Lattice Sandwich Panels Research Articles

Numerical investigation of core plate of pyramid-type lattice sandwich with resonant rings

The pyramid-type lattice sandwich panel is known for its exemplary mechanical characteristics. In this study, we draw inspiration from the local resonance mechanisms observed in acoustic metamaterials and introduce a resonant ring to enhance the capabilities of the panel for damping low-frequency vibrations. We use the finite element method to develop a model to explore the band structure and the corresponding vibrational responses, with a particular emphasis on the significant influence of the bandgap. A comprehensive comparison between the results of experiments and those of simulations unequivocally validated our proposed model. Crucially, our findings underscore that the damping-related effect can be enhanced and the desired range of frequencies can be fine-tuned by appropriately selecting the geometric and periodic parameters of the lattice sandwich panel. These insights have important implications for tailoring materials to specific engineering applications.

A homogenization method for natural frequencies and damping of sandwich panels based on representative volume elements

The existing representative volume element (RVE) homogenization method, grounded in finite element analysis, assumes a planar configuration for the sections of sandwich panels, implying rigidity. To accommodate non-planar displacements, this study introduces a novel homogenization method reliant on the displacements obtained from four-point bending and four-point torsion. The present method is employed to investigate the mode shapes, natural frequencies, and loss factors of sandwich panels utilizing an equivalent single-layer shell model. Validation of the present method is conducted through the analysis of lattice sandwich panels and corrugated sandwich panels incorporating viscoelastic layers. Comparative analyses encompassing the results of the experiment, the conventional solid model method, the present method, and the conventional plane method are undertaken. The universality of the present method is substantiated. The present method enhances the precision of natural frequency prediction.

Experimental study on the impact response of the polyurea-coated 3D auxetic lattice sandwich panels subjected to air explosion

A series of air explosion experiments were carried out on the 3D polyurea-coated auxetic lattice sandwich panels in order to combine the advantages of auxetic materials and polyurea. The deformation, dynamic strain, and acceleration of the front and back plate were obtained. The results show that the dynamic response of the 3D polyurea-coated auxetic lattice sandwich panel could be divided into four stages: the shock wave action stage, the auxetic effect stage, the overall deformation stage, and the oscillation stage. The “N” type displacement time history of the back plate center due to the auxetic effect is found through the experiments. It is also found that the concave “hat-shaped” deformation mode of the back plate is opposite to the impact direction. This anomalous deformation mode is of great significance for impact protection. Finally, three dynamic response mode of the 3D polyurea-coated auxetic lattice sandwich panel subjected to air explosion is revealed. This study could provide a reference for the shock resistance design of structures.

The influence of sizing on the compressive performance of foam-reinforced woven lattice sandwich panels

Woven lattice truss sandwich panels (WLTSPs) structure has excellent anti-stripping ability and energy absorption effect. The warp and weft distributions have an effect on the WLTSPs. Foam-filling technique and different heights of WLTSPs were double studied by the testing. Through the compression test and lateral compression test reveal the deformation, damage, failure and energy absorption. In the compression testing, the foam-filling can effectively increase peak force (PF) and energy absorption (EA), especially the weft distribution along the length direction-the specific energy absorption per unit mass of foam (△SEA) is 7.086 J/g. The foam filling transforms the piles from compression-shear coupled damage to progressive damage. In the lateral compression testing, when the WLTSPs at a low height the foam filling leads the load-displacement curve changes from brittleness to ductility. Foam filling improves the PF of PB by up to 459% at the height of 80 mm and restrain the decrease of bearing capacity with the increased height. The failure modes of the WLTSPs includes bending failure to progressive failure, concave, and the end fracture compression.

Ballistic performance of composite armor impacted by 7.62 mm armor projectile

The purpose of this study is to investigate the effectiveness of composite armor against 7.62 mm ballistic threats. A sandwich panel construction consisting of a 96% alumina ceramic strike face, an annealed aluminum alloy 7075 cubic lattice sandwich panel, and a thin aluminum backing plate were used to create hard armor. The ballistic test based on NIJ standard level III was performed using 7.62 mm × 51 mm NATO projectiles at an impact velocity of 847 ± 9.1 m∙s-1. The influences of the alumina strike face panel with thicknesses of 7, 10, and 14 mm on the ballistic performance were investigated. The results of the ballistic test suggest that hard armor designs can resist a ballistic impact of 7.62 mm × 51 mm NATO projectiles without penetrating them. With the increase in thickness of alumina ceramic tile, the deformation of the aluminum backing plate decreased. Furthermore, the annealed aluminum alloy 7075 cubic lattice sandwich panel could be able to absorb the residual kinetic energy of the projectile after it was eroded by the ceramic strike panel. The damaged targets after ballistic impact were presented. Collectively, these results indicate that the armor composites in this study may be used in military vehicle applications.

