Various studies have reported the changes in the mechanical properties and the modification in morphology of polyamide due to the absorption of water. However, the relation between the local water content and the alteration in the properties has not been consolidated in a coupled model yet. In the current work, a simulation model is proposed that can capture the diffusion of water as well as simulate the effect of the local moisture content on the stiffness of polyamide (PA6). To this end, a finite element model was developed by coupling of a nonlinear diffusion model and a viscoelastic material model. The Galerkin finite element method was used to formulate the weak form of the equations for the two physical processes. The coupled nonlinear equations were solved with the help of the Newton method. The diffusion process was studied experimentally with the help of gravimetric measurements. Relaxation tests were conducted on the polyamide specimens that were saturated under different moisture levels. Based on these experimental results, the dependency of the material parameters on the local moisture content was identified and an efficient and stable numerical simulation model has been developed.

中文翻译：

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PA6中的水分传输及其对机械性能的影响

各种研究已经报道了由于吸水而引起的机械性能的变化和聚酰胺形态的改变。但是，局部水含量与性质变化之间的关系尚未在耦合模型中得到巩固。在当前的工作中，提出了一个模拟模型，该模型可以捕获水的扩散以及模拟局部水分含量对聚酰胺（PA6）刚度的影响。为此，通过非线性扩散模型和粘弹性材料模型的耦合建立了有限元模型。使用Galerkin有限元方法来表示两个物理过程方程的弱形式。借助于牛顿法求解了耦合的非线性方程。借助重量分析法对扩散过程进行了实验研究。对在不同水分含量下饱和的聚酰胺样品进行松弛测试。基于这些实验结果，确定了材料参数对局部含水量的依赖性，并开发了有效而稳定的数值模拟模型。