Graduate Thesis Or Dissertation
 

Characterization of load transfer in wood-based composites

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2r36v238c

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  • The mechanical performance of composite materials is determined by the mechanical properties of their individual components and the effective load transfer between these components. Binders are commonly used to bond composite components together and to provide effective load transfer between them. In wood-based composites the binder-component load transfer occurs at the micro-scale (1-100 μm), where complex morphologies are in play. The bonding of these materials is relatively well understood on the molecular level with respect to the chemical compatibility of the binder and components, but the load transfer and the relative contribution of surface adhesion forcesof wood tissue at the micron- and sub-micron scale remains a subject of limited understanding. Understanding of the load transfer at this scale requires experimental observation of the responses of complex bond morphologies to external loads. It should be noted however, that load transfer in bonds in terms of internal force distribution and stress cannot be measured directly. Instead, methodologies are needed that allow back calculating complex stress distributions in the bond interphase from experimental measurements of displacements and strains. Recently, a conceptual framework for an integrated method for multi-scale/multi-modal investigation of micro-mechanical interaction in bond interphases has been proposed where measurements of properties associated with the load transfer across composite bonds were integrated with predictive numerical modeling tools (Muszynski et al. 2013) (reproduced in Appendix C). This general framework and the modeling tools used are generic and can be applied to a variety of composite materials. The general goal of this dissertation was to develop the crucial non-generic components for this approach, which are the specialized, experimental measurement tools, methods and procedures that are paired with modeling tools. Consequently, measurement methodologies have been developed to assess the deformations and strain patterns across the particle-matrix bonds in WPCs and across adhesive bonds in layered composites. The measurements in these methodologies are valuable as input data and are spatially tied to coordinate systems making them easily compatible with three-dimensional numerical modeling tools. A measurement methodology has also been developed to investigate local surface free energies of wood tissue at a micron and sub-micron scale. These measurements are able to further inform and enrich the predictions made by numerical models with respect to the bonding morphology. Currently these methods are being used to further develop, refine and ultimately validate the numerical model used to quantify and analyze load transfer in wood composite bonds.
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file details SchwarzkopfMatthewJ2014.pdf 2017-08-22 Pubblico Scaricare