Environmental Engineering Reference
In-Depth Information
The.principal.of.the.Nibe.blades.is.that.the.inner.8.m.has.a.steel.spar.and.
the.outer.12.m.is.an.all.composite.blade.
6
The.airfoil.was.hand.lay-up.glass/polyester.with.a.balsa.core.sandwich.in.
the.afterbody,.and.the.airfoil.was.adhesively.bonded.to.the.spars..The.thick-
ness.of.the.spar.was.easily.varied.along.the.length.from.24.mm.at.the.root.
end.to.6.mm.at.the.tip,.by.changing.the.length.of.travel.of.the.tape.place-
ment.apparatus.along.the.length.of.the.spar..Because.the.spar.was.tapered.
toward.the.tip.end.and.the.warp.glass.ibers.in.the.tape.could.not.stretch,.
it. was. necessary. to. insert. and. withdraw. a. wedge. underneath. the. tape,. at.
the. shear. web. position. of. the. spar,. for. each. revolution. of. the. mandrel. in.
order. to. control. and. maintain. straight. ibers. with. the. desired. orientation.
in.the.upper.and.lower.part.of.the.spar..All.the.slack.at.the.one.side.of.the.
tape.was.taken.up.by.the.wedge,.and.the.surplus.of.tape.and.mismatch.of.
iber.orientation.was.concentrated.at.the.web.where.it.actually.improved.the.
shear.properties.of.the.cured.laminate..After.the.inal.layers.of.glass.iber.
tape.was.wound,.a.peel.ply.was.applied,.and.the.spar.was.parked,.lined.up,.
and.cured.
4.4
PrepregTechnology
The.prepreg.(preimpregnated).technology.has.been.adapted.from.the.aero-
space. and. aircraft. industry.. It. is. based. on. the. used. of. a. semiraw. product.
where. the. iber. fabrics. are. preimpregnated. by. resin. and. the. curing. has. a.
portion.character.
Golfman
7
. demonstrated. a. way. to. manufacture. sophisticated. blades. by.
preliminary. curing. of. spars. at. 50. to. 70. percent.. At. room. temperature,. the.
resin.resembles.a.tacky.solid,.and.the.tacky.prepregs.can.be.stacked.on.top.
of.each.other.to.build.the.designed.laminate.
By.increasing.the.temperature,.the.resin.becomes.liquid/viscous,.and.the.
laminate.can.be.consolidated.under.pressure.and.cured.into.the.inal.com-
ponent.. Prepreg. is. available. in. many. varieties. and. combination. of. ibers,.
style. of. fabrics,. and. resin. systems.. Different. processes. of. curing. tempera-
tures.range.from.70.to.225°C..For.large.wind.turbine.blades,.a.process.tem-
perature.of.around.80°C.is.most.common.
The.required.pressure.to.consolidate.the.stacked.layers.of.prepregs.is.achieved.
by.vacuum..The.entire.lay-up.of.prepreg.is.covered.by.a.polymer.ilm,.which.is.
sealed.to.the.mold.along.the.edge..A.vacuum.is.pulled.underneath.the.polymer.
ilm,.and.the.atmospheric.pressure.outside.the.ilm.presses.the.prepreg.pack-
age..The.shelf.life.of.the.prepreg.at.room.temperature.normally.ranges.from.a.
few.days.to.a.few.weeks.depending.on.the.resin.system..Therefore,.the.prepreg.
is.typically.stored.at.-18°C,.which.results.in.a.shelf.life.of.from.6.to.12.months.
Search WWH ::
Custom Search