ASTM F520-97
(Test Method)Standard Test Method for Environmental Resistance of Aerospace Transparencies
Standard Test Method for Environmental Resistance of Aerospace Transparencies
SCOPE
1.1 This test method covers determination of the effects of exposure to thermal shock, condensing humidity, and simulated weather on aerospace transparent enclosures.
1.2 This test method is not recommended for quality control nor is it intended to provide a correlation to actual service life.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F 520 – 97
Standard Test Method for
Environmental Resistance of Aerospace Transparencies
This standard is issued under the fixed designation F 520; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 Type B specimens are used to determine the effect of
environmental exposure on bond integrity.
1.1 This test method covers determination of the effects of
exposure to thermal shock, condensing humidity, and simu-
4. Significance and Use
lated weather on aerospace transparent enclosures.
4.1 This test, when applied to aerospace transparencies of
1.2 This test method is not recommended for quality control
either monolithic glass/plastic or laminated combinations, is a
nor is it intended to provide a correlation to actual service life.
measure of the ability of the transparency to withstand the
1.3 This standard does not purport to address all of the
effects of artificially induced environments. The test may be
safety concerns, if any, associated with its use. It is the
used on configurations employing electrically conductive coat-
responsibility of the user of this standard to establish appro-
ings, and also to evaluate the integrity of noncoated materials.
priate safety and health practices and determine the applica-
4.2 The resistance of the transparent enclosure to environ-
bility of regulatory limitations prior to use.
mental effects may vary appreciably depending on the size,
2. Referenced Documents geometry, material of construction, coating integrity, coating
density, and other factors.
2.1 ASTM Standards:
D 1003 Test Method for Haze and Luminous Transmittance
5. Test Specimens
of Transparent Plastics
5.1 Each Type A specimen shall be a 250 by 250-mm (9.8
F 521 Test Methods for Bond Integrity of Transparent
3 by 9.8-in.) cross section of the design and shall contain, as
Laminates
applicable, surface coatings of operational, electrically con-
G 23 Practice for Operating Light-Exposure Apparatus
ducting coating systems complete with bus bars, braids, and
(Carbon-Arc Type) With and Without Water for Exposure
temperature sensors.
of Nonmetallic Materials
5.1.1 Type A test specimens shall have a fully operational
G 26 Practice for Operating Light-Exposure Apparatus
coating system, when applicable, with an average resistivity
(Xenon-Arc Type) With and Without Water for Exposure
4 consistent with the average resistivity of the representative
of Nonmetallic Materials
design. Reproduction of multiphase electrical circuits is not
G 53 Practice for Operating Light- and Water-Exposure
required for these test specimens since this type of circuitry is
Apparatus (Fluorescent UV-Condensation Type for Expo-
4 only a design technique used to accommodate limited voltage
sure of Nonmetallic Materials
resources at installation.
3. Summary of Test Method 5.2 Each Type B test specimen shall be 50 by 50 mm (2 by
2 in.) and shall be of a cross section consistent with the edge
3.1 Two types of test specimens, duplicating the aerospace
configuration of the representative design. Type B test speci-
transparent enclosure design, are subjected to thermal shock,
mens are not intended to be operational electrically, but they
condensing humidity, and artificial weathering. Edge sealing
shall be representative of the average resistivity of the design.
may be used if representative of the design.
3.1.1 Type A specimens are used to determine the effect of
6. Preparation of Test Specimens
environmental exposure on electrical and optical properties.
6.1 Prepare a minimum of three Type A specimens for each
design configuration. If the design contains an electrically
This test method is under the jurisdiction of ASTM Committee F-7 on
activated coating, only one temperature sensor per specimen is
Aerospace and Aircraft, and is the direct responsibility of Subcommittee F 07.08on
required.
Transparent Enclosures and Materials.
6.2 Prepare a minimum of five Type B specimens for each
Current edition approved April 10, 1997. Published August 1997. Originally
published as F 520 – 77. Last previous edition F 520 – 77 (1989).
design configuration. Prepare the specimen in such a manner as
Annual Book of ASTM Standards, Vol 08.01.
to produce smooth edges and corners to prevent chipping
Annual Book of ASTM Standards, Vol 15.03.
4 during testing. Polish at least one edge of each specimen to
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 520
allow inspection of the internal bonded surfaces during tensile continue. Gradually apply and remove the potential at no
loading. Do not apply edge sealant to the specimens. greater rate than 500 V rms/s.
6.3 Condition all test specimens by exposing them to not 7.3.5 Electrically Conductive Coating Test—Test each Type
less than 40 h at 23 6 2°C (73.4 6 3.6°F) and 506 5% A specimen for electrically conductive coating uniformity by
relative humidity. energizing with the same level of controlled power as proposed
in the design while viewing between polarized plates. Identify
7. Procedure all detectable coating hot spots during this heat-up cycle. These
thermally induced stress concentrations are generally charac-
7.1 Visual Examination—Carefully examine Type A and
terized by a “butterfly” shape and are to be noted for later
Type B specimens for any signs of material or manufacturing
specimen evaluation.
defects. A microscope or magnifying lens, dark background,
7.3.6 Overvoltage Test—Subject each of the electrical heat-
and cross lighting may be used, as appropriate, to assist in the
ing circuits of Type A specimens to the application of an
identification and classification of visible defects.
overvoltage of 150 % maximum operating voltage for the
7.2 Optical Tests—Measure each Type A specimen for
circuit. Apply this voltage to the power leads for a minimum of
luminous transmittance and haze in accordance with Procedure
5 s. After no less than a 2-min wait, apply the same voltage for
B of Test Method D 1003. Make at least two measurements,
a minimum of 5 s, observing the sample in a darkened room
one in the center and one near the edge, on each specimen. Six
with specific emphasis being on the bus bars for signs of
measurements are preferred. If greater than 1 % variation
arcing.
exists, prepare a template from polyester film or other suitable
7.3.7 Bond Integrity Test—Test individual Type B speci-
material to record these locations for indexing and correlation
mens in accordance with Test Methods F 521.
to readings to be taken after environmental exposure.
7.4 Specimens that fail due to some obvious, non-
NOTE 1—Paragraphs 7.3-7.6 are applicable to systems using electri-
representative defect shall be disqualified and retests con-
cally conductive coatings.
ducted.
7.5 Environmental Exposure:
7.3 Electrical Tests:
7.5.1 Artificial Weathering—Expose test specimens to arti-
7.3.1 Bus Bar-to-Bus Bar Resistance—Measure each Type
ficial weathering in accordance with one of the two standards
A specimen for bus bar-to-bus bar resistance. Take precautions
listed below.
to minimize the effects of variable contact resistance. Record
7.5.1.1 Practice G 53 for Operating Light- and Water-
results and repeat the measurement after environmental expo-
Exposure Apparatus (Fluorescent UV-Condensation Type) for
sure prior to application of over-voltage power.
Exposure of Nonmetallic Materials—Use UVB-313 bulbs and
7.3.2 Sensing Element—Test the sensing elements for open
a cycle of7hUV followed by 5 h condensation, all at a
or shorted circuits by applying an ele
...
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