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Imaging Inelastic Fracture Processes in Biomimetic Nanocomposites and Nacre by Laser Speckle for Better Toughness
Advanced Science ( IF 15.1 ) Pub Date : 2017-12-18 , DOI: 10.1002/advs.201700635
Tuukka Verho 1 , Pasi Karppinen 2 , André H. Gröschel 3 , Olli Ikkala 1
Affiliation  

Mollusk nacre is a prototypical biological inorganic–organic composite that combines high toughness, stiffness, and strength by its brick‐and‐mortar microstructure, which has inspired several synthetic mimics. Its remarkable fracture toughness relies on inelastic deformations at the process zone at the crack tip that dissolve stress concentrations and stop cracks. The micrometer‐scale structure allows resolving the size and shape of the process zone to understand the fracture processes. However, for better scalability, nacre‐mimetic nanocomposites with aligned inorganic or graphene nanosheets are extensively pursued, to avoid the packing problems of mesoscale sheets like in nacre or slow in situ biomineralization. This calls for novel methods to explore the process zone of biomimetic nanocomposites. Here the fracture of nacre and nacre‐inspired clay/polymer nanocomposite is explored using laser speckle imaging that reveals the process zone even in absence of changes in optical scattering. To demonstrate the diagnostic value, compared to nacre, the nacre‐inspired nanocomposite develops a process zone more abruptly with macroscopic crack deflection shown by a flattened process zone. In situ scanning electron microscopy suggests similar toughening mechanisms in nanocomposite and nacre. These new insights guide the design of nacre‐inspired nanocomposites toward better mechanical properties to reach the level of synergy of their biological model.

中文翻译:

通过激光散斑成像仿生纳米复合材料和珍珠母中的非弹性断裂过程,以获得更好的韧性

软体动物珍珠质是一种典型的生物无机-有机复合材料,通过其实体结构使高韧性,刚度和强度相结合,从而激发了几种合成模拟物。其卓越的断裂韧性取决于裂纹尖端加工区的非弹性变形,从而消除了应力集中并阻止了裂纹的产生。微米级结构允许解析过程区域的大小和形状,以了解断裂过程。但是,为了获得更好的可扩展性,人们广泛追求具有取向的无机或石墨烯纳米片的拟真纳米复合材料,以避免诸如珍珠母或原位生物矿化缓慢等中尺度片材的堆积问题。这要求探索仿生纳米复合材料的加工区的新颖方法。在这里,利用激光散斑成像技术探索了珍珠质和珍珠质粘土/聚合物纳米复合材料的断裂,即使没有光学散射的变化,也能揭示出加工区域。为了证明其诊断价值,与珍珠质相比,受珍珠质启发的纳米复合材料更陡峭地形成了一个加工区域,而平坦的加工区域显示出了宏观的裂纹挠度。原位扫描电子显微镜表明在纳米复合材料和珍珠质中类似的增韧机理。这些新的见解指导了以珍珠为灵感的纳米复合材料的设计朝着更好的机械性能迈进,以达到其生物学模型的协同作用。受珍珠质启发的纳米复合材料更突然地形成了一个加工区域,其宏观裂纹变形表现为平坦的加工区域。原位扫描电子显微镜表明在纳米复合材料和珍珠质中类似的增韧机理。这些新的见解指导了以珍珠为灵感的纳米复合材料的设计朝着更好的机械性能迈进,以达到其生物学模型的协同作用。受珍珠质启发的纳米复合材料更突然地形成了一个加工区域,其宏观裂纹变形表现为平坦的加工区域。原位扫描电子显微镜表明在纳米复合材料和珍珠质中类似的增韧机理。这些新的见解指导了以珍珠为灵感的纳米复合材料的设计朝着更好的机械性能迈进,以达到其生物学模型的协同作用。
更新日期:2017-12-18
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