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The honeycomb sandwich panel presents a highly promising solution for enhancing ballistic behavior owing to its excellent strength-to-weight ratio and impact resistance. This study focuses on investigating the shock mitigation properties of honeycomb sandwich panels through experimentation and numerical simulation of high-velocity impact tests. Single-scale and double-scale hierarchical honeycomb cores are manufactured using selective laser melting with AlSi10Mg powder, combined with a pair of stainless steel (SS 316) sheets. High-velocity impact experiments were conducted within a velocity ranging from 100 to 270 m/s to examine the effects of different cores and projectile nose shapes on the dynamic response of the panels. Numerical simulations using ABAQUS/Explicit software were performed and validated against the experimental results. The sandwich panel with a double-scale hierarchical honeycomb core exhibited 7.8% and 6.1% more energy absorption compared to the single-scale hierarchical honeycomb core against conical and hemispherical nose projectiles, respectively. Additionally, the ballistic limit for the hemispherical projectile was found to be 8.9% higher than the conical-nose projectile under the same impact velocity and panel thickness. Moreover, an increase in panel thickness from 12 mm to 25 mm prompted a significant improvement of approximately 39% in specific energy absorption and a 44% increase in ballistic limit velocity. These findings highlight the considerable potential of single-scale and double-scale hierarchical honeycomb sandwich panels for the development of threat-resistant structures in critical dynamic loading applications. [ABSTRACT FROM AUTHOR]

By utilizing 3D printing technology, experimental three-point bending (TPB) tests, and finite element analysis, six honeycomb structures with a variety of overall Poisson's ratios (PR) are studied and compared in terms of bending properties and failure mechanisms. Four novel honeycombs that are designed by hybridizing hexagonal and re-entrant units outperform benchmark conventional honeycombs in terms of load-carrying capacity. Architected hybrid geometry honeycombs with zero PR show excellent specific energy absorption capability in comparison to benchmark honeycombs, absorbing approximately 136.9% and 475.1% more energy under TPB. 3D-printed honeycombs consisting of hexagonal units face layer separation damage mode under bending, while honeycombs with re-entrant cells in their lattice fail with joint shear due to the angle of their struts towards loadings. Designing honeycombs with a hybrid geometry lattice can enhance the load-carrying capacity, specific energy absorption, flexibility, and flexural modulus of the structure under bending. Due to their superior performance, the proposed architected hybrid geometry honeycombs with various Poisson's ratios own promising applications in automotive, protective, and construction industries. [ABSTRACT FROM AUTHOR]

In this study, dynamic explicit analysis was performed to examine the air-blast performance of various hybrid sandwich designs in terms of face plate deflections and energy dissipation capacity under the conventional weapons effects program (CONWEP) air-blast loads ranging from 3 kg to 8 kg trinitrotoluene for stand-off distance ranges from 150 mm to 200 mm. The blast resistance of honeycomb sandwich configurations was evaluated using steel honeycomb with different core topologies, crushable Al foam-filled steel honeycomb, and steel or steel with 3D Kevlar/polypropylene laminate employing fiber metal laminate (FML) front face. For an accurate prediction of the deformation mechanism of all steel parts, the Johnson-Cook (J-C) model was used. The composite failure criteria of Hashin, Puck, and Matzenmiller were implemented to accurately examine the fiber and matrix damage behavior. The novel hybrid design of the honeycomb sandwich structure's blast resistance is improved by the employment of foam-filled honeycomb, an FML front face, and a circular honeycomb core. In comparison to other sandwich configurations, a novel designed hybrid sandwich construction composed of foam filled circular honeycomb with FML front facing and steel back facing (FCH-1KP0.5) achieved the highest blast resistance due to its lowest face deflection with the smallest plastic dissipation energy. [ABSTRACT FROM AUTHOR]

