Physical Properties of Wood and Wood-Based Materials

This chapter describes the basic physical properties of wood and wood-based materials such as density, thermal properties, electrical properties, friction, optical properties, corrosion, and aging. In addition, selected new innovative testing methods are presented, which are still mainly used in research. Together with the very high influence of (i) wood moisture on the properties of wood and wooden materials, (ii) the mechanical properties (elasticity and strength) as well as (iii) the heterogeneity and orthotropy of wood and wood-based materials, knowledge of the physical properties described in this chapter is very important. This is necessary, for example, for processes such as the drying of wood, mechanical processing (e.g., machining, defibration, bonding), as well as the design and manufacture of products made of wood. Sound and thermal insulation of buildings, color change of wood during use, wood aging with changes in physical and mechanical properties are further examples. Numerous processes from the area of nondestructive testing of wood are used to control the production. Examples are color measurement, the detection of the fiber angle by means of the tracheid effect, wood moisture measurement using electrical, dielectric, or spectrometric properties. Ultrasound and eigenfrequency measurement already have a place in the industry for grading the quality of wood (strength) or blister detection with air-coupled ultrasound in particleboards or plywood.