Additive Functionalization: Combining the Benefits of Additive Manufacturing and Conventional Composite Production by Overprinting

Additive functionalization is a novel additive manufacturing approach that aims to combine design freedom and process agility at low tooling costs through thermoplastic additive extrusion with the extraordinary performance of conventionally manufactured thermoset composites by overprinting the latter. A key prerequisite for enabling this production scenario is to achieve sufficient bond strength between the thermoset composite substrate and the overprinted thermoplastic material. Therefore, thermoset composite plates with different surface modifications were prepared and subsequently overprinted with thermoplastic material. The bond strength of the thermoset–thermoplastic hybrid specimens was evaluated by mechanical testing, while optical and laser scanning microscopy was used to analyze the thermoset–thermoplastic interface and the failure mode. Significant improvements in bond strength for overprinted specimens were achieved by modifying the thermoset composite surface, either through plasma treatment or the integration of thermoplastic films as skin layers.