Use of the direct wave amplitude to analyse timber grain at different frequencies

Dielectric permittivity governs the propagation of electromagnetic waves in materials with low electrical conductivity, as it is the case of wood. This fact makes ground-penetrating radar (GPR) a potential technique for the nondestructive testing of timber. In addition, working with the direct wave has great advantages to physically characterize building materials. In particular, this study analyses the capability of the direct wave to study timber. In order to study the sensitivity of this wave, laboratory experiments were conducted on timber samples of different species and densities, with a GPR system using two different frequencies antennas (2 GHz and 1,6 GHz). Results showed that direct waves had a differential behavior regarding the grain direction analyzed and frequency of radiation. Therefore, the direct wave observation can provide accurate information regarding the physical parameters of timber and making possible to identify probable pathological areas.