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Measurement of damping of graphite epoxy composite materials and structural jointsThe damping capacity of graphite epoxy materials and structural joints was evaluated. The damping ratio of different composite specimens and bonded joints were systematically evaluated under normal atmospheric conditions and in a vacuum environment. Free and forced vibration test methods were employed for measuring the damping ratios. The effect of edge support conditions on the damping value of a composite tube specimen was studied by using a series of experiments performed on the specimen with different edge supports. It was found that simulating a free-free boundary conditions by having no constraints at the ends gives the lowest value of the material damping of the composite. The accuracy of the estimation of the damping ratio value was improved by using a curve-fitting technique on the response data obtained through measurement. The effect of outgassing (moisture desorption) on the damping capacity was determined by measuring the damping ratio of the tube specimen in a vacuum environment before and after outgassing had occurred. The effects of high and low temperatures on the damping was also investigated by using a series of experiments on tube and beam specimens. An analytical model to study the vibrations of a bonded lap joint system was formulated. Numerical results were generated for different overlap ratios of the system. These were compared with experimental results. In order to determine the influence of bonded joints on the material damping capacity, experiments were conducted on bonded lap-jointed and double-butt-jointed specimens. These experimental results were compared with simple beam specimens with no joints.
Document ID
19900004970
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Crocker, Malcolm J. (Auburn Univ. AL, United States)
Rao, Mohan D. (Auburn Univ. AL, United States)
Raju, P. K. (Auburn Univ. AL, United States)
Yan, Xinche (Auburn Univ. AL, United States)
Date Acquired
September 6, 2013
Publication Date
August 1, 1989
Subject Category
Composite Materials
Report/Patent Number
NAS 1.26:183802
NASA-CR-183802
Accession Number
90N14286
Funding Number(s)
CONTRACT_GRANT: NAS8-36146
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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