Fused Filament Fabrication Interface Bonding and Analysis

Additive Manufacturing (AM) and Fused Filament Fabrication (FFF) are taking off around the world as versatile and effective ways to produce numerous items efficiently, without needing expensive molds and machinery for each new item (which traditional injection molding requires). While general criteria exist for optimizing print quality and product strength, no concrete understanding of the interface exists beyond theoretical ideals and extrapolations from well-understood problems. This lack of understanding hinders the ability of manufacturers to better support product strength and quality. Additionally, better strength characterizations would allow for more efficient use of materials when predicted strength exceeds requirements. Current lack of understanding causes significant waste and inefficiency in the FFF field. To address this issue within the scope of my project, my goal is to effectively predict the tensile strength of a product from a small simulation (a few µm or larger) that constitutes an intersection between hot liquid polymer and cooled solid polymer. I will use LAMMPS to simulate this area, first constructing the simulation of hot polymer on cool, letting it reach equilibrium (during which the polymer chains will intermix and intertwine), then pulling the simulation apart and measuring the force required. Given 3D printing is fairly inexpensive, a good extension would be experimental tests to validate results, especially if differing bonding conditions may be simulated and then validated. A final note is that even PLA filament polymer nanostructure isn’t well known and thus preliminary findings (polymer chains length predictions) may be still significant results.