Consolidation of Flakeboard Mats Under Theoretical Laboratory Pressing and Simulated Industrial Pressing
Keywords:
Densification, consolidation, density profile, compression, <i>in-situ</i> measurement, flake-board, pressing, radiation, moisture, bonding, resin, unsteady stateAbstract
To achieve a more fundamental understanding of material behavior during the pressing process, a radiation-based system for measuring density of wood composite mats during consolidation is used to build in-situ cross-sectional density distributions of flakeboard mats with pressing time. The fundamentals of densification within flakeboard mats during hot and cold pressing are discussed in this paper. The pressing schedules included theoretical laboratory pressing schedules and schedules simulating industrial pressing. All tests were conducted at either ambient or 204°C temperature. The results include stress relaxation of flakeboard mats during cold and hot pressing, stress-strain behavior, in-situ density-strain behavior, and in-situ cross-sectional density distributions of flakeboard mats with pressing time. Results of laboratory studies indicate that the stress relaxation during hot pressing after the press reached final position was much quicker than during cold pressing. The observed stress-strain responses of flakeboard mats in hot pressing and cold pressing were similar, characterized by a long stress plateau followed by a rapid increase in stress and an immediate fall-down after the press reached final position. The process to simulate the industry operation resulted in another stress plateau. The stress-strain responses of flakeboard mats were characterized by a long stress plateau followed by a rapid increase in stress, and an additional high stress plateau followed by an immediate fall-down after the press reached final position. There was no clear indication that the maximum gas pressure attained is affected by press closing time.References
Adcock, T., and M. Irle. 1996. Stress relaxation of hot pressed particles. Pages - in Proc. 2nd International Conference on the Development of Wood. Science/Technology and Forestry, Sopron, Hungary.nDai, C., and P. R. Steiner. 1993. Compression behavior of randomly formed wood flake mats. Wood Fiber Sci. 25(4):349-358.nHarless, T. E. G., F. G. Wagner, P. H. Short, R. D. Seale, P. H. Mitchell, and D. S. Ladd. 1987. A model to predict the density profile of particleboard. Wood Fiber Sci. 19(1):81-92.nKamke, F. A., and L. J. Casey. 1988. Fundamentals of flakeboard manufacture: Internal-mat conditions. Forest Prod. J. 38(6):38-44.nKelly, M. W. 1977. Critical literature review of relationship between processing parameters and physical properties between processing parameters and physical properties of particleboard. Gen. Tech. Rep. FPL-10. USDA Forest Serv., Forest Prod. Lab., Madison, WI.nLang, E. M., and M. P. Wolcott. 1996a. A model for viscoelastic consolidation of wood-strand mats. Part I. Structural characterization of the mat via Monte Carlo simulation. Wood Fiber Sci. 28(1): 100-109.nLang, E. M., and M. P. Wolcott. 1996b. A model for viscoelastic consolidation of wood-strand mats. Part II. Static stress-strain behavior of the mat. Wood Fiber Sci. 28(3):396-379.nLenth, C. A., and F. A. Kamke. 1996a. Investigations of flakeboard mat consolidation. Part I. Characterizing the cellular structure. Wood Fiber Sci. 28(2): 153-167.nLenth, C. A., and F. A. Kamke. 1996b. Investigations of flakeboard mat consolidation. Part II. Modeling mat consolidation using theories of cellular materials. Wood Fiber Sci. 28(3):309-319.nPark, B-D., B. Riedl, E. W. Hsu, and J. Shields. 1999. Hot-pressing process optimization by response surface methodology. Forest Prod. J. 49(5):62-68.nSteiner, P. R., and C. Dai. 1994. Spatial structure of wood composites in relation to processing and performance characteristics. Part 1. Rationale for model development. Wood Sci. Technol. 28:45-51.nWang, S. 1986. A study and application of density gradient of wood-based panel. Science Report of Postgraduate 1(1):3-6. (in Chinese).nWang, S. 1987. A study of single-step hot pressing technology of oriented strand composite plywood. J. Nanjing Forestry Univ. (2):74-84. (in Chinese, English abstract).nWang, S., and P. M. Winistorfer. 2000. Fundamentals of vertical density profile formation in wood composites. Part II. Methodology of vertical density formation under dynamic conditions. Wood Fiber Sci. 32(2):220-238.nWang, S., P. M. Winistorfer., W. W. Moschler, and C. Helton. 2000a. Hot pressing of oriented strandboard by step-closure. Forest Prod. J. 50(3):28-34.nWang, S., P. M. Winistorfer., T. M. Young, and C. M. Helton. 2000b. Step-closing pressing of mediate density fiberboard. Part I: Influence on the vertical density profile. Holz Roh Werkst. (in press).nWang, S., P. M. Winistorfer., T. M. Young, and C. M. Helton. 2000c. Step-closing pressing of medium density fiberboard. Part II: Influences on panel performance and layer characteristics. Holz Roh Werkst. (in press).nWinistorfer, P. M., and S. Wang. 1999. Densification of wood composite mats during pressing: Implications of mat structure and pressing schedules on density profile formation and panel properties. Pages 375-382 in Proc. Fourth International Conference on the Development of Wood Science, Wood Technology, and Forestry, July 14-16, 1999. Missenden Abbey, England.nWinistorfer, P. M., S. Wang., and W. W. Moschler. 1998. Dynamics of wood composite mats during consolidation: Monitoring density development during pressing with an in-situ density monitoring system. Pages 12-23 in Proc. Second European Panel Products Symposium, October 21-22, 1998. Llandudno, Wales.nWinistorfer, P. M., W. W. Moschler, S. Wang, E. DePaula, and B. Bledsoe. 2000. Fundamentals of vertical density profile formation in wood composites. Part I. In-situ density measurement of the consolidation process. Wood Fiber Sci. 32(2):209-219.nWolcott, M. P. 1989. Modeling viscoelastic cellular materials for pressing of wood composites. Ph.D. dissertation, Virginia Polytechnic Inst. and State Univ., Blacksburg, VA.n
Downloads
Published
Issue
Section
License
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.
