an analytical model for the plastic behaviour of the clamped double-layer FDNPS beam is developed. Furthermore, the bending characteristics of the sandwich beam are investigated by finite element analysis, and the numerical results agree well with the theoretical results. Additionally, it is used to analyze the impact of geometric parameters on the bending behaviour of the double-layer FDNPS beams with constant-thickness layers. The results show that as the thickness of the folded-plate and the angle θ of the folded-plate increase, the beam bears more load and absorbs more energy. In comparison, the effect of the folded-plate angle φ is the opposite, with an increase in φ resulting in a decrease in both the bearing-load and energy absorption. The theoretical model proposed can effectively describe the static-plastic behaviour of clamped double-layer FDNPS beam.
Composite plate shear walls (CPSWs) are increasingly employed in protective structures due to their high strength, stiffness, and energy absorption capacity under extreme loading conditions. While the blast resistance of CPSWs and the seismic performance of systems equipped with Replaceable Corner Tension–Compression Dampers (RCTCDs) have been investigated separately, the blast behavior of CPSWs incorporating such replaceable devices remains largely unexplored. Understanding the interaction between impulsive blast loads and replaceable corner devices is essential for the development of multi-hazard-resistant structural systems. This study numerically investigates the blast response of composite plate shear walls equipped with RCTCDs using a three-dimensional finite element model developed in LS-DYNA. Twelve full-scale wall configurations were analyzed considering three blast intensities, two blast orientations (normal and in-plane), and structural systems with and without damping devices. The numerical framework incorporates strain-rate-sensitive material models and was verified using available experimental and numerical blast benchmarks. Key response parameters including peak displacement, Von Mises stress, effective plastic strain, and damage distribution were evaluated during the impulsive phase of blast loading. The results indicate that the presence of RCTCDs significantly modifies blast-induced load-transfer mechanisms and damage localization characteristics. Under normal blast loading, the damped walls exhibited reduced peak displacements and more uniform stress distributions compared with conventional configurations. Under in-plane blast loading, the devices altered force-transfer paths and promoted a broader spatial distribution of damage within the wall system. The analyses further revealed a pronounced directional dependency, demonstrating that the effectiveness of the corner devices is strongly influenced by blast orientation. Overall, the findings provide new insight into the interaction between replaceable corner devices and blast-loaded composite wall systems and contribute to the development of future multi-hazard-resistant protective structures.
Natural gas explosions in civil buildings can impose transient overpressure on brick masonry walls and may trigger wall failure, fragment generation, and even progressive structural damage. This study characterises the dynamic response and failure mechanisms of brick masonry walls subjected to natural gas explosion loading. Static mechanical tests were conducted on ordinary fired clay bricks and mortar to obtain the material parameters. Dynamic impact tests were subsequently performed on masonry components constructed using standard procedures. A finite element model with calibrated material parameters was established in LS-DYNA, and its dynamic response and damage modes were validated against the impact test results to assess the accuracy of the predicted response of the brick masonry components. The validated finite element model was then used to simulate wall response under a triangular pressure–time history representing natural gas explosion loading. The parametric analysis focused on the effects of peak overpressure and edge restraints on mid-span displacement, velocity response, and failure-mode evolution. The findings support blast protection, boundary-detailing optimisation, local strengthening, and post-blast damage assessment of masonry structures under natural gas explosion loading.
Analytical modeling and numerical simulations are employed in this study to examine the plastic behavior of fully clamped foam-filled hexagonal core sandwich beams (FHCSBs) under transverse loading. A yield criterion is developed for the FHCSB cross-section by considering the combined strength contributions of the folded plates and the metallic foam filler. By coupling this criterion with the associated flow rule, an analytical model is developed to predict the large-deflection behavior of FHCSB, specifically accounting for the interaction between bending and axial stretching. To verify the theoretical framework, numerical calculations using Abaqus/Explicit software are performed. The results show that the analytical predictions for post-yield response match the numerical results for both mid-span and offset loading cases. Additionally, a parametric study investigates how face-sheet thickness, foam strength, and cell inclination angle influence the structural performance. The analysis indicates that face-sheet thickness is the primary factor determining the membrane hardening rate, whereas the hexagonal core configuration offers a stable cushioning effect during early-stage deformation. This analytical approach provides an effective tool for assessing the load-carrying capacity and energy absorption of FHCSB structures.
