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Green building practices have created an opportunity for the forest products industry to become a leader in the creation of in- novative building products derived from renewable materials. In other industries, sandwich composites have proven to be efficient structures by meeting structural demands of traditional panel products while consuming less material. A prototype molded-core sandwich panel made of span-rated oriented strand board (OSB) facings and a bidirectional molded wood-strand core was produced. Critical mechanical properties were evaluated to determine the feasibility of this product for use in building applications. The goals of this study were to generate details on structural performance of the product, validate the design, and provide suggestions for future product development. Results indicate that this molded-core panel performs particularly well in flexure while connection properties had the largest scope for improvement. Sufficient performance was observed to validate the design, warranting production and testing of panels sized for end-use. Future product development should explore different connection systems, perform detailed engineering analyses of the mechanical properties necessary for complete structural design, and characterize physical properties of the panel. [ABSTRACT FROM AUTHOR]

The importance of adhesion in production of wood-based composites is well-known. Adhesive penetration and interphase morphology play an important role in bond strength and product performance. Many studies offered different methods for interphase characterization and analysis. Both qualitative and quantitative methods have been used to analyze the bondline. Most of the quantitative methods were developed for bonded assemblies of veneer or wood blocks. Adhesive penetration measurement in particulate wood-based composites is the main scope of this study. For this purpose, uniform oriented strand board with veneer strands was produced by the use of phenol formaldehyde resin with 2, 6, and 10 % strand moisture content (MC). The strands were formed into well-organized mats to achieve a uniform structure for the composite. Cross-section specimens were prepared from each board and observed by epifluorescence microscopy. Six positions for growth-ring angle in adhesive joints were denoted to evaluate penetration in different directions of the wood. Four parameters were also determined to quantify resin penetration patterns by counting the quantity of the main anatomical elements of wood, which were filled with resin. Finally, it was determined that this method could recognize the differences between adhesive penetration in boards produced with different level of strand MC. Resin penetration in strands with 6 and 10 % MC was the greatest. Growth-ring angle of the strands influenced penetration as it was increased when both strands meet each other in an oblique position, although this effect was significant only in maximum penetration depth in fibers. [ABSTRACT FROM AUTHOR]

A mathematical model of the hot-pressing consolidation process for manufacturing a multi-layered oriented strand composite is developed and tested. Such a process model requires independent physical properties and user-specified structure for each layer of the mat. The model uses two-dimensional (slow variation is assumed in the third dimension) heat- and mass-transfer theory and a viscoelastic compression model. The through-the-thickness (vertical) density profile (VDP) was found to be highly dependent on the initial moisture content gradient, internal mat strand properties, and hydrothermal compressive response of the mat. The VDP predicted by the model showed good agreement with experimental results. The proposed mathematical model thus shows promise as a tool to analyze optimally design-oriented strand composites. [ABSTRACT FROM AUTHOR]

A novel wood-based composite has been developed for use in structural applications. The process was designed to utilize rapidly-grown, low density, wood species. Plantation grown radiata pine is particularly well suited to this process. This is a laminated composite, where the lamina may be comprised of various materials, some of which have been treated with the viscoelastic thermal compression (VTC) process. The VTC process increases the density of wood, without causing fractures in the cell wall, thus increasing strength and stiffness of the wood material. The process may be applied to veneer, sawn wood, or strand composites. The VTC lamina is then bonded to other lamina to produce the final product. The strength and stiffness of this VTC composite exceeds any wood-based composite that is currently on the market. For example, modulus of elasticity in bending of over 20 GPa is easily obtainable. [ABSTRACT FROM AUTHOR]