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 investigate the quasistatic pressure load characteristics of an explosion in a confined cabin in a water mist environment, explosion tests were conducted under different explosive and water mist masses. The concentration of water mist, droplet diameter, and quasistatic pressure inside the cabin were measured. On the basis of the theoretical model of quasistatic pressure in adiabatic ideal gas cabins, a theoretical model of the quasistatic pressure in a confined cabin in a water mist environment was established. On the basis of experimental data and theoretical models, an empirical formula was proposed for the peak quasistatic pressure of implosion in a water mist environment. A model for a cabin explosion in a water mist environment was established, and the load characteristics of a cabin explosion under high water mist concentrations were analyzed. The relevant research results contribute to the prediction of the quasistatic pressure of explosions in a confined cabin in a water mist environment.

When a quadrotor unmanned aerial vehicle crosses the water–air interface, it encounters strongly unsteady multiphase interactions that induce abrupt and irregular load variations. To resolve this process, a numerical framework integrating the overset grid method with a volume-of-fluid approach was developed, allowing detailed capture of the water-exit dynamics. The model was validated against classical sphere water-exit experiments, where the predicted free-surface peak differed by less than 6%, supporting its reliability. The flow evolution exhibits distinct stages, including initial surface disturbance, liquid film attachment, and subsequent fragmentation and shedding, rather than following a continuous progression. The influence of key control parameters on both aerodynamic loading and vehicle stability was systematically examined. Increasing rotational speed not only enhances thrust and exit velocity but also intensifies flow-induced fluctuations, which may lead to noticeable attitude instability. This trade-off is particularly sensitive to the timing of speed transition. A switching height of approximately 0.05 m yields a more balanced response, whereas earlier switching introduces torque asymmetry due to persistent fluid coupling. Vehicle attitude further affects the dynamics. Even slight deviations from vertical alignment produce asymmetric near-surface interactions, altering thrust distribution among rotors. As the inclination increases, this imbalance grows rapidly; for example, an initial tilt of 15° can result in pitch deviations exceeding 30°, indicating loss of control. These findings highlight the nonlinear nature of cross-medium transitions and emphasize the need for coordinated structural and control design.

Flexible anti-collision airbags are lightweight and highly deformable and are used for mitigating vessel–bridge collision loads, while reliable analysis requires accurate descriptions of the mechanical behaviour of the airbag materials. A three-layer single-chamber airbag comprising an inner thermoplastic polyurethane fabric (TPU) and two outer woven ultra-high-molecular-weight polyethylene (UHMWPE) reinforcing layers stitched locally by polyamide webbings is investigated. Uniaxial tensile tests are conducted on TPU and UHMWPE in the warp and weft directions, and anisotropic hyperelastic models are established. Based on model comparison and parameter identification, a three-parameter Yeoh base with a weak orthotropic correction is adopted for TPU, while a neo-Hookean base with a strong orthotropic correction is used for UHMWPE. Comparisons of the numerical and experimental results yield R² values exceeding 0.9854 for force and 0.9995 for pressure, with relative differences of 4.183% and 0.348% at the maximum compression ratio $\eta =0.7$, respectively. The test results show that increasing the initial pressure from 0.12 to 0.14 MPa raises the force and pressure increments by 51.1% and 19.7%, respectively. Numerical analysis indicates that prescribed loading rates up to 10 m/min preserve the quasi-static response at $\eta$ of 0.7 with less than approximately 1% deviation. At $\eta =0.7$, increasing the axial loading length ratio ${\eta }_L$ from 0.2 to 0.6 raises the force by 208.7%, while the unit-length force changes by only 7.56%, whereas a larger airbag aspect ratio $\mathsf{\Lambda }$ increases the force but reduces the unit-length force and pressure increment under constant ${\eta }_L$. When the axial eccentricity reaches 0.20, the force and pressure increments rise by 45.5% and 31.3%, respectively. The established models provide a reliable basis for the localized compression analysis of the anisotropic multilayer airbag.

Slamming-induced whipping has been recognized as a key contributor to fatigue damage of large ships operating under severe sea states. However, accurate prediction of whipping responses remains challenging because of complex nonlinear fluid–structure interactions. This study aims to investigate the characteristics of slamming-induced whipping and quantitatively analyze its influence on the fatigue damage of an ultra-large container ship. A three-dimensional fully nonlinear time-domain hydroelastic method, in which the boundary element model is coupled with a Timoshenko beam model, is employed to predict the slamming-induced whipping responses. Segmented model tests in long-crested irregular waves are conducted to provide wave loads of hull girders under severe sea states. The total and wave-frequency vertical bending moments are separated by the fast Fourier transform, and their statistical characteristics are evaluated through probability distributions. Fatigue damage is assessed on the basis of the rainflow counting method and the Palmgren–Miner cumulative damage rule. The contribution of high-frequency whipping responses to fatigue damage is quantitatively evaluated using a fatigue damage factor. It is demonstrated that slamming-induced whipping can significantly amplify fatigue damage by increasing stress amplitudes and cycle counts, particularly under high forward speeds and severe sea conditions. The findings provide a reliable reference for the fatigue design and safety assessment of ultra-large container ships.