Effect of Water on the Mechanical Properties of Wood Cell Walls – Results of a Nanoindentation Study

BioResources

Karin de Borst¹  Clémence Bos¹  Thomas Karl Bader²  Leopold Wagner³ 

[1]Austria

[2]Institute for Mechanics of Materials and Structures, Vienna University of Technology Institute for Applied Materials, Karlsruhe Institute of Technology

[3]Vienna University of Technology, Institute for Mechanics of Materials and Structures

关键词: Nanoindentation;    Cell wall;    Creep;    Moisture effects;    Hardwood;    Softwood;   

DOI  :  10.15376/biores.10.3.4011-4025

来源: DOAJ

【 摘 要 】

The paper presents a nanoindentation study on five different wood species in which the elastic and creep properties of the S2 cell wall layer and the middle lamella were determined. Measurements were carried out at relative humidities (RH) ranging from 10 to 80% as well as underwater. Indentation moduli were found to decrease by about a third in the S2 layer and by about half in the middle lamella between RH of 10 and 80%. Hardness dropped by 50 to 60% in this humidity range in both the S2 layer and the middle lamella. Creep parameters were almost constant up to a relative humidity of 40%, but they increased considerably at higher RH. The most pronounced change of reduced moduli and creep properties occurred between 60 and 80% RH, which is consistent with the expected softening of hemicellulose and amorphous parts of cellulose in this humidity region. Immersion into water resulted in a further decrease of the reduced moduli to about 20 to 30% of their values at 10% RH and to only about 10 to 20% for the hardness. This can be explained by additional softening of the less ordered regions of cellulose.

【 授权许可】

Unknown