Assessment of the dielectric anisotropy in timber using the nondestructive GPR technique

In the realm of architecture ground-penetrating radar has been used as nondestructive technique to assess physical properties of wood structures in situ. However, a better understanding of the dielectric anisotropy of timber is needed to develop this application. An experiment was conducted on samples of sawn timber of different species (densities) to study their dielectric responses according to the grain directions using a GPR with a 1.6 GHz antenna. Interesting differences were found: the propagation velocities, as well as the amplitudes of the direct and reflected waves always presented lesser when the electric field was longitudinal to the grain than when transverse. But when the field was propagated in whatever transverse direction some of those parameters not differ greatly. On the other hand, this work is supported partly by the "Programa de Apoyo a la Investigacion y Desarrollo (PAID-00-11)" of the Universitat Politecnica de Valencia. The authors would like to acknowledge the contribution of Dr Briggs of the School of Forest Resources at the University of Washington, Seattle (USA). Martínez Sala, RM.; Rodríguez Abad, I.; Díez Barra, R.; Capuz Lladró, R. (2013). Assessment of the dielectric anisotropy in timber using the nondestructive GPR technique. Construction and Building Materials. 38:903-911. doi:10.1016/j.conbuildmat.2012.09.052