Fusion bonding simulations of semi-crystalline polymer composites in the extrusion deposition additive manufacturing process

Extrusion Deposition Additive Manufacturing (EDAM) is a technology where 3-D digital objects are manufactured extruding beads of molten material in a layer-by-layer basis. This technology offers the flexibility for processing pelletized material, and thus a semi-crystalline polymer highly-filled with carbon fiber has been used for printing. Significant technology improvements in the EDAM technology have been made recently, however, the design of the printing strategy is still mostly driven by empirical development. Hence, there is a need for simulation tools that capture the phenomena involved in the EDAM process to drive the development and optimization of this technology. Currently, one limitation of printed parts in terms of mechanical properties is the strength of the interface developed between printed layers. Therefore, the focus of this work is to couple the phenomena involved in the bonding process of adjacent layers to predict the degree of bonding, such as the temperature history, the melting and crystallization of the semi-crystalline polymer and the diffusion of polymer chains. The models utilized to describe these phenomena and their couplings were implemented in a UMATHT user subroutine in Abaqus to predict the evolution of the degree of bonding during the EDAM process. The effects of the couplings implemented in this approach are demonstrated by predicting the evolution of the degree of bonding throughout the simulation of the printing process of a geometry with sections that undergo different cooling and crystallization rates.