This paper analytically and numerically investigates the plastic behavior of double-layer sandwich beams with foam-filled X-shaped cores (DSBFXs). Accounting for the strength of X-shaped core and metal foam, a yield criterion of double-layer sandwich structure with foam-filled X-shaped cores is established. Analytical solution for large deflection of DSBFXs under lateral loading is developed according to the yield criterion. Finite element analysis is conducted. The analytical results match the finite element results well. In additions, the effects of foam strength, face-sheet thickness and inclination angle of the folded plates on plastic behavior of DSBFXs are discussed. The findings indicate that both load-bearing and energy absorption capacities of DSBFXs significantly increase with the increase of the foam strength, face-sheet thickness and inclination angle of the folded plates, the increment decreases as the foam strength and inclination angle of the folded plates increase. The presented analytical model can be employed to predict the large deflection of the DSBFX.
This paper investigates the interaction between closed-cell polyethylene (PE) foam and a brass front plate under shock wave loading. Through experimental testing and kinematic analysis, we demonstrate that the brass plate functions as a momentum-redistribution mechanism rather than a simple energy absorber. Comparative results under a 2.3 Mach incident shock wave indicate that the composite configuration significantly extends the momentum transfer duration, effectively transforming shock-driven compression into inertia-controlled densification. While the composite structure exhibits higher peak reflected pressures (1.54 MPa vs 0.94 MPa) compared to pure foam, it achieves superior protection by fundamentally modifying the temporal characteristics of force transmission. These findings provide a mechanistic basis for designing advanced momentum-buffering protective materials, shifting the focus from mere energy dissipation to the temporal control of impulsive loads.
Composite systems based on natural fibers have attracted renewed attention in the search for lightweight, sustainable, high-performance ballistic armor. This review presents a comprehensive, hierarchically classified overview of critical performance parameters associated with the use of natural fibers for ballistic applications, focusing on fiber systems and hybridization strategies, failure mechanisms, and energy-absorption characteristics. Special focus is given to natural–natural hybrid composites, as well as to the correlations among fiber structure, interfacial properties, and mechanical performance, including ballistic behavior. Through a structured literature review of relevant data within a verified benchmarking framework for structure–property–performance relationships, the review characterizes the dominant design drivers of energy dissipation, penetration resistance, and back-face signature reduction in multilayer armor systems. The work also illustrates that new interfacial engineering and machine learning methods can facilitate the design of advanced protective materials. In general, these results demonstrate that natural-natural hybrid composites lay the scientific foundation for lightweight, sustainable, and high-performance armor systems, as well as a platform for optimizing these materials.
Contact blast loading of crystalline rocks can produce a rapid transition from localized cratering to macroscopic splitting and back-face spalling. This study experimentally characterizes this transition in natural marble by combining quasi-static mechanical characterization, replicated field contact C-4 blast tests, free-field overpressure measurements, and backface peak particle acceleration measurements. The tested marble showed apparent static isotropy under low-rate loading, with a mean uniaxial compressive strength of 93.2 MPa, elastic modulus of 42.1 GPa, Poisson’s ratio of 0.30, indirect tensile strength of 7.7 MPa, and directional strength variation not exceeding 10.1%. Under contact blast loading, however, the observed failure mode changed from stable local cratering at 50 g to scattered transition behavior at 60 g and consistent macro-rupture at 70 g. The back-face peak particle acceleration increased from 2435.5 g at 50 g to 10,028.1 g at 60 g, indicating activation of tensile reflection and spalling. Comparison with TM5-855-1 showed that crater dimensions were overpredicted for the tested marble blocks; however, the resulting correction ranges are presented only as preliminary, material-specific estimates for the tested geometry and charge configuration. The results provide an experimental benchmark and a cautious mechanics-based interpretation for contact blast-induced failure in bounded crystalline rock blocks.
