Date of Award

Summer 1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Engineering Mechanics

Committee Director

Thomas E. Alberts

Committee Member

Jen-Kuang Huang

Committee Member

Gene J.-W. Hou

Committee Member

Paul A. Coper

Abstract

A new composite damping material is investigated, which consists of a viscoelastic matrix and high elastic modulus fiber inclusions. This fiber enhanced viscoelastic damping polymer is intended to be applied to light-weight flexible structures as surface treatment for passive vibration control. A desirable packing geometry for the composite material is proposed, which is expected to produce maximum shear strain in the viscoelastic damping matrix. Subsequently, a micromechanical model is established in which the effect of fiber segment length and relative motion between neighboring fibers are taken into account. Based on this model, closed form expressions for the effective storage and loss properties of the damping material are developed, and an optimal relation between design parameters, such as the length, diameter, spacing, and Young's modulus of fibers and the shear modulus of vicoelastic matrix, is derived for achieving a maximum damping capability. The theoretical development is validated by a NASTRAN finite element analysis. Upon comparison of an enhanced viscoelastic damping treatment with a conventionally constrained layer damping treatment, it is found that the enhanced polymer provides a significant improvement in damping abilities.

The proposed fiber enhanced viscoelastic damping polymer can be used either by itself as a passive damping measure for light-weight flexible structures or as an augmentation for active controllers to enhance control performance. Two examples are presented to demonstrate these two most important applications. The results show that the fiber enhanced damping polymer can provide significant damping to base structures at a broad frequency range and the performance of active controllers can be substantially improved by the addition of an optimally designed passive damping treatment. To allow comparison between theoretical and experimental analyses, dynamic scale testing techniques for structures with viscoelastic components are also examined.

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DOI

10.25777/fxt9-3c64

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