1、Designation: F520 16Standard Test Method forEnvironmental Resistance of Aerospace Transparencies toArtificially Induced Exposures1This standard is issued under the fixed designation F520; the number immediately following the designation indicates the year of originaladoption or, in the case of revis
2、ion, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers determination of the effects ofexposure to thermal shock, condensing humidity, an
3、d simu-lated weather on aerospace transparent enclosures.1.2 This test method is not recommended for quality controlnor is it intended to provide a correlation to actual service life.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisst
4、andard.1.3.1 ExceptionsCertain inch-pound units are furnished inparentheses (not mandatory) and certain temperatures in Fahr-enheit associated with other standards are also furnished.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is there
5、sponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1003 Test Method for Haze and Luminous Transmittanceof Transparent PlasticsF319 Practice
6、 for Polarized Light Detection of Flaws inAerospace Transparency Heating ElementsF521 Test Methods for Bond Integrity of Transparent Lami-natesG53 Practice for Operating Light-and Water-Exposure Ap-paratus (Fluorescent UV-Condensation Type) for Expo-sure of Nonmetallic Materials (Withdrawn 2000)3G15
7、4 Practice for Operating Fluorescent Ultraviolet (UV)Lamp Apparatus for Exposure of Nonmetallic Materials3. Summary of Test Method3.1 Two types of test specimens, duplicating the aerospacetransparent enclosure design, are subjected to thermal shock,condensing humidity, and artificial weathering. Edg
8、e sealingshall be used if representative of the design.3.1.1 TypeAspecimens shall be used to determine the effectof environmental exposure on electrical and optical properties.3.1.2 Type B specimens shall be used to determine the effectof environmental exposure on bond integrity.4. Significance and
9、Use4.1 This test method, when applied to aerospace transpar-encies of either monolithic glass/plastic or laminatedcombinations, is a measure of the ability of the transparency towithstand the effects of artificially induced environments. Thetest applies to on configurations employing electrically co
10、n-ductive coatings, and also to uncoated materials.4.2 The resistance of the transparent enclosure to environ-mental effects may vary appreciably depending on the size,geometry, material of construction, coating integrity, coatingdensity, and other factors.5. Test Specimens5.1 Each Type A specimen t
11、o be evaluated for externalcoating durability shall be a 250 by 250-mm (9.8 by 9.8-in.)cross section of the design and shall contain, as applicable,surface coatings of operational, electrically conducting coatingsystems complete with bus bars, braids, and temperaturesensors.5.1.1 Type A test specime
12、ns shall have a fully operationalcoating system, when applicable, with an average resistivityconsistent with the average resistivity of the representativedesign. Reproduction of multiphase electrical circuits is notrequired for these test specimens since this type of circuitry isonly a design techni
13、que used to accommodate limited voltageresources at installation.5.1.2 Type A specimen testing exposure of an externalcoating only, are independent of size but shall be of sufficientsize to produce representative coatings. When testing externalcoatings the recommended specimen size is 250 by 250-mm1
14、This test method is under the jurisdiction of ASTM Committee F07 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved April 1, 2016. Published May 2016. Originallyapproved in 1977. Last previous edition appro
15、ved in 2010 as F520 10. DOI:10.1520/F0520-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approv
16、ed version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1(9.8 by 9.8-in.). Type A specimens which are monolithic, orlaminated samples where only an external coating system isb
17、eing tested shall be tested to the same exposure intervals as 50by 50-mm (2 by 2-in.), Type B specimens (5.2).5.1.3 Type A specimen testing for effects of exposure tocomponents within a laminated construction, such as electricalcomponents, heating films, and interlayers, taking place due tomoisture
