Project Report

Biological materials, such nacre, are of interest to materials scientists as they have outstanding mechanical properties beyond those that can be achieved using the same synthetic materials. Past investigations on the properties of mollusk nacre established that mollusk shells are natural multilayered composite structures that usually exhibit excellent mechanical properties due to the hierarchical organization of calcium carbonate layers and organic membrane. However, there is still a lack of a complete description of the influence of each individual constituent on the outstanding mechanical properties of the whole. The EAPSI summer program was extremely beneficial to this research project as it provided an opportunity to perform experiments which are complementary to those performed at home. It allowed for a chance to learn novel testing techniques and to train in a variety of equipment and procedures. In this study, the contribution of the organic interlayer on the overall mechanical properties of the abalone nacre is investigated. Nanoindentation and nanoscratch tests are employed on untreated and deproteinized abalone nacre. Contrast in the mechanical behavior of these materials demonstrates the impact of the organic matrix to the toughness of the entire structure. Nanoindentation and AFM experiments are performed on the organic interlayer. These results can quantitatively asses the relationship between the overall strain and expansion undergone by the organic membrane. Specimens are characterized by SEM to verify the toughening and deformation mechanisms. Results obtained contribute as they provide insight into the fundamental linkages that comprise the hierarchy of the abalone nacre. This approach generates a comprehensive picture of the mechanical response of each constituent and its effect on the mechanical properties of the abalone nacre which is vital to the improvement of bioinspired synthetic materials.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
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Program Officer
Carter Kimsey
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Lopez Maria I
La Jolla
United States
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