Truss Core Sandwich Structures Research Articles

Blast-Resistant Performance of Steel Petrochemical Control Room with 3D-Kagome Sandwich Wall

As the control brain of the petrochemical plant, blast-resistant performance requirements are important for the sustainability of the petrochemical control room and should be guaranteed when the vapor cloud explosion occurs in the petrochemical production process. The 3D-Kagome truss core sandwich structure is a kind of blast-resistant material with high energy absorption and recycling. Considering the influential factors of the radius of the truss core rod and thickness of the upper and lower panels, in this paper, the blast-resistant performance of a real steel petrochemical control room with a 3D-Kagome truss core sandwich wall was analyzed. With the optimization goal of plastic deformation energy and panel displacement, the optimal wall thickness and radius of the truss core rod were obtained. The optimized blast-resistant walls were assembled, and the dynamic response of the steel petrochemical control room with the 3D-Kagome truss core sandwich blast-resistant wall was analyzed. The simulation results indicate that the truss core layer is ineffective in dissipating blast energy when the radius ratio of the truss core rod exceeds 2.7% of the total wall thickness. Moreover, as the thickness of the upper and lower panels increases from 0.5 cm to 3 cm, the proportion of plastic deformation energy in the truss core layer gradually rises from 55% to 95%, stabilizing at around 90%. The optimal configuration for blast resistance is achieved when the panel thickness ratio is 6.7% of the total wall thickness; the truss core rod radius ratio is 2.7% of the total thickness. This study establishes the effectiveness of the optimized 3D-Kagome sandwich wall as a blast-resistant solution for steel petrochemical control rooms.

Dynamic compressive response of gradient truss–core sandwich structure subjected to underwater shock loading

The dynamic compressive responses of a multi–layer sandwich structures with the truss core were studied experimentally and numerically under the underwater explosion shock loading. A three–layer truss-core sandwich specimen was designed and fabricated from the stainless steel. The density gradient between core layers is realized by changing the cross-sectional size of the truss members in the core layer. A water tank explosion testing device was employed to carry out the underwater explosion experiment. The finite element method was used to investigate the influences of the layered strategy of structures and the density gradient between core layers on the dynamic response. The results reveal that the density–decreasing sandwich panels CBA has the optimal underwater explosion resistance, and the explosion resistance increases as the decrease of the density gradient ratio.

Doubly curved truss core composite shell system for broadband diffuse acoustic insulation

The lattice sandwich structure as a new periodic sandwich model involves high stiffness and superior strength to density ratio, which can be applied for modeling lightweight systems. Compared to conventional sandwich models, it includes additional potential due to the presence of open space in the core. In other words, because of the property of 3D open-pore, the pyramid truss core can be considered as a creative model in process technology. Nevertheless, the acoustic characteristics of these types of cores can also be important in vibroacoustic performance of doubly curved sandwich systems. Accordingly, this study develops an analytical model for the first time to determine the sound transmission loss (STL) coefficient of a doubly curved sandwich shell with solid trusses considering various unit cells containing pyramidal, tetrahedral, and 3D-kagome. Modeling the system based on diffuse field, a numerical strategy is developed to obtain the limiting angle wherein no sound transmits into the system. To verify the accuracy of the offered formulation based on shear deformation shallow shell theory (SDSST), the results are validated with those experimental and numerical outcomes. It is found that modeling a shell as a truss core sandwich structure either attenuates the sound transmitted into the system or shifts the first dip point of the STL curve (curvature frequency) to lower frequencies. Numerical simulations indicate that the various terms of truss core have a different effect on STL of the modeled structure.

