Combining Micro and Macro Relative Density: An Experimental and Computational Study on Hierarchical Porous 3D-Printed Polylactic Acid Structures

Polymer foams and cellular solids have gained significant interest due to their enhanced properties. This study introduces a novel approach by employing foamed fused filament fabrication printing of cellular solids. A composite polylactic acid filament containing chemical blowing agents is used to create structures with varying micro relative density, which is examined through scanning electron microscopy and tensile testing, with comparisons made to a Mori Tanaka analytical model and representative volume elements investigation. Two different types of cellular solid structures, specifically body-centered cubic and Gyroid triple periodic minimal surface structures, have been created with different thicknesses and printed at various temperatures. This is done to attain a range of micro- and macroporosity, leading to samples with equal total relative densities. Compression tests, coupled with finite element analysis, provide insights into the influence of each type of porosity. The fabricated specimens exhibit compressive strengths ranging from 1.07 to 79.14 MPa and elastic moduli ranging from 0.064 to 3.35 GPa. The findings suggest that porous structures relying on macroporosity exhibit higher compressive strength, while those relying on microporosity demonstrate more appealing energy absorption properties, particularly under stresses approaching the plateau region.