Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Synthetic materials that behave like mollusk shells

03.02.2011
Nacre, commonly known as mother-of-pearl, is the iridescent material lining many mollusk shells. It is part of a two-layer armor system that protects the animal from predators. The brittle outer layer of the shell absorbs the initial impact, but is prone to cracking.

To prevent these cracks from catastrophically propagating through the shell to the animal itself, the nacreous layer is surprisingly strong and tough, with outstanding crack arresting properties. Thus it acts as a lining to maintain the integrity of the shell in the event of cracking of the outer layer.

"What makes this natural material unique is that it is composed of relatively weak constituents," said Owen Loh, a graduate student at Northwestern University. At the microscale, brittle calcite tablets are stacked in a brick-and-mortar-like structure with thin layers of biopolymer lining the interfaces between tablets. This results in a material that well outperforms its individual constituents. For example, the toughness of nacre is orders of magnitude greater than that of the tablet material itself. In addition, nacre is at once strong and tough, a combination that is generally mutually exclusive in engineering materials.

As a result, nacre has been the object of significant interest within the materials community and serves as a model after which numerous man-made composite materials are designed. This includes composites for light-weight armor systems and structural elements in transportation and aerospace applications.

Nacre's outstanding performance has long been attributed to its brick-and-mortar microstructure. However, the specific attributes of this hierarchical structure, which contribute to the toughness of nacre, have been the subject of debate. As a result, efforts to translate deformation mechanisms observed in nacre into man-made composite materials have been widespread but mostly unsuccessful.

In a paper published online in the journal Nature Communications, Horacio Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at the McCormick School of Engineering and Applied Science at Northwestern, Loh and colleagues report the identification of specific characteristics of the material microstructure that enable its outstanding performance. By performing detailed fracture experiments within an atomic force microscope, the group was able to directly visualize and quantify the way the tablets slid relative to each other as the material is deformed.

The group previously found that the tablets are not perfectly flat but instead have an inherent waviness in their surfaces. As a result, they tend to interlock as they slide relative to each other, spreading damage and dissipating energy over large areas. "We published these results before but it took atomic scales experiments to confirm our hypothesis on the origin of toughness in these biomaterials," Espinosa said.

The group then applied the findings to the design of artificial composites. "We took what we learned from natural nacre and designed a scaled-up artificial composite material with an interlocking tablet structure," said Pablo Zavattieri, a co-author of the paper and assistant professor of civil engineering at Purdue University. "By applying nacre's highly effective toughening mechanism to this material, we were able to achieve a remarkable improvement in energy dissipation."

The findings have important implications for future design of high-performance composite materials. "We believe these findings may hold a key to realizing the outstanding potential of nanocomposites," Espinosa said. "While carbon nanotubes and other nanoscale reinforcements utilized in these materials have unprecedented properties, their performance has yet to be translated to bulk composites. By implementing toughening mechanisms such as those we found in natural nacre, we may be able to achieve this."

In addition to Espinosa, Loh and Zavattieri, the paper was co-authored by Allison Juster, Felix Latourteand David Gregoire.

Megan Fellman | EurekAlert!
Further information:
http://www.northwestern.edu

More articles from Materials Sciences:

nachricht Melting solid below the freezing point
23.01.2017 | Carnegie Institution for Science

nachricht An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Arctic melt ponds form when meltwater clogs ice pores

24.01.2017 | Earth Sciences

Synthetic nanoparticles achieve the complexity of protein molecules

24.01.2017 | Life Sciences

PPPL physicist uncovers clues to mechanism behind magnetic reconnection

24.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>