Free and random vibration analyses of hourglass lattice sandwich panel using an equivalent model based on variational asymptotic method

The hourglass lattice sandwich panel (hourglass LSP) represents a novel type of lightweight and high-strength structure, showcasing new random vibration characteristics related to its distinct geometric configuration. In this paper, a two-dimensional equivalent plate model (2D-EPM) is constructed based on the equivalent stiffness obtained by the variational asymptotic homogenization of the unit cell. The accuracy of 2D-EPM in analyzing the random vibration characteristics (power spectral density (PSD) and root mean square (RMS) responses, as well as effective mass fraction) is validated by the three-dimensional direct numerical simulation and experiments, and its computational efficiency is greatly improved due to the reduced degree of freedoms. On this basis, the effects of structural parameters on the free and random vibration characteristics are systematically analyzed by using the novelty of unit-cell tailorability. The investigation revealed direct correlations between the displacement PSD and RMS with the aspect ratio and lattice rod radius, whereas the inclination angle and face-to-core thickness ratio exhibited inverse correlations. Furthermore, similarities in the low-frequency behaviors of hourglass, pyramid and auxetic LSPs were evident. Specifically, the displacement–RMS curve of the auxetic LSP was comparatively lower, and the hourglass LSP exhibited a similar response, with the second-lowest RMS curve implying correspondingly strong deformation resistance.

Study on thermal buckling of a lattice sandwich panel (2nd Report, Effects of core stiffness and micro-architectures on the buckling temperature)

In this paper, the critical buckling temperature of a lattice sandwich panel was investigated using FE analysis. In the previous study[Sebata, Y., Ushijima, K., Study on thermal buckling temperature of a lattice sandwich panel, Transaction of the JSME (in Japanese), Vol. 88, No. 905 (2022)], a Pyramid-shaped core unit was selected and the effects of unit-cell height and width on the buckling temperature were investigated. In the present study, two kinds of lattice core, BCC and f2BCC were added for investigation, and the effects of the core stiffness and micro-architecture on the buckling temperature were discussed. It was revealed from this study that the constraint of rotational angle at the connection point between the face sheet and the core strands could enhance the local buckling temperature. Also, enlarging the core stiffness could enhance the local buckling temperature. Moreover, the local buckling temperature can be predicted theoretically based on the thick shell theory by considering the effective width of the face sheet for one unit-cell reflected by the cross-sectional area for a strut.

Experimental and numerical investigation on the buckling of 3D printed sandwich structure with lattice core

In this paper, theoretical analysis, numerical simulation and mechanical test on the 3D printed lattice sandwich structures are carried out to study the buckling performance. 2 types of lattice structures, body centered cubic (BCC) and rhombic dodecahedron (DOD) are included. The lattice sandwich panels are made of ALSi10 Mg alloy materials and manufactured using the selective laser melting technique. The comparative results show that DOD lattice sandwich panel not only has higher bearing capacity, but also shows stronger toughness in the post-buckling stage than BCC type panel, even they have the same characteristic size. The buckling mode depends on the topology of the unit cell. For BCC and DOD type panels, the main buckling modes are local buckling and global buckling respectively. The reasons of different buckling modes are discussed. Moreover, the buckling evolution and failure modes of the two types of panels in the post-buckling stage are investigated.

Fabrication and vibration isolation capacity of multilayer gradient metallic lattice sandwich panels

Sandwich structures have been widely used in ship, aerospace, vehicle and other fields, due to their lightweight and high load bearing properties. With the rapid development of ship stealth technology, multifunctional structures with lightweight, high loading capacity and excellent vibration reduction performances are urgently needed. To achieve the above multifunctional characteristics, we design and fabricate novel gradient metallic lattice sandwich structures via cutting and snap-fit approach. The gradient is governed by the size of the truss width. Modal test and shaking table sweep frequency test are conducted to characterize the vibration characteristics and vibration isolation performances of the structures. The frequency responses are simulated by modal superposition method, which is verified by experimental results. Furthermore, the influences of interlayer gradient, face sheet thickness and hybrid materials on the vibration performances are explored. Results show that the interlayer gradient and face sheet thickness have significant effects on the vibration characteristics of the present structures. The positive gradient structure has the best vibration isolation performance among all the gradient structures. What’s more, reducing the thickness of the face sheets and using hybrid materials are beneficial to achieve low-frequency vibration isolation effect, which can provide a reference for ship vibration and noise reduction technology.

