Feedstock development and in-operando experiments for 3D printing of polymer matrix composites for demanding defense applications

Additive manufacturing, especially extrusion-based 3D printing, plays a critical role in areas where traditional composite manufacturing is too labor intensive, costly or even impossible. The ability to produce previously un-manufacturable designs combined with attractive economic and lead time benefits has led to significant interest in industry and government to invest in polymer-based 3D printing. Complexity enabled capabilities, part reduction and rapid prototyping are key drivers for DoD applications. While the current state-of-the-art in engineering solutions is progressing at a fast pace, the physics-based understanding of the process is lacking and at best poorly implemented in commercial machines. This inevitably leads to the issue of poor reproducibility with vastly different results from the same equipment conducted in different laboratories, between two pieces of the same equipment within a single laboratory and even between builds in different build plate locations of the same equipment. The fast, non-equilibrium processing space necessitates implementation of novel in-situ metrology controls. In addition, demanding applications that require materials to survive higher temperatures and survive extreme conditions with optimal thermo-oxidative stability are not available in commodity polymer feedstock. This presentation summarizes our efforts in designing and creating new feedstock materials for polymer matrix composite manufacturing via fused deposition modeling (high temperature thermosets) or direct write processes (carbon fiber reinforced epoxy thermosets), including advanced concepts for real-time, in-operando characterization of materials during the additive manufacturing process. The ultimate goal is to provide real-time data for closed-loop feedback control that leads to a sufficiently robust process.