This study investigates the effects of build orientation and naturally occurring surface irregularities on the tensile behavior and fracture mechanisms of PLA specimens fabricated via Fused Deposition Modeling (FDM). Specimens were printed with tensile directions aligned either parallel (0°) or perpendicular (90°) to the build layers. Tensile tests revealed significant reductions in yield stress, yield strain, and Young’s modulus in 90° specimens, indicating strong anisotropic behavior caused by weak interlayer bonding. Fractographic observations and 3D scans confirmed that the 90° specimens primarily fractured along interlayer boundaries. Furthermore, quantitative analysis of surface irregularities using stress intensity factor calculations showed that some fractures initiated at regions with pronounced notch-like asymmetries. These findings demonstrate the need to consider not only build orientation but also surface geometry when designing reliable FDM components. The insights presented here contribute to the development of design guidelines for as-printed parts, especially in applications that require structural integrity, such as heat exchangers with complex internal flow paths.
Kobayashi et al. (Wed,) studied this question.