THE EFFECT OF MOISTURE CONTENT ON ELECTRICAL PROPERTIES OF SELECTED SOFTWOODS; CEDAR, JUNIPER, AND PINE

Natural woods as a raw material have been taking a considerable interest topic by industries such as the forest industry, furniture manufacturing, and nowadays suitable electronics. One of the most essential steps of manufacturing for those industry purposes is RF heating/drying of raw wood material nowadays. However, knowing the electrical properties, such as the dielectric constant of wood-based material before processing is tremendously important. It is well-known that the moisture content and density levels of material directly affect the dielectric properties. Moisture and density conditions are different in each material because it’s related directly to the absorption and affection of material towards moisture sources. Therefore, in this study of wood material under varying conditions, proper empiric models have been generated to express this relationship. This study is based on three different softwood specimens widely used in the forest industry. The dielectric properties were determined in the frequency range of 2.17 GHz-6.0 GHz as a function of moisture content and density for wood species. Each measurement contains 500 raw data points; a vector network analyzer collected 49,500 S-parameter data. Each wood specimen consists of six samples; the average of data obtained from these samples was considered as a dielectric measure for the examined wood specimen. The proposed empiric models have RMSE better than 0.05 for the relation between loss tangent and density, while the proposed empiric models for dielectric permittivity have better than 0.90 with density relation, which is considered an acceptable ratio for model generation.