This study examines the ballistic impact behavior of individual and multilayered polymer targets using both experiments and finite element (FE) simulations. The materials investigated include a Polystyrene-Polyisobutylene-Polystyrene Star Block Copolymer (SIBSTAR), High-Density Polyethylene (HDPE), and A36 steel. Ballistic tests employed 12.7-mm spherical steel projectiles at velocities from 200 to 1700 m/s, enabling evaluation of ballistic limits, energy absorption, and failure mechanisms. High-speed imaging revealed distinct responses. For instance, SIBSTAR displayed a fluid-like large-deformation behavior with full strain recovery, refilling the projectile path without a residual cavity, while HDPE failed in a brittle manner through craze nucleation and plugging. Remarkably, repeated impacts at the same location produced only a minor reduction in energy dissipation for SIBSTAR, underscoring its pseudo self-healing under multiple strikes. Complementary FE simulations were conducted with the Arbitrary Lagrangian–Eulerian 3D (ALE3D) software. High-rate Kolsky bar tests provided data for calibrating a hyperelastic material model of SIBSTAR, which enabled accurate reproduction of the experimentally observed deformation and recovery behaviors. The validated simulations demonstrate that the FE models accurately capture the ballistic and material responses of the polymer targets. The results demonstrate that multilayered target configurations enhance energy dissipation across a wide range of impact velocities. These findings highlight the potential of advanced polymer systems, particularly copolymer architectures such as SIBSTAR, for use in lightweight, reusable, and damage-resistant protective systems.
To address the dynamic response of hollow rods under axial impact, this study establishes a 3-mode model, incorporating axial displacement, overall radial motion of the rod wall, and thickness distortion, by introducing a radial-gradient-independent term into the Mindlin-Herrmann theory. The wave propagation of the hollow rod-lumped mass system under complex boundary conditions is solved using the Laplace transform. By calibrating the shear correction factor κ based on the circumferentially integrated signed radial reaction at the impact end, the proposed model achieves high accuracy in transient response prediction in impact. Through theoretical and numerical analyses, κ depends strongly on the rod wall thickness/outer radius ratio and the Poisson’s ratio. Besides, the radial boundary effects are localized near the impact end, leaving the remaining part weakly affected. The lateral inertia of the hollow rod can be decoupled into overall wall inertia and local thickness distortion inertia, dominating the double-peak characteristics and the dispersion effect of the strain waveform, respectively. Finally, the whole hollow rod-lumped mass system is studied. An increased lumped mass inertia amplifies the post-wave strain and introduces a delayed strain peak.
This study experimentally investigates the low-velocity impact (LVI) behavior of sandwich structures composed of glass fiber reinforced polymer (GFRP) face sheets and three types of Miura-ori-inspired foldcores: V-type, S-type, and M-type. The GFRP face sheets were fabricated using 14 layers of bidirectional E-glass fiber woven fabric (200 gsm), and the foldcore structures were 3D-printed using PLA+ and bonded to the face sheets with epoxy adhesive. The core geometries were developed using the following parameters: fold angle (α), dihedral angle (β), wall thickness (t), side length (L), weight (W), and unit cell distribution, all aimed at maintaining a constant number of folds within a fixed volume of 100 mm × 100 mm × 15 mm. Low-Velocity impact tests were conducted using a guided in-house drop-weight system equipped with a 16 mm-diameter hemispherical indenter, dropped from two heights: 1 m (4.43 m/s, 52.97 J) and 1.5 m (5.42 m/s, 79.46 J). The results demonstrated that the impact response is strongly influenced by both fold topology and loading orientation. Under identical impact conditions, all three foldcore configurations absorbed comparable amounts of energy, ranging from 50.16 to 52.20 J at 52.97 J impact energy and from 73.02 to 78.68 J at 79.46 J impact energy. Oblique impacts generated peak forces approximately 25–70% higher than those of transverse impacts. Residual damage-depth measurements revealed that the V-type consistently exhibited the lowest average damage depths under transverse impacts (15.26 mm at 52.97 J and 16.29 mm at 79.46 J), whereas the M-type exhibited the lowest average damage depth (0.82 mm) under oblique impacts at 79.4 J. Experimental observations further revealed distinct damage-evolution mechanisms involving localized penetration, facesheet-core debonding, core crushing, and cell wall buckling. The results indicate that while all three foldcore topologies have similar energy absorption capabilities, the V-type offered superior impact resistance to through-thickness damage under transverse impacts, whereas the M-type provided a more balanced response under high-energy oblique impact. These findings suggest that Miura-ori-inspired foldcores are potentially suitable for developing lightweight, impact-resistant protective structures.
