Environmental Engineering Reference
In-Depth Information
Newly.developed.braiding.technology.for.aerospace.components.has.used.
carbon-carbon. or. graphite. epoxy. dry. fabric,. injected. epoxy,. and. curing.
was.shown.by.thermal.cameras..Cooling.processes.were.not.free.of.thermal.
stresses.and.were.also.seen.by.NDT.methods.
Composite.structures.had.a.low.thermal.conductivity.during.the.faster.heat-
ing.process.and.a.high.gradient.ield.of.temperature.changes..Additionally,.
an. irregular. ield. of. temperature. had. signiicant. thermal. stresses,. which.
could.result.in.failure.in.structures.in.the.process.of.fabrication..These.also.
were.seen.by.NDT.
Curing. and. cooling. processes. for. high. thickness. structures. with. a. low.
speed.of.heat.up.rate.can.avoid.a.signiicant.thermal.stress,.but.they.increase.
time.and.labor.costs.
The. task. of. determining. the. optimal. regime. is. sophisticated. because,. in.
the.process.of.curing.epoxy.matrix,.the.exothermic.reaction.appears.in.adia-
batic.conditions,.which.avoid.contact.with.the.outside.environment..All.the.
heat.is.used.in.preheating.the.epoxy.resin.
Finally,. the. velocity. of. reaction. increases. by. the. exponent. of. tempera-
ture. and. self-heat. in. these. conditions. and. could. delaminate. graphite.
epoxy.composites.
Theoretical.investigation.of.this.subject.had.been.done.by.Golfman.
15
Dynamic.stresses.for.orthotropic.components.could.be.described.as:
2
2
2
d
dx
φ
d
dy
φ
d
dxdy
φ
.
σ
x
=
; y
σ
=
; xy
τ
=
;
.
(6.20)
2
2
Here:. x,y. are. the. vectors. describing. the. directions. in. which. the. dynamic.
stresses.act;.ϕ,.the.stress.function,.can.be.shown.as:
ϕ=Qij.φ.
(6.21)
Qij.are.the.nine.stiffness.constants.described.in.Equation.(6.21)..φ.is.the.con-
tour.of.proile.for.the.orthotropic.parts.
Thus,.Equation.(6.21).is
d
dx
2
φ
σ
x
=
=
h C
ρ
2
x
2
2
d
dy
φ
2
σ
y
=
=
h C
ρ
..
.
(6.22)
y
2
2
d
dxdy
φ
2
τ
xy
=
=
h C
xy
ρ
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