Lena LeichtMatteo ColomboPaolo MartinelliCesare Signorini...
105149.1-105149.17页
查看更多>>摘要：This study compares the blast performance of reinforced concrete (RC) slabs with and without strengthening on the impact-facing side. The strengthening strategy employed the application of two thin layers of materials with a high mutual stiffness offset, i.e., high-contrast layers. The first is a low-strength, low-modulus damping layer made of infra-lightweight concrete, followed by a second layer of high-ductility fiber-reinforced concrete. The plain RC slabs under investigation vary in thickness of either 40 mm or 100 mm. The layered specimens consist of a 40 mm thick RC slab strengthened with a 40 mm damping layer and a 20 mm cover SHLC3 layer. This configuration enables a comparison of its behavior with the unstrengthened specimen (a plain 40 mm thick RC slab) and a specimen with a similar eigenfrequency (the plain 100 mm thick RC slab). The employed shock tube subjects the specimens to two rapidly rising areal pressures: a low-pressure wave reaching approximately 0.4 MPa and a high-pressure wave peaking at around 1.2 MPa. The study assesses the specimens' response in terms of accelerations, velocities, and deformations. Additionally, it evaluates damage by analyzing crack patterns, Ultrasonic Pulse Velocity (UPV) measurements, and damping analysis. Overall, the layered specimens exhibited performance nearly equivalent to the 100 mm thick specimens, displaying similar deformations and velocities despite having lower mass and bending stiffness. The high-pressure shock wave hardly damaged the layered specimens, unlike the 40 mm thick slabs.
Ioan I. FeierMichael L. AndersonJames R. BoudrieErin M. Jarrett-Izzi...
105150.1-105150.17页
查看更多>>摘要：The increasingly congested orbital environment around Earth threatens the safety of space assets. Micromete-oroids and orbital debris (MMOD) less than 1 cm but traveling at hypervelocities pose a serious but defensible hazard. Traditional shields are installed during spacecraft assembly and must survive launch loads, constraining their size, shape, and ultimately, effectiveness. Recent advances in on-orbit additive manufacturing have created new opportunities for shield design and deployment. This work describes the modeling and testing of additively manufactured polyetherimide shields. The finite element code CTH was used to model hypervelocity impacts (HVIs) of such shields, and though imperfect, the models were useful for shield design. Several shield designs were additively manufactured and underwent HVI testing with a two-stage light gas gun in the regime of 4 mm diameter aluminum projectile impacts at 5 - 6.5 km/s. All successfully survived the HVIs, indicating their potential effectiveness as MMOD spacecraft shielding.
查看更多>>摘要：In the present study, the ballistic perforation resistance of steel/titanium/aluminum (STA) multilayer protective systems impacted by spherical, ogival, conical, and blunt projectiles was investigated experimentally, numerically, and analytically. The targets were manufactured via explosive welding technique to achieve a strong interfacial strength. The projectile nose shape was found to significantly affect the failure modes and ballistic limit velocities of the STA composite plate. Detailed three-dimensional finite element simulations were performed to provide insights into the penetration process and energy absorption characteristics of the STA composite plate. An analytical model was developed to predict the entry and exit penetration phases of a rigid projectile of different nose shapes into the STA target through ductile hole expansion. The model simplified the STA composite plate to be an equivalent monolithic based on the weighting of material resistance and specific cavitation energy in each layer. The analytical and numerical predictions of the residual velocity were in excellent agreement with the experimental data. The predicted evolution of projectile velocity with penetration depth was found to be in satisfactory correlation with those from the numerical simulation. The proposed analytical model shall be useful for designers of multilayer metallic protective structures against fragments from improvised explosive devices.
查看更多>>摘要：The response of solid rocket motors (SRMs) to high-speed fragment impacts is crucial for their safety design and operational use in scenarios such as rocket launches and space applications. The visualized Burn to Violent Reaction (BVR) test is used to observe intense reactions induced by high-speed projectile impacts. Employing a two-stage light gas gun and optical diagnostic techniques including high-speed schlieren imaging and direct photography, the impact-induced deflagration/explosion behavior, and reaction growth behavior were investigated. The damage mechanisms of the casing and propellant samples were assessed, and the reaction growth and afterburn effects of the impact-induced fragment cloud were quantitatively analyzed. The results indicate that the ignition delay time is inversely correlated with the impact velocity, decreasing from ms to μs scale. Across a wide range of velocities (1050-2058 m/s), higher projectile velocities induce more sustained and vigorous combustion reactions within the propellant. Furthermore, increasing the propellant air gap to 7.8 cm does not trigger further reactions under the studied configurations. The reaction mechanisms are closely linked to the characteristics of the fragment cloud induced by the impact. The developed Smoothed Particle Hydrodynamics (SPH) method, incorporating material constitutive models, ignition criteria, and reaction growth models, was used to study the influence of projectile velocity on the reaction mechanisms. The simulation results were compared with experimental data, demonstrating satisfactory accuracy.
Christoph GrunwaldMake von RaminWerner RiedelAlexander Stolz...
105154.1-105154.17页
查看更多>>摘要：Malicious acts, but likewise unintended accidental explosions, can lead to severe structural damage and resulting debris throw, which poses a significant threat to humans and facilities. Until now, risk analysis is based mainly on empirical data, since the reliable simulation of structural break-up, dissolution and emergence of secondary fragments for real structures is still challenging. In this paper, we investigate the application of a mesoscale description of concrete with finite elements to predict the dispersal of fragments out of dynamically loaded concrete specimens. We demonstrate that the approach delivers accurate predictions for maximum velocity and total debris mass. Further, it is even able to resolve the debris mass distribution with very reasonable quality, a result rarely found in literature up to today. The detailed resolution of the debris field allows furthermore a more thorough determination of the aerodynamic factors governing the subsequent flight phase. We compare the results using different assumptions in terms of flight distances and safety maps.
