Yielding and post-yielding behavior of FDM parts under compression stress at different strain rates

The present study investigates the compression behavior of components made by material extrusion, also known as fused filament fabrication (FFF) or fused deposition modeling (FDM). An experimental plan was conducted by adopting a high-density fulfillment and varying the material flow. Additional tests were performed by thermomechanical compaction to produce full-density samples. Compression tests were performed at various strain rates ranging between 5 × 10−4 and 5 × 10−1 s−1. Yielding and post-yielding behaviors were analyzed. Morphological analysis was carried out to determine the mesostructural features (interlayer neck and void sizes) and how they behave during the compression test. The results indicated that the principal dimension of the voids ranged between 65 mm and 170 mm depending on the adopted value of the extrusion multiplier. On the other hand, thermomechanical compaction enabled the restriction of the voids of printed samples to 10 mm. The cross-sectioning of samples at different strains indicated the formation of shear banding strain localization. In addition, printed samples behaved like porous media during the compression tests and showed different characteristic regions with different void dimensions. The samples printed at the higher material extrusion showed similar behavior to compacted samples. Post-yielding analysis indicated that strain softening observed on compacted samples was more severe as compared to that observed on printed samples. This behavior is dramatically reduced by decreasing the extrusion multiplier.