A data-driven simple design of single-level nacre-inspired composites with high strength and toughness

Achieving a good strength–toughness match in nacre-inspired composites (NICs) is a difficult issue since it involves an optimum combination of many microstructural parameters. A multi-parameter design rule for the strengthening and toughening of NICs, which is based on extensive finite element (FE) data analysis and experimental verification, is given in this paper. Extensive FE calculations of NICs under uniaxial tension are firstly performed, with which the effects of the aspect ratio of hard phase (ARHP), the volume fraction of soft phase (VFSP) and the hard/soft-phase modulus ratio (HSMR) on the strength and toughness of composites are analyzed. Combinatorial conditions of these parameters for NICs with low strength and low toughness, high strength and low toughness and well-matched strength and toughness are determined, respectively, by comparisons of FE data samples. Furthermore, 3 D-printed NIC specimens consistent with FE models are prepared and tested by tensile experiments. The experimental results agree well with the FE results, both of which disclose the microscopic mechanism behind the strength and toughness of composites. It is found that a mixed failure mode including tensile fracture of hard phase and shear failure of soft phase can be realized by the combination of a large ARHP, a moderate VFSP and a large HSMR, which consequently leads to an excellent strength–toughness match in NICs. Compared with existing nacre-inspired composites with the same hard phase but more complex microstructures such as interlocking interfaces, deflected hard phases and graded soft phases, the present composite not only shows superior strength and toughness but is also easier to produce. Therefore, a highly-efficient and simple method can be provided for the design of strong and tough biomimetic composites.