Abstract
AbstractThe use of wood in high-performance composites based on laminated veneer products, plywood or wood hybrid elements thereof requires accurate prediction of strength of each individual ply. Previous research has shown that one dominating factor influencing the strength of birch veneers is the fibre orientation. The present study investigates the validity of the failure criteria after Tsai-Hill, Hoffmann and Kollmann for thin birch veneers under tensile loading. The fibre orientation in- and out-of-plane was measured by means of wide-angle X-ray scattering. Tensile strength and threshold values were determined in laboratory experiments. Pearson correlation between the predicted strength and actual strength ranged from 0.836 up to 0.883. Best correlation (r = 0.883) was achieved for Kollmann using a combined angle between in- and out-of-plane fibre orientation. It was shown that the failure criteria commonly used for manmade fibre reinforced composites are also applicable for thin birch veneers.
Highlights
On a macroscopic scale manmade fibre reinforced composites are a combination of fibres such as glass or carbon embedded in an amorphous matrix e.g. epoxy (Nielsen and Landel 1994)
Previous research has shown that one dominating factor influencing the strength of birch veneers is the fibre orientation
The present study investigates the validity of the failure criteria after TsaiHill, Hoffmann and Kollmann for thin birch veneers under tensile loading
Summary
On a macroscopic scale manmade fibre reinforced composites are a combination of fibres such as glass or carbon embedded in an amorphous matrix e.g. epoxy (Nielsen and Landel 1994). Wood is a natural material structured at multiple hierarchical levels (Fratzl and Weinkamer 2007). On the cell-wall level it can be understood as a natural fibre reinforced composite made up of fibrous cellulose embedded in amorphous lignin and hemicellulose (Fratzl 2007). On the tree ring level fibre orientation is the predominating factor influencing strength and stiffness (Kollmann and Cote 1968). Wood can be seen as a biological fibre reinforced composite with somewhat arbitrary fibre orientation. It is usually considered in applications with static loads that require high elastic stability e.g. beams or columns for building constructions (Bodig and Goodman 1973; Panshin and Zeeuw 1964). Due to its variability within the same species as well as within a single tree (Marra 1979) predictability of different properties of individual wood elements (i.e. lumber, beams, veneers, etc.) for load-bearing structures is an important issue (Bucur 2003; Ross 2015)
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