Study on the energy dissipation mechanism of the pyramidal lattice sandwich panel subjected to underwater explosion

The energy dissipation mechanism of a pyramidal lattice sandwich panel subjected to underwater explosion (UNDEX) is studied. Firstly, a three-layer pyramidal lattice sandwich panel with a dimension of 500 mm × 500 mm × 120 mm was fabricated by welding. The deformation mode of the pyramidal lattice sandwich panel subjected to UNDEX is revealed through an experiment. Furthermore, the deformation process of the front and back plates, interlayer sheets, and pyramidal lattices is demonstrated by simulation. The energy absorbed by every component is attained according to simulation results. Finally, the theoretical solution of the dynamic response of the experiment model in the stage of fluid-solid coupling, lattice collapse, and whole deformation is presented. Simulation and theoretical results are consistent with experimental results. Theoretical analysis shows that the advantage of the pyramidal lattice sandwich panel in the resistance to UNDEX is that the fluid-structure coupling effect could be controlled by strength design of the pyramidal lattice. The impulse transmitted to the experiment model could be considerably attenuated to 54.97% of the incident impulse, which is more efficient than the reported literature. This research could support the protection of ship structures subjected to UNDEX.

Dynamic crushing behavior of multi-layered hybrid foam-filled composite graded lattice sandwich panels

The research and development of novel protective structures with excellent mechanical load-bearing and energy-absorbing characteristics are one of the current interests in aerospace, marine, and automobile industries. In this research, we fabricate foam-filled multi-layered hybrid composite graded lattice sandwich panels (MHCGLSPs) with different configurations and investigate their dynamic response characteristics experimentally and numerically. The influences of strain rate, relative density, filled foam, and graded arrangement on the crushing behavior of the present panels are depicted, and three main failure modes including core buckling (CB), facesheet breakage (FB), and polyurethane foam breakage (PB) are revealed. Furthermore, the numerical results obtained by finite element models based on the Hashin failure criterion and Johnson–Cook model are in good agreement with the experimental results. It is shown that all the present MHCGLSPs possess excellent energy absorption performance, and the non-graded specimens and gradually weaker specimens possess better ultimate load-bearing capacity under the premise of equal relative density, which can provide guideline for further studies on the novel multi-layered protective structures.

Design of a New Engine Hood based on Lattice Structure for Pedestrian Protection

This paper designs four kinds of three-dimensional negative Poisson’s ratio lattice structures, based on the two-dimensional concave hexagonal negative Poisson’s ratio honeycomb structure. Different parameters are designed for simulation analysis and experimental research, and the influence of different parameters on Poisson’s ratio is studied respectively. The main contents are as follows: Firstly, the three-dimensional solid model of lattice structure is established by modeling software, and the different structural parameters are determined, and the equivalent mechanical model is established. And according to the relevant structural parameters to establish the test scheme. Then, the finite element software is used to simulate the test core material with different parameters. According to the simulation results, the influence of different parameters on Poisson’s ratio is found out. Then the crashworthiness of the test board with different parameters is simulated and analyzed. According to the results, the most suitable structure is selected and applied to the engine hood. Finally, the simulation experiment of collision between pedestrian head and engine hood is carried out. The results of this paper compare the performance of lattice sandwich panels with different parameter structures in different tests and select the optimal combination of structural parameters. The adjustment and optimization direction of the structure is put forward according to the test results.

Fabrication and compression performance of continuous fiber Octet-truss lattice sandwich structure

Octet-truss is a three-dimensional lattice structure with light configuration and multi-function characteristics. In order to analyze and verify its compression resistance, a method of preparing Octet-truss lattice sandwich panel with continuous fiber was proposed. A set of Octet-truss structure molding tools was designed by this method. Different types of glass fiber and Kevlar fiber specimens were prepared by spatial weaving method and resin curing process, and the axial compression test was carried out. The experimental results show that the mechanical properties of different materials and different sizes of sandwich panels prepared by this method are stable, and the reliability of the preparation process is verified, Combined with the experimental process and electron microscope images, the main failure mode of glass fiber samples is fracture of the struts near the nodes induced by fiber microbuckling, while the Kevlar fiber samples failed by the Euler buckling of the struts.

