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Sculptured Thin Films: Non-Linear Nanomechanics and Homogenization for a New Class of Engineered Thin Composites with Evolving Nanostructure

Sponsor: NSF: CAREER Award—(Grant No. CMS 9733653)

Start Date: April 1, 1998

Description

The project's objectives are:

to use nanomechanics to characterize the non-linear thermo-mechanical properties of sculptured thin films: an exciting new class of advanced nonlinear composites with evolving nanostructure. Also, a homogenization theory of sculptured thin films will be formulated to analytically and computationally derive the effective constitutive and evolution equations of these nano-engineered systems.
To develop the software and the necessary computer-based courseware to simulate the experimental activity used in the identification of the thermomechanical properties of homogeneous as well as composite materials.

This is a unique research effort in that the mechanical properties of sculptured thin films have never been systematically studied before. Furthermore, a nanomechanics and homogenization theory of inelastic phenomena with evolving nanostructure is proposed which offers the capability of determining the effective constitutive equations for any thermo-mechanical load path. From an educational viewpoint, this project will incorporate new research material to innovate undergraduate mechanics courses dealing with constitutive theories for both homogeneous and composite materials. By following the proposed approach and using commonly available software such as Mathematica and MATLAB, new interactive and multimedia educational material can be developed that will allow both instructors and students to simulate various types of experiments in class, including those too expensive or impossible to run in a real laboratory, while offering "on-line" access to pertinent theoretical information.

The theoretical basis for the project is provided by Continuum Thermodynamics and Homogenization Theory of composites. The practical foundation is a general {\em representative volume element} discretization methodology recently developed by the proposer, which, when combined with homogenization theory, delivers the overall homogenized (or effective) response functions of the composite even when inelastic phenomena and microstructure (or nanostructure) evolution occur simultaneously.

This project will contribute to the improvement of fabrication and life prediction techniques for a new class of composite thin films with promising applications in electroluminescent devises, optical sensor technology, high speed/high efficiency electrochromic films, micro-sieves for the entrapment of viruses or for growth of biological tissues on surfaces of biological or non-biological origin. This project will also contribute to a transformation of the way engineering students learn the theory and practice of material property identification.

Results

The following is a list of pulications dealing with various aspects of this project:

Caiazzo, A. A. and F. Costanzo (2000). "On the Constitutive Relations of Materials with Evolving Microstructure due to Microcracking." International Journal of Solids and Structures, Vol. 37, pp. 3375–3398.
Caiazzo, A. A. and F. Costanzo (2000). "On the Effective Elastic Properties of Composites with Evolving Microcracking." Journal of Reinforced Plastics and Composites, Vol. 19, pp. 152–163.
Caiazzo, A. A. and F. Costanzo (2001). "Modeling the Constitutive Behavior of Layered Composites with Evolving Cracks." International Journal of Solids and Structures, Vol. 38, No. 20, pp. 3469–3485.
Caiazzo, A. A. and F. Costanzo (2001). "Effective 3D Constitutive Relations of Composites with Evolving Damage." Journal of Engineering Mechanics, Vol. 127, No. 7, pp. 661–666.
Andia, P. C., F. Costanzo, and G. L. Gray (2000), "On the estimation of intrinsic stresses and elastic moduli in thin films," in "Complex Mediums," A. Lakhtakia, W. S. Weiglhofer and R. F. Messier (eds.), Proceedings of SPIE Vol. 4097 (45th Meeting of SPIE, July 30-August 1, 2000, San Diego, USA), pp. 280–290.
Andia, P. C., F. Costanzo, G. L. Gray, and T. J. Yurick (2001). Calculation of Intrinsic Stresses and Elastic Moduli in Nonhomogeneous Thin Films. Multiscale Modeling of Materials—2000. L. P. Kubin, R. L. B. Selinger, J. L. Bassani and K. Cho. Pittsburgh, PA, Materials Research Society. 653: Z10.3.1–Z10.3.6.
P.C. Andia (2000), A Discrete-Continuum Approach to the Mechanical Properties of Inhomogeneous Materials, Master's Thesis, The Pennsylvania State University.