Mechanical Properties of Model Two-Phase Composites with Continuous Compared to Discontinuous Phases

Composites with stiff and soft phases are widely used in engineering applications and are found in nature. Geometrical arrangements of phases in composites can significantly influence overall properties. This study focuses on the numerical and experimental investigation of the mechanical behavior of model two-phase composites with different phase geometries including an interpenetrating phase composite with two continuous phases, a matrix-inclusion composite with a continuous and a discontinuous phase, and a discontinuous phase composite where both phases are discontinuous. These different types of composites are fabricated by additive manufacturing and their mechanical performance is studied both experimentally, using compression testing and digital image correlation, and numerically by a finite element analysis. It is observed that continuity of the stiff phase leads to a stiffer overall response of composites. Furthermore, while the stiff phase enhances the overall elastic modulus by enduring a larger fraction of the load, the soft phase provides load redistribution resulting in a higher load-bearing capacity. Finally, these composite types are simulated using properties of bone constituents (collagen and hydroxyapatite) and results imply that bone may be an interpenetrating phase composite. The findings of this study provide guidance for the design of advanced composites with superior properties.