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In the field of lightweight structures, foldcore sandwich structure is regarded as a promising replacement for conventional honeycomb sandwich structure. In this study, a new M-type glass fiber foldcore structure was fabricated by hot-pressing molding technology, and the effects of various factors on the low-velocity impact characteristics were investigated. In addition, a 3 D progressive damage numerical model matching the experimental results was established. The results showed that the impact energy exerted a certain influence on the response characteristics of the sandwich structure, but did not change the development trend of the load curve. The sandwich panel was able to achieve the overall load-carrying potential for the impactor whose size was longer than the foldcore span (25 mm). In addition, as the sharpness of the impactor increased, the damage range of the sandwich panel became concentrated and the load-bearing capacity gradually decreased. As revealed by the findings, the maximum load and specific energy absorption of laminated sandwich panels were improved by 150 and 40% respectively compared to single sandwich panel at base position. Therefore, it is beneficial to appropriately reduce the core span and increase the number of laminations to improve impact resistance of foldcore sandwich in practical applications. [ABSTRACT FROM AUTHOR]

In this study, a three-rib intersecting composite diamond honeycomb structure is fabricated by interlocking technology. The mechanical properties of the composite interlocked diamond honeycomb (CIDH) and corresponding sandwich structure (CIDHSS) are experimentally tested. The stiffness, strength, and failure characteristics of CIDH and CIDHSS are analyzed. The results show that CIDH has better mechanical properties than the interlocked Kagome and square honeycombs. The edge effect limits the edge compressive strength and stiffness of CIDH. Debonding is the main failure mode that limits both bending and compressive strength of CIDHSS. The reinforced plate added to the edge effectively improves the anti-debonding ability. [ABSTRACT FROM AUTHOR]

This paper aims to introduce the hierarchy design into sandwich beams and bumper systems to improve their mechanical performance. Two kinds of reentrant hierarchical sandwich beams are proposed and their energy absorption characteristics have been systematically investigated. Based on its excellent energy absorption ability, the reentrant hierarchical honeycombs with equilateral triangle substructures (RHT) core are introduced to the design of the bumper system, and the hierarchical bumper system exhibits better mechanical properties than the traditional bumper and the aluminum foam-filled bumper under different loading conditions. Then, the multi-objective optimization model of the hierarchical bumper system is established by combining the optimal Latin hypercube design method (OLHD) and the response surface model (RSM). The non-dominated sorting genetic algorithm-II (NSGA-II) algorithm is adopted to optimize the design parameters. The optimization results show that the objectives are optimized efficiently, and it performs remarkable performances in bumper system design. [ABSTRACT FROM AUTHOR]

Sandwich structure is one of the blasts protecting and energy absorbing materials with different types of light weight cores. This article aimed at investigating blast response of hexagonal honeycomb sandwich structure having perforations along the cell height of core over conventional honeycomb cores. The study discussed the mechanics of deformation behavior of perforated sandwich structure to improve the energy absorption characteristics of the bare honeycomb core sandwich structure. Detailed numerical analysis is conducted to accurately produce the deformation process with finite element analysis using explicit software LS-DYNA®. Blast load resulting from 1 kg TNT on the sandwich structure is applied using Conventional Weapons Effects Program (ConWep) function available in LS-DYNA. Several different parameters consisting of varying sizes of perforation by changing d/l ratio, shape, number of perforations and different facesheet and backsheet thicknesses, and different scaled distances are investigated in detail. The results indicated that both size and shape and number of perforations have significant influence on reduction of blast impulse. The variation of facesheet and backsheet thicknesses without changing the overall thickness of the structure also has evident effect in blast resistance capability of perforated honeycomb sandwich structure. The blast mitigation and energy absorption capacity of honeycomb core sandwich structure can be improved with the provision of perforations and optimizing the arrangement of holes. The perforated honeycomb core is further investigated based on analytical formulation developed using single degree of freedom (SDOF) system analysis approach. Optimization study is done further to get the best configuration based on different design variable limits. [ABSTRACT FROM AUTHOR]

