Environmental Engineering Reference
In-Depth Information
The.stiffness.of.the.composite.is.controlled.and.calculated.according.to:
.
E
c
.=.η.V
f
.E
f.
.+.V
m
E
m
.
(2.14)
where
E
c.
is.the.stiffness.of.composite
η.is.the.orientation.factor.for.the.ibers
V
f.
is.the.iber.volume.fraction
E
f.
is.a.modulus.of.elasticity.for.iber
V
m.
is.the.matrix.volume.fraction
E
m.
is.a.modulus.of.elasticity.for.matrix
The.orientation.factor.is.equal.to.1.for.aligned.parallel.ibers.loaded.along.
the.iber.direction..For.the.randomly.oriented.iber.assembly,.the.orientation.
factor.equals.1/3.
5
.The.ibers.are.normally.the.dominant.contributor.to.the.
composite. properties.. In. case. of. wind. turbine. blade. stiffness,. calculate. as.
combination.of.shell.stiffness.and.core.stiffness.according.to:
.
E
c
.=.E
sh
.+.E
cor
.
(2.15)
We.reduce.the.thickness.of.the.shell.by.increasing.stiffness.of.the.core.
material.
2.5.2
Experimental Investigation
The. current. coordinate. x. for. the. root. section. we. will. assume. as. half. of. all.
length.. For. the. middle. density. of. iberglass,. we. have. 2.5×10
3
. kg/m
3
.. The.
speed.rotation.of.wind.turbine.blades.varies.from.5.to.25.m/sec..We.select.
the.angle.of.twist.at.3
°
..Values.of.bending.and.torsion.moments.are.presented.
in.Table 2.1.(see.Equation.(2.8).to.Equation.(2.10)).
TABLE 2.1
Values.of.bending.and.torsion.moments
BendingMoment,
M
x
10
-6
,kgm
2
/s
2
BendingMoment
M
y
10
-6
,kgm
2
/s
2
TorsionMoment,
kgm
2
/s
2
346.4
346.4
13.8
1040.0
1040.0
55.4
2340.0
2340.0
124.7
4160.0
4160.0
221.7
6500.0
6500.0
346.4
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