Experimental material damping estimation for planar isotropic laminate structures

Athree-dimensional material damping estimation methodology is proposed for planar isotropic material symmetry by using a constitutive viscoelastic vibration model. The proposed material model is verified, via finite-element techniques, on three laminate structures. The first one is a numerical test structure composed by stacked aluminium and plexiglas plates. In this case the effective three-dimensional planar isotropic material properties are given in terms of homogeneous material damping functions in connection with homogenised elastic laminate properties. Comparisons made between the results from the detailed (layer-wise) model of the laminate and the effective three-dimensional model show that the estimated homogenised model is reasonably accurate, in terms of predicted vibration responses. Finally, estimations of planar isotropic material damping are done for two practically interesting experimental structures, a carbon fibre–epoxy laminate structure and an aluminium laminate including a constrained viscoelastic layer damping treatment. In this context, it is found that the dominating damping mechanisms are different in these two cases. The dynamic homogenisation process, with damping included, is evaluated quantitatively in terms of predicted forced vibration response for the laminate structure, using effective planar isotropic frequency dependent material properties. The dynamic three-dimensional effective homogeneous material models, for these two cases, are found to be close to measurements in a frequency interval corresponding to the first 17 modes