Vibration Damping Response of Composite Materials
Research and development rept.
DAVID TAYLOR RESEARCH CENTER BETHESDA MD SHIP MATERIALS ENGINEERING DEPT
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This report involves the investigation of the mechanical vibration damping characteristics of glassepoxy and graphiteepoxy composite materials. The objective was to develop an analytical model which incorporates the frequency dependence of the vibration damping loss factor and to experimentally characterize the loss factor for frequencies up to 100 Hz. Numerous mathematical models have been proposed to determine the loss factor of composites, including micromechanical, macromechanical and structure models. Of these generic types, the macromechanical models incorporate important material characteristics which can affect the loss factor. The most widely accepted model utilizes the elastic viscoelastic correspondence principle. Although investigators acknowledge the viscoelasticity of composites, they fail to incorporate the frequency dependence in their analysis. In this effort, the elastic viscoelastic correspondence principle is extended to incorporate the frequency dependence of the composite material. The analytical model requires as input the inplane material loss factors as a function of frequency. Cantilever beam specimens were utilized which excited using an impulse from an instrumented force hammer. The loss factor was calculated using the half power bandwidth technique. The apparatus was calibrated using a well characterized low damping material. The effect of clamping pressure and of the clamp block to specimen interface material was also investigated.
- Laminates and Composite Materials