In-Situ Structural Characterization of Rubber during Deformation and Fracture
In-Situ Structural Characterization of Rubber during Deformation and Fracture
复制标题
橡胶变形和断裂过程中的原位结构表征
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
G. Heinrich
中科院分区：
文献类型：
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作者：
K. Brüning;K. Schneider;G. Heinrich
为了深入了解弹性体的机械和断裂行为，必须对材料进行彻底的表征，以建立结构-性能关系。同步加速器 X 射线衍射和散射用于表征填充和未填充天然橡胶在原位变形下的特性，并使用定制的微型拉伸试验机来测试准静态、动态循环和冲击载荷。应变诱导结晶的程度和动力学解释了天然橡胶优异的机械和撕裂性能，在各种载荷情况下确定了时间和空间分辨率。采用应变步法，建立了一个新模型来描述应变诱导结晶的动力学。 1 Hz 循环加载期间的在线表征可以深入了解实际加载条件下快速时间尺度的结构过程，从而更好地了解静态和动态裂纹扩展。有关填料取向和空化的信息通过超小角 X 射线散射 (USAXS) 获得。发现单轴应变大小和不等轴模型填料颗粒方向之间的直接联系并将其应用到模型中，从而能够根据第一原理对散射图案进行定量分析。显示了疲劳载荷下填料取向的可逆性。填充橡胶中的空化过程被认为对于应变能的耗散至关重要，但也是宏观裂纹的潜在前兆。由于新相边界的形成，空腔显着增加了散射强度。通过扫描 USAXS，采用三相模型量化空化程度，识别了拉伸炭黑填充橡胶的本体和裂纹尖端附近的空化过程。这些对弹性体在应变下结构变化的新见解为开发物理上健全的本构力学模型开辟了新的可能性。
To obtain an in-depth understanding of the mechanical and fracture behaviors of elastomers, a thorough material characterization is inevitable to establish structure-property relationships. Synchrotron X-ray diffraction and scattering were used to characterize filled and unfilled natural rubber under deformation in situ, using tailor-made miniature tensile testing machines for quasistatic, dynamic cyclic and impact loads. The degree and kinetics of strain-induced crystallization, which accounts for the excellent mechanical and tear properties of natural rubber, were determined under various loading cases with unraveled resolution in time and space. Employing a strain-step method, a new model was established to describe the kinetics of strain-induced crystallization. On-line characterization during cyclic loading at 1 Hz gave insight into structural processes on fast time scales under realistic loading conditions, enabling a better understanding of static and dynamic crack growth. Information about filler orientation and cavitation was obtained by ultra small-angle X-ray scattering (USAXS). A direct connection between the magnitude of uniaxial strain and the orientation of anisometric model filler particles was found and implemented into a model, enabling a quantitative analysis of the scattering patterns from first principles. The reversibility of filler orientation under fatigue loading was shown. Cavitational processes in filled rubbers are thought to be crucial for the dissipation of strain energy, but also are potential precursors of macroscopic cracks. Cavities significantly increase the scattering intensity due to the formation of new phase boundaries. Cavitation processes were identified in the bulk and in the vicinity of crack tips of stretched carbon black-filled rubbers by scanning USAXS, employing a three-phase model to quantify the extent of cavitation. These new insights into the structural changes in elastomers under strain open new possibilities for the development of physically sound constitutive mechanical models.