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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]

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]