FATIGUE BEHAVIOR AND DESIGN OF WOOD COMPOSITES AS FURNITURE COMPONENTS

Strength design of upholstered furniture frames should take into account member material fatigue strength properties since most service failures of the frames appear to be fatigue related [10]. As more wood composites such as plywood, oriented strandboard (OSB), and particleboard (PB) are used as furniture frame stock, the information related to fatigue strength properties of various types of wood composites becomes more essential.
Plywood is described as a flat panel built up of sheets of veneer called plies,wood polymer composite prices in usa united under pressure by a bonding agent to create a panel with an adhesive bond between plies [17]. OSB is an engineered structural-use panel manufactured from thin wood strands bonded together with waterproof resin under heat and pressure.
Orientation of wood strands with a typical aspect ratio (that is, strand length divided by width) of at least three can produce a panel product with greater bending strength and stiffness in the oriented or aligned direction. PB is produced by mechanically reducing the material into small particles, applying adhesive to the particles, and consolidating a loose mat of the particles with heat and pressure into a panel product.
Fatigue study results of wood and plywood subjected to repeated and reversed flat-wise bending stresses 1,790 cycles per minute [13] indicated that the S-N curves (percentage of mean control static modulus of rupture versus the number of cycles to failure) for wood does not exhibit a “knee” as do the curves of ferrous metals. No endurance limits were established for tested wood specimens and the experimental data indicates that if an endurance limit for wood exists, it occurs above 50 million cycles. The fatigue strength for 50 million cycles of reversed stress is approximately 27 percent of the static modulus of rupture (MOR) for the species investigated (yellow birch, yellow-poplar, Sitka spruce, and Douglas fir) whether in the form of solid wood or plywood.cheap plastic wood balustrades The fatigue strength of solid Sitka spruce and Douglas fir at 50 million cycles of repeated stress is approximately 36 percent of their respective static modulus of rupture. The values of the endurance ratio for some species of solid wood, which is the ratio of endurance limit to ultimate static stress, are of the order one-quarter to one-third of the ultimate static stress [5].
The edge-wise fatigue bending resistance of medium density fiberboard (MDF), OSB, and PB was investigated [4] with the stress-based and matched piece approach.[url=http://www.woodplasticcompositepanel.com/project-case/different-wpc-materials-projects-and-end-use/]WPC materials,Wood Powder + PVC,PP,HDPE Extruded Profile[/url] Experimental results indicated that all three materials would be expected to have fatigue lives of at least 200,000 cycles at the load stress levels of 40 percent of MOR or less.

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