Characterization of wood micromorphology from gas permeability measurements

International audienceThis paper presents a method for identifying wood morphological parameters from gas apparent-permeability measurements. The apparent permeability at a given mean pressure is typically determined from the pressure relaxation kinetics when the gas permeates through the wood sample between two compartments which have different initial pressures. Using the proposed setup apparent permeability values ranging from 10-10 to 10-18 m 2 can be measured with a mean gas pressure varying from 2 bar down to 35 mbar. Morphological and topological parameters are then identified from the variations in apparent permeability as a function of the mean gas pressure using a pore network model. The network consists of elements such as pipes or orifices connected in series or in parallel. The rarefied gas flow is described in each element by an appropriate model and the unknowns are determined by an inverse method. This approach was first applied to track-etched polycarbonate membranes for validation purposes. The calculated pore radius and pore density values were compared to observations by environmental scanning electron microscopy. Softwood specimens were then investigated. The mean radius of the pores controlling permeability in the longitudinal and tangential directions was determined and found to be in good agreement with literature data