A Novel Test Method for the Assessment of the Hoop Performance of Composite Pipes

Abstract

One of the key functions of composite pipes used for Oil and Gas production is their ability to withstand the high internal pressures exerted by the conveyed fluids. In order to qualify such pipes, burst tests under various environmental conditions shall be performed. Such tests are expensive to conduct at full scale, however, alternative smaller scale methods such as the Split-D test (ASTM, 2019) are found to underestimate the burst capacity of the pipe. In this paper, the authors present a novel test method for the assessment of the hoop capacity of composite pipes and compare the obtained results against Split-D and larger scale burst tests. It is shown that the proposed method is representative of the larger scale burst test and can be used as an alternative thus resulting to the reduction of both cost and time required for composite pipe qualification.

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A Novel Test Method for the Assessment of the Hoop Performance of Composite Pipes
Author Name(s): Milan Bujdoso, Angelos Mintzas
Baker Hughes, Flexible Pipe Systems, Technology Department
Newcastle upon Tyne, UK
ABSTRACT
One of the key functions of composite pipes used for Oil and Gas
production is their ability to withstand the high internal pressures exerted
by the conveyed fluids. In order to qualify such pipes, burst tests under
various environmental conditions shall be performed. Such tests are
expensive to conduct at full scale, however, alternative smaller scale
methods such as the Split-D test (ASTM, 2019) are found to
underestimate the burst capacity of the pipe. In this paper, the authors
present a novel test method for the assessment of the hoop capacity of
composite pipes and compare the obtained results against Split-D and
larger scale burst tests. It is shown that the proposed method is
representative of the larger scale burst test and can be used as an
alternative thus resulting to the reduction of both cost and time required
for composite pipe qualification.
KEY WORDS: Thermoplastic Composite Pipe; Burst; Test Method,
Split-D
INTRODUCTION
Over the last two decades, significant effort has been placed in the
development and qualification of fully bonded Thermoplastic Composite
Pipes (generally referred to as TCPs) along with the qualification of
Hybrid Composite Flexible Pipes (generally referred to as HCFPs) for
use in onshore and offshore Oil and Gas production by a number of major
companies operating in this field such as Strohm, TechnipFMC / Magma
and Baker Hughes. The cross section of a TCP pipe usually consists of
an internal thermoplastic barrier layer, a thermoplastic composite layer
and a thermoplastic cover layer as shown in Fig. 1(a). The cross section
of an HCFP usually consists of a metallic interlocked layer called carcass
(in some designs it is omitted), a thermoplastic barrier layer, a
thermoplastic composite layer, metallic tensile wires layers, insulation
layers and a thermoplastic sheath layer as shown in Fig. 1(b). It should
be noted that a TCP is one of the building blocks of the HCFP structure
and therefore the understanding of the TCP behavior is a prerequisite for
the design of the more complex HCFPs. To that end, a number of
analytical (Hastie et al, 2019; Xia et al, 2001; Xia et al 2021; Shi et al,
2022) as well as experimental (Mintzas et al, 2013; Yao et al, 2021) work
has been conducted in order to determine the burst capacity of TCP pipes
and thus provide the analysis tools as well as the experimental validation
required in order to qualify such structures.
Fig. 1 (a) Cross section of Thermoplastic composite Pipe (TCP) and (b)
cross section of Hybrid Composite Flexible Pipe (HTCP)
To facilitate qualification, DNV has issued F119 standard (DNV, 2019)
which defines the tests that shall be performed for the qualification of
TCP pipes. One of the key tests required by the F119 standard, is the
open-ended burst test. For this scope, the standard proposes the use of
Split-D ring test (ASTM, 2019) for the determination of the apparent
hoop strength of thermoplastic pipes and the validation of the predictive
tools. A schematic of the Split-D test set up is shown in Fig. 2. The
advantage in testing such coupons, is that they can be cut from an as
manufactured pipe and are therefore representative of the actual
manufacturing process. In their work, (Kastennmeier et al, 2017),
compared the moduli and the tensile strengths from coupons as extracted
from; curved tubes, from tubes with plane areas and standardized flat
specimens and discussed the advantages and disadvantages of each test
and the corresponding manufacturing method.

