Parameters to measure nonlinearity in polymethylmethacrylate (PMMA) and carbon fiber
reinforced polymer (CFRP) materials have been determined with nonlinear ultrasound (NLUS). The
nonlinear parameter b has been determined using the variation of the Finite Amplitude Method
(FAM) with harmonic generation. Using this as a reference, the first contribution of this work consists
of deducting the experimental configuration necessary to measure this nonlinear parameter in a
correct and feasible way. Excitation level, frequency of the wave generated, number of cycles analysed
and the distances transducer-specimen and specimen-hydrophone have been determined in both
materials. The second contribution is a semi-analytical model that allows to obtain the nonlinear
parameter in materials by removing water contribution and considering geometric and viscous
attenuation, using the data obtained in an immersion tank. Finally, an application of this model has
been carried out in PMMA in order to determinate the nonlinear parameter in this material. From
the results, we confirm that the configuration determined in this paper to obtain the parameter β
decreases the noise in the measurements.This research was funded by the Ministry of Education DPI2017-83859-R