Comparison of transverse compression creep of Pseudotsuga menziesii and Populus sp. in high-temperature steam environments

Abstract

Compression creep experiments of Douglas-fir wood (Pseudotsuga menziesii) were performed at high temperature (150°C, 160°C, and 170°C) and under various conditions of steam pressure. The results established that environment conditions had a significant effect on compressive deformation, with the largest deformation obtained under saturated steam conditions. While the temperature significantly affected the compressive deformation of specimens under transient conditions, the temperature within the range studied had little effect on the compressive deformation in saturated steam. Furthermore, in specimens compressed under superheated and transient steam conditions, primary creep behavior was exhibited; while in specimens compressed under saturated steam conditions, creep deformation appeared to enter directly into secondary creep. Moreover, in saturated steam specimens very little creep was observed due to high initial deformation and little potential for additional cell wall buckling. The compressive creep measurements of Douglas-fir were compared with compressive creep of hybrid poplar (Populus deltoides × Populus trichocarpa). Due to lower initial density, and perhaps smaller microfiber angle and lower lignin content of tension wood, the compressive creep modulus of hybrid poplar was lower than Douglas-fir. Therefore, compressive deformation of Douglas-fir, at nearly all examined steam conditions and temperatures, was smaller than compressive deformation of hybrid poplar.

Keywords:

• Rheology
• thermo-hydro-mechanical
• time-dependent

Acknowledgments

The project was supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant number [2006-35504-17444] and USDA Wood Utilization Research Center Special Grant number [2008-34158-19302].