Abstract

The in-situ consolidation of thermoplastic composites (TPCs) via automated fiber placement (AFP) represents a promising method for manufacturing advanced high-performance structures, utilizing the distinct advantages of thermoplastics and enabling out-of-autoclave production. However, the widespread adoption of this method is impeded by various, poorly understood defects that can undermine structural integrity. This thesis begins by systematically identifying and characterizing these defects, providing a foundation for future research on their potential impact on mechanical performance. Subsequently, a novel experimental technique is introduced to monitor the temperature of incoming tape during in-situ consolidation, which is the most critical parameter controlling defect development. This is followed by an in-depth theoretical and experimental analysis of the transverse deformation of incoming tape under the compaction roller, a phenomenon that controls the size of gaps and overlaps as key defects in AFP-manufactured composite parts. The insights from this work can deepen the understanding of how specific process and material parameters directly influence the final tape width, paving the way for developing practical strategies to optimize AFP processes to manufacture higher-quality thermoplastic composites free of gaps or overlaps, and minimized dependent defects, e.g. fiber/ply waviness.