Nondestructive stress wave measurements of decay and termite attack in experimental wood units

This report presents the results of longitudinal stress wave analysis of wood material exposed to brown rot decay fungi (Gloeophyllum trabeum) and of wood material exposed to various degrees of attack by subterranean termites. Field testing of candidate wood preservatives is necessary before a proposed preservative can be accepted in the Standards. This mandate for field testing stems from the inadequacy of laboratory tests in producing results which predict ultimate field performance. Field testing is time-consuming, travel-intensive, and to date, based upon subjective visual observation. As a consequence, mathematic analysis of certain results are not very definitive. The need for nonsubjective, responsive field experimentation is critical because of environmental concerns about broad-spectrum pesticides. The purpose of this study was to determine if stress wave analysis could be used to monitor the degradation of wood test materials that were exposed to brown rot decay fungi or subjected to attack by termites. Longitudinal stress wave analysis was used to monitor a gradient of biological attack. Statistical comparisons were made between these stress wave measurements and alternative schemes for rating biological attack.