Graduate Thesis Or Dissertation
 

Bending property enhancement of wood strand composite using viscoelastic thermal compression

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cc08hj10c

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  • The fundamental intent of the study was to develop an innovative wood-strand composite for use in structural applications. Plantation grown, low density, hybrid poplar was used in the study which was found to be appropriate for the underlying Viscoelastic Thermal Compression (VTC) process. Wood modified by this process has high density and a proportional increase in its flexural strength and stiffness. The VTC process increases the density of wood in the presence of steam, which acts as a plasticizer, mechanical compression and high temperature. Steam pressure is manipulated to induce the mechanosorptive effect during VTC processing, increasing density without fracturing the cell walls. There were three components of this research project. Firstly, the scale-up VTC device was successfully constructed to process samples of dimension: 61 x 25 cm (24" x 10"). Secondly, the influence of high density VTC wood strands in an oriented strand composite was evaluated. The novelty of this objective was that the overall panel density was not increased. Lastly, a three-layer laminated composite was made, where the lamina were comprised of wood strand panels that were VTC processed prior to lamination. Both methods of VTC composite manufacture improved bending properties in comparison to control specimens. Two treatments were studied for the VTC strand composites. The treatments included the addition of 20% and 40% of VTC strands, by weight, oriented on the surface of the panel. Panels with 20% by weight of VTC strands oriented on the surface showed no statistically significant increase of MOE and MOR. The addition of 40% VTC strands improved the MOE and MOR by 30% and 18%, respectively. The MOE of the strand composites that were processed by VTC increased by approximately 150% to 160%. The VTC laminates were then bonded to produce the final three-layer product. Visual inspection revealed that the VTC process did not disrupt the phenol-formaldehyde bond.
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