Mechanical properties and anisotropy evaluation of FDM-printed porous gyroid biodegradable PLA-Scaffolds

Porous polymer framework (scaffolds) are widely used in regenerative medicine for the restoration of various tissues, including bone tissue as well. The predetermined porous architecture at the micro- and macroscales ensures cell proliferation and tissue regeneration. Additive manufacturing gives an opportunity of designing personalized scaffolds for patients with complex bone defects. In this case, the framework should have mechanical properties comparable to those of native bone tissue. The work is aimed at investigating the mechanical properties and 3D-printing-induced anisotropy of a porous scaffold for regenerative medicine. Experimental specimens of biodegradable scaffolds based on gyroid geometry with a porosity of 85% and a pore diameter of 1.6 mm were manufactured from polylactide (PLA) via FDM printing. Anisotropy of mechanical properties under loading in longitudinal (L) and transversal (T) directions was investigated in the following tests: uniaxial tension, compression and three-point bending. Creep and relaxation curves in uniaxial compression tests were plotted for T-specimens at initial stresses of 0.5, 0.75, and 1 MPa. The stress intensity factors (SIF) KQ for L-specimens are determined in tensile and three-point bending fracture toughness tests. It was shown that mechanical properties are significantly anisotropic due to the orientation of the specimen on a printing bed. The obtained values of the mechanical properties of PLA-scaffolds fall within the range of the corresponding mechanical properties for native cancellous bone, which makes these scaffolds promising for the regeneration of bone defects.