Introducing the hierarchy into cellular materials has attracted increasing attention in the effort to pursue improved absorbed-energy abilities and impact resistance. In this paper, the dynamic crushing properties and energy absorption capacities of joint-based hierarchical honeycombs with different topologies were explored by means of explicit dynamic finite element (FE) analysis using ANSYS/LS-DYNA. Four types of joint-based hierarchical honeycombs with uniform cell-wall thickness were firstly constructed by substituting each vertex of regular honeycombs with a smaller self-similar cell (hexagon or square). The respective influences of hierarchical parameters and impact velocities on in-plane dynamic deformation modes, mechanical characteristic and energy absorption of joint-based hierarchical honeycombs were discussed. Research results showed that the hierarchy had a far greater influence on the in-plane deformation modes of honeycombs. Compared with regular honeycombs, the dynamic plateau stress and specific energy absorption of joint-based hierarchical honeycombs can be improved if the proper hierarchical parameters were chosen. Adding the joint-based hierarchy into regular honeycombs can enhance the crushing stress efficiency (CSE) of the specimens. In addition, by introducing a non-dimensional dynamic sensitivity index, the dynamic shock enhancement of hierarchical honeycombs was also investigated. These researches are useful for the multi-objective dynamic optimization design and controllable properties of cellular materials. [ABSTRACT FROM AUTHOR]

Hierarchical structures have been viewed as promising candidates to offer superior performance compared to regular structures. In this study, six hierarchical honeycombs are constructed by replacing each joint of regular hexagonal and square honeycombs in three different ways. Numerical simulations are performed to study the out-of-plane dynamic crushing behavior and energy absorption performance of these hierarchical honeycombs. The results show that the three ways of introducing structural hierarchy can enhance the plateau stress, crash load efficiency, and specific energy absorption of regular honeycombs. Moreover, hierarchical honeycomb constructed by replacing each joint of regular hexagonal honeycomb with a smaller circle has the highest energy absorption capacity. In addition, the optimal configurations for different hierarchical honeycombs are presented, and the region of optimal structural parameter for these hierarchical honeycombs is determined, which are useful for the selection and design of hierarchical honeycomb configuration with desirable energy absorption performance. [ABSTRACT FROM AUTHOR]

The energy-absorbing behaviour of an aluminium honeycomb core reinforced with unidirectional and woven carbon fibre reinforced plastic composite tubes has been investigated experimentally at quasi-static rates of strain. Small diameter carbon fibre reinforced plastic tubes, with chamfered ends, were inserted into the cells of an aluminium honeycomb in order to yield a lightweight energy-absorbing material. The resulting data are compared with crushing tests on arrays of free-standing composite tubes, supported on a specially designed compression test fixture. The study continues with an investigation into size effects in the energy-absorbing response of these cellular materials, where compression tests are undertaken on four scaled sizes of reinforced honeycomb core. Crushing tests on the multi-tube arrays have shown that woven carbon fibre reinforced plastic tubes absorb significantly greater levels of energy than their unidirectional counterparts. Here, the specific energy absorption did not vary with the number of tubes in the array, with values for the woven tubes averaging 110 kJ/kg and those for the unidirectional tubes averaging 75 kJ/kg. Inserting composite tubes into aluminium honeycomb served to increase the measured specific energy absorption of the core, resulting in values of specific energy absorption of up to 100 kJ/kg being recorded in the woven-based system. Tests on four scaled sizes of core have shown that the measured SEA does not vary with specimen size, indicating that data generated on small samples can be used to represent the energy-absorbing response of larger, more representative components. [ABSTRACT FROM AUTHOR]

To study the protection property of aluminum alloy sandwich panels with honeycomb cores under the attack of bullets or debris, quasi-static perforation, and ballistic impact tests were conducted, in which the thicknesses of the face sheet and core were 0.5–2.0 and 12.7 mm, respectively, while projectiles with diameter 7.5 mm and impact velocity 50–220 m/s were employed. Based on the experiments, the influences of impact velocity, face sheet thickness, core density as well as the nose shape of the projectiles were investigated. The results showed that in the impact tests, the sandwich panels dissipated much more energy than those in quasi-static perforation tests, and the energy absorption and ballistic limit of the sandwich panels increased with the increase of impact velocity. The influence of face sheet thickness was more remarkable than the core density, which was due to the relative density of honeycomb is too small. Although the increase of core density could induce the increase of energy absorption, this effect is more effective for thinner face sheet. Moreover, under the same impact velocity about 200 m/s and face sheet thickness 1.0 mm, the ballistic limit for conical-nosed projectile is highest, while it is lowest for flat-nosed projectile. [ABSTRACT FROM AUTHOR]

