Combination of stiffness, strength, and toughness in 3D printed interlocking nacre-like composites

Abstract

Constituted by mineral tablets and organic interlayers, nacre is known for its attractive combination of stiffness, strength, and toughness. The impressive mechanical property of nacre can be attributed to the ‘brick-and-mortar’ structure which is usually defined with two geometric parameters: tablet aspect ratio and volume fraction of the stiff phase. Inspired by the interlocking tablets found in red Abalone and Hyriopsis cumingii, we study the effect of interlock by introducing a third parameter: tablet waviness angle. Tension tests and single edge notched bend fracture tests are performed on the specimens of interlocking and non-interlocking nacre-like composites that are fabricated using a high-resolution multi-material 3D printer. Stress distribution, deformation pattern and parameter analysis reveal the mechanical behavior of interlocking and non-interlocking nacre-like composites and how these three parameters affect the performance. Two failure patterns (soft phase failure and tablet break) and three toughening mechanisms (uncracked-ligament bridging, constrained microcracking, and crack deflection/twist) are found in three-point bending fracture tests, which uncovers the key to high toughness. Interlocking nacre-like composites clearly show enhanced tensile and fracture performance with an unusual combination of stiffness, strength, and toughness.