18、ingress are dependent on size and shall receiveincreasing exposure levels as the length of the sides of thespecimen increase. 250 by 250-mm specimens shall be ex-posed to humidity 27 times the duration of 50 by 50-mmspecimens. Use of 150 by 150-mm specimen shall be allowedwith exposure of 9 times th
19、at of corresponding 50 by 50-mmspecimens, or 1/3 the duration of 250 by 250-mm specimens.5.1.4 Type A that are both laminated and contain externalcoatings where both external and internal effects are to betested after exposure, must be tested independently as exter-nally coated samples, and as lamin
20、ated samples, since theexposure durations will be different. To test effects on bothlayers of a particular design, the number of samples must bedoubled, the external coating tested on one set, and internalcomponents tested on a second set of specimens.5.2 Each Type B test specimen shall be 50 by 50
21、mm (2 by2 in.) and shall be of a cross section consistent with the edgeconfiguration of the representative design. Type B test speci-mens are not intended to be operational electrically, but theyshall be representative of the average resistivity of the design.6. Preparation of Test Specimens6.1 Prep
22、are a minimum of three Type A specimens for eachdesign configuration. If the design contains an electricallyactivated coating, only one temperature sensor per specimen isrequired.6.2 Prepare a minimum of five Type B specimens for eachdesign configuration. Prepare the specimen in such a manner asto p
23、roduce smooth edges and corners to prevent chippingduring testing. Polish at least one edge of each specimen toallow inspection of the internal bonded surfaces during tensileloading. Do not apply edge sealant to the specimens.6.3 Condition all test specimens by exposing them to notless than 40 h at
24、23 6 2C (73.4 6 3.6F) and 50 6 5%relative humidity.7. Procedure7.1 Visual ExaminationCarefully examine Type A andType B specimens for any signs of material or manufacturingdefects. A microscope or magnifying lens, dark background,and cross lighting shall be used, as appropriate, to assist in theiden
25、tification and classification of visible defects.7.2 Optical TestsMeasure each Type A specimen forluminous transmittance and haze in accordance with ProcedureB ofTest Method D1003. Make at least two measurements, onein the center and one near the edge, on each specimen. Sixmeasurements are preferred
26、. If greater than 1 % variationexists, prepare a template from polyester film or other suitablematerial to record these locations for indexing and correlationto readings to be taken after environmental exposure.NOTE 1Paragraphs 7.3 7.6 are applicable to systems using electri-cally conductive coating
27、s.7.3 Electrical Tests:7.3.1 Bus Bar-to-Bus Bar ResistanceMeasure each TypeA specimen for bus bar-to-bus bar resistance. Take precautionsto minimize the effects of variable contact resistance. Recordresults and repeat the measurement after environmental expo-sure prior to application of over-voltage
28、 power.7.3.2 Sensing ElementMeasure the resistance of the sens-ing elements at a specified temperature to assure conformanceto the temperature resistance ranges certified by the elementmanufacturer.7.3.3 Electrical InsulationTest the electrical insulation bymeasuring leakage current on each test spe
29、cimen. Apply analternating current potential between 1500 and 2500 V rms,depending upon the design application and specifiedrequirements, at 50 or 60 Hz for a period of 1 min between thefollowing:(1) each sensor lead and each heater lead;(2) each sensor lead and metal insert or spacer;(3) each heate
30、r lead and the metal insert or spacer;(4) each heater lead and metal strip placed in contact withthe edge of the glass panel; test the entire edge of the glasspanel;(5) each anti-ice and defog heater lead.Leakage current in excess of 1 mA at 1500 V rms or 4 mA at2500 V rms is objectionable. Monitor
31、the current during apreliminary low voltage application and terminate the test if thecurrent leakage exceeds the allowable amount prior to fullvoltage application. Determine the resistance and decidewhether to proceed to full voltage in conformance with the testprocedure.7.3.4 Monitor the current du
32、ring gradual application of a dcvoltage. Current in excess of 5 A is objectionable. If thecurrent exceeds 5 A dc before 500 V dc is reached, suspendthe test and determine the resistance before deciding whether tocontinue. Gradually apply and remove the potential at nogreater rate than 500 V rms/s.7.
