sin αst

E
Structural analysis of blades
This appendix contains a general description of the material used for the blades, followed
by a statement of its mechanical properties. It further encloses a verification of the struc-
tural integrity of blades through finite element analysis.
E.1 Material description
For purpose of analysis the engineering properties of pinus taeda are used. This type of
wood is commonly known as loblolly pine, native to the South-eastern United States and
widely available in regions such as Africa and South East Asia [51]. It is therefore a likely
material candidate in the countries targeted by the present wind turbine design.
For future designs the selected wood may be substituted by other types of wood, e.g. dif-
ferent wood species, jointed wood, glued laminated wood or wood composites. Substitu-
tion requires that the new material has equal or greater strength and stiffness, and that
proper consideration is taken to manufacturing issues, described in section 6.2.3.
The mechanical properties presented in the following section assume that the blades are
produced from wood pieces that are termed clear and straight grained, i.e. considered
homogeneous within wood mechanics. This implies that the wood has growth rings that
occur in consistent patterns and that it does not contain characteristics such as knots,
cross grain and splits.
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