LAUSR

This research examines the effect of thermal modification on the mechanical properties of the soft wood cell wall in order to clarify the relationship between the micro-level behavior (cellulose microfibrils) and macro-level behavior (bulk wood). The thermal modification of three stages at two different temperatures was conducted on the specimens. Then, the synchrotron radiation XRD under tensile loading in the axial direction of thermally modified bulk wood was performed. Simultaneously, the lattice strain of cellulose in the S1 and S3 layers and the strain of bulk wood were obtained. As a result of the tensile test, for unmodified specimens, the load–strain relationship of the cellulose microfibrils in the S1 and S3 layers showed linear behavior similar to bulk wood. In contrast, for thermally modified specimens, it was found that the load–strain relationship of the cellulose microfibrils in the S1 and S3 layers was not linear. The effects of thermal modification on tensile properties of bulk wood differed from that of the cellulose microfibrils in the S1 and S3 layers. Furthermore, when compared with the results of the cellulose microfibrils in the S2 layer, the effect of thermal modification was different between the cell wall layers. The reason for this was suggested by the orientation angle and linearity of the cellulose microfibrils.