查看更多>>摘要：Polymeric composite sandwich materials are critical for marine structures, but their behavior under near-field underwater explosions is not well understood. This study investigates the dynamic response of carbon-fiber-reinforced sandwich composites with varying core densities subjected to near-field underwater explosions. Lab-scale experiments were conducted at two explosive stand-off distances using high-speed imaging and Digital Image Correlation (DIC) to capture the evolution of gas bubble dynamics, surface cavitation, and structural deformation. Results showed that reducing the stand-off distance led to a 0.7 ms increase in gas bubble period, along with an 80 mm increase in horizontal migration of the bubble, while vertical migration remained unaffected. The interaction between the gas bubble and surface cavitation, driven by fluid-structure interaction (FSI), significantly influenced the structural response. In particular, the simultaneous collapse of the gas bubble and surface cavitation resulted in higher localized impulsive loading, causing catastrophic failure in low-density core panels. Meanwhile, panels with higher core densities exhibited a 40 % reduction in out-of-plane deflection, demonstrating enhanced resistance to blast loading. This study provides new insights into the fluid-structure interaction mechanisms that occur during near-field underwater explosions and offers a basis for improving the design of marine structures by optimizing material selection and geometric configurations. These findings contribute to a deeper understanding of shock mitigation strategies in composite materials and inform future research in marine structural design under extreme loading conditions.
Jacopo LavazzaQicheng ZhangCharles de KergariouGianni Comandini...
105156.1-105156.16页
查看更多>>摘要：Rigid polyurethane foams (RPUFs) are widely used in impact protection applications due to their tunable mechanical properties. Recently, RPUFs derived from bio-based sources such as castor oil have been investigated as a greener and more sustainable alternative to replace fossil-based polyurethane foams. It is thus important to understand the mechanical response of these materials to low-velocity impact (LVI), which still needs to be explored. This study aims to fill this gap by evaluating the performance of three types of RPUFs developed from commercially available castor oil-based resins. Drop weight impact tests at different impact energies were performed to investigate the LVI characteristics of the foams. Furthermore, an extensive micro-computed tomography investigation was carried out to improve the understanding of the microstructure of RPUFs and how the composition of these porous materials affected the foam architecture and the macroscopic mechanical response. Finally, a constitutive relationship is proposed to describe and predict the materials' response at different impact energies.
查看更多>>摘要：Experimental, theoretical and numerical simulations were carried out to investigate the dynamic response and blast resistance for the cylindrical sandwich shells with toroidal tubular cores under internal blast loading. The typical deformation modes of internal/external shells and toroidal tubular core layers were observed through experiments. A theoretical model considering the circumferential plastic membrane forces and the axial moment components was performed to predict the blast response of sandwich shells. The mid-points deflections and velocities of internal/external shells obtained by theoretical predictions are consistent with the experimental and numerical results. Influences of wall thicknesses of internal/external shells and the axial/radial gradient of toroidal tubular cores on the blast resistance of single and triple layers sandwich shells were investigated by numerical simulations. The results show that the negative gradient structures have the smallest normalized deflection, while the hybrid gradient structures have the highest energy absorption. On this basis, multi-objective optimization of the sandwich shells was carried out by combining the response surface method (RSM) and the multi-objective genetic algorithm (MOGA). The optimization results yielded a trade-off between deformation, energy absorption and structural mass, and demonstrated the advantages of the "Pareto front" in these design cases.
查看更多>>摘要：Hole defects can lead to non-uniform strain distribution under the impact load, thereby influencing crack propagation behavior. In this paper, 2D-DIC technology was employed to examine the effects of holes of varying sizes and loading rates on crack dynamics in PMMA materials, aiming to elucidate detailed knowledge into the characteristics of crack propagation under complex strain fields. Through DIC analyses, the dynamic evolution of strain fields around the crack tip and hole periphery could be precisely captured, enabling tracking of crack propagation behavior including crack propagation velocity, crack propagation path, and crack deflection angle. It is concluded that the non-uniform strain zones generated by holes exert both inhibitory and attracting effects on crack growth. The influence of non-uniform strain zones on crack propagation increases with the elevation of loading rate and hole size. However, as the loading rate increases, the kinetic energy of the crack itself also increases, necessitating sufficiently large hole sizes to effectively influence crack propagation. Overall, this study provides a detailed experimental explanation of the effects of holes on cracks, which will aid engineers in maximizing the positive impact of holes on material performance and their application in the design of micro-structure materials.
查看更多>>摘要：A new experimental setup to study the interaction between two brittle bodies which can experience crushing, comminution or fragmentation during impact is herein presented. The system consists of a free falling body and an instrumented impacted plate, onto which an accelerometer is installed, lying on three force ring cells. The recorded acceleration is decomposed into Intrinsic Mode Functions thanks to a Variational Mode Decomposition technique to obtain relevant time-histories associated with specific vibration frequencies. The mass participating to each mode is obtained by comparing the discrete Fourier transforms of force and acceleration. Finally, the adoption of a high-speed camera provides additional insights into the interaction, in particular when non-spherical bodies are considered. The results of a small experimental campaign serving as a benchmark are presented and discussed.
NETL
NSTL
Elsevier