Bio-inspired interfacial strengthening strategy through geometrically interlocking designs

Many biological materials, such as nacre and bone, are hybrid materials composed of stiff brittle ceramics and compliant organic materials. These natural organic/inorganic composites exhibit much enhanced strength and toughness in comparison to their constituents and inspires enormous biomimetic endeavors aiming to synthesize materials with superior mechanical properties. However, most current synthetic composites have not exhibited their full potential of property enhancement compared to the natural prototypes they are mimicking. One of the key issues is the weak junctions between stiff and compliant phases, which need to be optimized according to the intended functions of the composite material. Motivated by the geometrically interlocking designs of natural biomaterials, here we propose an interfacial strengthening strategy by introducing geometrical interlockers on the interfaces between compliant and stiff phases. Finite element analysis (FEA) shows that the strength of the composite depends strongly on the geometrical features of interlockers including shape, size, and structural hierarchy. Even for the most unfavorable scenario when neither adhesion nor friction is present between stiff and compliant phases, the tensile strength of the composites with proper interlocker design can reach up to 70% of the ideal value. The findings in this paper would provide guidelines to the improvement of the mechanical properties of current biomimetic composites.