Mahajan Dhiraj K, Hartmaier Alexander
Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, Stiepeler Strasse 129, Bochum 44801, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2012 Aug;86(2 Pt 1):021802. doi: 10.1103/PhysRevE.86.021802. Epub 2012 Aug 10.
Mechanisms leading to initiation of crazing type failure in a glassy polymer are not clearly understood. This is mainly due to the difficulty in characterizing the stress state and polymer configuration sufficiently locally at the craze initiation site. Using molecular dynamics simulations, we have now been able to access this information and have shown that the local heterogeneous deformation leads to craze initiation in glassy polymers. We found that zones of high plastic activity are constrained by their neighborhood and become unstable, initiating crazing from these sites. Furthermore, based on the constant flow stresses observed in the unstable zones, we conclude that microcavitation is the essential local deformation mode to trigger crazing in glassy polymers. Our results demonstrate the basic difference in the local deformation mode as well as the conditions that lead to either shear-yielding or crazing type failures in glassy polymers. We anticipate our paper to help in devising a new criterion for craze initiation that not only considers the stress state, but also considers local deformation heterogeneities that form the necessary condition for crazing in glassy polymers.
导致玻璃态聚合物出现银纹化类型破坏起始的机制尚未完全明晰。这主要是因为在银纹起始位点充分局部地表征应力状态和聚合物构型存在困难。利用分子动力学模拟，我们现在能够获取这些信息，并表明局部非均匀变形会导致玻璃态聚合物中银纹的起始。我们发现高塑性活动区域受到其相邻区域的限制而变得不稳定，从而从这些位点引发银纹化。此外，基于在不稳定区域观察到的恒定流动应力，我们得出结论，微空洞化是触发玻璃态聚合物银纹化的基本局部变形模式。我们的结果展示了局部变形模式以及导致玻璃态聚合物发生剪切屈服或银纹化类型破坏的条件之间的基本差异。我们预计我们的论文将有助于设计一种新的银纹起始判据，该判据不仅考虑应力状态，还考虑形成玻璃态聚合物银纹化必要条件的局部变形非均匀性。
