Mechanical properties of nacre constituents: An inverse method approach

Nacre, also known as mother-of-pearl, is the iridescent layer found inside some mollusk species such as oyster or abalone. It is made of relatively weak materials, but its hierarchical microstructure is so well optimized that its macroscopic mechanical properties are far superior to those of its constituents. For this reason there is a great interest in nacre as a source of inspiration for novel designs of composites. Despite many years of research on nacre, an accurate characterization of its constituents is lacking. In this work nacre was tested as a layered composite material using low depth indentation and uniaxial compression. The first test was modeled using finite element analysis and the second test was modeled as a Reuss composite in compression. A micromechanical model of the interface was also pursued to gain insight on the relevance of the interface features such as tablet roughness and biopolymer hydrated response. The results of the two experiments were combined to solve an inverse problem that yielded the needed properties for tablets and interfaces. These findings are expected to make possible computational models of nacre with a new degree of accuracy and therefore contribute to a better understanding of the mechanisms leading to its remarkable properties.