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Honeycomb structures exhibit outstanding mechanical properties with specific unit cell configurations. We introduce a novel honeycomb structure that can enhance the compression property and energy absorption capacity by utilizing four-dimensional (4D) printing technology with polylactic acid (PLA) materials. In the designed honeycomb structure, the walls of the adjacent unit cells are independent, and the shape of the unit cells can be transformed between a hexagon and triangle under external loading and temperature stimulus. 4D printing technology is employed to prepare the honeycomb specimens, and the deformation processes of the innovative honeycombs are implemented. Structure I (a novel hexagonal honeycomb structure) and Structure II (a semi-triangular honeycomb structure) can be transformed into each other. Uniaxial quasi-static compression and impact tests are conducted to investigate the compression property and energy absorption capacity of the designed honeycomb structures. The results indicate that the novel honeycomb had a high compression property with Structure II, and had high energy absorption capacity with Structure I; thus, the developed honeycomb structures have broad application prospects for the multifunctional applications of honeycomb structures in the future. [ABSTRACT FROM AUTHOR]

In order to efficiently evaluate and design honeycomb structures with excellent energy-absorbing ability, in-plane dynamic response and multi-objective optimization of negative Poisson's ratio (NPR) honeycomb structures with sinusoidal curve are performed in this work. By establishing the in-plane impact finite element model, the deformation modes and in-plane dynamic responses of the sinusoidal NPR honeycomb structures under different impact velocities are detailed studied. And the geometric parameters (e.g., the amplitude and period) of the sinusoidal curve that affect the energy absorption performance of the structure are analyzed. Combining the optimal latin hypercube design method with the double-points infilling criterion, the high-precision adaptive Kriging models of the peak crush force (PCF) and the specific energy absorption (SEA) with respect to the amplitude and period are constructed. And then, a multi-objective crashworthiness optimization is carried out by non-dominated sorting genetic algorithm (NSGA-II). The Pareto optimal solution set is gained and the final compromise solution is then obtained based on the fitness function. The optimized results show the PCF of the sinusoidal NPR honeycomb structure decreases by 30.53%, while the SEA increases by 38.55%. It indicates that the optimized sinusoidal honeycomb structure has better energy absorption performance than the conventional concave hexagonal honeycomb. The results can provide some important design guidance for other honeycomb energy-absorbing structures. [ABSTRACT FROM AUTHOR]