Widening the Band Gaps of Hourglass Lattice Truss Core Sandwich Structures for Broadband Vibration Suppression

Abstract This paper proposes a novel phononic crystal sandwich beam (PCSB) for low-frequency and broadband vibration suppression. The representative volume element (RVE) consists of two hourglass truss unit cells with the same span but different rod radii. After validating the modeling method, a model of the PCSB is established to calculate band structure and transmittance response, and the results show good agreement. It is found that the PCSB can open wider and lower band gaps compared to a traditional sandwich beam (TSB). The band-folding mechanism is applied. The PCSB breaks the spatial symmetry, becomes diatomic, and opens the folding points, finally leading to two band-folding-induced gaps. The experiment is conducted on the PCSB, and the vibration band gap property is confirmed. Subsequently, the impacts of geometric parameters on the PCSB’s band gaps are investigated in detail. Design guidelines for tuning the geometric parameters toward lower frequency and broadband band gap are provided based on the parametric study results. In addition, the higher-order band-folding strategy is proposed. It is shown that a multi-folding PCSB can produce more band gaps. However, through two examples, i.e., second-folding and third-folding PCSBs, it is known that simply increasing the folding order may not be effective and even could deteriorate the vibration attenuation ability. In summary, this work explores a general strategy for designing sandwich beams with low-frequency and broadband vibration suppression ability.

Study on damage failure for a new double-triangular truss core sandwich structure

In order to solve the inherent problems of low bonding strength between face and core, a new double triangular truss core sandwich structure with reinforced frame is proposed, and the face and core are melt connected by thermoplastic composite carbon fiber reinforced polyether ether ketone (CF/PEEK). The response of the new double-triangular truss core sandwich structure under three-point bending load is investigated by both theoretical and finite element methods. Firstly, the theoretical prediction equation of bending stiffness and strength of double-triangular truss core sandwich structure is established, and the failure mechanism diagram is constructed. A valid three-point bending finite element model is established by Abaqus to predict the damage pattern of the structure and obtain the results of damage initiation location, damage process, final failure modes and load-displacement curve. The effect of geometric parameters on the bending performance of the sandwich structure was investigated. The results show that the calculated theoretical deflection curves and the ones obtained by numerical simulation are in good agreement. The average error between the two is 7.94%, verifying the reasonableness of the theoretical prediction model. The effect of geometric parameters on the bending performance of the sandwich structure was investigated. The new sandwich structure has stronger bending resistance and better ultimate load capacity than traditional honeycomb and V-shaped structures. Failure modes such as panel crumpling and crushing, fracture of reinforcement frames, buckling and fracture of core rods occur in sandwich structures under bending loads.

Designs of lattice truss core sandwich structures with improved compressive strength and stiffness

Lattice truss core sandwich composite (LTCSC) panels can exhibit high compressive performance until failure is caused by compressive fracture of the composite strut. Early failure of the core-facesheet and central nodes, as well as fiber misalignment, can hinder the full potential of an LTCSC. This study aimed at improving the compressive stiffness and strength of LTCSC panels through minimizing the fiber misalignment and fabrication issues, while strengthening the central and core-facesheet nodes. The lost-molding technique was used to fabricate LTCSC panels, which were then subjected to quasi-static flatwise compression testing. Relative positioning of neighboring composite struts, modification of the carbon fiber path, and strengthening of the core-facesheet node significantly improved the compressive performance of the panels. Based on the findings, compressive strength and stiffness of LTCSC panels can be improved about 100% and 300%, respectively, with minimal increase in weight. Fabricated LTCSC panels were found to demonstrate competitive specific compressive properties in comparison with conventional core materials.

Vibration Attenuation Performance of Meta-lattice Sandwich Structures with Truss-cores

Abstract In recent years, lattice sandwich structures with truss-cores have shown great potential in lightweight, high load-bearing and multifunctional applications. However, there is still a lack of research on the vibration attenaution characteristics of such structures. In this paper, combined with the design concept of elastic metamaterial with the lattice truss-core sandwich structures, a meta-lattice sandwich structure with double-layer pyramidal truss core is proposed to realize superior vibration attenuation performance. Theoretical and numerical investigations are conducted on the bandgap mechanisms of the proposed meta-lattice structures. The efficient vibration suppression within the bandgap range is verified by numerical simulations. The results of this paper are of reference value for the design and engineering application of the lattice truss structure for vibration attenuation.

