Scale and size effects on the mechanical properties of bioinspired 3D printed two-phase composites

Multi-material 3D printing offers design flexibility for the manufacture of new architectured composite materials and has been increasingly used to explore the mechanical properties of bioinspired composites. In this study, the influence of scale and size on mechanical properties of periodic two-phase composites with various architectures of a stiff and a soft phase are explored. The studied composites include an interpenetrating phase composite with two continuous phases (inspired by bone), a matrix-inclusion composite with a continuous and a discontinuous phase, and a discontinuous phase composite where both phases are discontinuous. These composites are fabricated by additive manufacturing, and their mechanical properties are evaluated experimentally using a compression test complemented by digital image correlation, and numerically through finite element analysis. Overall trends show that the elastic moduli and yield strengths decrease as the scale is increased. Our results on size effects reveal an increase in elastic modulus and yield strength with increasing size of the sample. Our investigation outcomes help to better understand some of the challenges in studying and applications of additively manufactured composites and shed light on scale and size effects on mechanical properties of 3D printed two-phase composites. This paper illustrates a need for further studies of scale and size effects in additively manufactured materials.