Mechanical behavior of multiple-layered gradient cellular scaffolds with constant density: experimental, analytical, and numerical investigation

Multiple-layered scaffolds with diverse three-dimensional architectures have been successfully fabricated using additive manufacturing (AM) and can be used in tissue engineering. Regarding the regular scaffolds that consist of a connected lattice of solid beams, various researches have been carried out, but multilayered scaffolds with this structure have been less studied. This research tries to investigate the factors affecting the mechanical properties by keeping the percentage of porosity constant. This study aimed to investigate the effect of unit cell shape, struts diameter, and number of layers on the mechanical properties of multiple-layered scaffolds with constant porosity. All the lattice scaffolds were designed in cylindrical form (outer diameter of 30 mm and length of 60 mm) and fabricated from 18 various types with 70% porosity, in single, double, and triple layers using the selective laser sintering (SLS) method. In all the samples, the outer layers had a higher density compared to the inner layers. The mechanical properties of the scaffolds were determined through uniform compression tests. The stress–strain curves of the samples revealed that as the struts diameter increases, the yield strength increases due to the reduction of manufacturing defects. This improvement in yield strength was greater in homogeneous scaffolds than in other scaffolds. Additionally, numerical simulations showed that the maximum strength occurred in the two-layer scaffolds. Furthermore, the position of the maximum radial displacement shifted from the middle region to the top and bottom regions of the scaffold with the increase in the number of layers. Based on the findings of this study, in scaffolds with constant porosity, increasing the number of layers and the diameter of the struts, without changing the Young’s modulus, can increase the yield strength of the scaffolds.