The effect of weak interface on the fracture behavior of material extrusion 3D-printed polyetherimide

Understanding the mechanical response and toughening behavior of 3D printed high-performance polymers, with regarding to the weak interface and undesirable internal voids is essential for potential fracture resistant design. However, current study on material extrusion 3D printed (MEX-3DP) part is usually based on linear elastic fracture mechanics, with minor study focused on the post-yield fracture behavior of MEX-3DP parts. Here, the essential work of fracture (EWF) is used for characterizing the weak interface-dependent fracture behavior of MEX-3DP high-performance plastic material polyetherimide (PEI), for the first time, at plain-stress condition. To experimentally measure the post-yield fracture behaviors and toughness, various MEX-3DP double-edge-notched-tension specimens with different raster angles were fabricated and tested based on the EWF principles. The results indicate that both the brittle, quasi-brittle and ductile fracture mechanisms are correlated with the deposited filament slippage, plastic yielding, necking, and interfilamentous debonding behavior, strongly influenced by the raster angle and printing orientation. The highest EWF value was obtained with ±45° raster orientation and the lowest with 0° raster orientation that parallel to crack plane, both controlled by the weak interface between filaments. Furthermore, the fracture surfaces and digital image correlation (DIC) are also tested and evaluated to identify the dominant failure mechanisms. The results clearly indicate the extent and quality of fusion bonding have to be fine regulated in making fracture resistant MEX-3DP PEI components.