ABSTRACT
Abstract. The 21 polymeric materials reviewed are selected as representative o f those useful for large scale damping applications, and for which there are available wide frequency and temperature ranges of relevant experimental data given by values o f complex shear compliance, J* = J' - iJ", and shear modulus, G* = G' + G" = 1/J*. For effective damping high energy loss in the damping material is needed as measured by the loss tangent, J"/J' = G"/G', together with values o f mechanical impedance that match the vibration source impedance. Brief summaries listing some of these damping parameters are given for the 21 systems divided into seven groups as follows: 1. Polyisobutylene, 2. Plasticized polyvinyl chloride (10, 40, 60% polyvinyl chloride), 3. Butadiene-acrylonitrilecopolymer (0, 15.6, 26.9, 35.0% carbon black), 4. Polybutadiene (0, .04, .2% curing agent), 5. Natural and synthetic rubber tire stocks ( effects of rayon, nylon cord), 6. Plasticized polyvinyl acetate (50, 100% polyvinyl acetate), 7. Polyethylene (3 molecular weight distributions). Numerical values of complex shear compliance, modulus, and loss tangent chiefly at frequencies from 25 to 5000 Hz in a temperature range from -50 to 150°C have been transferred in ASCII format to a computer disk for convenient access in damping design applications. Measurements on combinations o f plasticized polyvinyl chloride compositions are used to demonstrate the use of varying polymer concentrations in blended and/or laminated composites to give "smart” damping materials with large loss tangents over extended frequency and temperature ranges. 1
1. Introduction
The twenty one materials reviewed are selected as representative o f polymer materials that are suitable for vibration damping applications, and for which dynamic mechanical data are available over wide frequency and temperature ranges. These materials can be prepared in amounts and shapes for use in vibration damping o f panels, base plates, and structural members o f vehicles, aircraft, and spacecraft. Not considered here are supply issues o f easy availablity, cost, and uniformity o f properties through adequate production controls which are important factors to be considered in material applications to noise and vibration control. The relevant dynamic mechanical properties are those provided by the elastic (J', G') and viscous (J", G") values o f complex shear compliance, J* = J' - iJ", and shear modulus, G* = G' + iG", = 1/J*, and/or the extensionalcompliance and modulus (D*, E*). For effective damping high energy losses in the damping materials are needed as measured by the loss tangent (loss factor), J"/J\ =G"/G'. In order to assure maximum energy transfer to the damping material, its mechanical load impedance, Z *^ , should match the effective mechanical impedance, Z*MG, o f a vibration source considered as a vibrational force generator.
