UWE Bristol Engineering showcase 2015

Heather Arnall
MEng Mechanical Engineering
Project Supervisor
Ramin Amali
Repair of Filament Wound Composite Pipes
Modelling the pipe repair in ABAQUS
An internal pressure of 6MPa were applied to the
pipes, which had one end of the pipe closed to
consider both the longitudinal and hoop stress.
Partitions were used to model the removed
damage and wrap. The wrap has a fibre
orientation of [0 90 0 90]s, whilst the pipe is [54.75
-54.75]4 and glass fibre properties were applied to
both. An intensive mesh study found that a global
mesh of 7mm was required to be applied to satisfy
nominal stress. The region surrounding the hole
was refined with 15 elements per line and four
additional lines were applied to structure the
mesh, providing a mesh of 8,860 elements.
Pipe parameter investigations
Three different pipe diameters (0.1m, 0.3m and
0.5m) were considered to determine the FOS of
the pipes when undamaged, damaged and
repaired. The FOS damage reduction factor, FOS
wrap gain factor and FOS overall reduction factor
were then obtained.
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Formulas were created through plotting each of
these factors against pipe diameter. Two additional
diameters (0.08m and 0.2m) were analysed to
determine the formulas have an accuracy of 95%.
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Glass fibre Air Units
Poisson’s Ratio 0.3 0.03 -
Young’s Modulus - 0.01 MPa
long. modulus E1 120 - GPa
trans. modulus E2 8 - GPa
shear modulus 6 - GPa
long. tension Xt 1800 - MPa
long. comp. Xc -1200 - MPa
trans.tension Yt 80 - MPa
trans. comp. Yc -200 - MPa
shear S 150 - MPa
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−11.69DD 2 + 9.016DD + 1.1013
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3.1873DD 2 − 2.1499DD + 0.708
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2.7236DD 2 − 1.2208DD + 1.0848
Formulas for pipe thickness for thin walled
pipes were obtained through the same process for
three pipe thicknesses: 3mm, 4mm and 5mm. Pipe
thicknesses of 2mm and 3.5mm were modeled to
determine formula accuracy of 99% for following
repair, whilst 66% for following removal. The
overall FOS reduction factor was constant for
varying thicknesses, this was also confirmed
through modelling a 0.3m diameter pipe with
thicknesses of 3mm and 15mm.
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0.0174TT 2 − 0.178TT + 2.1234
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−0.0066TT 2 + 0.0669TT + 0.449
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−0.0012TT 2 + 0.01TT + 1.01TT + 1.0109
Investigation into damage removal
Damage should be removed with a circular cut
out, but this is not always possible. Three cut out
areas were considered, finding that using a square
cut out at 45 degrees reduces the FOS following
damage removal by 40%, but does not significantly
affect the FOS following repair compared to a
circular cut out. The three circular cut outs
(diameters: 30mm, 50mm and 70mm) were used
to create the formulas shown. By analysing a 0.4m
damage diameter it was found that the accuracy
for the FOS following damage removal was 72%,
whilst 99.98% for following repair.
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−222.32dd 2 + 27.23dd + 0.839
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117.05dd 2 − 14.232dd + 1.1695
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2.6216dd 2 − 0.2097dd + 1.2382
Wrap Width W (mm)
Investigation into wrap dimensions
Nine different wrap thicknesses were considered
between 2.4mm and 28mm and as expected as
the wrap thickness increased, so did the FOS
following repair. Three different wrap thicknesses
(4, 8 and 13mm) and three different damage sizes
(0.3m, 0.5m and 0.7m) were then used for an
extensive trial and error method to determine the
required wrap width for each scenario to obtain
the following graph.
Wrap width for damage diameters less than 0.07m
400
350
300
and wrap thicknesses less than 13mm
W = 100000d 2 - 6500d + 305
250
200
150
W = 112500d 2 - 8500d + 263.75
100
50
0
W = 75000d 2 - 5500d + 187.5
0.03 0.04 0.05 0.06 0.07
Damage diameter d (m)
13mm Wrap thickness 8mm Wrap thickness 4mm Wrap thickness
Investigation into adhesives
Epoxy and Polyester test pieces were produced
and tensile tested to find the failure of the
polyester pieces were less predictable, at a lower
stress and more catastrophic. From these
experiments the young’s moduli were obtained
and used to FEA model the adhesive used when
repairing composite pipes (polyurethane was also
considered). It was found that the adhesive
material had no effect on the FOS following repair,
but there was S 11 . Varying thicknesses were
considered to see that when plotted against S 11
there was a quadratic relationship.
Project summary
Composite pipes are used in a variety of industries
and put under a variety of loads. If loaded too much
then damage or failure could occur. Composite pipes
can be repaired through the use of a composite wrap,
however it is important to ensure the procedure is
done correctly to ensure a good quality repair.
Project Objectives
The main aim of this investigation is to use FEA
software to determine the effect of the parameters
involved in filament wound pipe repair during both
the removal of damage and the application of the
wrap. Investigations will consider pipe diameter and
thickness, damage size and shape, wrap thickness
and optimum width and adhesive material and
thickness.
Project Conclusion
In this project over 150 FEA models were used to
investigate the effect of the repair parameters.
Formulas, which will save time and ensure correct
repair methods, have been created to predict the FOS
following damage removal and following repair for
varying pipe diameters, circular cut out sizes and
optimum wrap width. It was found that if the pipe is
thin walled then the pipe thickness has no effect on
the FOS following repair. It was also found that
removing damage with a square cut out reduces the
FOS following damage removal by 40% compared to a
circular cut out, but there was no significant
difference in FOS once the pipes had been repaired.
As expected as the wrap thickness increased the FOS
following repair increased. From the adhesive study it
is suggested that an Epoxy adhesive should be used in
the repair of composite pipes due to a higher
ultimate strength and a less catastrophic failure than
polyester. FEA confirmed this by finding the least
stress was caused through Epoxy, compared to
Polyester and Polyurethane.