Simulation Based Materials Design of Biomimetic Nanocomposites


Dr. Kalpana S. Katti

Dr. Dinesh R. Katti


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Dr. Kalpana S. Katti

Dr. Dinesh R. Katti


TV Interviews

June 2005
(9 MB)

Fall 2002
(6 MB)



Dr. Kalpana S. Katti

Dr. Dinesh R. Katti

Department of Civil Engineering
North Dakota State University, Fargo, ND, USA



To develop multiscale models for predicting mechanical behavior of biological materials by bridging molecular, nano to macro scale mathematical models. This research answers fundamental reasons for the extraordinary mechanical properties like toughness and strength exhibited by biological nanocomposite nacre, the inner layer of seashells.  



3D Finite Element Simulation of Nacre Micro-Architecture : Laminated Structure: Inelastic Response

RESULTS: The purely laminated structure of nacre as widely proposed would require the organic phase in nacre to have an extraordinarily high yield stress of 400 MPa. (Our discovery of platelet interlocks in 2005 will eliminate this requirement - see below)

Katti, D. R. Katti, K. S., Sopp J., and Sarikaya, M., (2001)3D Finite Element Modeling of Mechanical Response in Nacre-Based Hybrid Nanocomposites, J. Theo. Comp. Poly. Sci. 11 (5), pp. 397-404.





Mineral Contacts
Modeling The Organic-Inorganic Interfacial Nanoasperities (Platelet Roughness)

RESULTS: The nanoasperities or surface roughness has small contribution to the elastic modulus of nacre and almost no contribution to its yield stress. The roughness may provide better adhesion between organic phase and the mineral phase and may provide some level of confinement to the organics.

Katti, D.R., Pradhan, S.M., and Katti, K.S., (2004), Modeling The Organic-Inorganic Interfacial Nanoasperities In A Model Bio-Nanocomposite, Nacre, J. Reviews on Advanced Materials Science, n 6, 162-168.





Red Abalone

Natural Nanocomposite: The Seashell

Seashell is a perfect natural armor

  • Design of high performance new nanocomposites taking inspiration from biological materials
  • Development of computational and analytical tools for a truly simulation based design of materials
  • Multiscale models for prediction of mechanical response of a variety of biological materials for applications in bioengineering


3D Finite Element Simulation of Nacre Micro-Architecture : Laminated Structure

RESULTS: The elastic modulus of the organic phase in nacre has a magnitude much higher than that expected for typical proteins. The simulations predict elastic modulus of the order of 15 to 20 GPa for the organic phase. (This was later confirmed experimentally by another group)

Katti, Dinesh R. and Katti, Kalpana S., (2001) Modeling Microarchitecture and Mechanical Behavior of Nacre Using 3D Finite Element Techniques, Part I: Elastic Properties, Journal of Materials Science, 36 (6):1411-1417




Modeling Mineral contacts in aragonite platelets and relative rotation of platelets

RESULTS: The mineral contacts have minimal contribution to the elastic modulus and yield stress of nacre. In fact, the mineral contacts break long before nacre exhibits yielding. It appears the mineral contacts are present for the biological growth of nacre.

Katti, K.S., Katti, D.R., Tang, J. and Sarikaya, M.,(2005), Modeling Mechanical Responses In A Laminated Biocomposite, Part II, Nonlinear Responses And Nuances Of Nanostructure, Journal of Materials Science, n 40, 1749-1755








Scale bar: 50 nm



Discovery of Interlocks in Nacre: Key to Toughness and Strength


RESULTS: Interlocks accurately predict the observed fracture toughness in nacre when yield stress of organic is close to that of typical proteins about 5 MPa.
Interlocks predict mechanism of failure:
progressive failure of individual interlocks and large deformation of organic.

They are the key to why nacre is tough and strong



Katti, K.S., Katti, D.R., Pradhan, S.M., and Bhosle, A., (2005), Platelet Interlocks are the Key to Toughness and Strength in Nacre, Journal of Materials Research, v 20, n5, May,  1097-1100.




Click Here to See Television Interview About the Discovery of Interlocks

(JUNE 2005) (9MB-mpeg-1 format)

SUMMARY(Katti, etal. 2005)

Features observed in the microstructure of nacre, such as relative rotation between platelet layers, platelet penetration, and other geometrical abnormalities such as an elongated side etc appear not to be accidents of nature; they seem to exist for a purpose. In this instance, these abnormalities lead to high toughness and strength.

lSmall features such as penetration, rotations, misalignments of structure appear to have very significant impact on physical properties of biological materials and should not be disregarded in modelling and design of biomimetic composites as has often been done in the past.

Graduate Students:

Pijush Ghosh (Ph.D.)

Shashindra Pradhan (Ph.D.)

Devendra Verma (Ph.D.)

Bedabibhas Mohanty (Ph.D.)

Arundhati Bhosle (M.S.) (Graduated)

Jingpeng Tang (Ph.D.) (Graduated)



Dr. Dinesh R. Katti, North Dakota State University, Fargo, ND

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