Flexural wave propagation in anisotropic laminates and inversion algorithms to recover elastic constants

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Authors
Elliott, Brian B.
Subjects
Anisotropy
Composites
Flexural waves
Elastic constants
Advisors
Gorman, Michael R.
Date of Issue
1992-09
Date
September 1992
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Knowledge of the elastic properties of composite materials can be an invaluable tool for both the quality assurance of manufacturing techniques and design verification. Recent advancements in ultrasonic velocity measurements have demonstrated the ability to recover elastic properties in anisotropic laminates. A simplified experimental setup was investigated to recover the elastic properties based on the flexural wave propagation in anisotropic laminates. The initial objective of this thesis was to verify flexural wave propagation in composite laminates through the comparison of experimental and theoretical phase velocities. In the second part of this thesis, the experimental phase velocities were used to calculate the elastic properties of the material by inverting the governing equations. The initial method used to recover elastic constants was successful in the recovery of a partial set of the bending and extensional stiffnesses. The inability to recover all bending stiffnesses dictated the investigation of a second method. This method used an iterative method based on a nonlinear Newton's method to recover the bending stiffnesses. This method did not converge due to ill conditioning of the solution matrix. Although this method did not converge, it is believed that other more robust methods suggested herein would converge to the proper solution.
Type
Thesis
Description
Series/Report No
Department
Department of Aeronautics and Astronautics
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Funder
Format
62 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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