To investigate the effect of nodal configuration on the mechanical properties of hexachiral honeycombs, three specimens, namely, a standard honeycomb, a thickened-node honeycomb, and a filled-node honeycomb, were prepared using 3D-printing technology. Several quasi-static compression tests were performed, which revealed that nodal reinforcement can inhibit nodal aberrations during ligament winding, thus facilitating the “rotational” mechanism and improving the negative Poisson’s ratio properties of the honeycomb. Experiments performed using the finite element method showed that nodal reinforcement mainly played a role in the stage of stress rise, and the role of nodal filling was more significant than that of nodal thickening. Low-strain standard honeycombs presented the highest specific absorption energy. However, the specific absorption energy of the filled-node honeycomb and the thickened-node honeycomb exceeded that of the standard honeycomb at a strain of 0.71. The conclusions presented herein can aid in the optimal design of honeycombs and contribute to the design of protective structures.

Numerical simulations are carried out to investigate the vortex-induced vibrations of a two-degree-of-freedom (2DOF) near-wall rotating cylinder. Considering the effects of gap ratio, reduced velocity and rotational rate, the amplitude response, wake variations and fluid forces are analyzed, with the Reynolds number of 200 and the mass ratio set to 1.6. The correlative mechanism in the wake–hydrodynamics–vibration is revealed. The results show that the influence of the wall dominates the vortex-induced vibration of the cylinder. The effect of the wall on the vibration weakens as the gap ratio increases, and the effect of the wall on the vibration is negligible when H/D > 1.1. The forward rotation of the cylinder enhances the wall effect, while the backward rotation presents the reverse effect. The vortex-induced vibration of the cylinder is suppressed when 0 < α < 1, and the amplitude range is concentrated at V_r ∈ (3, 5). The wake mode can be divided into five modes, and the wake modes are clarified under different rotation rates and reduced velocities.

An improved star-shaped honeycomb (ISSH) is a kind of honeycomb structure with excellent performance. The main objective of this study was to provide some ideas for the optimization of the ISSH structure in ships. As a result, 2D-ISSH specimens were fabricated using 3D printing technology, and a quasistatic compression test was carried out to investigate the deformation mode and mechanical properties. The experimental results showed that the 2D-ISSH structure exhibited “V”-shaped and “-”-shaped deformation patterns with a double-platform stress stage. To further utilize the excellent performance of the structure and obtain a better negative Poisson’s ratio effect and broader application, based on the properties of the 2D-ISSH specimen, a 3D-ISSH structure was proposed and a finite element simulation was carried out. The simulation results of the 3D-ISSH structure showed different deformation patterns, including “X”- shaped and “-”-shaped patterns. According to the deformation mechanism of typical cells, the stress formula for the 3D-ISSH double platform was derived, and the theoretical results agreed well with the numerical results. The effects of the structural design, materials, and dimensions on the mechanical properties, such as the energy absorption and negative Poisson’s ratio, of the ISSH and similar structures were explored. The combined performance of various honeycombs was evaluated from multiple perspectives.

Sandwich structures are often used as protective structures on ships. To further improve the energy-absorbing characteristics of traditional honeycomb sandwich structures, an energy-absorbing mechanism is proposed based on the gradient folding deformation of lotus root nodes and a leafy stem vein homogenizing load mechanism. A honeycomb sandwich structure is then designed that combines lotus root nodes and leafy stem veins. Four types of peak-nest structures, traditional cellular structure (TCS), lotus root honeycomb structure (LRHS), leaf vein honeycomb structure (LVHS), and lotus root vein combined honeycomb structure (LRVHS), were prepared using 3D printing technology. The deformation modes and energy absorption characteristics of the four honeycomb structures under quasistatic action were investigated using a combination of experimental and simulation methods. It was found that the coupling design improved the energy absorption in the structural platform region of the LRHS by 51.4% compared to that of the TCS due to its mechanical mechanism of helical twisting and deformation. The leaf vein design was found to enhance the peak stress of the structure, resulting in a 4.84% increase in the peak stress of the LVHS compared to that of the TCS. The effects of the number, thickness, and position of the leaf vein plates on the honeycomb structure were further explored. The greatest structural SEA effect of 1.28 J/g was observed when the number of leaf vein plates was four. The highest SEA of 1.36 J/g was achieved with a leaf vein plate thickness of 0.6 mm, representing a 7.3% improvement compared to that of the 0.2 mm thickness. These findings may provide valuable insights into the design of lightweight honeycomb sandwich structures with high specific energy absorption.

To study the load-transfer law and shock environment of a pipe–float system, an experimental model was designed, manufactured, and installed on a floating shock platform. Two underwater explosion cases were studied, focusing on vertical and horizontal shock cases. The experimental results show that the structure of the system on the floating raft significantly influences the load acceleration transfer and the composition of the vertical and horizontal components. Furthermore, the flexible connector can effectively block the response behavior of the two ends of the pipe, and the peak acceleration difference between the two pipe ends is 98.9%. The vertical and horizontal components of the shock-wave load affect the stress concentration locations on the pipe. The main frequency in the shock environment at the connection point between the floating raft and the upper equipment shifts toward middle and low frequencies under the influence of the upper equipment, and it will be closer to the natural frequency of the upper equipment.