Measurements of complex Young's and shear moduli of a transversely isotropic GFRP are described. These were deduced from measured values of natural frequencies and modal loss factors of bars vibrating longitudinally and of beams vibrating flexurally. Shear moduli were deduced from flexural mode frequencies using a method based on the Timoshenko theory of bending. Poisson's ratios were also found from direct strain gauge measurements. Complex Young's moduli were found with good consistency over the frequency range 3-20 kHz. Some reliable Poisson's ratios were measured but others appeared to be inconsistent, reasons for which are presented. Measured shear moduli also lacked consistency but the values obtained are probably sufficiently accurate for use in dynamic analyses of thick GFRP structures. Shear loss factors could be obtained only very approximately.
