COMPARING MECHANICAL-PROPERTIES OF SECONDARY WALL AND CELL CORNER MIDDLE LAMELLA IN SPRUCE WOOD

Mechanical characterizations of the S-2 layers and the cell corner mid dle lamella in the axial direction were investigated in spruce wood. A mechanical properties microprobe capable of measuring hardness and Yo ung's modulus on a spatially resolved basis similar to that of an elec tron beam microprobe was used. Hardness of the cell corner middle lame lla was found to be almost as high as that of the secondary wall, but the Young's modulus of the cell corner middle lamella was 50% less tha n that of the S-2. The S-2 showed constant hardness over its range of Young's modulus, but the cell corner middle lamella exhibited a strong correlation (R-2 = 0.55) between hardness and the Young's modulus. Fu rther investigations are needed to directly combine chemical and micro mechanical properties and also to investigate the mechanical effects o f the high variability of cell corner middle lamella chemistry.