Possible use of scanning acoustic microscopy to study local wood properties: Preliminary study of experimental conditions

To understand wood macroscopic behaviour, it is useful to know its properti es at the microscopic level. For this, several imaging techniques can provi de information about the geometrical structure in 2 or 3 dimensions, chemic al composition, density, crystal lattice and crystal orientation. Wood mech anical properties are determined either by testing isolated fibre, or troug h modelling based on stiffness data of the various cell wall components obt ained outside the cellular context. Only nanoindentations methods can be us ed to estimate in situ mechanical properties on a limited number of sites. On the other hand, this can be done on high stiffness materials (metals, gl asses, ceramics...) by using acoustic microscopy. To apply this technique t o wood, experimental procedure should be assessed. Trials on a scanning aco ustic microscope show that for high resolution images, thin slices (approxi mate to 5 mu m) after resin inclusion with water or potassium iodure as cou pling liquid respectively at 600 MHz or 1 GHz give good results giving way to quantitative measurement of cell wall stiffness by image analysis.