Konrad Julian, Pfaller Sebastian, Zahn Dirk
Lehrstuhl für Theoretische Chemie/Computer Chemie Centrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstr. 25, 91052 Erlangen, Germany.
Lehrstuhl für Technische Mechanik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 5, 91058 Erlangen, Germany.
Polymers (Basel). 2022 Aug 9;14(16):3240. doi: 10.3390/polym14163240.
Epoxy resin plasticity and damage was studied from molecular dynamic simulations and interpreted by the help of constitutive modelling. For the latter, we suggested a physically motivated approach that aims at interpolating two well-defined limiting cases; namely, pulling at the vanishing strain rate and very rapid deformation; here, taken as 50% of the speed of sound of the material. In turn, to consider 0.1-10-m/s-scale deformation rates, we employed a simple relaxation model featuring exponential stress decay with a relaxation time of 1.5 ns. As benchmarks, deformation and strain reversal runs were performed by molecular dynamic simulations using two different strain rates. Our analyses show the importance of molecular rearrangements within the epoxy network loops for rationalizing the strain-rate dependence of plasticity and residual stress upon strain reversal. To this end, our constitutive model reasonably reproduced experimental data of elastic and visco-elastic epoxy deformation, along with the maximum stress experienced before fracturing. Moreover, we show the importance of introducing damage elements for mimicking the mechanical behavior of epoxy resins.
通过分子动力学模拟研究了环氧树脂的塑性和损伤，并借助本构模型进行了解释。对于后者，我们提出了一种基于物理原理的方法，旨在对两种明确的极限情况进行插值；即，在应变速率趋近于零和非常快速变形（此处取材料声速的50%）时的拉伸。反过来，为了考虑0.1 - 10米/秒尺度的变形速率，我们采用了一个简单的松弛模型，其应力呈指数衰减，松弛时间为1.5纳秒。作为基准，使用两种不同的应变速率通过分子动力学模拟进行了变形和应变反转运行。我们的分析表明，环氧网络环内的分子重排对于合理化塑性对应变速率的依赖性以及应变反转时的残余应力至关重要。为此，我们的本构模型合理地再现了弹性和粘弹性环氧变形的实验数据，以及断裂前经历的最大应力。此外，我们展示了引入损伤元素以模拟环氧树脂力学行为的重要性。
