RVE homogenization of fused deposition modeling (FDM) printed parts: From microscale void characterization to elastic property prediction

Abstract

Inter-raster voids formed during fused deposition modelling (FDM) printing are among the primary microstructural features governing the directional elastic behavior of unidirectional printed parts. In the present work, a measurement-driven representative volume element (RVE) homogenization framework is developed to predict the elastic constants of FDM-printed polylactic acid (PLA) under a 0° raster configuration as a function of two key process parameters: layer height and material flow rate. A full factorial design of experiments (DoE) is conducted, and cross-sectional microscopy images at each design point are analyzed to extract void fraction, void base width, and void height. A curvilinear triangle void model is fitted to the measurements, and response surfaces are calibrated from the DoE points, enabling complete void geometry prediction for new process parameter combinations. The homogenization pipeline is verified against two independent implementations from the literature, with Young's moduli agreeing within 3.7%, shear moduli within 5.3%, and Poisson ratios within 6.2%. The through-thickness modulus E 3 is identified as the dominant process-sensitive constant, ranging from 2176 to 3146 MPa across the design space, governed primarily by layer height, while E 1 remains nearly constant at 3119–3331 MPa. Poisson ratios are found essentially insensitive to process parameters. Framework predictions are validated numerically against RVE homogenization results at four hold-out design points, with deviations within 2.1%. Experimental validation of the three orthotropic Young's moduli is further carried out through tensile tests at the same points, with values consistently below predictions by up to 12.5% across all directions and process conditions.