Infiltration behavior of liquid thermosets in thermoplastic powders for additive manufacturing of polymer composite parts in a combined powder bed fusion process

Polymer-based multimaterial additive manufacturing (AM) has developed into one of the most promising technologies of recent times. A processing concept was developed in previous studies, which targets the implementation of reactive liquids in a thermoplastic powder-bed for the creation of multimaterial polymer composite parts. This process aims to be the first AM process of its kind to fully utilize the potentials of both thermoplastic and thermoset polymers simultaneously. A highly important aspect for this process is the investigation of the infiltration behavior of the reactive liquids within the powder bed, since premature or delayed curing of the liquids could lead to deviations from the intended geometry as well as process errors due to material protrusions. This investigation presents an experimental and a mathematical approach to describe and predict the time which a droplet needs to completely infiltrate the powder bed. The results showed, that the experimental setup is viable to observe the droplet height over time at temperatures of up to 105°C and infiltration times below 500 ms. The mathematical model proved to be a powerful approximation to describe the infiltration behavior of a reactive liquid within a thermoplastic powder bed once a material-specific form factor is determined for each powder material. Through the process of elimination, the independence of the form factor was demonstrated for different powder parameters like the particle size. A theory is presented, which correlates the form factor to the microstructural shape and surface condition of the particles based on SEM images.