Influence of post-processing on the Mode I and Mode II static fracture toughness of additively manufactured carbon fiber composites

• Post-processing improves fracture toughness of AM carbon fibre composites. • Mode I fracture toughness increased by 15.25% after post-processing. • Mode II fracture toughness increased by 17.94% after post-processing. • SEM analysis reveals void reduction and improved fibre–matrix adhesion. • R-curve analysis provides insights into crack initiation and propagation. The layer-by-layer fabrication process of additively manufactured (AM) composites can introduce interlaminar defects that may impact interlaminar fracture toughness. This study investigates the effect of post-processing on the interlaminar fracture toughness of AM continuous carbon fibre/polyamide composites produced via fused filament fabrication. Post-processing samples in an oven at 150 °C enhanced the initiation interlaminar fracture toughness by 9.12 % in Mode I and 17.94 % in Mode II, while the propagation interlaminar fracture toughness increased by 18.14 % and 9.37 %, respectively. Optical microscopy revealed that post-processing reduced the void content, from 6.24 % to 1.12 %. Scanning electron microscopy highlighted that the fracture surfaces of the post-processed samples showed a reduction in void-related defects. These findings demonstrate that the interlaminar fracture toughness of AM composites can be improved through post-processing consolidation, which enhances the materials resistance to crack initiation and propagation.