Revealing the Century Old Technique of Slicing Japanese Cedar (Cryptomeria japonica) by Japanese Craftsmen by Assessing its Mechanism of Crack Propagation

The use of automation in the production of wood shingles is hampered by the lack of information regarding their fracture mechanisms. The fracture of natural materials like wood tend to be complex and depend on factors such as grain direction. The aim of this study is to probe into the fracture mechanisms of Japanese Cedar (Cryptomeria japonica) with respect to their grain direction through experimental investigation in 3-point bending test. From the bending test results, longitudinal-tangential specimen (LT) was found to display greatest critical force prior to fracture as compared to longitudinal-radial specimen (LR). Further observations under the scanning electron microscope revealed that LT specimens were better adapted to resist transverse fracture unlike LR specimens in which considerable delamination of fibres were observed. The observations made in this study will be useful to elucidate the complex fracture behavior observed in the manual production of wood shingles by craftsmen in Japan.