Accurate characterization of flow stress under very-high strain-rate loading remains challenging owing to the limited accessibility of direct experimental measurements and the large uncertainties associated with conventional extrapolation approaches. This study proposes a Tensor-Decomposition-Based Extrapolation and Dynamic Identification of Flow Stress (TEDI-FS) framework for inverse characterization of flow stress under very-high strain-rate conditions. Within the proposed framework, flow stress is represented by a non-negative rank-2 canonical polyadic (CP) decomposition, enabling structured separation of strain, strain-rate and temperature effects while preserving non-negativity and physical interpretability. Material parameters are first identified within an experimentally accessible domain spanning from quasi-static to split Hopkinson pressure bar (SHPB) strain-rates, avoiding predefined coupling assumptions embedded in conventional flow-stress equations. To extend the flow-stress representation beyond the SHPB-accessible strain-rates, the strain-rate-dependent latent modes are extrapolated under consistency constraints and subsequently identified through coupled Taylor-Hopkinson impact experiments and explicit finite-element simulations. The proposed rank-2 framework demonstrates improved extrapolation robustness and predictive accuracy, achieving good agreement with Taylor-Hopkinson impact responses up to strain-rates of approximately 10⁵ s⁻¹ and outperforming conventional and rank-1 extrapolation-based flow-stress models. The proposed TEDI-FS framework establishes a physically interpretable, mathematically consistent and experimentally constrained methodology for extending flow-stress characterization towards very-high strain-rate regimes.
To address the performance limitations of conventional orbital debris shields under space-constrained conditions, a compact shielding configuration is proposed by directly bonding an aluminosilicate fiber porous ceramic (AFPC) bumper to an aluminum rear wall. The AFPC material model was calibrated using mechanical tests and validated through hypervelocity impact experiments. On this basis, the shielding performance and protection mechanism of the AFPC/Al shield were investigated. The effects of impact velocity, AFPC bumper thickness, and aluminum rear-wall thickness on the energy dissipation and damage characteristics of the AFPC/Al shield were analyzed. The results show that, under conditions of equal areal density and equal total thickness, the AFPC/Al shield exhibits superior shielding performance compared with aluminum Whipple shields and Nextel/Kevlar stuffed Whipple shields. The AFPC/Al shield provides protection primarily through sustained and efficient dissipation of projectile kinetic energy within the AFPC bumper, which differs from the energy redistribution mechanism of Whipple shields and their derivatives. As the impact velocity increases, the energy dissipation of the AFPC bumper exhibits a velocity-strengthening effect. The AFPC bumper thickness is the primary parameter governing energy dissipation of the AFPC/Al shield, whereas the aluminum rear-wall thickness mainly influences the rear-wall damage mode, characterized by a transition from perforation to bulging. These findings provide new insights and valuable guidance for the design of orbital debris shields under limited space conditions.
This paper presents a comparative investigation of the high-velocity perforation behavior of a composite projectile and a conventional ogive-nosed projectile. Based on oblique perforation experiments on multi-layered steel plates at high velocities, the asymmetric evolution of the projectile nose and the characteristic failure morphologies of the targets are obtained. Combined with numerical simulations, the projectile-target interaction mechanisms are elucidated. Observations of projectile motion during multi-layered perforation reveal that the variations in pitch angle and angle of attack of the composite projectile are significantly smaller than those of the single projectile. Further comparative analysis indicates that the enhanced attitude stability originates from the protective mechanism of the cap. Under high-velocity oblique perforation, the cap dissipates a substantial amount of energy through its own plastic deformation, effectively redistributing the energy across different regions of the nose. This significantly attenuates the compressive and shear loads transmitted to the main body, thereby suppressing stress concentration and asymmetric deformation on the distal side of the nose and ensuring high structural integrity and minimal deformation of the main nose. The mechanism underlying the smaller attitude deflection is that the plastic deformation of the cap attenuates the compressive and shear forces acting on the main body, thereby reducing the deflection moment and angular acceleration experienced by the projectile and enhancing attitude stability. This stabilization advantage becomes increasingly pronounced with increasing obliquity. This study on the perforation behavior of composite projectiles provides mechanistic insights for the design and analysis of similar projectile configurations.
