Investigations on Transport Phenomena Governing Interfacial Bonding Evolution in Thermoplastic Composites

University Of Connecticut, Storrs CT

Investigators

Abstract

Thermoplastic-matrix composites are fabricated by incrementally stacking and fusion-bonding layers of fiber-reinforced thermoplastic prepreg tapes to a desired shape and thickness. The evolution of interlaminar bond strength---a principal product quality measure---is governed by the development of interfacial contact area through flattening of the prepreg surface asperities (referred to as the "intimate contact" process), and the interdiffusion 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 microscale processes of "intimate contact" and "healing" pose a fundamental challenge to a reliable description of interfacial bonding evolution during processing. The overall goal of the project is to overcome these impediments. The inherent geometric complexities of the microscale will be rendered tractable using an innovative fractal representation of surface asperity profiles. This will form the basis of microscale transport phenomena models to be developed for describing the asperity spreading and polymer interdiffusion processes. A coupling of the microscale process description with the macroscale heat and momentum transport phenomena models will be used to elicit a comprehensive understanding of interfacial bonding development as function of the process parameters. Complementary experimental studies will be conducted aimed at validating the theoretical developments.