Elastic wave mode conversion phenomenon in glass fiber-reinforced polymers

Purpose The purpose of this paper is to present the results of experimental analysis of the elastic-guided wave mode conversion phenomenon in glass fiber-reinforced polymers. The results of this research presented in this paper are strictly focused on S0/A0’ mode conversion phenomenon caused by discontinuities in the form of circular Teflon inserts (artificial delaminations) and impact damage. Results of this research could be useful in problems of damage detection and localization. Design/methodology/approach In the research, guided waves are excited using a piezoelectric transducer and sensed in a non-contact manner using a scanning laser Doppler vibrometer. Full wavefield measurements are analyzed. Analysis of the influence of investigated discontinuities on S0/A0’ mode conversion is based on the elastic wave mode filtration in frequency-wavenumber domain. Mode filtration process allows us to remove the effects of the propagation of unwanted type of mode in forward or backward direction. Effects of S0/A0’ mode conversion are characterized by a mode conversion indicator (MCI) based on the amplitude of new mode A0’ and the amplitude of incident S0 mode. Findings It was noticed that the magnitude of MCI depends on the depth at which the Teflon inserts were located for all analyzed excitation frequencies and diameters of inserts (10 and 20 mm). The magnitude of MCI also increases with increasing impact energies. The S0/A0’ mode conversion phenomenon could be utilized for the detection of surface and internal located discontinuities. Originality/value This paper presents the original results of this research related to the influence of discontinuity location with respect to the sample thickness and severity of discontinuity on S0/A0’ mode conversion.