Graphene, a two-dimensional nanomaterial has emerged as a potential material in the development of the new state of the art ballistic and impact resistant material due to its high tensile strength, Young’s modulus and energy dissipation capacity. This literature review critically summarizes the past 20 years in graphene-based nanocomposites customised to protective applications, which connects basic relations between structure and properties and multi-scale performance in high strain-rate environments. The specific focus is also put on interfacial toughening systems, processing, functionalization, and dispersion control, which determine improved stiffness, toughness, and impact energy absorption at ultra-low loadings (less than 1 wt.%). The review also draws a comparative insight against the standard Kevlar, UHMWPE, and carbon-fiber systems with an emphasis on the effects of graphene in minimising back-face signature (BFS), and depth of penetration (DoP). The review also combines both experimental findings and computational models to demonstrate failure modes, scale-transfer issues and nacre-inspired structures that can use the layered morphology of graphene to provide better crack deflections and energy dissipation. The aspects of environmental durability in extreme temperatures, moisture and salt fog environment and the new multifunctionalities that include EMI shielding and thermal management are also discussed and presented. Nevertheless, despite these promising results, the area has remained limited in the aspects of mass-scale, affordable, manufacture of defect free graphene, effective & uniform dispersion at the industrial scale, and the final performance confirmation in realistic service conditions. Shedding light on the potential opportunities and challenges in scaling the processing, quality assurance, and hybrid structural designs of graphene nanocomposites into next-generation lightweight armour systems in defence, aerospace, and automobile industry, the review offers a broad overview of the critical gaps in knowledge and recommends coherent roadmaps to support the extrapolation of the nanocomposites.
As a class of advanced functional structural materials with intrinsic negative Poisson’s ratio (NPR) characteristics, auxetic chiral structures have been continuously and thoroughly investigated by researchers worldwide, attributed to their superior mechanical properties characterized by the synergy of stiffness and strength, as well as unique anomalous deformation behaviors induced by the inherent auxetic effect. In the present work, a novel chiral lattice structure with circular nodal rings (designated as NCL) is proposed and introduced to improve the energy absorption capacity of auxetic sandwich beams. Systematic numerical simulations are performed using the commercial finite element software Abaqus, to compare the flexural mechanical response and energy dissipation performance of the proposed NCL structure with those of the four-handed chiral honeycomb structure (designated as QCL). Results indicate that the NCL exhibits a 40% higher specific energy absorption (SEA) than the QCL, demonstrating superior anti-bending performance. The deformation behavior of the NCL sandwich beam is affected by crushing position, node circle radius ratio (R/L), and core thickness (t). Loading above the unit (T-position) engages more cells in deformation, enhancing load capacity. Increasing R/L strengthens the negative Poisson’s ratio (NPR) effect and improves energy absorption, peaking at R/L = 0.75. Greater face sheet thickness also improves bending resistance, with a higher back face sheet thickness ( t f /t b < 1) significantly boosting energy dissipation. By means of the complex proportional assessment (COPRAS) method, the core layer thickness (denoted as t) is identified as the most dominant influencing parameter governing the structural mechanical performance, with the optimal comprehensive performance attained at t = 1.2 mm. Furthermore, a significant enhancement in the energy absorption capacity is achieved by allocating a larger thickness to the ligaments than to the nodal ring, which provides a novel and effective optimization strategy for the performance improvement of auxetic sandwich beam structures.
