Investigations on Transport Phenomena Governing Interfacial Bonding Evolution in Thermoplastic Composites

热塑性树脂基复合材料是通过将纤维增强热塑性预浸料胶带逐步堆叠和熔接成一定形状和厚度而制成的。层间粘结强度的演变-主要的产品质量衡量-由通过使预浸料表面平坦化而形成的界面接触区的发展(称为“亲密接触”过程)以及聚合物分子在接触区的相互扩散(称为“愈合”)所支配。表面粗糙结构的几何复杂性，以及“亲密接触”和“愈合”的强耦合微尺度过程的机制复杂性，对可靠地描述加工过程中界面结合的演变提出了根本的挑战。该项目的总体目标是克服这些障碍。微尺度固有的几何复杂性将通过使用创新的表面密度剖面的分形表示来处理。这将形成描述粗糙扩散和聚合物互扩散过程的微尺度输运现象模型的基础。微观尺度的过程描述与宏观尺度的热和动量输运现象模型的耦合将被用来引起对界面结合发展作为过程参数的函数的全面的理解。将进行补充的实验研究，以验证理论发展。

Thermoplastic-matrix composites are fabricated by incrementally stacking andfusion-bonding layers of fiber-reinforced thermoplastic prepreg tapes to adesired shape and thickness. The evolution of interlaminar bond strength---aprincipal product quality measure---is governed by the development ofinterfacial contact area through flattening of the prepreg surfaceasperities (referred to as the "intimate contact" process), and theinterdiffusion of polymer molecules across the contacted areas (termed"healing"). The geometric complexities of the surface asperity structures,and the mechanistic complexities of the strongly coupled microscaleprocesses of "intimate contact" and "healing" pose a fundamental challengeto a reliable description of interfacial bonding evolution duringprocessing. The overall goal of the project is to overcome theseimpediments. The inherent geometric complexities of the microscale will berendered tractable using an innovative fractal representation of surfaceasperity profiles. This will form the basis of microscale transportphenomena models to be developed for describing the asperity spreading andpolymer interdiffusion processes. A coupling of the microscale processdescription with the macroscale heat and momentum transport phenomena modelswill be used to elicit a comprehensive understanding of interfacial bondingdevelopment as function of the process parameters. Complementaryexperimental studies will be conducted aimed at validating the theoreticaldevelopments.