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 Switched-on DNA
20.02.2017 | Arizona State University

nachricht Using a simple, scalable method, a material that can be used as a sensor is developed
15.02.2017 | University of the Basque Country

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Viruses support photosynthesis in bacteria – an evolutionary advantage?

23.02.2017 | Life Sciences

Researchers pave the way for ionotronic nanodevices

23.02.2017 | Power and Electrical Engineering

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>