基于跨尺度建模和计算的纤维增强聚合物充填过程取向及应力研究

Fiber reinforced polymer injection molding is one of the hot and difficult problems in the research field of polymer processing. The traditional numerical simulation of injection molding process belongs to macroscopic-scale, and it cannot predict the effects of the microscopic molecular configuration and mesoscopic fiber orientation on the final mechanical properties and appearance quality of polymer products. In this project, the macroscopic-mesoscopic-microscopic trans-scale gas-liquid-solid three-phase flow models which can couple fiber motion are established based on the characteristics of viscoelastic melt flow and heat transfer in the filling process of fiber reinforced polymer injection molding. A framework of perturbational finite volume method on collocated grid coupled with high order AVLSMART scheme is proposed to solve the two and three-dimensional complicated multi-field coupled models. The domain extension method is introduced to handle the complex cavities, and the high precision numerical simulations for fiber reinforced polymer filling processes in complex cavities are realized. In particular, the effects of the evolution processes of molecular configuration, fiber orientation state, flow-induced stresses as well as the corresponding thermorheological behaviors of viscoelastic melt on the products properties are predicted accurately. The theoretical models and numerical methods developed in this research will contribute significantly in accurately predicting the fiber reinforced polymer dynamic filling process and clearly revealing the evolution mechanism of the molecular configuration, fiber orientation and flow-induced stresses, and will provide the theoretical foundation and guideline for practical production processes control.

纤维增强聚合物注塑成型问题是当前聚合物成型加工研究领域的热点和难点问题之一。传统的注塑成型过程数值模拟属于宏观尺度的研究，无法预测成型过程中微观分子构型及介观纤维取向对聚合物制品最终力学性能和外观质量的影响。本项目针对纤维增强聚合物注塑成型充填过程中粘弹性熔体流动及传热的特点，建立耦合纤维运动的宏观-介观-微观跨尺度气-液-固三相流模型。针对二维和三维复杂多场耦合模型，提出一种耦合高阶AVLSMART格式的同位网格摄动有限体积求解方案。针对复杂型腔引入区域扩充法，实现复杂型腔内纤维增强聚合物充填过程的高精度数值模拟，准确预测充填过程中分子构型演化、纤维取向状态、熔体流动诱导应力及其相应的热流变行为对成型制品性能的影响。本项目研究成果有助于更精准的预测纤维增强聚合物的动态充填过程，更清晰的揭示成型过程中分子构型、纤维取向和流动诱导应力的演变机理，进而为实际成型过程控制提供理论基础和指导依据。

注塑成型因具有生产效率高、易于成型复杂形状制品等优点而成为聚合物成型加工领域中最重要的方法之一。本项目从XPP粘弹性流动基准问题的高精度数值模拟研究、宏观-介观-微观跨尺度气-液-固三相流模型的建立和纤维增强聚合物充填过程的预测三个方面开展了纤维增强聚合物注塑成型充填过程取向与应力的数值预测研究工作。首先，采用同位网格有限体积CLEAR方法求解XPP粘弹性流动的控制方程，基于延时修正方法构造动量和本构方程对流项的高精度AVLSMART格式。基于该方法研究了不可压XPP粘弹性流体圆柱绕流和4:1收缩流等问题，精确预测了速度矢量、应力分量、拉升量、分子构型以及温度的分布规律。其次，基于高分辨率Level Set界面追踪方程和纤维运动方程建立了纤维增强粘弹性聚合物充填过程的气-液-固三相流动预测模型。再次，借助高精度数值方法求解多变量、强耦合、非线性的三相流模型，实现了纤维增强粘弹性熔体充填过程的动态数值模拟研究。准确预测了充填过程中分子构型演化、纤维取向状态、熔体流动诱导应力及其相应的热流变行为对成型制品性能的影响。本项目开展的研究工作实现了进一步完善纤维增强聚合物充填过程数值预测理论和算法的目的，计算模型和数值算法的适用性较强，并有助于解决工程实际问题中纤维增强粘弹性聚合物注塑成型相关问题。