Flexural Behavior of Material-Extruded PLA Components: Analytical, Experimental and Numerical Assessment of Stiffness and Strength

Additive Manufacturing (AM), particularly polymer 3D printing, enables the production of structural components with complex geometries; however, predicting mechanical stiffness and strength directly from manufacturing conditions remains a major challenge. In Material Extrusion (MEX) processes, as defined by ISO/ASTM standards, the layer-by-layer deposition strategy introduces process-dependent structural features that strongly influence the resulting mechanical response. This work presents an analytical, experimental and numerical investigation of the flexural behavior of PLA components manufactured by material extrusion, following ISO 178 guidelines, with the objective of linking processing characteristics to effective mechanical properties. For components subjected to bending-dominated loading, flexural response provides a representative framework to assess stiffness and strength while activating interlayer interactions that are not captured by uniaxial tests. Three-point bending experiments were conducted on specimens produced with different filament deposition orientations to validate analytically derived estimates of flexural stiffness and load-bearing capacity. Scanning electron microscopy (SEM) was used to characterize process-induced structural features, including voids, filament morphology and layer interfaces, providing a physical basis for interpreting the observed mechanical behavior. In parallel, finite element analysis (FEA) was employed to complement the experimental results by analyzing stress and shear distributions under bending. The combined analytical, experimental and numerical approach highlights the role of manufacturing-induced structure in governing flexural performance and demonstrates how process-informed modeling can be used to estimate stiffness and strength in material-extruded polymer components. The results contribute to a clearer understanding of process–structure–property relationships in additive manufacturing and support the development of predictive mechanical descriptions for 3D-printed structures, reducing reliance on extensive experimental testing.