Role of Microstructure on Impact Response and Damage Morphology of Ice‑Templated Porous Ceramics

The central focus of this study is to investigate the influence of microstructure and direction of impact (relative to the growth direction of ice crystals) on the impact behavior of ice-templated sintered alumina materials and understand the relationship between dynamic compressive strength and impact response. All materials were fabricated using alumina suspensions of the same solid loading but at three different freezing front velocity (FFV) regimes; very-high FFV, moderately-high FFV, and low FFV. Lamella wall thickness, pore size, and pore aspect ratio decreased, and wall connectivity increased with FFV. Materials also exhibited a structural gradient along the growth direction of ice crystals. As the templated microstructure became finer with FFV, the impact resistance of the materials increased, and radius of damage crater, depth-of-penetration, and mass loss decreased. Materials also exhibited radial cracking, and the materials fabricated at very-high FFV showed a greater propensity for radial cracking for impact along the growth direction. The impact process evolved in three phases; penetration phase, dwell phase and rebound phase. Analysis of high-speed videos revealed that modifying the microstructure affected not only the impact resistance but also the duration of these phases. Variation in microstructure caused a change in the mechanism of damage evolution during impact. Dynamic compressive strength increased with FFV, and the results revealed a direct relationship between impact response and strength. For both impact and dynamic compression, energy absorption per unit volume increased with FFV, further reinforcing the relationship between impact behavior and the dynamic compressive response of ice-templated materials.本研究的核心聚焦于探究微观结构与冲击方向（相对于冰晶生长方向）对冰模板（ice-templated）烧结氧化铝材料冲击行为的影响，并阐明动态抗压强度（dynamic compressive strength）与冲击响应之间的关联。所有试样均以相同固相负载的氧化铝悬浮液制备，但设置了三种不同的冷冻前沿速度（freezing front velocity, FFV）区间：超高速冷冻前沿速度、中高速冷冻前沿速度及低速冷冻前沿速度。随着冷冻前沿速度提升，片层壁厚、孔径及孔隙长径比均随之减小，而壁体连通性则有所提升。制备得到的材料沿冰晶生长方向呈现结构梯度分布。随着冷冻前沿速度提升，模板化微观结构愈发精细，材料的抗冲击性能随之增强，而损伤坑半径、侵彻深度及质量损失均有所降低。材料同时表现出径向开裂特征，且采用超高速冷冻前沿速度制备的试样，在沿冰晶生长方向受冲击时更易发生径向开裂。冲击过程可分为三个阶段：侵彻阶段、驻留阶段及回弹阶段。高速摄像分析结果表明，调控微观结构不仅会影响材料的抗冲击性能，还会改变上述三个阶段的持续时长。微观结构的差异会改变冲击过程中损伤演化的机制。动态抗压强度随冷冻前沿速度提升而增大，研究结果揭示了冲击响应与材料强度之间的直接关联。无论是冲击试验还是动态压缩试验，单位体积吸能能力均随冷冻前沿速度提升而增大，进一步验证了冰模板材料的冲击行为与动态抗压响应之间的内在联系。