Environmental Engineering Reference
In-Depth Information
can. be. very. useful. in. the. process. of. curing. and. cooling. composite.
structures.
.
4.. Probability.of.local.cracking.can.be.predicted.using.statistical.mod-
els,.the.irst.and.second.approach.in.the.law.of.normal.distribution.
.
5.. In.spite.of.the.visibility.of.cracks,.the.samples.tested.relect.90.per-
cent.of.initial.strength..However,.it.is.very.important.to.use.nonde-
structive.evaluation.methods.in.the.determination.of.cracks,.which.
are.not.visible.
6.3
NoncontactMeasurementofDelaminatingCracks
PredictstheFailureinHybridWindTurbineBlades
6.3.1 Introduction
Noncontact. measurement. of. delaminating. cracks. in. hybrid. wind. turbine.
blades. is. of. great. importance. in. predicting. fatigue. failure. of. these. blades..
Currently. used. failure. prediction. methods. lack. multifunctional. self-diag-
nostic.capabilities..In.previous.studies,.the.correlation.between.crack.delam-
inating.of.the.iber.reinforced.polymer.(FRP).matrix.resin.and.the.strain.on.it.
was.established..However,.laminate.stress-strain.curves.are.highly.nonlin-
ear,.especially.at.elevated.temperatures.
In.this.chapter,.we.examine.the.correlation.during.fatigue.testing.between.
temperature.gradients.and.the.appearance.of.nonlinear.deformation.cracks.
on.the.test.object.
We.also.show.that.measuring.the.boundary.surface.temperature.gradients.
of. a. turbine. blade. test. package. can. directly. self-diagnose. and. predict. the.
appearance.of.delaminating.cracks,.and.that.injecting.a.resin.agent.and.solid.
chemical.catalyst.can.create.an.automatic.self-healing.process.that.increases.
the.durability.of.the.hybrid.turbine.blades.
6.3.2
Damage Mechanisms of Failure
Recent. work. by. Gamstedt. and. Talrega
23
. describes. the. fatigue. damage.
mechanisms.of.carbon.FRPs..During.fatigue.tests,.FRPs.form.delaminating.
cracks.
24
.These.authors.found.a.correlation.between.crack.length.in.a.delami-
nated.matrix.resin.and.the.applied.strain.
We.are.looking.for.a.correlation.between.crack.length.and.applied.strain.
in.the.composites.like:.
.
1.. Carbon.iber.IM7.in.polyetheretherketone.(PEEK).polyamide
.
2.. Carbon.iber.IM7.in.polyphenylene.sulide.(PPS).polyamide
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