Micromechanical modeling and numerical homogenization calculation of effective stiffness of 3D printing PLA/CF composites

The inherent complex microstructure and the varied process parameters make predicting the mechanical properties of material extrusion additive manufacturing produced parts a troublesome problem. This paper proposes a SEM voids array mapping method for constructing micromechanical models of 3D printing PLA/CF laminates. By combining the numerical homogenization calculation technique, its effective stiffness was predicted. The printed PLA/CF parts were modeled as a continuum of 3D uniform linear elasticity with orthotropic anisotropy, and their elastic behavior was characterized by orthotropic constitutive relations. Micromechanical models of two typical deposition configurations of the printed parts were established based on the periodic RVE technique. The elastic constants of the RVE models were estimated by volume average method in the finite element stress analysis, and the effects of deposition configurations, layer thickness and raster angle on the effective stiffness were also investigated. Finally, the reliability of the constructed micromechanical models and numerical calculation method was verified through experimental methods. The results show that the layer thickness can change the constitutive behavior of the printed PLA/CF parts with 0° unidirectional aligned configuration, that is from orthogonal isotropy to transverse isotropy. The 0°/90° angle-ply configuration parts exhibited transversely isotropic characteristics along thickness in all layer thickness and raster angle. The Young's modulus E1 decreased by 28.4 % and E2 increased by 42.3 % with the increase in raster angle from 15° to 75°, whereas remained almost the same for E3. This work will assist in the establishing an accurate micromechanical model and selecting of the correct constitutive material model in the numerical calculation of effective stiffness of 3D printed parts.