Fig. 2 Schematic of Split-D test set up as per ASTM D2290-19
Despite Split-D coupons being representative of the as manufactured
pipe, it is known that the tensile strength values obtained through this
test method can be significantly lower than the strength obtained from
internally pressurized tubes. The main reason for this is claimed to be the
high flexural stresses developed in the specimen in the region between
the two D-fixtures as discussed in (Bert, 2016) and as noted in (ASTM,
2019). However, the effect of the bending stresses on the failure of the
coupon can be minimized by reducing the gap between the two D-
fixtures and by placing the reduced area of the ring sample away from
the split in the disc as shown in Fig. 2. The authors have found that even
when bending stresses are minimized, the tensile values from this test
are still significantly lower when compared to open-ended pipe burst
tests, suggesting that bending stresses are not the only reason for such
discrepancy. The authors also observed that the failure mode obtained
from the internally pressurized tubes was different to that obtained from
the Split-D test and that Split-D test values were also more sensitive to
high wall thickness (t) over pipe diameter (D) ratios. The discrepancy
between the Split-D and open-ended pipe burst test configurations
becomes even more prominent when testing composite lay-ups where
the fibers are not placed in the hoop direction, but at an angle to it with
the latter being the case for most thermoplastic composite pipe structures
for Oil and Gas applications. Further discrepancy between the two test
set ups is expected for the cases where the samples are tested at higher
temperature, conditioned in fluids or when hoop stress rupture capacity
of the pipe is to be obtained rendering the development of an alternative
small-scale burst test method critical for the reduction of both time and
cost for TCP qualification.
In this paper, the authors present a novel test configuration which has
been developed to obtain representative pipe hoop performance whilst
still testing short pipe sections. In the proposed test, which the authors
refer to as mini-burst, the hoop stress on the pipe wall is applied by
inflating a bladder placed inside the pipe and by adequately constraining
the pipe ends. Test results from all three Split-D, mini-burst and larger
scale burst tests are presented. The resulting hoop strength and failure
modes are compared and discussed thus justifying why the novel mini-
burst method proposed in this paper is the preferred test method for
defining the hoop performance of composite pipes.
PIPE MANUFACTURING
Thermoplastic pipe consisting of barrier and composite layer was
manufactured at the Baker Hughes facilities in Newcastle. The barrier
was manufactured by extruding PVDF pellets in the commercial
extrusion line. The barrier nominal Inner Diameter (ID) is 176.4 mm and
the nominal barrier thickness is 11 mm. The composite layer was then
built on top of the barrier via an automated winding process whereby
uni-directional PVDF-carbon fiber tapes were heated and consolidated
in-situ on the composite line. Each PVDF-carbon fiber tape has a
nominal thickness of 0.23 mm and pipe sections with three different
composite thicknesses were built; one consisting of 16 consolidated
layers with a nominal lay-up of [+854,-854]2, one of 24 layers with a
nominal lay-up of [+854,-854]3 and another of 32 layers with a nominal
lay-up of [+854,-854]4. It should be noted that the as manufactured
composite layer, has a variation of +- 0.15 degrees from the nominal lay-
up angle value.
SPLIT-D COUPON PREPARATION, GEOMETRY AND
TESTING
For the Split-D coupons, 50 mm sections were first cut from the as
manufactured pipe using a SIP 12” metal cutting bandsaw. The ID of
these 50 mm sections was then machined using a CNC lathe to ensure
the barrier ID matched the Split-D fixtures’ Outer Diameter (OD) which
is 196 mm, and that the final coupon width is achieved. A CNC milling
machine was then used to form the notches.
A wide number of different Split-D geometries compliant with
Procedures A, B and C of (ASTM, 2019) standard have been tested by
the authors in an attempt to investigate the coupon geometry effect on
the apparent hoop strength and the resulting failure mode. Due to the
extent of that study, the results from all the different Split-D
configurations tested will be presented in a separate paper. In the current
paper, the results for the Split-D geometry that provided the highest
apparent hoop strength, and the most representative failure mode will be
compared against the novel mini-burst test configuration. This geometry
was found to be the one that is more compliant with Procedure B with
the sample width W = 45 mm, the reduced area section width b = 5 mm,
the notch radius R = 5 mm and the distance from the coupon edge to the
center of the notch c = 10 mm with all dimensions shown Fig. 3. It shall
also be noted that in this study, pipes consisting of both barrier and
composite were tested with their corresponding thicknesses denoted as
db and dc respectively. The material properties and the equation for back
calculating the apparent composite hoop strength of the composite layer
are given in APPENDIX A.
Fig. 3 Schematic of Split-D test set up as per ASTM D2290-19 Procedure
B
All split-D tests were performed on a Zwick SMZ250/SN5A type 250
kN capacity tensile machine at laboratory conditions (approximately 23
C temperature and 50 % humidity) and a cross head speed of 2 mm/min.
The dimensions and the corresponding apparent composite hoop
strengths of all the coupons tested are given in Table 1.