Multiscale modeling and design of lattice truss core sandwich metastructures for broadband low-frequency vibration reduction

Lattice truss core sandwich structures are advanced lightweight structures that have broad application prospects in many fields, but the attenuation of low-frequency vibrations in these structures is still challenging. To achieve broadband low-frequency vibration reduction in lattice truss core sandwich structures, we propose a design of multiscale lattice truss core sandwich metastructures which exhibit a coupling effect of local resonance and Bragg scattering mechanisms. For ease of analysis and design of such multiscale metastructures, we develop an efficient semi-analytical multiscale modeling method based on a combination of the dynamic homogenization method and the spectral element method. The multiscale modeling method is verified by comparing it with the conventional finite element method, and it is further employed to design multiscale metastructures. Numerical and experimental results demonstrate that the low-frequency bandgap and vibration reduction band can be greatly broadened via an appropriate multiscale design. Specifically, a typical multiscale finite metastructure, fabricated by embedding only three identical local resonators, achieves a significant vibration reduction within the super-wide low-frequency range of 295–905.4 Hz. The normalized vibration reduction bandwidth is as large as 1.02, which is much broader than that of a conventional equi-scale metastructure designed with the same added resonator mass ratio.

Vibration of a Satellite Structure with Composite Lattice Truss Core Sandwich Panels

Composite materials are widely employed in spacecraft, aiming at increasing mass savings and load bearing capacities. Due to the excellent static and dynamic performance, lattice truss core sandwich structures have become one alternative of satellite structure materials. In addition, the dramatic potentials of multifunctional integration accelerate development of new spacecraft technology. In this investigation, a novel satellite structure concept with composite lattice truss core sandwich panels is proposed. A series of vibration tests and a finite element analysis campaign are conducted to determine the dynamic responses of the satellite structure. The developed finite element models provide a feasible numerical analytical scheme to address the vibration performance and structural integrity inspection. And the current satellite structure prototype demonstrates outstanding prospects of significant mass reduction and rapid assembly process.

Acoustic response analysis of periodic orthogonal stiffened composite sandwich structure with pyramidal truss cores

This paper presents analytical studies on the sound transmission loss behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) truss core sandwich structure plates subjected to plane sound wave excitation, wherein three different functionally graded patterns are introduced for the carbon nanotubes through the thickness direction of structures. The effective CNTs material properties for each type are determined by the extended rule of mixture and the governing equations are based on the first order shear deformation theory. The compatibility of displacements on the interface between the plate and the stiffeners is employed to derive the governing equation of each stiffener. By using the modal expansion approach and Rayleigh integral, the sound transmission loss is described analytically. Since no existing results of sound insulation can be found for such composite material plate structure, experimental measurements of composite stiffener sandwich plate which is composed of carbon fiber reinforced composite material are subsequently carried out to validate the theoretical model, and good agreement is achieved. Based on the developed theoretical model, the influences of the volume fractions of CNT, truss core type, distribution type of CNT, stiffener spacing, and truss core height on sound transmission loss are subsequently presented.

Sound insulation performance of pyramidal truss core sandwich structure with frame

Recently, sandwich structures have been widely used in different fields because of their good mechanical properties, but these structures are weak in acoustic performance. In this paper, by combining pyramidal truss core sandwich structure with frame, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the pyramidal truss core sandwich structure with frame is developed to investigate the sound transmission loss (STL) performance. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the incident wave angle and the geometrical parameters on the STL of the structure are discussed.

Optimization and Mechanical Properties of Fabricated 2D Wood Pyramid Lattice Sandwich Structure

In order to obtain a lightweight, high strength, and large design space wooden sandwich structure to meet the needs of modern wooden buildings, the mechanical properties of a fabricated 2D wooden pyramid lattice sandwich structure were studied. In this paper, the mechanical and compressive properties of the specimens with different arrangement of Lattice Sandwich unit cells are studied. The upper and lower panels and core materials are made into a single unit cell by inserting glue, and the prefabricated 2D wooden pyramid lattice truss core sandwich structure is prepared by the mortise tenon splicing method. The results show that the arrangement of the unit cells in the specimen has a significant effect on the bearing capacity, energy absorption, and failure mode of the specimen, and the flat compression performance of the panel-reinforced specimen is better than that of the specimen with unreinforced veneer. The results of finite element analysis are consistent with the test results. The main failure modes are core fracture and panel cracking. These results provide a theoretical basis for the system design of wood-based lattice sandwich structure in the future.

