O'Connor Thomas C, Robbins Mark O
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, United States.
ACS Macro Lett. 2016 Mar 15;5(3):263-267. doi: 10.1021/acsmacrolett.5b00838. Epub 2016 Feb 5.
We use large scale molecular dynamics (MD) simulations to determine the tensile yield mechanism of orthorhombic polyethylene (PE) crystals with finite chains spanning 10-10 carbons in length. We find the yield stress σ saturates for long chains at 6.3 GPa, agreeing well with experiments. We show chains do not break, but always yield by slip, after nucleation of 1D dislocations at chain ends. Dislocations are accurately described by a Frenkel-Kontorova model parametrized by the mechanical properties of an ideal crystal. We compute a dislocation core size ξ ≈ 25 Å and determine the high and low strain rate limits of σ. Our results suggest characterizing the 1D dislocations of polymer crystals as an efficient method for numerically predicting the ultimate tensile strength of aligned fibers.
我们使用大规模分子动力学（MD）模拟来确定正交晶系聚乙烯（PE）晶体的拉伸屈服机制，其中有限链的长度跨越10至100个碳原子。我们发现，对于长链，屈服应力σ在6.3 GPa时达到饱和，与实验结果吻合良好。我们表明，链不会断裂，而是在链端一维位错成核后，总是通过滑移产生屈服。位错由一个由理想晶体力学性质参数化的弗伦克尔-康托洛娃模型精确描述。我们计算出位错核心尺寸ξ≈25 Å，并确定了σ的高应变率和低应变率极限。我们的结果表明，将聚合物晶体的一维位错表征为一种数值预测取向纤维极限拉伸强度的有效方法。
