Inverse analysis for the amplitude-dependent damping properties of epoxy/glass fiber laminates

In this paper, we present the experimental results and corresponding inverse analysis for determination of the amplitude-dependent damping properties of laminates made of glass fiber reinforced plastic (GFRP). Free damped vibration tests for the cantilever beams with different symmetric stacking sequences are performed. Logarithmic decrement analysis is used to evaluate the effective amplitude-dependent loss factor of the samples. Inverse analysis is used to find the dynamic properties of single ply based on the laminated beam theory and the complex moduli approach. It is found that the loss factors of GFRP laminates almost linearly depend on the maximum strain amplitude. Maximum value of the loss factor of unidirectional ply is realized in the transverse direction to fibers and reaches ~0.023 for the strain amplitudes up to 0.1% in the frequency range 20-60 Hz.