ASTM E2981-15
(Guide)Standard Guide for Nondestructive Testing of the Composite Overwraps in Filament Wound Pressure Vessels Used in Aerospace Applications
Standard Guide for Nondestructive Testing of the Composite Overwraps in Filament Wound Pressure Vessels Used in Aerospace Applications
SIGNIFICANCE AND USE
4.1 The COPVs covered in this guide consist of a metallic liner overwrapped with high-strength fibers embedded in polymeric matrix resin (typically a thermoset) (Fig. 1). Metallic liners may be spun-formed from a deep drawn/extruded monolithic blank or may be fabricated by welding formed components. Designers often seek to minimize the liner thickness in the interest of weight reduction. COPV liner materials used can be aluminum alloys, titanium alloys, nickel-chromium alloys, and stainless steels, impermeable polymer liner such as high density polyethylene, or integrated composite materials. Fiber materials can be carbon, aramid, glass, PBO, metals, or hybrids (two or more types of fibers). Matrix resins include epoxies, cyanate esters, polyurethanes, phenolic resins, polyimides (including bismaleimides), polyamides and other high performance polymers. Common bond line adhesives are FM-73, urethane, West 105, and Epon 862 with thicknesses ranging from 0.13 mm (0.005 in.) to 0.38 mm (0.015 in.). Metallic liner and composite overwrap materials requirements are found in ANSI/AIAA S-080 and ANSI/AIAA S-081, respectively.
Note 5: When carbon fiber is used, galvanic protection must be provided for the metallic liner using a physical barrier such as glass cloth in a resin matrix, or similarly, a bond line adhesive.
Note 6: Per the discretion of the cognizant engineering organization, composite materials not developed and qualified in accordance with the guidelines in MIL-HDBK-17, Volumes 1 and 3 shall have an approved material usage agreement.
Note 1: POD(a), showing the location of the smallest detectable flaw and a90 (left). POD(a) with confidence bounds added and showing the location of a90/95 (right).
4.11.1 Given that a90/95has become a de facto design criterion it is more important to estimate the 90th percentile of the POD (a) function more precisely than lower parts of the curve. This can be accomplished by placing more targets in the region of the a90 v...
SCOPE
1.1 This guide discusses current and potential nondestructive testing (NDT) procedures for finding indications of discontinuities and accumulated damage in the composite overwrap of filament wound pressure vessels, also known as composite overwrapped pressure vessels (COPVs). In general, these vessels have metallic liner thicknesses less than 2.3 mm (0.090 in.), and fiber loadings in the composite overwrap greater than 60 percent by weight. In COPVs, the composite overwrap thickness will be of the order of 2.0 mm (0.080 in.) for smaller vessels and up to 20 mm (0.80 in.) for larger ones.
1.2 This guide focuses on COPVs with nonload-sharing metallic liners used at ambient temperature, which most closely represents a Compressed Gas Association (CGA) Type III metal-lined composite tank. However, it also has relevance to 1) monolithic metallic pressure vessels (PVs) (CGA Type I), 2) metal-lined hoop-wrapped COPVs (CGA Type II), 3) plastic-lined composite pressure vessels (CPVs) with a nonload-sharing liner (CGA Type IV), and 4) an all-composite, linerless COPV (undefined Type). This guide also has relevance to COPVs used at cryogenic temperatures.
1.3 The vessels covered by this guide are used in aerospace applications; therefore, the inspection requirements for discontinuities and inspection points will in general be different and more stringent than for vessels used in non aerospace applications.
1.4 This guide applies to 1) low pressure COPVs used for storing aerospace media at maximum allowable working pressures (MAWPs) up to 3.5 MPa (500 psia) and volumes up to 2 m3 (70 ft3), and 2) high pressure COPVs used for storing compressed gases at MAWPs up to 70 MPa (10,000 psia) and volumes down to 8000 cm3 (500 in.3). Internal vacuum storage or exposure is not considered appropriate for any vessel size.