Two kinds of innovative re-entrant and hexagonal cell honeycomb sandwich structures filled with reactive powder concrete were proposed, and the ballistic resistance and energy absorption of the sandwich structures were investigated by numerical simulations. The deformation and failure modes of the different structures were analyzed and evaluated in detail. The honeycomb sandwich structures filled with reactive powder concrete prisms improved the capacity of ballistic resistance and energy absorption significantly, compared to the normal reactive powder concrete plates and sandwich structures without reactive powder concrete prisms. The analysis shows that the auxetic re-entrant cell honeycomb sandwich structures have a better ballistic performance than the hexagonal cell honeycomb sandwich structures. The sandwich structures were subjected to impact by three kinds of projectiles: flat, hemispherical and conical nosed. The ballistic limit of the flat nosed projectile is the highest, while the impact performance of the conical and hemispherical nosed projectiles is obviously different from the flat nosed projectile, especially in a relative high velocity range. The sharper nose leads to a higher value of exit velocity and mass loss. In addition, effects of different design parameters on ballistic resistance were also studied by changing the thickness of honeycomb cell and face plates. Results indicate that the thickness of honeycomb walls and face plates have significant effect on the ballistic resistance and energy absorption in a relative low velocity range, while there are no big differences when the initial impact velocity exceeds 400 m/s. [ABSTRACT FROM AUTHOR]

The mechanical properties of paper honeycomb will be different from static situation with the changing of strain rate, which has an influence on the application of paper honeycomb. In this paper, the dynamic mechanical properties of paper honeycomb were discussed and the corresponding mathematic model was built in order to present the stress in different deformation stages and depict the energy absorption properties of honeycomb structure. The strain-rate effect was expressed by Comper-Symonds model. According to the mechanical model, the energy absorption diagram under different strain rates was also built from selecting materials of cushion packaging and optimum design of the packaging. Finally, serious experiments were taken and the result showed a good agreement with theoretical models. The proposed model can be used for practical application of the optimum design and material selection of honeycomb sandwich structure. [ABSTRACT FROM AUTHOR]

This paper presents an analytical study of the in-plane dynamic crushing and energy absorption of hexagonal honeycombs with density gradients under different impact loading. Explicit dynamic finite element method simulations are carried out by using ANSYS/LS-DYNA. Firstly, under the assumption that the cell wall length is the same, a density-graded honeycomb mode is established by the variation of the cell wall thicknesses along the crushing direction. The effects of density gradient and impact velocity on the crushing deformation modes, plateau stresses and energy absorption characteristics of the specimens are explored in detail. Numerical results show that except for the impact velocity, the dynamic crushing performance and energy absorption abilities of honeycombs also rely on the density/strength gradients. The weakest layer is suggested to be placed at the impact end or the output end, and the strongest layer at the intermediate stage to achieve higher energy absorbing efficiency. According to the one-dimensional shock wave theory, the simple empirical formulae for graded honeycombs to predict the plateau stress are given under high-impact velocities. These results will provide some useful guides in the multi-objective optimization dynamic design and shock energy absorbing control of sandwich structures. [ABSTRACT FROM AUTHOR]

Honeycomb sandwich panels of various skin thicknesses and core densities have been investigated under quasi-static loading in bending and indentation with both hemispherical (HS) and flat-ended (FE) indenters. Core crushing, top skin delamination, and top skin fracture are identified as major damage mechanisms. Their characteristics and energy-absorbing capabilities are established using load-displacement and load-strain curves and inspections of cross-sectioned specimens. The effects of varying skin thickness, core density and type, indenter nose shape, and boundary conditions on the damage and energy-absorbing characteristics are examined. The variation of the indenter nose shape is shown to induce a change in the damage mechanisms and have the most significant effect on energy absorption, especially for panels with relatively thicker skins. Increasing the skin thickness significantly increases not only the initial threshold and ultimate loads but also the absorbed energy (AE) of the panels. Increasing the core density has a very small effect on either the ultimate loads or the energy-absorbing capacity, while the effect of the support conditions on the damage and energy-absorbing characteristics is small. The larger 220 mm diameter panels absorb significantly more energy than the 100 mm diameter panels because of the much greater ultimate displacement. Different core materials with a similar density show little difference in either the daniage or the energy-absorbing characteristics due to the limited contribution of transverse shear resistance. Panels with a delaminated top skin have lower threshold loads under both indenters and lower ultimate load for the HS indenter. [ABSTRACT FROM AUTHOR]