Table 1. Test results from Split-D coupons with 16, 24 and 32 composite
layers. Coupons tested are compliant with Procedure B (ASTM, 2019)
geometry i.e., coupon width W = 45 mm, reduced cross section b =5 mm
and minimum notch radius R = 5 mm
Coupon
No.
Avg.
Comp.
Thick.
dc (mm)
Avg.
Barrier
Thick.
db (mm)
Red.
Sect.
Width
b (mm)
Failure
Load
(N)
Apparent
Comp.
Hoop
Strength
(MPa)
16 Layer Coupons [+854,-854]2
C2-1
3.41
5.63
5.25
77332
2109
C2-2
3.46
5.92
5.22
75275
2033
C2-3
3.36
5.81
5.25
80505
2226
24 Layer Coupons [+854,-854]3
C3-1
5.34
5.72
5.39
115886
1982
C3-2
5.27
6.01
5.38
111726
1938
C3-3
5.27
6.5
5.32
116030
2033
C4-1
5.41
6.04
5.38
108051
1827
C4-2
5.45
6.52
5.35
113209
1908
C4-3
5.42
6.2
5.36
115616
1957
C8-1
5.35
6.01
5.31
117137
2029
C8-2
5.98
5.74
5.33
109761
1698
C8-3
5.35
5.8
5.32
114432
1979
C10-1
5.42
6.19
5.34
108798
1849
C10-2
5.3
6.32
5.31
113741
1986
C10-3
5.36
6.03
5.21
111545
1965
32 Layer Coupons [+854,-854]4
C5-1
7
5.92
5.31
124911
1660
C5-2
7
5.61
5.28
117435
1570
C5-3
6.88
5.8
5.31
120814
1633
SMALL - SCALE BURST COUPON PREPARATION,
GEOMETRY AND TESTING
For the novel small scale burst coupons, or else referred to as mini-burst
coupons, 150 mm sections were first cut from the as manufactured pipe
using a SIP 12” metal cutting bandsaw. The ID of these 150 mm sections
was then machined using a CNC lathe to ensure a perfectly round barrier
ID. The ends of mini-burst coupons were also machined square to one
another whilst also machining them to their final length of L = 100 mm
as shown in Fig. 4. It shall be noted that the exact same tools and
machining parameters that were used for the preparation the Split-D
coupons were also used for the mini-burst coupons. This is to ensure that
similar cut quality is achieved and the machining effects on
corresponding test results are minimized.
Fig. 4 Schematic mini-burst coupon after machining
The mini-burst rig comprises of two metallic plates connected by a
number of metallic studs (tensile members) as shown in Fig. 5. To
perform the test, the coupon is placed between the top and bottom
metallic plates thus creating a constrained volume inside which a latex
rubber bag (bladder) is placed. The neck of the rubber bag is attached
onto a specially designed metallic sealing disc which is nested in the top
plate. Pressurized fluid (in this case water) is then supplied from a
Heskell Pump through the pressure inlet channel inflating the bladder
thus applying hoop tension on the coupon wall. It shall be noted that axial
load applied onto the top and bottom plates is taken by the studs thus
resulting to an open-ended burst test configuration. The internal pressure
also activates the sealing of the bag by compressing it between the
sealing disc and the upper plate.
Fig. 5 Schematic of mini-burst test rig
Despite the fairly simple design of the mini-burst rig, there are a number
of non-load-bearing components shown in Fig. 6 that shall be used in
order to achieve a valid burst failure. Once pressurized, the composite
coupon will contract in the axial direction due to Poisson’s effects. This
contraction will result to bladder failure since free space will be created
for the latter to extrude between the pipe ends and the top and bottom
metallic plates. To prevent this, anti-extrusion plates shall be placed at
the top and bottom, of the coupon. It shall be noted that the hoop-axial
Poisson’s ratio is a function of the composite lay-up. A calculation of the
coupon maximum axial contraction shall therefore be performed to
define the appropriate thickness for the anti-extrusion plates. Another
function of the anti-extrusion plates is to ensure that the hoop pressure
load applied is shifted towards the middle of the coupon and away from
its ends. The latter is very important as cut ends are usually weak points
due to the cut fibers and the potential defects introduced from coupon
machining process. Outer metallic rings can also be used to support the
top and bottom ends of the coupon as an additional preventive measure
for end effects. In this study, tests with different anti-extrusion plate
thicknesses i.e., 10mm, 15mm and 20mm were performed as well as one