Sandwich structure with honeycomb core and CFRP facesheets is increasingly used in the high-performance fields due to the high specific stiffness and strength. However, it is susceptible to localized low-velocity impacts such as tool drop during maintenance, and thus, understanding the damage behavior is important for a safety design and optimization. The objective of this article is to investigate the influence of the structural parameters and impact energy on the damage behaviors of the composite honeycomb sandwich panels subjected to localized low-velocity impact. An effective computational framework considering complicate damage mechanisms is proposed to predict the failure patterns, load history, and energy absorption. Comparisons with the experimental data show that the error of predictions is within 4% and thus the framework is validated. Then, a comprehensive parametric study is conducted to explore the effects of wall thickness and height of honeycomb, impact energy, and stacking sequences of the laminated facesheets on the impact resistance, damage behaviors, and energy absorption of the sandwich structure. The reported results may be useful in practice. [ABSTRACT FROM AUTHOR]

In this study, dynamically loaded sandwich panels with two different core materials and face sheets made of aluminum alloys (6061-T6) were investigated experimentally and numerically under low-velocity impact. Polypropylene, PP (C3H6)n honeycomb and extruded polystyrene foam, XPS (C8H8)n were preferred as core material. By using the contact force and kinetic energy changes, which were the impact test results of the sandwich panels, the contact and impact resistance was examined. As a result of the tests, damaged regions and permanent central displacement were determined and energy absorption capabilities were demonstrated for two different structures. The results obtained were compared with the results obtained by the open finite element method. In this study, it was shown that the face-sheet thickness of sandwich panels was an important parameter affecting the impact behavior. The behavior of the core material when the face-sheet loses its rigidity was investigated and it was found that polystyrene foam was more effective in preventing impact damage. However, it was found that using the PP honeycomb or XPS was affected the impact behavior in different points. [ABSTRACT FROM AUTHOR]

To improve the load carrying capacity, structural stiffness, and impact resistance of honeycomb sandwich structure, a novel tube-reinforced double-layer honeycomb sandwich structure was proposed by filling metallic tubes on the honeycomb holes. The low-velocity impact test was carried out on the tube-reinforced structure experimentally and numerically to evaluate its low-velocity impact response. It indicated that the stiffness, first linear stage slopes, and impact resistance of the honeycomb sandwich structure were increased by tube filling. Besides, the stress and deformation distribution of front and back panels were changed into more scattered and uniform, resulting in the reduction of maximum deflection. The maximum deflection of the front panel could be effectively reduced by filling the upper honeycomb core with aluminum tubes. Filling the lower honeycomb core with aluminum tubes could greatly reduce the maximum deflection of the middle and rear panels. The tube-reinforced honeycomb sandwich structure was a promising structure for weight sensitive applications owing to its improved load carrying capacity and impact resistance. [ABSTRACT FROM AUTHOR]

In this paper, the honeycomb sandwich panel (HSP) reinforced with bi-layer Ceramic (B4C)/Aluminum (Al7075-T6) facesheets is proposed to be used as a shield for spacecraft against meteoroid orbital debris. A modeling strategy based on Lagrange Finite Element-Smoothed Particle Hydrodynamics (FEM-SPH) coupled method to predict the damage characteristics and the hole morphology is presented for the proposed shielding subjected to hypervelocity impact. The results show good agreement with the experimental data. Based on this investigation, significant improvement in resistance capacities is obtained using the bi-layer B4C/Al7075-T6 facesheets compared to monolayer concepts for HSP. [ABSTRACT FROM AUTHOR]

To provide sufficient data and theoretical support for the practical application of Nomex honeycomb sandwich panels, the bending behavior and energy absorption characteristics of the Nomex honeycomb sandwich panels have been analyzed. Based on experiment, theory, and simulation, the relationship between bending performance and specification parameters was clarified, and the failure map of the Nomex honeycomb sandwich panels was plotted, which can provide strong data and theoretical support for the performance prediction and parameter selection of Nomex honeycomb sandwich panels. [ABSTRACT FROM AUTHOR]

Enlightened by face-centered cubic crystal structure, an ultra-lightweight composite sandwich panel with face-centered cubic core (CSPFCC) is proposed, which demonstrates excellent broadband sound insulation as well as great mechanical property. Sound insulation of the new structure was studied experimentally and numerically. Simulation models are established with considerations of acoustic–structure interactions. The experimental results are consistent with the simulation results of CSPFCC. Furthermore, the effects of boundary conditions, material parameters and so forth on the acoustic properties of CSPFCC are studied by numerical model. In addition, the CSPFCC is compared with the composite quadrilateral honeycomb sandwich structure, and its property is better than that of the latter. Sound insulation property of the CSPFCC exhibits good quasi-isotropy, which provides guidance for the research of structural-functional integration design and engineering application. [ABSTRACT FROM AUTHOR]

