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Composite sandwich structures with lattice truss cores have both lightweight characteristics and multifunctional potential, which attract a large number of studies on topological optimization, manufacture process and performance evaluation in recent years. However, reliability study on the joint is an inevitable research subject for engineering application, and few studies on inserts within sandwich panels with lattice truss cores are published. In this paper, composite pyramidal truss core sandwich panels with lightweight metallic quadrangular-prism inserts are designed and fabricated. Pull-out and shear tests are carried out to investigate their load capability and failure behaviors, respectively. It is observed that, compared to the honeycomb panels, the present sandwich panels with quadrangular-prism inserts normally can obtain a similar level of pull-out strength but a higher level of shear load capabilities. [ABSTRACT FROM AUTHOR]

• Exact analytical solutions of stress distributions in a hollow cylinder under contact interactions are established. • Governing equations are analytically uncoupled by introducing displacement functions. • Hertz contact is re-written as Fourier series to create a versatile description of contact interactions. • Effects of design parameters on stress fields are comprehensively discussed. • Novel maximum normalized stress maps are created for stress distribution mechanism analysis. Bundled hollow cylinders are extensively found in natural materials and engineering structures. Aiming at a theoretical basis of structural rigidity and integrity, the present study provides exact analytical solutions of stress distribution within a hollow cylinder under contact tractions by the neighbors in one-dimensional chains. Displacement functions are introduced to uncouple the governing equations, and explicit expressions of stress components are obtained. Hertz contact at the interaction surface is considered and re-written by Fourier series to determine the unknown coefficients. Traits of stress distribution within the hollow cylinder are addressed and significant non-uniformity is indicated along both the radius and circumference. Parameter studies are conducted to investigate the effects of material and geometry on the stress distribution. Furthermore, novel maximum normalized stress maps are developed, providing an effective approach to understand stress distribution mechanisms. The ultimate stress transits from the circumferential compressive type to the radial compressive type with the increasing thickness-diameter ratio. If excluding compressive stresses, the hoop tensile and the in-plane shear types are predominant for different thickness-diameter ratios, respectively. The present investigation should help to understand the failure mechanisms and can be utilized to create a versatile method of engineering materials constructed by bundled hollow cylinders. [Display omitted] [ABSTRACT FROM AUTHOR]

• An eco-friendly and low-cost sustainable sandwich structure with cork stopper cores is proposed. • Natural frequencies of the sustainable sandwich panel are theoretically predicted. • Effect of the cork stopper geometric parameters on modal performance is comprehensively addressed. • Influence of packing configuration of cork stoppers on dynamic behaviors is determined. Cork is a natural sustainable material, which is widely used for wine bottle stopper. This paper proposes an environment-friendly and low-cost sandwich concept consisting of cork stoppers and aluminum covering skins for a novel building material solution. A set of prototypes with natural and agglomerated cork stopper cores are fabricated respectively. Modal tests are carried out to address the effect of arrangement orientations in the cores on natural frequencies. Besides, theoretical and finite element analysis are conducted to determine vibration behaviors of the sustainable sandwich structures. The results show that the natural frequencies of the sustainable sandwich panels are highly affected by the parent materials and packing configurations. Furthermore, the effects of cork stopper core dimensions on the vibration performance are determined by a parametric study, providing comprehensive information for sustainable building structure development and waste management. [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]

[Display omitted] • Simple blade coating technique to achieve large-scale self-assembly of graphene oxide (GO) flakes into anisotropic films with gradient structures and controlled patterning. • Statistical analysis method utilizing scanning electron microscopy images for the characterization of materials with macroscopic surface morphology. • Sensing/actuation behavior, responding to external stimuli such as temperature, humidity, and light. • Robust and flexible materials are suitable for application as integral building elements in the bioinspired design of sustainable smart housing and green constructs. Sustainable structural design, utilizing material to imitate natural biological systems, presents both promise and challenges. By avoiding interfacial problems encountered in composite counterparts, such designs offer self-adaptive materials for smart housing and green architecture, etc. In this study, we demonstrate the feasibility of large-scale self-assembly of graphene oxide (GO) flakes into anisotropic films through a simple blade coating technique. Through the application of blade coating to a highly concentrated nematic GO suspension, we successfully fabricate GO films with morphological gradient and patterning. Additionally, we propose a statistical analysis method utilizing scanning electron microscopy (SEM) images for the characterization of materials with macroscopic surface morphology. Furthermore, we explore the application of these GO films as low-dimensional soft actuators, revealing their outstanding stimuli-responsive performance and self-adaptation to environment. Such robust and flexible films can be used as integral building elements in the bioinspired design of sustainable smart housing facilitating remote robotization and sensing capabilities. [ABSTRACT FROM AUTHOR]

• Novel bolt-connected precast concrete walls (PCWs) enhanced by UHPC were proposed. • The PCW enhanced by UHPC exhibited similar seismic behavior to the monolithic wall. • Theoretical calculations for the flexural strength of PCWs were formulated. Existing bolted precast concrete walls (PCWs) have shown disadvantages in terms of high precision in production or insufficient seismic performance compared with cast-in situ walls. Based on this background, new bolt-connected PCWs enhanced by ultra-high performance concrete (UHPC) and connected by spliced bolted joints for use in low-to mid-rise residential systems were proposed. Seven specimens, including one monolithic concrete wall and six bolt-connected PCWs, were tested at a low axial compression ratio and reversed cyclic loads. The effects of the UHPC enhancement area, bolt arrangement, joint position and bolt hole shape of the steel plate on the seismic performance of the PCW were evaluated. The test results indicate that three types of failure patterns could be observed in PCWs, i.e., wall toe compressive failure, joint shear failure and flexural failure. The PCW enhanced by UHPC was able to achieve equivalent performance to the monolithic wall in terms of lateral resistance and energy dissipation. In addition, theoretical calculations for the flexural strength of PCWs corresponding to different failure modes were proposed. The predicted results approximated the test values and were all within the safe range. [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]