Sound insulation performance of membrane-type metamaterials combined with pyramidal truss core sandwich structure

Recently, sandwich structures have been widely used in different field because of their good mechanical properties but these structures are slightly insufficient in acoustic performance. In this paper, by combining the pyramidal truss core sandwich structure with membrane-type metamaterials, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the membrane-type metamaterials combined with the pyramidal truss core sandwich structure is developed to investigate the sound transmission loss (STL) performance of the structure. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the additional block on the membrane, the tension of the membrane, the incident wave angle and the geometrical size of the structure to the STL of the structure are discussed.

Vibration characteristics of novel multilayer sandwich beams: Modelling, analysis and experimental validations

Multilayer sandwich structures have been extensively studied. However, very few results are reported on the vibration issues of some novel multilayer sandwich structures with lattice truss cores in the literature. To this aim, in this paper, the dynamic modellings of multilayer sandwich beams with pyramidal lattice truss cores are developed, and the vibration characteristics of multilayer lattice sandwich beams are numerically investigated and validated by vibration experiments. The deformation relations of multilayer sandwich beams are theoretically developed in this study, and consequently the constitutive relations of the truss core layers of multilayer sandwich beams are derived by using such a deformation energy based method. Hamilton’s principle and the assumed mode method are used to derive the equations of motion of the multilayer sandwich beams. The natural frequencies of the multilayer lattice sandwich beams are obtained and compared with those from the finite element method (FEM) and experimental tests, which all verified the correctness and feasibility of the proposed numerical method. Contributions of this study lie in the development of the novel deformation relations of multilayer sandwich beams, establishment of the dynamic models, and systematic analysis of vibration characteristics with both the numerical and experimental methods. The present work would facilitate the application of multilayer truss core sandwich structures in engineering fields.

A hybrid joining insert for sandwich panels with pyramidal lattice truss cores

Sophisticated and efficient technique of sandwich attachment for composite sandwich structure assembly is imperatively required by industries. Certain types of joining inserts are widely used to carry the localized loads, but little is known regarding to the joining method for composite lattice truss core sandwich structures. In this study, a novel hybrid insert fastener, which comprises a plurality of carbon-fiber-reinforced grid cells and a metallic part, is developed for pyramidal truss core sandwich structures. Finite element models are developed to predict the failure modes and the load capabilities of different insert locations. Static pull-out and shear experiments are carried out, and the failure behaviors for each load case are discussed. The results show that the shear performance is significantly improved, and the insert position greatly affects the static pull-out behavior. An optimization of the hybrid joining insert to enhance the pull-out characteristic is addressed and verified by the finite element analysis.

Bloch wave based method for dynamic homogenization and vibration analysis of lattice truss core sandwich structures

A unified semi-analytical method for dynamic homogenization and vibration analysis of lattice truss core sandwich beams is proposed. The method is developed based on prediction of both propagating and evanescent Bloch waves in the periodic truss core sandwich beam using a wave finite element method. This is accomplished very efficiently with the requirement of modeling only one unit cell of the periodic sandwich beam, which can be implemented simply by employing a conventional finite element package. A dynamic equivalent Timoshenko beam model is thereby built by matching its propagating and evanescent flexural wavenumbers to those predicted from the original sandwich beam. Dynamic equivalent beam parameters including equivalent flexural stiffness, equivalent shear stiffness, as well as equivalent Young’s modulus and shear modulus are identified and expressed as explicit formulations relating to the two matched flexural wavenumbers. Free vibrations of finite-length lattice truss core sandwich beams with various common boundary conditions are further examined based on analytical natural frequency equations and normal mode functions. It is demonstrated that the proposed method shows excellent agreement with conventional finite element method and provides much better accuracy of natural frequency prediction than a representative existing method.

