Fused filament fabrication of polymer materials: A review of interlayer bond

Fused filament fabrication (FFF), one of the most promising additive manufacturing (AM) methods has attracted considerable attention to date. Although FFF is evolving into a manufacturing tool with significant technological and material advancements, there remains a challenge to transfer FFF-printed parts into functional objects for practical applications. Polymer components fabricated by FFF technique exhibit weak and anisotropic mechanical properties compared to their counterparts by conventional processing. The limited mechanical property for the FFF-printed parts is a result of weak interlayer bond interface that develops during the layer-wise deposition process. This review documents recent advances on the bond interface in FFF-printed parts in aspects of its mechanisms, characterization and enhancement methods. The main objective is to provide a comprehensive understanding of the process-structure-properties of interlayer bond in FFF technique.