Verification of Mukudai's mechano-sorptive model

Summary

Mukudai and Yata have shown in the previous reports an interpretation of mechano-sorptive behavior that characteristic of viscoelastic behavior of wood under moisture change may be resulted from redistribution of applied stress in the cell wall because of change of friction between the S₁ and S₂ layers induced by moisture content change due to the looseness between the both layers, and have proposed a mechano-sorptive model based on the interpretation.

In this report, to find out evidence supporting the interpretation that mechano-sorptive behavior is resulted from the looseness between the S₁ and S₂ layers, surfaces of specimens fractured by increasing load during creep under moisture content change were observed with electron microscopes. And, characteristic features of mechano-sorptive creep and recovery deflection curves at 15%, 30% and 45% stress levels which were obtained by computer simulation were checked by comparison with those of the corresponding experiments.

As the results, it could be observed that fractures took place at the interface of the S₁ and S₂ layers in cells of the tension side of beams, and splits at the interface of the S₁ and S₂ layers took place here and there in the fractured surfaces. Furthermore, the characteristic features of creep and recovery deflection curves obtained by the simulations agreed well with those of the experiments.