| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
The purposes of this research project are; to establish the three dimensional( 3D ) electron-fractography (EF ) for the fracture surface of wood and paper by using stereo pairs of SEM fractoraphs, and to evaluate effect of minute defects within cell walls, such as slip planes, on the mechanical properties and on the fracture phenomena of them by means of the 3D-EF. The newly established method of the 3D-EF was very useful and powerful not only enough to visualize the topological features of the fracture surface precisely, but also enough to measure the size and the slope of the fracture surfaces without coming into the physical contact with them. In order to evaluate quantitatively the influence of the slip planes on the mechanical and fracture properties of the cell wall materials, the precompressed wood specimens, which had numerous slip planes within the cell walls induced artificially by the external force, were prepared, after which, tensile strength, elastic modulus and work to failure ( the toughness ) were measured, and the fracture surfaces of the fiber walls of the precompressed wood were analysed by using the newly established method of 3D-EF. It was found that the strength and the toughness of wood were drastically decreased as the number of slip planes increased. Therefore, the quality of the cell wall materials became fragile because of the presence of the slip planes within the cell wall. The fracture surfaces of the cell walls of the precompressed wood always showed the C II fracture mode, and the slant angles of the fracture surface were 60 to 65 to the fiber axis, which were closely in agreement with the slip plane angle. From these experimental evidences, it was concluded that the cell walls with the presence of the slip planes should repture at the slip-plane site, and the mechanical properties of the cell wall materials should be strongly influenced by the local properties at the slip-plane site.
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