十字嵌锁型格栅夹芯结构设计及低速冲击性能

针对传统复合材料格栅夹芯结构极限承载能力较低、单胞封闭易造成水汽凝结的问题，在分析管胞微观结构和功能性的基础上，提出一种新型十字嵌锁型格栅夹芯结构。首先选取最小体积(最小质量)和最小变形(最大刚度)为优化目标，利用第二代非支配遗传算法(NSGA-Ⅱ)完成多目标优化，采用三维Hashin失效准则和改进的刚度退化方法建立格栅夹芯板的冲击渐进损伤有限元分析模型，研究多种低速冲击载荷对不同相对密度夹芯结构的不同位置的破坏机制及力学响应。结果表明：新型格栅夹芯结构表现出良好的低速冲击阻抗，其随芯子的空间分布存在差异，格栅间隙处的抗冲击性能较弱，芯子密度的提高不能有效增强该位置处的冲击强度，夹芯结构所受到的破坏远远大于冲击器撞击格栅交点处的情况；受不同冲击位置和冲击速度的影响，载荷-时间和位移-时间曲线呈现出不同的典型模式，芯子出现屈曲、分层、粘接剥离、折弯变形等失效形式，复合材料上面板发生混合损伤，随着冲击速度的增加，芯子和面板的损伤程度也愈严重。

Structural design and low speed impact performance of cross recessed grid sandwich

Aiming at the problems of low ultimate bearing capacity of traditional grid sandwich structure and easy condensation of water vapor caused by single cell sealing, a cross-locked grid sandwich structure was proposed based on analyzing the microstructure and function of tracheids. Firstly, the minimum volume (minimum mass) and minimum deformation (maximum stiffness) were selected as the optimization objectives, and the second generation non-dominated genetic algorithm (NSGA-II) was used to complete the multi-objective optimization. The three-dimensional Hashin failure criterion and the improved stiffness degradation method were used to establish the finite element analysis model of progressive impact damage for the grated sandwich plate. The failure mechanism and mechanical response of a variety of low speed impact loads to different positions of sandwich structures with different relative densities were studied. Results show that the new type of sandwich structure shows good shock impedance at low speed. Its differences with the core of the spatial distribution, the shock resistance of grille gaps are weaker. Core density increase cannot effectively improve the impact strength of the location. The sandwich structure is much larger than all the damage by impact grid intersection point of the device. Under the influence of different impact location and impact velocity, load-time and displacement-time curves show different typical patterns. The failure of core appears, such as buckling, delamination, bonding stripping and bending deformation, and mixed damage occurs on the front panel of composite material. With the increase of impact velocity, the damage degree of core and panel becomes more serious.