Transport Phenomena and Microstructure Development in Thermoplastic Composites Processing

在纤维缠绕和拉挤等快速连续制造的情况下，目标是获得高体积分数的纤维，具有均匀的树脂浸渍和粘结良好的结构，没有空洞和残余应力。因此，树脂在非等温条件下的浸渍机理、聚合物在浸渍纤维束界面上的质量扩散以及结构固化时结晶度的变化是此类复合材料加工过程中的关键现象。这项研究将系统地了解质量、动量和能量在连续变形的各向异性定向纤维多孔介质中的传输机制，并检查它们的相互作用并估计它们的相对重要性。然后可以将其集成到工艺模型中，该模型将允许计算作为制造工艺、材料形状和工艺条件的函数的纤维体积分数、孔隙率和残余应力。该方法将包括在严格控制的实验室条件下进行模型实验研究，这将有助于识别和理解剪切变稀粘性流体的流动物理，并将形成理论建模的基础。同时，将探索微观水平上的输运方程在代表各向异性介质的单胞几何中的作用。其目的是建立一个基于微观分析的宏观过程模型，该模型将不同材料形态和工艺条件下的纤维体积分数、孔洞含量和残余应力分布联系起来。为了确定所建立的工艺模型的有效性和实用性，将在包括纤维缠绕和拉挤加工技术在内的实际加工环境中进行实验。这项研究将允许从复合材料中生产更均匀、更高强度的部件。

In rapid and continuous manufacturing situations such as filament winding and pultrusion, the goal is to obtain a high volume fraction of the fibers with uniform resin impregnation and a structure that is well bonded and free from voids and residual stresses. Hence, the mechanics of resin impregnation under non- isothermal conditions, the mass diffusion of the polymer across the interfaces of impregnated fiber bundles and the changing crystallinity as the structure solidifies are key phenomena during the processing of such composite materials. This research will develop a systematic understanding of the mechanisms of transport of mass, momentum and energy in a continuously deforming anisotropic porous media of aligned fibers and examine their interactions and estimate their relative importance. This can then be integrated into process models which will allow calculation of the fiber volume fraction, void fraction and residual stresses as a function of the manufacturing process, material form and processing conditions. The approach will involve model experimental studies in carefully controlled laboratory conditions, which will serve to identify and understand the physics of flow of shear thinning viscous fluids and will form the basis for theoretical modeling. Simultaneously, the role of transport equations at the microscopic level in a cell geometry representative of the anisotropic medium will be explored. The intent being to develop a macroscopic process model based on microscopic analysis that will relate the fiber volume fraction, void content and residual stress distribution of different material forms and processing conditions. To establish the validity and usefulness of the formulated process models, experiments in actual processing environment encompassing of filament winding and pultrusion processing techniques will be carried out. The study will allow the production of more uniform, high strength components from composite materials.