The dynamic behavior of the fully clamped self-similar hierarchical corrugated foam-filled sandwich (SHCFS) beams subjected to a heavy mass with low-velocity impact is investigated using theoretical and numerical methods. An analytical model for the dynamic behavior of the fully clamped SHCFS beams subjected to a heavy mass punch with low-velocity impact is established based on the yield criterion with consideration of the interaction between axial force and bending moment. Numerical studies are performed by finite element analysis. The analytical predictions match the numerical results well. The influences of the foam strength, inclined plate thickness and vertical plate thickness, the panel thickness, and the impact point location on the low-velocity impact (LVI) response of the SHCFS beams are discussed. It is shown that the impact resistance of the SHCFS beams significantly improves with increases in the inclined plate thickness and vertical plate thickness of the SHCPs, the thickness of the face-sheets, and the foam strength. Furthermore, as the impact point is farther from the midspan of the beams, the better the impact resistance performance. The present model can provide effective prediction of the LVI response of the SHCFS beams.
As concerns about structural safety increase in civilian and military domains, understanding the responses of materials and structures to blast loads is essential. This study focuses on the behavior of steel plates under blast loading, emphasizing the significance of experimental testing alongside analytical and numerical methodologies. Utilizing small-scale models allows for the safe simulation of blast conditions, but achieving complete geometric similarity often poses challenges. This paper explores the concept of incomplete geometric similitude, arguing that despite deviations from ideal geometric principles, such models can still capture critical structural responses, including stress distribution and deflection. By reviewing historical and contemporary research on similarity in structural testing, we highlight the practical need for refined scaling laws that acknowledge real-world complexities. We introduce a novel modification to the scaling laws, thus enhancing the predictive accuracy of dynamic responses under blast loads. Through numerical simulations validated against experimental results, our results demonstrate the effectiveness of the proposed method in approximating the deflection ratios of scaled models to their prototypes. This work advocates for the integration of advanced material designs and scaling corrections to improve the reliability of structural performance assessments in extreme loading scenarios, paving the way for safer engineering practices in blast-resistant design.
Topographic features such as hills and valleys significantly affect the propagation of blast waves. This study investigates the mechanisms by which terrain influences blast wave behavior. Blast experiments are performed with various slope angles, and pressure measurements are obtained at multiple locations on rising and falling slopes, with comparisons to flat-terrain pressures. Numerical simulations are also conducted to further examine the effects of rising and falling slopes on blast wave propagation. The results show that blast wave pressure over sloped terrain is dependent on the slope angle, incident angle, and incident wave intensity. Empirical prediction models for blast wave pressure over rising and falling slopes are proposed and validated.
We review Codina and Ambrosini’s articles Full-scale testing of leakage of blast waves inside a partially vented room exposed to external air blast loading (2018), and Numerical and analytical study of overpressures and impulses inside a masonry box subjected to external blast loading (2019) concerning shock ingress into a room from a façade opening. The articles report the results of a full-scale experimental series for shock ingress loading of a room’s interior walls and compare them to predictions from CFD simulations and the widely used UFC 3-340-02 method. They conclude that the UFC overpredicts the impulse on the room interior side walls by up to 685%, while underpredicting the impulse on the back wall by up to 60%. Subsequently, they recommend applying modification factors to the UFC peak pressure and positive phase duration results to better match the experimental results. In this paper, we review the scarce published research on this subject to highlight the significance of the data presented within these two papers. We then critically assess the design, execution, and analysis of the reported experiments and simulations. We present an alternative analysis of their published data which accounts for the use of non-blast gauges and compare it with our own CFD simulations. These CFD simulations closely predict the alternative analysis of the experimental results and offer amendments to the original papers’ conclusions.
