Structural damping of composites under sustained vibratory stresses

Abstract

AbstractThe dynamic properties of a fiber‐reinforced composite under uniaxial sinusoidal stresses have been studied and the dynamic modulus and loss coefficients have been evaluated. Effects of fiber orientation to applied stress, the magnitude of static biaxial stresses, frequencies of fluctuating stresses and the temperature on the dynamic properties have been studied. The paper describes a dynamic biaxial testing machine specially developed for the measurement of dynamic properties of fiber‐reinforced materials for a low frequency range. Results indicate that the single laminate material displays very little damping. However, the multilaminate material reveals an appreciable damping that is dependent on the frequency of fluctuation of applied stress. The loss coefficient for the multilaminate material was found to decrease with frequency and was appreciably affected by fiber orientation, magnitudes of mean biaxial stresses, and temperature. Finally, an examination of data indicated that the time‐temperature equivalence hypothesis can be applied. Using this principle, master loss coefficient curves for an extended frequency range have been obtained.