Investigations on interface and interphase development in polymer-matrix composite materials

The properties and performance of polymer-matrix composite materials depend critically on the microstructure and properties of the interface or interphase developed during the material processing. The term “interface” as used in the study refers to the interlaminar region between two thermoplastic surfaces, while an “interphase” is the region near the fiber surface where the chemical composition and mechanical properties are distinct from those of the fibers and of the bulk. Interface/interphase formation is governed by the transport processes that occur during manufacturing at both the macroscale and microscale. While the past years have observed extensive activities in the study of macroscale phenomena, relatively little research has been conducted in the microscale domains. The difficulties arise primarily from the complexity of geometry and of mechanisms at the microscale; the proposed investigation is aimed at systematically addressing these challenges. There are two parts in the present thesis studying the interface/interphase processes. The first part focuses on the microscale interfacial bonding phenomena during the manufacturing of layered thermoplastic and thermoplastic-matrix composites. The second part of the thesis will investigate the “interphase” formation mechanisms during the processing of thermosetting-matrix composite materials.