High-strength homogeneous metal structures, high-performance fiber composite structures, cellular sandwich panels, especially sandwich panels, exhibit excellent energy absorption matching characteristics by synergistically dissipating shock wave energy through core plastic deformation and panel bending and stretching, and have been widely used in the field of anti-explosion. Sandwich panels are an important way to achieve lightweight and high anti-explosion performance, but the relationship between the anti-explosion performance of sandwich panels and their material properties remains unclear, and there is a lack of research on the material failure mechanisms of sandwich panels. The lack of multi factor collaborative analysis leads to limitations in the conclusions, which restricts the optimization and matching of structure and material properties. The results show that the core characteristics, core combination, the thickness of the core and the front face sheet, the strength and stiffness of the structure, and the interfacial bond performance are the main internal factors affecting the dynamic response and anti-explosion performance of the sandwich panels. And the interfacial bond performance has a great influence on the anti-explosion performance. In the future, it is necessary to deeply explore the mechanism of material mechanical properties and structural failure response in energy absorption, combine innovative design methods, such as gradient design and multi-scale optimization, develop interdisciplinary collaborative optimization technologies, and develop lightweight and high anti-explosion sandwich panels.
This study investigates the dynamic failure mechanisms of underground reinforced concrete (RC) dome bunkers subjected to both surface and subsurface blast loading, addressing a gap in literature regarding 3D monolithic geometries. A high-fidelity numerical model was developed using the Coupled Eulerian-Lagrangian (CEL) method in Abaqus/Explicit, incorporating the Johnson-Holmquist II (JH-2) constitutive model for concrete and the Mohr-Coulomb model for soil. The framework was validated against numerical and experimental data, achieving less than 5% deviation in near-field peak pressures. Parametric investigations assessed the influence of burial depth, charge orientation, and shell thickness. Results reveal a critical “geometric vulnerability” to lateral blast vectors, where horizontal detonations induced 75% more concrete volume loss than equivalent overhead blasts due to the bypass of the dome’s compressive arching action. Furthermore, a counter-intuitive “Stiffness-Damage Paradox” was identified: increasing shell thickness from 0.5 m to 1.25 m exacerbated damage under specific impulsive loads. Analysis of internal energy histories indicates that rigid, thicker shells trap elastic strain energy, leading to brittle comminution, whereas compliant shells facilitate soil-structure interaction and plastic dissipation. These findings suggest that ductility and geometric efficiency, rather than pure mass, govern survivability in underground protective design. However, readers are cautioned that the manifestation of this stiffness-damage paradox is subjected to the specific structural compliance, soil acoustic impedance, and explosive conditions investigated herein, highlighting the critical need for coupled SSI analysis in protective design.
This study presents a probabilistic assessment of the seismic performance of a mid-rise soft-first-story building retrofitted using a hybrid strengthening strategy, addressing the limited integration of hybrid energy dissipation systems within a reliability-based framework for vertically irregular structures. The structure consists of a confined masonry system with a reinforced concrete irregular first story, where buckling-restrained braces (BRBs) are implemented at the ground level and shear-link energy dissipation devices are incorporated at the upper stories. The retrofit aims to mitigate deformation concentration at the soft story while promoting a more uniform distribution of seismic demands along the building height. The proposed methodology is based on bidirectional nonlinear time-history analyses conducted in ETABS v21, using ground motion records associated with return periods of 72, 475, and 975 years. Inter-story drift ratios are treated as random variables to account for record-to-record variability, and probabilistic models are employed to estimate exceedance probabilities and reliability-based performance metrics. The original structure exhibited low reliability levels, with beta values ranging from 1.30 to 2.05 across performance levels, indicating a high probability of unacceptable performance and a pronounced soft-story mechanism. After retrofitting, the structural reliability increased significantly, reaching mean values of 7.76 and 7.65 at the immediate occupancy level, 7.43 and 7.73 at life safety, and 7.42 and 7.32 at collapse prevention for the EW and NS directions, respectively. These values greatly exceed the commonly accepted target of beta = 3.5 and are associated with probabilities of unacceptable performance on the order of 10-14 to 10-15. Overall, the hybrid retrofit strategy effectively eliminates the soft-story mechanism, ensures a stable redistribution of seismic demands, and significantly enhances the reliability and seismic resilience of buildings with vertical irregularities.
