System identification of adaptive composites

Modern composites are non-homogeneous materials having high strength fibers embedded in a polymeric or metal matrix, and having directional properties. Shape Memory Alloys (SMAs) such as Nitinol can be embedded in composites for active control of structures. Since the micromechanics of composites in general and adaptive composites, in particular, are poorly understood, accurate values of material elastic properties and in-plane loads generated are seldom available. It is possible to determine these parameters if natural frequencies of the structure are available. The techniques used to determine these parameters from the modal response of a structure are generically called ‘System Identification’. This thesis reviews the various System Identification techniques applicable to vibrating structures. Three techniques are then adapted to an orthotropic laminate and implemented in FORTRAN. These techniques, being iterative in nature, require an initial estimate of the parameters to be identified as input. Because all the techniques discussed here are iterative, they are sensitive to the values of initial estimates. The robustness of these techniques in face of a scatter in the input data is tested using a randomized statistical analysis. The techniques are compared based on certain attributes and recommendations are made.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Mechanical Engineering

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1990

Author dc:creator

• Mohammedshah, Juzer Mohsin

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-04072009-040827

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/41935