Abstract
The primary aim of this work was to assess the fatigue performance of scarf-jointed laminated wood composites used to manufacture wind turbine blades and establish simple fatigue design procedures. Laminates made from poplar (Populus canadensis/serotina), Khaya (Khaya ivorensis) and beech (Fagus sylvatica), incorporating typical scarf joints, were assessed under reversed loading (R =−1). Scarf joints were found to be great equalizers of fatigue performance for wood species with different static strengths. Poplar was investigated at several other R ratios (+3, −3, −0.84 and 0.33). The application of 95% survival probability limits derived from pooled data increases the statistical reliability of σ–N curves and gives an improved estimate of a material's minimum performance. The σ–N curves derived for all three wood species at R =−1 were normalized with respect to ultimate compressive strength values and found to be practically coincidental. This allowed the derivation of a master curve for a generic scarf-jointed wood laminate under reversed load conditions. This relationship was verified using data from the literature and found to be a good predictor of fatigue performance. The construction of simple triangulated constant life diagrams based on static tensile and compressive tests and fatigue testing at R =−1 brings about a rapid assessment of the overall fatigue performance of any wood composite. These can then be used in the fatigue design or life prediction of wood composites under cyclic loading.
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Bond, I.P., Ansell, M.P. Fatigue properties of jointed wood composites Part I Statistical analysis, fatigue master curves and constant life diagrams. Journal of Materials Science 33, 2751–2762 (1998). https://doi.org/10.1023/A:1017565215274
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DOI: https://doi.org/10.1023/A:1017565215274