A physically based constitutive model of Ti-6Al-4 V and application in the SPF/DB process for a pyramid lattice sandwich panel

A physically based constitutive model of Ti-6Al-4 V and application in the SPF/DB process for a pyramid lattice sandwich panel

Shape optimization of lattice sandwich panels for enhansing failure load using linear buckling load factor

Shape optimization of lattice sandwich panels for enhansing failure load using linear buckling load factor

Study on vibration characteristics of sandwich beam with BCC lattice core

In this study, the vibration characteristics of a sandwich lattice beam have been studied using an analytical approach and finite element(FE) analyses. In the analytical approach, a sixth-order partial differential equation for expressing the motion in terms of the transverse displacement has been solved, which is assumed that the sandwich core is deformed mainly by the shear load. Here, a new theoretical approach for predicting the equivalent shear modulus GC∗ of the lattice core is proposed. The analytical prediction of the natural frequency, accounting for transverse shear, agrees well with the FE results. Also, the vibration response of the first-order natural frequency f1 exhibits a upwardly convex curve as the strut diameter increases, suggesting that there is a maximum value of the frequency f1 for a given facesheet thickness tf. Moreover, it is observed that the maximum frequency of the sandwich lattice beam is always greater than that for a continuum beam, which ensures the effectiveness of the lattice core in enhancing the vibration response. Therefore, vibration suppression in aircraft structures can be achieved by introducing lattice sandwich panels.

Compression and hysteresis responses of multilayer gradient composite lattice sandwich panels

In order to improve the combat effectiveness, stealth and safety of the marine structures, we design and fabricate the multilayer gradient composite lattice sandwich panels (MGCLSPs) to achieve excellent mechanical properties, vibration isolation characteristics and lightweight features of structures in the present study. The ideas of bionic gradients and material mixtures are incorporated in the design to improve the damping and vibration isolation behaviors of the MGCLSPs. The compression and hysteresis responses of the empty and polyurethane foam-filled MGCLSPs are investigated experimentally and numerically. It is found that the MGCLSPs have better energy absorption characteristics than the non-gradient panels, and the MGCLSP specimen D1 which is positive gradient absorbs the most energy. The experimental results also show that the addition of polyurethane foam can enhance the strength and energy absorption characteristics of MGCLSPs.

Quasi-static and dynamic behavior of sandwich panels with multilayer gradient lattice cores

The static/dynamic compressive performances of sandwich panels with density gradient lattice core were investigated by experimental and numerical methods. A three-layer stainless steel lattice sandwich panel was proposed, and the density gradient between core layers of the sandwich panels was achieved by varying the cross-sectional dimensions of truss bar of each layer. A large diameter Hopkinson pressure bar device was employed to carried out the dynamic impact experiment. The three-dimension finite element method was used to investigate the effects of gradient scheme of core layers and the impact velocity on the structural response. The results reveal that, there exists different failure mechanism between non-gradient lattice sandwich panels and gradient lattice sandwich panels, and the ABC gradient configuration is optimal due to its higher impact strength and better energy absorption capacity at a higher impact velocity which can buckle the truss bars of all layers of gradient lattice sandwich panel.

Enhanced heat transfer in a pyramidal lattice sandwich panel by introducing pin-fins/protrusions/dimples

Three different heat transfer augmentation techniques namely pin-fins, protrusions and dimples applied to the substrate of a pyramidal sandwich panel are investigated. The flow and heat transfer characteristics of the three modified panels are numerically analyzed and the results are compared with those of the base pyramidal sandwich panel with no surface modification. The heat transfer augmentation techniques applied here change the fluid flow pattern and accelerate the flow adjacent to the substrate leading to higher heat transfer rates compared to the base case. At a fixed Reynolds number, the introduced pin-fins and protrusions enhance the overall Nusselt number by 11.4%–13.3% and 7.2%–7.6%, respectively, while the dimples slightly enhance the overall Nusselt number by 1.8%–3.1% compared to the base pyramidal sandwich panel. All of these surface modification techniques increase the pressure drop. The goodness factor for the four cases are also presented.

Effective thermal conductivity and heat transfer characteristics for a series of lightweight lattice core sandwich panels

The body-centered cubic lattice sandwich panels have superior mechanical performance, and current works only focus on their mechanical performance. The effective thermal conductivity and heat transfer characteristics for a series of body-centered cubic lattice sandwich panel were explored by theoretical analysis and numerical modeling. It is revealed that through the rational design of the geometry, the relative density is modulated to be within 5%, suggesting the excellent lightweight character is obtainable. The numerical simulation agrees well with the theoretical predictions, indicating the theoretical expressions can well predict the effective thermal conductivity with the consideration of the heat conduction and cavity radiation. The effective thermal conductivity is within 3.5 W/(m·oC) which is much lower than that of the constituent, indicating the design of the lattice core sandwich panel reduces the effective thermal conductivity as well as gives the lightweight design. It is revealed that the sandwich panel PY always presents the low relative density and high insulation efficiency. The results obtained in this work provide a basic reference to the parameter selection of the body-centered cubic lattice core sandwich panels for the potential applications in hot structures.