A Natural 3D Interconnected Laminated Composite with Enhanced Damage Resistance

Due to their lightweight, high specific stiffness and strength, cost effectiveness, corrosion and fatigue resistance, laminated composites have been widely used in many engineering applications, such as aircraft, automobiles, sporting products, and civil infrastructure. However, delamination damage along in-plane interfaces has been one of the issues that still remain unsolved. Although many natural load-bearing materials are also essentially laminated composites composed of mineral and organic phases, the underlying mechanisms for antidelamination are still largely unexplored. Here it is reported that the remarkable resistance to macroscopic indentation damage in the highly mineralized shell of the bivalve Placuna placenta originates from a characteristic nanoscale structural motif, i.e., screw dislocation-like connection centers, which join adjacent mineral layers together in the laminate structure. This leads to the formation of a complex interconnected network of microcracks surrounding the damage zone, which allows for both efficient energy dissipation and damage localization even when the shell is completely penetrated. Both theoretical analysis and experiment-based calculations suggest that the interfacial fracture toughness is enhanced by almost two orders of magnitude in comparison to classic laminated composites without connection centers. This design strategy for achieving a 3D integrative laminate architecture can be potentially applied in the design of advanced laminated composite materials.