環境条件変化に伴う繊維板の反り変形と内部応力の挙動

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The modulus of elasticity and the dimensinal changeability parallel to the plane of fiberboard are known to vary with depth, and furthermore both of the outer layers of board are directly exposed to the atmosphere, while the inner layer is more or less sheathed with the outer layers. Consequently, the internal stress appearing in the direction parallel to the plane of board is distributed well over the cross section, which can be examined by the slicing method. Under the normal condition of 20℃・RH 60%, the screen back of SIS (wet-process) hardboard was found to be subjected to little internal stress, with the tempered face layer of S2S (wet-forming・dry-pressing) hardboard was exerted by a steeply high stress. However, the distribution of internal stress in the MDF (dry-process, medium density) was found to be reverse to that in the above-mentioned S1S or S2S, being symmetrical with respect to the center line of cross section. In the case of a board conditioned at 20℃・RH 60%, the moisture absorption at 40℃・RH 90% and the desoption at 40℃・RH 30%, from the face or from the back, gave so much influence on internal stress, as to cause the undue warp of board as the result of shifting the warp ability of layer within the cross section of board. The internal stress was distributed complicantedly over the cross section when a rapid moisture-absorption was given by spraying water or when a rapid desorption was achieved by the infrared rays radiation. In particular, the warp of the board almost disappeared after the moisture absorption under restraint of distortion.
1985-08-15

著者

又木義博
九州大学農学部

環境条件変化に伴う繊維板の反り変形と内部応力の挙動

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