In-situ full-field measurements for 3D printed polymers during mode I interface failure

The fracture behavior of parts manufactured by fused filament fabrication (FFF) is highly driven by their mesoscale architecture characterized by the presence of weak interfaces between layers and filaments, likely to fail under loading. We propose an in-situ characterization approach to study the local phenomena driving the mode I interlayer and interfilament failure of FFF polymer specimens and support the development of a constitutive model for the interface damage. We provide full-field displacement and strain measurements by microstereoscopic digital image correlation (DIC) over a region of interest of around 4 × 3 mm2 in the proximity of the propagating crack for differently oriented interfaces. The high-resolution camera framework promotes the crack propagation monitoring and the crack length tracking until the specimen’s brittle failure. The local strain distribution reveals the distinctive mesoscale failure and damage mechanisms of 0°−0° and 0°−90° polylactic acid interlayer and interfilament interfaces. Overall, the 0°−90° stacking ensures higher fracture properties when compared to the 0°−0° counterpart, in agreement with the specimens’ force–displacement response recorded by the electromechanical testing device. Additionally, we propose a correlation between the strain contour plot heterogeneities observed for 0°−90°interlayer interfaces and 0°−0° interfilament interfaces and the specimens’ architecture inspected by scanning electron microscopy or X-ray computed tomography. Ultimately, the full-field measurements promote the development and validation of a constitutive model explicitly capturing the mechanical behavior of the interface.