test with 20mm anti-extrusion plate thickness plus an outer support ring
in order to check which configuration is adequate to successfully negate
end effects.
Another key component for a successful mini-burst test is the use of two
rubber sheets placed on top of the anti-extrusion plates. On top of these
rubber sheets, polymeric cones shall also be placed as shown in Fig. 6.
The purpose of these components is to prevent the bladder from piercing
after being trapped in the space created between the coupon ID and the
metallic plates OD as the coupon expands in the radial direction due to
the application of internal pressure.
.
Fig. 6 Schematic of mini-burst test rig
Four strain gauge rosettes were bonded on the outer surface of each
coupon in the center line location around the circumference in: 0ᵒ, 90ᵒ,
180ᵒ and 270ᵒ orientations, respectively. Each coupon was then
pressurized with water at a rate of 90 bar/min till failure. All tests were
performed at laboratory conditions (approximately 23 C temperature and
50 % humidity). The dimensions, the test burst pressures, the average
hoop failure strains (as measured from the 4 strain gauges bonded at the
OD of the coupon) and the average composite hoop strength as
calculated from FEA models (see APPENDIX B) are given in Table 2.
Table 2. Test results from mini-burst coupons with 16, 24 and 32
composite layers
Coup.
No.
Barrier
ID
(mm)
Barrier
Thick.
(mm)
Burst
Pressure
(MPa)
Average
Hoop
Failure
Strain at
OD (%)
Average
Composit
e Hoop
Strength
(MPa)
16 Layer Coupons [+854,-854]2
M2-1*
185.12
6.47
83.05
1.75
2241
24 Layer Coupons [+854,-854]3
M3-1**
184.80
7.09
121.25
1.43
2191
M4-1*
184.48
6.88
125.39
1.52
2261
M8-
1***
184.97
7.00
120.54
1.46
2180
M10-
1****
184.93
7.04
129.48
1.54
2341
32 Layer Coupons [+854,-854]4
M5-
1***
185.16
6.57
144.80
1.21
1966
M5-
2***
185.13
6.43
141.23
1.19
1917
M5-
3***
184.89
6.55
137.70
1.08
1858
* Test performed with 10mm anti-extrusion plate and no outer ring
** Test performed with 15mm anti-extrusion plate and no outer ring
*** Test performed with 20mm anti-extrusion plate and no outer ring
**** Test performed with 20mm anti-extrusion plate and outer ring
LARGE - SCALE BURST COUPON PREPARATION,
GEOMETRY AND TESTING
For the larger scale burst coupons, 1200 mm pipe sections were first cut
from the as manufactured pipe using a SIP 12” metal cutting bandsaw.
100 mm form the composite layer were then machined off from each end
of the pipe using a proprietary clamp shell cutting tool. This is in order
to reveal the barrier layer so that the seal ring can be swaged on it thus
creating a seal configuration which is very similar to that of unbonded
flexible pipe end-fittings used in the field. The pipe is then strain gauged
with eight rosettes on the outer surface of each coupon, four placed at
the center line location and four 220 mm from the center line location at
0ᵒ, 90ᵒ, 180ᵒ and 270ᵒ orientations, respectively as shown in Fig. 7.
Fig. 7 Larger scale pipe dimensions and strain gauge positions
The large burst rig comprises of two end caps which are held together
via an inner mandrel and an outer housing as shown in Fig. 8. The latter
two components carry all the axial load exerted by internal pressure thus
resulting to an open-ended burst test configuration. A composite collar
is used to butt against the composite cut face on the inner side and to butt
against the seal ring on the outer side, whereas a transition collar is used
to support the composite close to the end fittings in order to
accommodate pipe axial movement due to Poisson effects and to ensure
that failure will occur at the pipe mid-section.
Fig. 8 Larger scale pipe test configuration
It shall be noted that the barrier ID and the barrier thickness of larger
scale pipes can vary along the pipe length within Baker Hughes
manufacturing tolerances. Since the barrier ID of these coupons is not
machined, the average barrier ID and thickness values as measured
during the manufacturing run are used for the calculation of the hoop
stresses reported in Table 3.

