Structural hierarchies define toughness and defect-tolerance despite simple and mechanically inferior brittle building blocks

• Published in: Scientific reports Vol. 1; no. 1; p. 35
• Main Authors: Sen, Dipanjan, Buehler, Markus J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.07.2011; Nature Publishing Group
• Subjects: 639/301/1023/303; 639/301/1034; 639/301/54; Alloys; Compressive Strength; Computer Simulation; Crack propagation; Defects; Hardness; Humanities and Social Sciences; Mechanical properties; Minerals - chemistry; Models, Chemical; Models, Molecular; multidisciplinary; Science; Silica; Silicon Dioxide - chemistry; Tensile Strength
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep00035

Mineralized biological materials such as bone, sea sponges or diatoms provide load-bearing and armor functions and universally feature structural hierarchies from nano to macro. Here we report a systematic investigation of the effect of hierarchical structures on toughness and defect-tolerance based on a single and mechanically inferior brittle base material, silica, using a bottom-up approach rooted in atomistic modeling. Our analysis reveals drastic changes in the material crack-propagation resistance (R-curve) solely due to the introduction of hierarchical structures that also result in a vastly increased toughness and defect-tolerance, enabling stable crack propagation over an extensive range of crack sizes. Over a range of up to four hierarchy levels, we find an exponential increase in the defect-tolerance approaching hundred micrometers without introducing additional mechanisms or materials. This presents a significant departure from the defect-tolerance of the base material, silica, which is brittle and highly sensitive even to extremely small nanometer-scale defects.