Fiber reinforced composites are used in applications where lightweight, strength, stiffness, fatigue life, and corrosion resistance are critical. Thermoplastic composites (TPC) offer several advantages over thermosetting ones, including higher toughness, recyclability, weldability, and ease of repair. Over the last decade, the interest in in situ consolidation additive manufacturing (AM) of TPCs has increased exponentially due to their potential for rapid cycle out-of-autoclave processes. To this end, several limitations need to be resolved. Specifically in situ consolidation of TPCs usually result in low interlaminar bonding, weak matrix/fiber adhesion, high void content, and low crystallinity. This dissertation aims to provide a new understanding and solutions to these issues. The material system used in this work is carbon fiber reinforced low-melt polyarlyletherketone (LM-PAEK), processed via two AM methods: fused filament fabrication (FFF) and directed energy deposition (DED) in the form of laser-assisted automated fiber placement (AFP). By combining experiments and modeling, this work aims to develop an understanding of how processing parameters affect interlaminar bonding, void development, and crystallinity for both processes. This dissertation also investigates in situ consolidation of TPCs by examining the underlying physics that control bond strength and fracture toughness at inter-layer interfaces. Overall, this dissertation contributes to the knowledge base in the field, toward the adoption of low-energy and high-rate processes for manufacturing high-performance TPC structures.Mechanical Engineerin
