NDE Digital Methods for Predicting Stiffness and Strength of Wind Turbine Blades - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 163

6

NDE Digital Methods for Predicting Stiffness
and Strengt h of Wind Turbine Blades

6.1 UltrasonicNondestructiveMethodtoDetermine

ModulusofElasticityofWindTurbineBlades
6.1.1 Introduction

The.ability.of.ultrasonic.waves.to.travel.in.a.web.direction.over.a.minimum.
time.for.composites.was.advanced.by.the.author.in.1966. 1 .This.effect.can.be.
used.for.different.applications.in.composites,.ceramics,.and.metal.alloys. 2,3 .
Nondestructive. evaluation. (NDE). of. the. material. properties. of. a. structure.
makes.this.method.very.useful..Research.has.been.conducted.to.determine.
the. modulus. of. elasticity. of. high-speed. turbine. blades. 4 . In. this. research,. a.
general.nondestructive.test.method.for.deterring.the.modulus.of.elasticity.in.
different.directions.was.examined.
Modules. of. elasticity. predictions. of. turbine. blades. using. an. ultrasonic.
method. probably. give. the. option. of. estimating. the. strength. of. the. blades..
Gershberg 5 .determined.the.parameters.of.elasticity.for.specimens.fabricated.
from.iberglass..Golfman.and.Gershberg.determined.the.parameters.of.elas-
ticity.in.the.blades.of.screw.propellers.fabricated.from.orthotropic.iberglass.
using.a.nondestructive.ultrasonic.method. 6 .The.advantage.of.a.nondestruc-
tive.evaluation.of.the.properties.of.new.materials.used.for.manufacture.of.
turbine.blades.is.that.they.can.be.predicted.with.little.dificulty.

6.1.2 Theory and Application of Ultrasonic Method

Knowledge.of.the.parameters.of.elasticity.is.necessary.to.calculate.stress.and.
estimate.the.strength.of.turbine.blades..If.we.assume.that.composite.turbine.
blades.to.be.manufactured.from.orthotropic.material.having.three.planes.of.
elasticity.symmetry,.its.technical.behavior.can.be.completely.characterized.
by.nine.classic.constants. 7
The.elastic.constants.for.orthotropic.materials.are.listed.in.Table 6.1.
For.a.composite.turbine.blade,.there.are.nine.independent.parameters:.E z ,.
E y ,. and. E x . are. the. modulus. of. elasticity. in. the. three. principal. directions. z,.

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