The Dynamic Properties of Unidirectional Fibre Reinforced Composites in Flexure and Torsion

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Abstract
Theoretical predictions of the damping of composites are presented. New results are given for the damping and dynamic modulus in flexure and longitudinal shear using very carefully prepared specimens and improved apparatus. Comparison of these results, and others taken from the literature, with the theory reveals that the measured damping in flexure is higher and in torsion lower than predicted. Reasons for this discrepancy are investigated in detail and it is suggested that although specimen defects and extraneous losses always increase the damping, fibre misalignment may either increase or decrease it, and hydrostatic stresses may decrease it. The measured flexural modulus is less than that predicted by the law of mixtures, while the longitudinal shear modulus agrees closely with the square array prediction of Adams and Doner.