Accession Number : ADA544306


Title :   Improvement in Mechanical Properties through Structural Hierarchies in Bio-Inspired Materials


Descriptive Note : Doctoral thesis


Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE


Personal Author(s) : Sen, Dipanjan


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a544306.pdf


Report Date : Feb 2011


Pagination or Media Count : 171


Abstract : Structural biological materials such as bone, nacre, insect cuticle, and sea sponge exoskeleton showcase the use of inferior building blocks like proteins and minerals to create structures that afford load-bearing and armor capabilities. Many of these are composite structures that possess the best of the properties of their base constituents. This is in contrast to many engineering materials, such as metals, alloys, ceramics and their composites which show improvement in one mechanical property (e.g. stiffness) at the cost of another disparate one (e.g. toughness). These excellent design examples from biology raise questions about whether similar design., and improvement in disparate properties, can be achieved using common engineering materials. The identification of broad design principles that can be transferred from biological materials to structural design, and the analysis of the utility of these principles have been missing in literature. In this thesis, we have firstly identified certain universal features of design of biological structures for mimicking with engineering materials a) presence of geometric design at the nanoscale, b) the use of mechanically inferior building blocks, and c) the use of structural hierarchies from the nanoscale to the macroscale. We firstly design. in silico, metal-matrix nanocomposites, mimicking the geometric design found at the nanoscale in bone. We show this leads to improvements in flow strength of the material. A key finding is that limiting values of certain of these parameters shuts down dislocation-mediated plasticity leading to peak in flow strength of the structure. Metals are however, costly constituents and we next confront the issue of whether it is possible to use a single mechanically inferior and commonly available constituent, such as silica, to create superior bioinspired structures.


Descriptors :   *STRUCTURAL ENGINEERING , STRUCTURAL PROPERTIES , THESES , GEOMETRY , CONSTRUCTION MATERIALS , MECHANICAL PROPERTIES , COMPOSITE STRUCTURES


Subject Categories : Structural Engineering and Building Technology


Distribution Statement : APPROVED FOR PUBLIC RELEASE