Traditional energy absorption structures struggle to balance the demands of lightweight design, high-efficiency blast resistance and acoustic regulation. Integrating honeycomb structures with acoustic metamaterials offers an important solution to this problem. In this paper, the dynamic response of such honeycomb based acoustic metamaterials is investigated, in which Helmholtz resonators are embedded. Three metamaterial configurations and conventional aluminum honeycomb sandwich panels were fabricated. Their performances were examined and compared through impedance-tube measurements and blast tests. Compared with regular honeycomb panels with poor acoustic absorption capacity, all metamaterial panels were designed to have absorption peaks near 100 and 200 Hz, which were demonstrated by acoustic tests. The blast tests showed that the failure modes of metamaterial panels were strongly dependent on stand-off distance and the detonation point offset to the center of panel. Under close-in blast loading, the front face sheet suffered severe localized tearing, whereas at larger stand-off distances the response shifted to global deformation-dominated behavior. The three metamaterial configurations exhibited similar blast-resistant performance within the investigated loading range. At an identical vertical detonation distance, the damage to the metamaterial plate intensifies as the explosive charge approaches the center of the honeycomb cell (the cell opening). Compared with conventional honeycomb panels, this metamaterial panel exhibits superior performance in low-frequency sound absorption. However, its blast resistance is significantly degraded, with the final deflection increasing by up to 27.7%. This is attributed to the weakened structural stiffness caused by the perforated structure on its front surface. These results demonstrate the feasibility of integrating acoustic and mechanical functionalities in a single sandwich structure and provide experimental guidance for future optimization toward a better balance between sound absorption and blast protection.
A physics-constrained prediction method for normalized penetration depth is developed for tungsten-alloy long rods penetrating semi-infinite steel targets. First, a dedicated database is constructed by screening experimental data specifically for this projectile-target class. Based on typical long-rod penetration conditions, the geometric parameters, material properties, impact conditions, and penetration results are standardized in a unified manner. Subsequently, dimensional analysis is conducted in conjunction with the characteristic variation of normalized penetration depth with impact velocity. The basic controlling parameters are identified as the geometric ratio, density ratio, the ratio of projectile strength to target resistance, and the inertial driving level. By introducing a quasi-static target-resistance scale derived from cavity expansion theory, a unified baseline predictive formula is established, and its parameters are then identified through data-driven learning. The results indicate that the formulation incorporating the quasi-static target resistance effectively captures the overall variation of normalized penetration depth for tungsten-alloy long rods penetrating semi-infinite steel targets. Further validation using reserved database samples and publicly available literature data demonstrates that the model has good predictive capability for conventional tungsten-alloy long-rod penetration into steel targets, while also exhibiting a certain degree of extrapolation capability for closely related tungsten-based material systems. The proposed method provides a basis for the unified characterization of long-rod penetration into semi-infinite steel targets and for subsequent data-driven studies.
This study investigates the shear localization behavior and dynamic failure mechanisms of 10MnNiCr steel under controlled dynamic shear and fragment-simulating projectile (FSP) penetration conditions. Multi-scale characterization, including macroscopic observation, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD), was employed to reveal deformation, damage evolution, and microstructural responses. Under controlled dynamic shear, plastic deformation is strongly localized within the forced shear zone. The competition between strain hardening and thermal softening promotes the formation of adiabatic shear bands (ASB), while damage evolves through microvoid nucleation, growth, and coalescence, leading to shear-dominated fracture. During projectile penetration, the stress state evolves with projectile geometry and penetration depth, transitioning from compression-dominated to multiaxial conditions. A pronounced through-thickness stress gradient develops during penetration of the wedge-shaped nose, resulting in deformation and damage heterogeneity: severe plastic deformation dominates the upper region, whereas crack initiation and propagation are more significant in the lower region. Representative EBSD observations indicate that the damage regions exhibit a zonal microstructure, consisting of crack-adjacent dynamically recrystallized fine grains and surrounding deformed grains. Under penetration, recrystallization is more localized, while elongated grains are more widely distributed in high-strain regions. The failure mechanism is associated with the coupling of shear localization and tensile effects, leading to a transition from shear-dominated fracture to plugging failure.
