NDE Digital Methods for Predicting Stiffness and Strength of Wind Turbine Blades - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 178

Finally,.the.dynamic.strength.of.construction.could.be.predicted.as:

σ d =1-P(t).. (6.29)

Matrix.of.material.parameters.was.described.as.a.fourth-rank.polynomial.
equation..The.matrix.of.strength.properties.was.described.in.the.same.man-
ner.as.a.fourth-rank.polynomial.equation. 21 .The.load.of.dynamic.response.
doesn't.follow.Hook's.law.and.has.a.nonlinear.character.

6.2.2 Experimental Investigation Results

The.thermal.stresses.in.the.nose.cap.manufacturing.of.graphite.epoxy.or.car-
bon-carbon.composites.can.reach.a.signiicant.value;.however,.it.can.never.
reach.the.threshold.of.failure.
For.the.experimental.data,.we.selected.a.nose.cap.with.geometrical.dimen-
sions.Ro.=.10”.(.254.m);.Ri.=.9”.(.228.m);.r.=.9.5”.(.241.m)..The.nose.cap.was.
fabricated.from.graphite.epoxy.and.the.material.had.a.density.of.ρ.=..420*10 3.
kg/m 3 ..The.Poisson.ratio.was.μ 12. =μ 21. =..036.
When.the.modulus.of.elasticity.was.calculated.E 1 ,.E 2 .for.the.nose.cap,.the.
velocity.of.rotation.changed.from.3,627.rad/sec.to.4,800.rad/sec.and.to.7,000.
rad/sec.. The. modulus. of. elasticity. in. the. radial. direction. was. E 1. =. 3.4*10 10 .
N/m 2 ,. while. the. modulus. of. elasticity. in. the. tangential. direction. was. E 2.
=. 2.5*10 10 . N/m 2 . (see. Table 6.8).. The. coeficient. of. thermal. expansion. in. the.
radial. direction. was. α 11. =. -5.45*10 -6 . m/m/°C,. while. in. the. tangential. direc-
tion,.it.was.α 22. =.-5.34*10 -6 .m/m/°C.
A.second.nose.cap.was.fabricated.from.carbon-carbon.and.had.a.density.
of.ρ.=..548*10 -3. kg/m 3 ;.the.modulus.of.elasticity.in.the.radial.direction.was.E 1.
=.1.74*10 10 . N/m 2 .and.the.modulus.of.elasticity.in.the.tangential.direction.was.
E 2. =.1.45*10 10 . N/m 2 .
The.Poisson.ratio.was:.μ 12. =μ 21. =..036;.while.the.coeficient.of.thermal.con-
ductivity.for.carbon-carbon.β.was.-.903*10 -4 .m/hrm 2. / . °C.
Table 6.8.shows.the.properties.for.graphite.epoxy.composites.that.were.used.
to.calculate.the.thermal,.radial,.and.tangential.stresses.in.Equation.(6.25).

TABLE 6.8
Properties.of.Elasticity.for.Graphite.Epoxy.Composite

Description Values of Characteristics in N/m2

Properties.
of.elasticity.
on.the.
patterns

E 11
3.56*1010

E 22 .
2.59*1010

E 45 .
2.24*1010

G 12 .
.818*1010

G 21.
.68*1010

μ 12 .
.13

μ 21 .
.10

μ 45 .
.34

Properties.
of.elasticity.
on.the.nose.
cap

3.4*1010 2.5*1010 2.2*1010 .818*1010 .68*1010 .13 .10 .34