Thermal buckling and sound radiation behavior of truss core sandwich panel resting on elastic foundation

Due to high stiffness and other potential multifunctional application characteristics, truss core sandwich structure offers a promising alternative to traditional stiffened or corrugated sandwich plates used in aerospace and marine industry. And sound radiation from plate structures is a design factor indicating the power reduction, which can help the lattice truss core sandwich structure meet the acoustic requirements for practical engineering design, but the sound radiation performance of this sandwich structure remains unclear. Based on that, the thermal buckling and sound radiation behavior analyses of truss core sandwich structure resting on elastic foundation in thermal environment are presented in this paper. The mechanical behavior of structure–foundation interaction is modeled as two-parameter model including Winkler and shear foundation. The sound radiation due to a concentrated harmonic force in thermal environment is computed by solving the Rayleigh integral. By comparing with numerical simulation results calculated by commercial finite element software, the accuracy and feasibility of theoretical model developed in this paper are validated. The effects of several key parameters including the truss core radius, inclination angle and height, temperature field and elastic foundation stiffness coefficient on thermal buckling and sound radiation behavior have been subsequently investigated.

Mechanical response of pyramidal lattice truss core sandwich structures by additive manufacturing

ABSTRACTIn this study, metallic pyramidal lattice truss core sandwich structures, including single-layered as well as multi-layered ones, are fabricated from EOS Aluminium AlSi10 Mg, utilizing additive manufacturing method. Out-of-plane and in-plane compression as well as shear tests were carried out in order to measure the stiffness and strength properties of the structures. The out-of-plane compressive strength is determined by buckling of struts, and specimens fail in plastic yielding of face sheets for in-plane tests. And for the shear performance of the specimens, the strength is dominated by the node failure. In addition to experimental testing, finite element models have been developed for simulating the stiffness and strength properties and the numerical results agree well with experimental performance.

A novel meta-lattice sandwich structure for dynamic load mitigation

In this article, a novel meta-lattice sandwich structure is proposed and designed for impulsive wave attenuation and dynamic load mitigation. This original meta-lattice truss core sandwich structure has a similar configuration as a normal lattice sandwich structure, except that its truss bars are composed of meta-lattice truss unit cells. The design philosophy of locally resonant elastic metamaterials is integrated into the meta-lattice truss unit cell whereby a relatively heavier metal core (the resonator) is coated with a soft material layer (rubber coat), which is then connected to an outer shell. Based on this unique construction, several frequency band gaps are created by the locally resonant behavior of the specially designed resonators, in which stress waves within the stopping band gaps are not able to propagate through the material. Analytical spring-mass model is employed to predict the frequency band gaps, whereas numerical finite element simulation is utilized to model the continuum structure under impulsive loadings. The impact response, wave attenuation, and stress distribution contours between normal sandwich structure and meta-lattice sandwich structure are compared and analyzed. The mechanisms of wave mitigation and energy absorption by the internal resonators are thoroughly investigated. Results evidently show that the proposed meta-lattice sandwich structure has a more superior ability for impact mitigation and higher kinetic energy absorption capability due to the locally resonant behavior of the internal resonators.

Influence of manufacturing defects on modal properties of composite pyramidal truss-like core sandwich cylindrical panels

Defects can easily appear in composite lattice truss core sandwich structures during the complex preparation process, which may significantly affect the structural response and decrease the load-carrying capability. The purpose of this paper is to investigate the manufacturing defect sensitivity of modal vibration responses of carbon fiber composite pyramidal truss-like core sandwich cylindrical panels by modal experiments and finite element analysis. Defects including debonding between face sheets and truss cores (DFT), truss missing (DTM), face sheet wrinkling (DFW) and gap reinforcing (DGR) are introduced into the present intact specimen artificially and modal testing is conducted to study their dynamic behavior under free-free boundary conditions. Finite element models consistent with the experiments are then developed to further study the effect of defect extents, locations and forms on the modal parameters of the present sandwich cylindrical panels. Results indicate that the degree of sensitivity of natural frequencies of the present sandwich cylindrical panels mainly depends on the vibration modes, defect extents, locations and forms. In addition, damping loss factors are much more sensitive than their corresponding frequencies. Some conclusions and essential mechanisms are summarized, which is helpful to vibration-based non-destructive evaluation (NDE) of such kind of composite lattice sandwich structures.