Materials for Turbine Power Blades, Reinforcements, and Resins - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 55

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Materials for Turbine Power Blades,
Reinforcem ents, and Resins

3.1 MaterialsRequirements

Material.requirements.concentrate.on.stiffness,.density,.and.long.time.fatigue:

•. High.material.stiffness.supports.aerodynamic.performance
•. Low-density.reduces.gravity.forces
•. Long.fatigue.life.reduces.material.degradation

Design. process. focuses. on. the. materials. and. the. inluence. that. technol-
ogy.has.on.the.stiffness.and.strength.of.the.materials..Development.weight-
length.correlation.is.illustrated.in.Figure 3.1. 1
Symbols. indicate. different. manufacturers. and. processing. technologies..
Shown.in.the.igure,.the.blade.length.of.55.m.weighs.approximately.20.tons..
The.lower.end.of.the.curve.represents.the.relatively.short.blades.of.lengths.
from. 12. to. 15. m.. These. were. common. in. the. early. years. of. wind. turbine.
design.(1980s).
The. materials. property. requirements,. which. include. high. stiffness,. low.
weight,. and. long-fatigue. life,. can. be. used. to. select. materials. and. to. make.
a. consideration. on. what. deformation. exists. within. a. ield. of. stress.. The.
mechanical. design. of. a. rotor. blade. corresponds. nominally. to. a. beam,. and.
the.metric.index.is,.for.this.case:

. M b .=.E 1/2 /r. (3.1)

where:
E.is.material.stiffness;
r.is.the.material.density.

In.Figure 3.2,.the.diagram.shows.stiffness.versus.density.for.all.materials..
The.metric.index.M b .is.equal.to.0,003.(lower.line).and.0,006.(upper.line)..The.
criterion.of.absolute.stiffness,.E.=.15GPa,.is.indicated.by.the.horizontal.line.

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