1.5 The composite overwraps under consideration include but are not limited to ones made from various polymer mat...
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Designation: E2981 − 15
Standard Guide for
Nondestructive Testing of the Composite Overwraps in
Filament Wound Pressure Vessels Used in Aerospace
1
Applications
This standard is issued under the fixed designation E2981; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 The composite overwraps under consideration include
but are not limited to ones made from various polymer matrix
1.1 This guide discusses current and potential nondestruc-
resins (for example, epoxies, cyanate esters, polyurethanes,
tive testing (NDT) procedures for finding indications of dis-
phenolic resins, polyimides (including bismaleimides), and
continuities and accumulated damage in the composite over-
polyamides)withcontinuousfiberreinforcement(forexample,
wrap of filament wound pressure vessels, also known as
carbon, aramid, glass, or poly-(phenylenebenzobisoxazole)
composite overwrapped pressure vessels (COPVs). In general,
(PBO)).Themetalliclinersunderconsiderationincludebutare
these vessels have metallic liner thicknesses less than 2.3 mm
not limited to aluminum alloys, titanium alloys, nickel-
(0.090 in.), and fiber loadings in the composite overwrap
chromium alloys, and stainless steels.
greater than 60 percent by weight. In COPVs, the composite
overwrap thickness will be of the order of 2.0 mm (0.080 in.)
1.6 ThisguidedescribestheapplicationofestablishedNDT
for smaller vessels and up to 20 mm (0.80 in.) for larger ones.
methods; namely, Acoustic Emission (AE, Section 7), Eddy
CurrentTesting(ECT,Section8),LaserShearography(Section
1.2 This guide focuses on COPVs with nonload-sharing
9), Radiologic Testing (RT, Section 10), Thermographic Test-
metallic liners used at ambient temperature, which most
ing (TT, Section 11), Ultrasonic Testing (UT, Section 12), and
closely represents a Compressed GasAssociation (CGA) Type
VisualTesting(VT,Section13).Thesemethodscanbeusedby
III metal-lined composite tank. However, it also has relevance
cognizant engineering organizations for detecting and evaluat-
to 1)monolithicmetallicpressurevessels(PVs)(CGATypeI),
ing flaws, defects, and accumulated damage in the composite
2) metal-lined hoop-wrapped COPVs (CGA Type II), 3)
overwrap of new and in-service COPVs.
plastic-lined composite pressure vessels (CPVs) with a
nonload-sharingliner(CGATypeIV),and 4)anall-composite,
NOTE 1—Although visual testing is discussed and required by current
linerless COPV (undefined Type). This guide also has rel-
range standards, emphasis is placed on complementary NDT procedures
evance to COPVs used at cryogenic temperatures.
that are sensitive to detecting flaws, defects, and damage that leave no
visible indication on the COPV surface.
1.3 The vessels covered by this guide are used in aerospace
NOTE 2—In aerospace applications, a high priority is placed on light
applications; therefore, the inspection requirements for discon-
weight material, while in commercial applications; weight is typically
tinuities and inspection points will in general be different and
sacrificed to obtain increased robustness. Accordingly, the need to detect
more stringent than for vessels used in non aerospace applica-
damagebelowthevisualdamagethresholdismoreimportantinaerospace
tions. vessels.
NOTE 3—Currently no determination of residual strength can be made
1.4 This guide applies to 1) low pressure COPVs used for
by any NDT method.
storing aerospace media at maximum allowable working pres-
1.7 All methods discussed in this guide (AE, ET,
sures (MAWPs) up to 3.5 MPa (500 psia) and volumes up to 2
3 3
shearography, RT, TT, UT, and VT) are performed on the
m (70 ft ), and 2) high pressure COPVs used for storing
composite overwrap after overwrapping and structural cure.
compressed gases at MAWPs up to 70 MPa (10,000 psia) and
3 3
For NDT procedures for detecting discontinuities in thin-
volumesdownto8000cm (500in. ).Internalvacuumstorage
walledmetalliclinersinfilamentwoundpressurevessels,orin
or exposure is not considered appropriate for any vessel size.
the bare metallic liner before overwrapping; namely, AE, ET,
laserprofilometry,leaktesting(LT),penetranttesting(PT),and
RT; consult Guide E2982.
1
This test method is under the jurisdiction of ASTM Committee E07 on
Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on
1.8 In the case of COPVs which are impact damage sensi-
Specialized NDT Methods.
tive and require implementation of a damage control plan,
Current edition approved July 1, 2015. Published September 2015. DOI:
10.1520/E2891-15. emphasis is placed on NDT methods that are sensitive to
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