爆炸载荷下仿贝壳结构的动态响应

贝壳珍珠层是一种具有高强度和高韧性的天然材料，这种优异的性能主要来源于多尺度、多层级的“砖泥”结构。本文受贝壳特殊结构的启发，构建了仿贝壳砖泥结构的有限元模型，并进行了爆炸实验。通过实验发现:在爆炸冲量为0.047 N·s时，试件发生灾难性破坏，使得中心处发生掉落，且伴随着试件夹持端的剪切破坏，与数值模拟结果具有良好的一致性。在实验基础上，对仿贝壳砖泥结构在爆炸载荷下的动态响应进行了数值模拟。研究发现，在爆炸载荷下仿贝壳砖泥结构会产生五种不同的破坏模式，包括:Ⅰ，结构整体无损伤；Ⅱ，结构前表面无明显破坏，后表面发生破坏；Ⅲ，结构发生掉落型贯穿破坏，夹持端无剪切破坏；Ⅳ，结构发生小块掉落型贯穿破坏，夹持端发生剪切破坏；Ⅴ，结构发生大块掉落型贯穿破坏，夹持端发生剪切破坏。并且给出了不同破坏模式的临界阈值，单层砖泥结构的破坏阈值为0.019 N·s，五层砖泥结构的破坏阈值为0.047 N·s，当冲量超过破坏阈值时，试件发生灾难性破坏。研究分析了堆叠层数对仿生结构的力学响应，在同一冲量下，随着层数的增加，结构的破坏模式发生改变，由贯穿型破坏逐渐变为仅发生一定塑性变形。随着层数增加，结构的损伤阈值增加。最后提出仿贝壳砖泥结构的增韧机理主要有裂纹偏转和微裂纹。

Dynamic response of nacre-like structure under explosion load

Shell nacre is a nature material with high strength and toughness, and the excellent performance is mainly derived from multi-scale, multi-hierarchy with “brick and mortar” structure. Inspired by the special structure of shell, a finite element model of nacre-like brick and mortar structures was created and the explosion experiment was carried out. In the experiment, the sample was destroyed catastrophically at the explosion impulse of 0.047 N·s, with the fall of the center. Additionally, shear failure existed around the clamping end of the specimen, which is in good agreement with the numerical simulation results. On this basis, the dynamic response of nacre-like brick and mortar models under explosive load was explored. Five different failure modes were analyzed, including: mode Ⅰ, inelastic deformation without damage; mode Ⅱ, partial damage with damage in the back surface; mode Ⅲ, through-wall failure in the center of specimen; mode Ⅳ, through-wall failure in the center of specimen and shear failure at the clamping end; mode Ⅴ, devastating damage with large drop through in the center and shear failure. The thresholds critical of different failure modes were obtained based on the simulation results. The threshold value for the one-layer brick and mortar structure was 0.019 N·s, and this value increased to 0.047 N·s for the five-layer brick and mortar structure. When the impulse exceeds the threshold value, catastrophic damage occurrs. The effects of the number of stacked layers on the response of the brick and mortar models were analyzed. With the increase of the number of stacked layers, the failure mode of the structure changes from devastating damage to inelastic deformation. Additionally, the threshold value for brick and mortar structure under explosion load increased with the increase of the number of stacked layers. Finally, the toughening mechanism of nacre-like brick and mortar structure was given, including crack deflection and microcrack.