Concrete remains the predominant construction material for military and protective infrastructure due to its structural robustness and cost-effectiveness. This study investigates the penetration behaviour of concrete targets subjected to scaled shaped charge detonation, with emphasis on stand-off distance effects. Controlled experiments were conducted using small-scale shaped charges with oxygen-free copper liners. Jet formation and tip velocity were characterised using flash X-ray radiography, incorporating magnification factor corrections for enhanced accuracy. Concrete targets (compressive strength 43.8 +/- 1.87 MPa, n = 3) were tested at stand-off distances of 30-150 cm (11 tests total: n = 3 at 150 cm; n = 2 at each remaining distance), assessing observed perforation occurrence, crater diameter, and surface damage extent. Results indicate that increasing stand-off distance is associated with reduced observed perforation occurrence and generally increased surface damage area and crater diameter within the tested configuration. At shorter stand-off distances, concentrated jet momentum produces deeper penetration; at larger stand-off distances, jet breakup and energy dispersion yield broader but shallower damage zones. This study provides three primary contributions: (i) a reproducible experimental benchmark with fully specified charge geometry, target properties, and measurement procedures; (ii) uncertainty-aware crater and perforation metrics reported as mean +/- standard deviation with explicit sample sizes at each stand-off; and (iii) preliminary experimental evidence of a stand-off-dependent transition trend that can support calibration and validation of high-fidelity hydrocodes. The observed damage pattern is consistent with the hypothesis that, as stand-off distance increases, part of the effective jet energy shifts from axial penetration toward broader surface cracking and spall formation. The results are therefore framed primarily as an experimental benchmark for model calibration and comparative protective assessment rather than as direct full-scale design guidance.
This study investigates the impact response of gyroid lattice structures as liner-absorbing pads for motorcycle helmets. An experimental drop test analysis was conducted on a commercial helmet, utilising its overall dimensions to develop a numerically modelled helmet. The impact performance was then validated, demonstrating good agreement between the experimental and numerical acceleration histories. After, the helmet liner was then segmented into four impact regions (i.e., Impact Liner: Rear, Frontal, Superior, and Lateral) and coupled into a biomechanical head model (THUMS male detached head), where an oblique impact was conducted at 7 m/s, and the helmet responses were evaluated through brain damage levels. A transversely anisotropic crushable foam was used to analyse sensitivity and identify the most influential parameters influencing brain damage levels. This led to a numerical optimisation process that resulted in the development of an idealised helmet liner. Finally, the gyroid lattice structure was integrated into the liner to optimise the thickness for oblique impact conditions in all impact liner regions. The results demonstrated a significant reduction in brain damage across all impact regions, with improvements of 1% to 28% in Lateral and frontal areas, respectively, highlighting the potential of lattice structures to enhance motorcyclist safety. The methodology proposed here can support future developments in the use of lightweight lattice structures as helmet liners.
This study focused on the anti-explosion performance of rapidly assembled modular blast walls under a 117.5 kg TNT explosion. The test recorded diffracted overpressure on the rear side of the wall, revealing a nonlinear spatial distribution of overpressure behind the wall. Under the combined effects of Mach reflection and wave system superposition, a secondary pressure peak occurred at a position 1.0 times the wall height behind the wall. A numerical model validated by experiments was established using LS-DYNA software to quantitatively analyze the influence weights and threshold effects of wall proportional height, proportional distance, and proportional thickness on protective effectiveness. For the first time, this study reveals the unique four-peak diffraction mechanism for this specific configuration, elucidating the local overpressure enhancement law induced by Mach reflection at 1.0 times the wall height behind the wall. By combining cranial injury criteria, the safe area behind the wall was qualitatively divided for this working condition. An empirical formula for predicting overpressure was established, comprehensively considering the coupling effects of TNT equivalent, blast wall geometric parameters, and distance behind the wall. The results show that the maximum overpressure reduction rate of this type of blast wall is 78.2%, and the average near-field protection effectiveness is approximately 1.76 times that of the far field. The research findings can offer valuable references and optimization strategies for protective structures against hundred-kilogram-level explosion impact.
