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This paper presents the theoretical model of sandwich plate with pyramidal truss cores to investigate the acoustic property of transmission loss. The two-dimensional periodic model is established based on the assumption that the trusses are regarded as Euler-Bernoulli beams. The fluid-structure interaction is considered by imposing velocity continuity condition at fluid-structure interfaces. The periodic governing equations are derived by using space harmonic expansions and the principle of virtual work. Meanwhile, the practical specimens are fabricated by slitting and snap-fit assembly to conduct sound insulation experiment via standing wave tube method. The theoretical result shows satisfactory agreement with experimental data. The numerical discussions are conducted to demonstrate the effects of incident angles and topological parameters which should be helpful for practical design. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM AUTHOR]

Composite sandwich panels with lattice truss cores have dramatic static and dynamic characteristics, which are widely used in aerospace industry. Owing to the inability to sustain localized loads of joining, valid inserts are required to enable the interconnection of the sandwich panels. The present study develops a novel boundary insert parallel to the facesheets for pyramidal lattice truss core sandwich panels. Analytical-mechanical models are addressed for the proposed boundary insert subjected to in-plane pull-out, in-plane shear as well as out-of-plane shear loads and experimental tests are carried out to characterize mechanical behaviors. Failure sequences and mechanisms are discussed comprehensively and good correspondence is obtained with analytical prediction. Finite element simulation models are developed for visualization of internal load distribution. Experimental results show that significant improvements in load capacities can be achieved by the developed boundary insert compared with the interconnection concepts for honeycomb sandwich panels. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Valid configuration of inserts is commonly used for assembly in sandwich structures. Inherently, various uncertainty results in variability in mechanical characteristics of inserts, and need to be addressed adequately. This study explores the reliability of inserts in composite pyramidal lattice truss core sandwich panels. Finite element method is utilized to analyze the sources and sensitivity of uncertainty in mechanical properties of constituent materials and geometry of sub-components. To quantify the reliability of the insert structure in the presence of uncertainty, machine learning technology is used to investigate the uncertainty propagation by a statistical description. Failure probability is observed and the insert structure shows outstanding stability under pull-out loading. The thickness of face-sheets and the properties of the bonding interface play large roles in stiffness and strength, respectively. Suitable process controls should be implemented to maintain the both critical parameters at a high and stable level. [ABSTRACT FROM AUTHOR]

Hybrid composite pyramidal truss sandwich panels combined with multiple damping configurations are fabricated in this work. Modal and quasi-static compressive tests are carried out to investigate the damping and stiffness efficiency of the candidate structures. Experimental results show that such structures combined with damping materials would significantly improve the damping loss efficiency but decrease simultaneously the stiffness efficiency in varying degrees compared with the bare hybrid sandwich panels. In order to evaluate the compatible effect of total damping and stiffness efficiency of the present sandwich structures, a synthetic evaluation criterion is developed, which shows that bare sandwich panels filled with hard polyurethane foam (B-II-HPF) and soft polyurethane foam (B-II-SPF) can yield the best performance up to 2–4 times higher than the base hybrid sandwich panels. It is also shown that multiple patch damping treatments based on the finite element-modal strain energy (FE-MSE) approach are suitable and effective to further improve the total damping efficiency. [ABSTRACT FROM AUTHOR]