Table 3. Test results from large scale burst coupons with 16, 24 and 32
composite layers
Coup.
No.
Barrier
ID
(mm)
Barrier
Thick.
(mm)
Burst
Pressure
(MPa)
Average
Hoop
Failure
Strain at
OD (%)
Average
Composite
Hoop
Strength
(MPa)
16 Layer Coupons [+854,-854]2
L2-1
176.4
11.15
84.23
1.47
2199
24 Layer Coupons [+854,-854]3
L3-1
176.4
11.48
125.59
1.55
2204
32 Layer Coupons [+854,-854]4
L5-1
176.4
11.24
149.25
1.36
1970
ANALYSIS OF RESULTS AND COMPARISON OF THE
DIFFERENT TEST METHODS
Fig. 9 shows the hoop strengths as derived from Split-D, mini-burst and
larger-scale tests plotted against the number of composite layers. For the
cases where more than three tests have been performed, the hoop
strength range is also shown. From this plot it is evident that the apparent
hoop strength derived from the Split-D tests is always lower than that
derived from mini- and larger-scale burst tests with the difference
increasing for coupons with more composite layers (i.e., with the
increase in composite thickness over diameter ratio). From Fig. 9 it is
also evident that the average hoop strength as obtained from mini-burst
test is almost identical to that obtained from the larger-scale tests for all
three different composite layer pipe configurations tested.
Fig. 9 Plot of hoop strengths as derived from Split-D, mini-burst and
large-scale burst tests vs number of composite layers
The hoop strength trends and results can be explained by comparing the
resulting failure modes from each coupon configuration and each test
method. Fig. 10 a) and b) show typical post-failure pictures from Split-
D coupons with 16 and 32 composite layers respectively. The failure
mode of the 16 layer Split-D coupon is primarily fiber failure in tension
(failed fibres have a brush like appearance) however, some
delaminations are also evident at the reduced cross section where the
sample failed. For the 32 layer coupon, delaminations are much more
prominent and extend beyond the reduced section area with the latter
also showing less evidence of along fiber tensile failures. This shift to a
lower energy failure mode explains why this test configuration gives a
high reduction in apparent hoop strength especially for the cases where
the coupon composite thickness over diameter ratio is increased.
On the contrary, all mini-burst and larger-scale test coupons give the
same failure mode which is fiber failure in tension. Typical post failure
pictures from mini-burst and larger-scale pipe tests are shown in Fig. 11
a) and b) respectively. The more consistent and higher energy failure
mode explains why these two burst test configurations result to higher
hoop strength when compared to Split-D test and why they also show a
much lower reduction in apparent hoop strength when the coupon
composite thickness over diameter ratio is increased.
As part of tape quality checks, Baker Hughes performs tape pull tests
along the fiber direction using an in-house developed procedure. Photos
of the tape pull test set up and the failures obtained are shown in Fig. 12
a) and b) as a benchmark example for along fiber explosive brush like
failures. It shall be noted that the tests shown in Fig. 12 were performed
on the specific batch used for the manufacturing of the pipe coupons
reported in this paper.
Fig. 10 Typical failure modes from Split-D coupons with a) 16 (Coupon
C2-2) and b) 32 (Coupon C5-1) composite layers respectively
Fig. 11 Typical failure modes obtained from a) mini-burst (Coupon C4-
1) and b) larger-scale (Coupon L5-1) tests

