Experimental, numerical and analytical study to develop a design method for bending and shear resistances of 3D printed beetle elytron inspired sandwich plate (beetle elytron plate)

Beetle elytron plate (BEP) is a new type of sandwich structure inspired by the internal architecture of beetle
elytra and characterized by trabeculae in the core to achieve better mechanical resistance compared to
conventional honeycomb sandwich plate under lateral loads. To take advantage of this improved performance
in design, this paper presents, for the first time, a series of static four-point bending and shear tests for
buckling and post-buckling behaviour of small-scale 3D printed BEPs until failure. Tensile coupon tests were
also carried out on the 3D printed material. The experimental results are then used to validate ABAQUS
numerical modelling that previously could only be partially carried out due to a lack of experimental data. The
test results confirm large increases in BEP resistances compared to conventional honeycomb sandwich plates of
the same dimensions. The observed BEP failure mode under bending is post-buckling of the compressive skin.
Assuming that the post-buckling stress of BEP can be calculated in the same way as conventional sandwich
plate, and making use of the elastic–plastic buckling stress solution for BEP that had previously been proposed
by the authors, this paper proposes a simple method to calculate the post-buckling stress of BEP for design
purpose. For shear resistance, the shear buckling stress of the trabecular core of BEP can be calculated in
the same way as for conventional honeycomb sandwich plate except for using the web width between the
near edges of the two adjacent trabeculae. The proposed calculation methods give results in good agreement
with experimental results, with the maximum difference being 8%. The difference would be even lower if the
smooth 3D printed surface is under compression.