33、3.5 Electrically Conductive Coating TestTest each TypeA specimen for electrically conductive coating uniformity inaccordance with Test Method F319.7.3.5.1 For electrically conductive coatings on plasticmaterials, apply a minimum of 110 % of the nominal designvoltage.7.3.5.2 For electrically conducti
34、ve coatings on glass, applya minimum of 125 % of the nominal design voltage.7.3.5.3 Alternative voltage levels and power-on times maybe as specified by contractual documents.7.3.6 Overvoltage TestSubject each of the electrical heat-ing circuits of Type A specimens to the application of anovervoltage
35、 of 150 % maximum operating voltage for thecircuit.Apply this voltage to the power leads for a minimum of5 s.After no less than a 2-min wait, apply the same voltage fora minimum of 5 s, observing the sample in a darkened roomwith specific emphasis being on the bus bars for signs ofarcing.7.3.7 Bond
36、Integrity TestTest individual Type B speci-mens in accordance with Test Methods F521.F520 1627.4 Specimens that fail due to some obvious, non-representative defect shall be disqualified and retests con-ducted.7.5 Environmental Exposure:7.5.1 Artificial WeatheringExpose test specimens to arti-ficial
37、weathering in accordance with G154 for testing compo-nents internal to laminates. Test in accordance with G53 fortesting external coatings or surfaces exposed to the environ-ment.7.5.1.1 Practice G154 for Operating Light- and Water-Exposure Apparatus (Fluorescent UV-Condensation Type) forExposure of
38、 Nonmetallic MaterialsUVA-340 is recom-mended when testing internal components of both glass andplastic laminates. The recommended G154 cycle is Cycle 4,UVA-340, UVA-340 bulbs operating at 1.35 W/m2/nm typicalirradiance, and a cycle of8hUVataconstant temperature of158F (70C) followed by 4 h condensa
39、tion at a constanttemperature of 120F (50C). Exposure shall be a mutuallyagreed total number of hours and number of testing intervals.A suggested total exposure time is 1850 h (77 days) with aminimum of 7 test intervals of 264 h (15 days).Apply the cyclecontinuously for 264 h (15 days) to constitute
40、 each interval.7.5.1.2 Practice G53 for Operating Light- and Water-Exposure Apparatus (Fluorescent UV-Condensation Type) forExposure of Nonmetallic MaterialsUse UVB-313 bulbs anda cycle of7hUVfollowed by 5 h condensation, all at aconstant temperature of 120F when testing external coatings,surfaces o
41、r surface treatments.Asuggested total exposure timeis 1176 h (49 days) with a minimum of 7 test intervals of 168h (7 days). Apply the cycle continuously for 168 h (1 week) toconstitute each interval.NOTE 2Practice G53 has been shown to produce acceptable acceler-ated weathering results. Practice G53
42、 is used most extensively in theTransparency Community due to its simplicity, ease of use and lowoperational costs. The UVB-313 cycle of7hUVfollowed by 5 hcondensation, all at 120F have been standard practice for coatingsexposures, representing a substantial database of test results.NOTE 3Accelerate
43、d weathering results shall only be compared forsamples exposed using the same practice. Comparison of test resultsobtained using different practices may result in erroneous conclusions,particularly when comparing the relative performance of different mate-rials.7.5.2 HumidityExpose Type B test speci
44、mens to a mini-mum exposure of 10 cycles of condensing humidity in achamber with a controlled temperature of 49 6 3C (120 65F) and relative humidity of 95 to 100 %.7.5.2.1 Type B specimens and Type A specimens testing anexternal coating or exposed surface shall be tested in intervalsof 10 cycles, a
45、minimum of 1 interval is required, and testingshall be continued until the desired level of degradation isverified. Water used to maintain the humidity shall not containmore than 200 ppm total solids. Each cycle shall be a 24-hexposure in the condensing humidity chamber and an 8-hexposure to ambient
46、 temperature and humidity. As analternative, continuous exposure to humidity may be used incycles of 24 h.7.5.2.2 Type A specimens exposed to test internal compo-nents using 150 by 150-mm laminated Type A specimens,intervals of 90 cycles are recommended with a minimum of 1interval exposure.7.5.2.3 T
47、ype A specimens exposed to test internal compo-nents using 250 by 250-mm laminated Type A specimens,intervals of 270 cycles are recommended with a minimum of 1interval exposure.7.5.3 Thermal ShockPlace the test specimen in an oven ata temperature of 71C (160F) and leave until stabilized at71C (160F)
48、 as determined by a thermocouple attached to thespecimen face.After the temperature has stabilized, transfer thespecimen as rapidly as possible (within 3 min) to a chambermaintained at 54C (65F). Let the specimen stabilizeat 54C (65F) and as rapidly as possible return it to theoven at 71C (160F). Af
49、ter each 54C (65F) cold soak,and while the specimen is stabilized at 54C (65F), ener-gize the conductive coating on Type A specimens using thedesign watt density until the temperature at the sensor stabi-lizes. Then switch off the power and place the specimen in the71C (160F) oven. Repeat this for two cycles unless specifiedotherwise.7.6 Upon completion of environmental exposure in accor-dance with either 7.5.1, 7.5.2, 7.5.3, or any combinationthereof, allow all specimens to return to ambient conditionsand examine them for s