The buckling phenomenon in spherical shells continues to attract interest in various fields, such as impact mechanics, soft robotics and biomechanics due to its characteristic and abrupt shape changes. While static analyses of snap-through are well documented, the dynamics of snap-through remains underexplored, especially in structures with natural curvature. In particular, further studies are required to understand the behavior of spherical shells under various loading conditions. To address this problem, experiments on two types of ping-pong balls, representative for thin spherical shells, were conducted when statically compressed on a flat surface and impacted against a flat rigid surface to evaluate the dynamic effect on their snap-through buckling response. Normal and oblique impacts with initial velocities up to 16 m/s, causing axisymmetric buckling, are analyzed. It is observed that the maximum contact force and contact diameter at snap-through increase with the increase of the impact velocity. The oblique impacts at two different incidence angles show that the critical value of the normal component of the impact velocity governs the dynamic snap-through. A theoretical model on the response of an elastic shell to quasi-static and impact loading is developed to explore the reasons for the increased critical force and contact diameter when using simplified material properties. Three phases of shell deformation are identified under impact loading. The pre-buckling phase is defined by flat contact between the shell and rigid surface; the second phase is characterized by partially flat contact and inward displacements of the shell while the contact force continues to increase. The snap-through occurs when the normal contact force reaches its maximum at the onset of the third deformation phase. It is revealed that the rate of growth of the deformation energy reduces during the second deformation phase, while the inertia forces increase rapidly, leading to a significant increase in the contact force. The model predictions are verified by numerical simulation and partially validated by the experimental results. A brief parametric study is discussed.
Gabion has been widely used in engineering projects such as slopes and riverbanks. Although the concept of using gabions in tunnel engineering has been proposed, its application at the tunnel portal is rarely seen. It is worth noting that rockfall impact disasters at tunnel entrance occur from time to time, which is likely to cause damage to the tunnel structure and even affect people’s normal travel. The strong deformation adaptability and good load - bearing capacity of the gabion can provide some solutions to the above problems. Therefore, this paper introduces gabion to the lining structure of tunnel engineering, and takes the tunnel lining component constructed with gabion (TLCCG) at the vault as the research object. By combining tests as well as discrete element modelling (DEM), the dynamic response influence laws of TLCCG being impacted by rockfall are revealed. Furthermore, the influence mechanisms of the impact height of rockfall, the rockfill type, the number of gabion netting layers, and the rockfill gradation on the above - mentioned law are also explored. It was found that increasing the rockfall height simultaneously increases both the peak acceleration and residual deformation of the TLCCG. The buffering efficiency of TLCCG rises from 45% to 55% as impact energy increases. TLCCG filled with concrete exhibit slightly higher buffering efficiency than those filled with granite, but show greater residual deformation; thus, granite gravel is recommended for engineering applications. A double-layer gabion net can increase buffering efficiency from 32.9% to 65.7%, significantly suppressing residual impact deformation. Discrete element analysis reveals that TLCCG with natural natural gradation have lower internal porosity, more stable force chains, and minimal vertical penetration deformation, although their peak frictional energy dissipation is higher. For single-sized rockfill, the particle bonding failure rate decreases continuously with increasing average particle size, and larger particles effectively reduce transmitted deformation at the lining base. Compared to brittle concrete linings, gabion structures rely on multiple energy dissipation mechanisms—including particle friction and mesh stretching—resulting in only half the impact strain energy absorbed by concrete, demonstrating a significant advantage in resisting rockfall impacts.
This paper discusses the development of a consistent and controllable test method for evaluating the response of materials and structures to combined blast wave and fragment impact. The experimental setup enables the synchronised arrival of a planar blast wave and a single fragment impact, with both loads controlled independently. An explosive-driven shock tube used to generate repeatable blast loads is combined with a weapon system accelerating a 1.102g NATO STANAG Fragment Simulating Projectile. The two loads are synchronised to simulate an explosive event corresponding to a specific charge and stand-off distance from a target. The method is demonstrated on aramid fabrics to evaluate their fragment-impact resistance in the presence of a blast wave. A total of 55 samples, 15 layers each, are tested across a range of overpressures (4–10MPa), fragment velocities (396–637m/s), and time intervals between the arrival of the blast wave and the fragment (–210 to +516 μs). The results are compared to reference single impact tests on 23 samples. Initially, the blast wave accelerates the fabric while stress waves propagate from its edges towards the centre point. At short time intervals an impacting fragment requires 18% higher impact velocity in order to perforate when compared to ballistic single-impact tests, as the fragment’s relative impact velocity is reduced. At longer time intervals, the blast wave-loaded fabric reaches its maximum out-of-plane displacement which increases the accumulated strain energy and reduces the fabric’s impact resistance by 14.5%.