The present study develops a new type of epoxy resin–aluminum honeycomb composite sandwich panel. Failure modes and typical force–displacement curves are measured through quasi-static localized indentation tests. The effects of different parameters on the elastic ultimate load and energy absorption are analyzed. The results indicate that the newly developed composite sandwich panel has good integrality, stability, and energy absorption capacity. The typical force–displacement curve exhibits three types and all of them consist of six phases, namely: elastic phase, local damage phase, strengthening phase, global damage phase, compaction phase, and bottom destruction phase. The strength and the energy absorption capacity of the composite sandwich panel are affected by composite layer thickness, additional layer thickness, boundary condition, and indenter type. Compared to those of traditional sandwich panel, the mechanical properties of the integrated composite sandwich panel are significantly improved, as the specimen maintains good stability under indentation without undergoing detachment or cracking between the composite layer and the core. [ABSTRACT FROM AUTHOR]

In this article, the quasistatic penetration tests were investigated on unfilled and polyurethane foam filled honeycomb sandwich panels. Failure mechanisms, specific energy absorption, interaction mechanisms, and some structural responses were studied. Comparing the three types of the foam filled sandwich panels with unfilled type, indicates that the absorbed energy of the first, second, and third type of the panels are 23%, 33%, and 58% more than unfilled ones, respectively. In addition, the results showed the enhancement in the dynamic strength and remarkably decrease in the damage area of the sandwich structure when its honeycomb core was filled with polymer foam. [ABSTRACT FROM AUTHOR]

Miura-ori core sandwich structures have aroused considerable research interests as a potential alternative to conventional honeycomb sandwich structures due to various superiorities, e.g., open channels and continuous manufacturing process. Although quasi-static or impact mechanical behaviors have been extensively studied, modal response of Miura-ori core sandwich structures has not been investigated yet. In this paper, carbon-fiber-reinforced Miura-ori core sandwich panels (MSPs) were fabricated with an autoclave processing method. Modal tests were carried out to investigate the structural vibration performances. A finite element analysis of MSPs was developed and validated with the tests results. Fiber orientation influences of both face sheets and core on the natural frequencies were investigated. Furthermore, a parametric study on the modal response of various MSPs models subjected to virtual free vibration was performed, through which the relationships between the fundamental frequencies and the geometric parameters were established. Compared with corrugated core sandwich panel under identical dimension and weight, MSP always possesses higher fundamental frequency, with an increase of 11.7% in the optimum case. It indicates that MSP is much stiffer and could be designed even lighter in aerospace applications. [ABSTRACT FROM AUTHOR]

In this work, a modelling strategy based on damage mechanics is presented for Nomex honeycomb core. The proposed approach is based on the experimental analysis presented by the authors in [1] and consists of the decoupled modelling of the buckling and collapse of cells for the HRH-78 Nomex honeycomb core with two damage parameters. The proposed approach shows good agreement with the experimental tests. The computational cost is low, proving the efficacy of this technique. This strategy may avoid using full 3D models that mimic the real shape and is a step toward a full compression/shear nonlinear model for honeycomb core. [ABSTRACT FROM AUTHOR]

Frequencies and energies of vibrations for a honeycomb sandwich plate with negative Possion's ratio are investigated. Based on Reddy's third-order shear deformation plate theory, von Karman type nonlinear theory and Hamilton theory, the equations of motion for the plate are obtained, free vibrations and vibrations with the damping and in-plane force of the plate are considered, respectively. The changes of real parts of the eigenvalues with the damping and in-plane forces of the plate are obtained. In order to obtain the analytic solutions of the frequencies and energies of the plate, lateral free vibrations are considered by using the Hamilton energy method, and we compare the results with that of the previous free vibrations. The potential energies and the total energies variation with parameters of the plate are given. The research results from the two methods show that the change trends of the frequencies and energy of the plate are exactly consistent, but the values of natural frequencies and potential energies are lager in lateral vibrations. [ABSTRACT FROM AUTHOR]

The dynamic response of honeycomb sandwich panels under aluminum foam projectile impact was investigated. The different configurations of panels were tested, and deformation/failure modes were obtained. Corresponding numerical simulations were also presented to investigate the energy absorption and deformation mechanism of sandwich panels. Results showed that the deformation/failure modes of sandwich panels were sensitive to the impact velocity and density of aluminum foam. When the panel was impacted by the aluminum foam projectile with the back mass of nylon, the “accelerating impact” stage can be produced and may lead to further compression and damage of the sandwich structures. [ABSTRACT FROM AUTHOR]