生物体在形成复合体方面拥有非凡的进化优势,不同长度尺度的分层结构,表现出优异的机械性能。模仿这些结构来合成高性能材料长期以来一直很着迷,并且由于高分辨率显微镜,最近已经看到了快速增长。设计,合成,和测试方法。在天然材料类别中,Nacre,在软体动物贝壳中发现,具有非常高的机械强度和韧性。不同长度尺度的高度组织化的“砖和砂浆”结构是优异的机械性能以及在珍珠母中耗散能量和传播能力的基础。这里,我们采用大规模的原子粗粒分子动力学模拟来研究珍珠层微结构的力学和粘弹性行为。进行了单轴拉伸和振荡剪切模拟,以深入了解复杂的结构-性质关系的作用。具体来说,阐明了微观结构(晶畴的排列)和聚合物-晶体相互作用对机械和粘弹性行为的影响所起的作用。纳米复合材料的拉伸性能被认为是敏感的微观结构,与柱状排列相比,结晶片剂的交错排列产生20-30%更高的模量和更低的拉伸强度。重要的是,交错的微观结构显示出相对于聚合物-晶体相互作用具有高度可调的机械性能。通过显示聚合物链移动性和取向以及成分的承载能力的影响来解释机械性能的根本原因。在频率上研究了三十年的储能,损耗模量和损耗角正切方面的粘弹性响应,并再次强调了微观结构带来的差异。我们证明了我们的粗粒度模型为结构应用的新型仿生结构设计提供了有希望的见解。
Organisms hold an extraordinarily evolutionary advantage in forming complex, hierarchical structures across different length scales that exhibit superior mechanical properties. Mimicking these structures for synthesizing high-performance materials has long held a fascination and has seen rapid growth in the recent past thanks to high-resolution microscopy, design, synthesis, and testing methodologies. Among the class of natural materials,
nacre, found in mollusk shells, exhibits remarkably high mechanical strength and toughness. The highly organized \"brick and mortar\" structure at different length scales is a basis for excellent mechanical properties and the capability to dissipate energy and propagation in
nacre. Here, we employ large-scale atomistic coarse-grained molecular dynamics simulations to
study the mechanical and viscoelastic behavior of
nacre-like microstructures. Uniaxial tension and oscillatory shear simulations were performed to gain insight into the role of complex structure-property relationships. Specifically, the role played by the effect of microstructure (arrangement of the crystalline domain) and polymer-crystal interactions on the mechanical and viscoelastic behavior is elucidated. The tensile property of the nanocomposite was seen to be sensitive to the microstructure, with a staggered arrangement of the crystalline tablets giving rise to a 20-30% higher modulus and lower tensile strength compared to a columnar arrangement. Importantly, the staggered microstructure is shown to have a highly tunable mechanical behavior with respect to the polymer-crystal interactions. The underlying reasons for the mechanical behavior are explained by showing the effect of polymer chain mobility and orientation and the load-carrying capacity for the constituents. Viscoelastic responses in terms of the storage and loss moduli and loss tangent are studied over three decades in frequency and again highlight the differences brought about by the microstructure. We show that our coarse-grained models offer promising insights into the design of novel biomimetic structures for structural applications.