Fig. 12 a) Baker Hughes’ along fiber tape pull test set up and b) post-
failure coupons with fibers having a brush like appearance.
CONCLUSIONS
A novel test configuration which the authors call mini-burst has been
developed to obtain representative pipe hoop performance of
Thermoplastic Composite Pipes (TCP) and its design is thoroughly
presented in this study. The test results from this method have been
compared against the standard Split-D Method (ASTM, 2019) and a
large-scale pipe burst test method closely resembling the in-field end
fitting used for unbonded flexible pipes.
It has been found that the hoop strength obtained from the Split-D tests
is always lower than that obtained from mini- and larger-scale burst tests
with the difference increasing for coupons with higher composite
thickness over diameter ratios. Post-failure coupon examination showed
that Split-D coupons presented a mixed failure mode comprising of
delaminations and fiber tensile failure whereas for the mini-burst and
large-scale burst samples the dominant failure mode was always fiber
tensile failure. The latter explains why Split-D coupons underestimate
TCP pipe hoop performance and why mini-burst and larger-scale burst
tests give higher performance.
The test results also prove that the mini-burst test configuration is
representative of the actual pipe burst performance and can thus be used
to replace large scale pipe tests. It shall be noted that the cost and time
for performing a mini-burst test is about 1/10th of the cost and time
required to perform a larger scale burst test which renders the
qualification of TCP and HCFP pipe structures a less expensive and less
time-consuming process.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the contribution of all the
technicians at the Baker Hughes Newcastle Energy Technology
Innovation Centre who helped with the preparation and testing of the
coupons and especially Stewart Forster and Paul Robinson. The authors
would also like to thank the Baker Hughes manufacturing team and
especially Chris Dawson for manufacturing the pipes and Garry Kendall,
Richard Clements, Andrew Roberts and Eric Wilson who were
supportive of publishing this work.
REFERENCES
ASTM (2019). “Standard Test Method for Apparent Hoop Tensile
Strength of Plastic or Reinforced Plastic Pipe”, Standard ASTM D2290-
19.
DNVGL (2019). “Thermoplastic Composite Pipes,” Standard DNVGL-
ST-F119.
Hastie, J, Kashtalyan, M, Guz, IA (2019). “Failure Analysis of
Thermoplastic Composite Pipe (TCP) under Combined Pressure,
Tension and Thermal Gradient for an Offshore Riser Application”
International Journal of Pressure Vessels and Piping, 178(5), 103998.
Kastenmeier, A, Schmidt, V, and Ehrlich, I (2017) “Specimen Preparation
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Athens Journal of Technology and Engineering, 4(3), 191-205.
Mintzas, A, Hatton, S, Simandjuntak, S, Little, A, Zhang, Z (2013). “An
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APPENDIX A
The apparent hoop strength of the composite layer as obtained from testing
Split-D rings that consist of both barrier and composite layer (with
thicknesses db and dc respectively as shown in Fig. 3, can be calculated
from the following 2 equations.

             
(1)
    


 (2)
Where:
  
 
 
 
 
 
 
 
 
  
 
 
 󰆒
 
By using Hooke’s law and substituting Eq. 2 into Eq.1, the apparent
hoop strength of the composite layer is derived:

󰇡
󰇢 (3)
APPENDIX B
For the case of mini-burst and the larger-scale burst coupons the average
composite wall hoop stress was calculated using Baker Hughes’
proprietary software called FPS the results of which were also cross
checked against FEA. For the FEA model Ansys Classic 18.2 version
was used. The coupons were modelled using layered 20 node SOLID186
element. This element allows for the polymer and all the composite
layers to be modeled using only 1 element through the coupon thickness
which is accurate enough for the purpose of this study.
A typical mesh of the mini-burst coupon is shown in the Fig. 13 where
the boundary conditions applied are a) symmetry of axial displacements
(i.e. Uz=0) on the Z-axis mid-plane (half of the coupon length was
modelled, but whole shown in Fig. 13 for purposes of illustration) and b)
symmetrical radial displacements Ur around the coupon circumference.
For the case of the mini-burst configuration where outer support rig was
employed (i.e. coupon M10-1), as well as for all the large-scale burst
tests the radial displacements at the OD of the coupon under the
supported ends were also constrained i.e. Ur = 0.
Fig. 13 Ansys FEA model of mini-burst rig and applied boundary
conditions. FEA model of larger scale test is same with the only
difference being the increased coupon length and the increased number
of elements along the pipe axis so that both models have same element
length over thickness ratios
The material properties used in the FEA model are given in Table 4. The
effective laminate properties required for the calculations in APPENDIX
A were calculated using classical laminate theory and are also shown in
Table 4.
Table 4. Material properties used in the FEA and for the calculation of
effective laminate properties
Property
Value
Units
PVDF Barrier
Young’s Modulus E
640
MPa
Poisson’s Ratio v
0.46
-
PVDF Carbon Fiber Layer / Ply
Along Fiber Modulus E11
133
GPa
Transverse to Fiber Modulus E22
6.69
GPa
Shear Modulus G12
2.38
GPa
Poisson’s Ratio v12
0.292
-
Poisson’s Ratio v23
0.290
-
Effective [+854,-854]n Laminate Properties
Composite Laminate Modulus in
Hoop direction Ec
127
GPa