In-plane transverse mechanical properties in material extrusion components: critical evaluation of sample preparation methodologies

Abstract Material extrusion (MEX) components exhibit anisotropic mechanical behavior due to their layer-by-layer fabrication process. While extensive research has focused on interlayer properties, the in-plane transverse mechanical behavior remains less thoroughly investigated, particularly regarding how specimen manufacturing strategies affect measured properties. This study compared three distinct fabrication methods: single-specimen direct printing, multiple-specimen simultaneous printing, and specimen extraction from larger printed components. The research combined tensile testing (ASTM D638 Type IV), multi-scale microscopy, and real-time infrared thermography during material deposition to analyze relationships between manufacturing strategy, thermal history, and mechanical properties in PLA specimens. Directly printed test specimens exhibited systematic overestimation of key mechanical parameters compared to specimens extracted from larger components: Young’s modulus (7.3% higher), tensile strength (22.3% higher), and elongation at rupture (27% higher). These discrepancies correlate with distinct thermal histories, with directly printed specimens experiencing shorter interfilamentous times (0.4 versus 3.6 s) and higher minimum temperatures between depositions (122 versus 72 °C), enhancing polymer chain entanglement at filament interfaces. SEM fractography revealed predominantly intralayer failure in directly printed specimens versus increased delamination tendency in plate-extracted specimens. The findings demonstrate that manufacturing strategy fundamentally alters both thermal evolution during printing and resulting polymer chain entanglement, significantly impacting mechanical properties. These results challenge the common practice of using directly printed test specimens to predict the mechanical properties of larger MEX components, highlighting the need for more representative testing approaches that account for scale-dependent thermal effects when designing components for specific mechanical requirements.