1、Designation: F 520 97 (Reapproved 2004)Standard Test Method forEnvironmental Resistance of Aerospace Transparencies1This standard is issued under the fixed designation F 520; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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, and simu-l
3、ated 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 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibi
4、lity 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:2D 1003 Test Method for Haze and Luminous Transmittanceof Transparent PlasticsF 521 Test Methods f
5、or Bond Integrity of TransparentLaminatesG 23 Practice for Operating Light-Exposure Apparatus(Carbon-Arc Type) With and Without Water for Exposureof Nonmetallic Materials3G 26 Practice for Operating Light-Exposure Apparatus(Xenon-Arc Type) With and Without Water for Exposureof Nonmetallic Materials3
6、G 53 Practice for Operating Light- and Water-ExposureApparatus (Fluorescent UV-Condensation Type for Expo-sure of Nonmetallic Materials33. Summary of Test Method3.1 Two types of test specimens, duplicating the aerospacetransparent enclosure design, are subjected to thermal shock,condensing humidity,
7、 and artificial weathering. Edge sealingmay be used if representative of the design.3.1.1 Type A specimens are used to determine the effect ofenvironmental exposure on electrical and optical properties.3.1.2 Type B specimens are used to determine the effect ofenvironmental exposure on bond integrity
8、.4. Significance and Use4.1 This test method, when applied to aerospace transpar-encies of either monolithic glass/plastic or laminated combi-nations, is a measure of the ability of the transparency towithstand the effects of artificially induced environments. Thetest may be used on configurations e
9、mploying electricallyconductive coatings, and also to evaluate the integrity ofnoncoated 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 fac
10、tors.5. Test Specimens5.1 Each Type A specimen shall be a 250 by 250-mm (9.8by 9.8-in.) cross section of the design and shall contain, asapplicable, surface coatings of operational, electrically con-ducting coating systems complete with bus bars, braids, andtemperature sensors.5.1.1 Type A test spec
11、imens 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 tec
12、hnique used to accommodate limited voltageresources at installation.5.2 Each Type B test specimen shall be 50 by 50 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 electricall
13、y, but theyshall be representative of the average resistivity of the design.6. Preparation of Test Specimens6.1 Prepare a minimum of three Type A specimens for eachdesign configuration. If the design contains an electricallyactivated coating, only one temperature sensor per specimen isrequired.1This
14、 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 Oct. 1, 2004. Published October 2004. Originallyapproved in 1977. Last previous edition approv
15、ed in 1997 as F 520 97.2For 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.3Withdrawn.1Copyright ASTM Internation
16、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 Prepare a minimum of five Type B specimens for eachdesign configuration. Prepare the specimen in such a manner asto produce smooth edges and corners to prevent chippingduring testing. Polish at least one edge
17、 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 23 6 2C (73.4 6 3.6F) and 50 6 5%relative humidity.7. Procedure7.1 Visual ExaminationCarefu
18、lly examine Type A andType B specimens for any signs of material or manufacturingdefects. A microscope or magnifying lens, dark background,and cross lighting may be used, as appropriate, to assist in theidentification and classification of visible defects.7.2 Optical TestsMeasure each Type A specime
19、n forluminous transmittance and haze in accordance with ProcedureB of Test Method D 1003. Make at least two measurements,one in the center and one near the edge, on each specimen. Sixmeasurements are preferred. If greater than 1 % variationexists, prepare a template from polyester film or other suit
20、ablematerial 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 coatings.7.3 Electrical Tests:7.3.1 Bus Bar-to-Bus Bar ResistanceMeasure each TypeA specimen for b
21、us 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 power.7.3.2 Sensing ElementTest the sensing elements for openor shorted circuits by applyi
22、ng an electrical potential of 10 rmsvolts ac for a minimum period of 1 min. Follow by measuringresistance in both directions. Measure the resistance of thesensing elements at a specified temperature to assure conform-ance to the temperature resistance ranges certified by theelement manufacturer.7.3.
23、3 Electrical InsulationTest the electrical insulation bymeasuring leakage current on each test specimen. Apply analternating current potential of either 1500 or 2500 V rms(depending upon the design application) at 50 or 60 Hz for aperiod of 1 min between the following:(1) each sensor lead and each h
24、eater lead;(2) each sensor lead and metal insert or spacer;(3) each heater 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 exc
25、ess of 1.5 mA at 1500 V rms or 2.5 mAat 2500 V rms is objectionable. Monitor 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 fu
26、ll voltage in conformance with the testprocedure.7.3.4 Monitor the current during 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. G
27、radually apply and remove the potential at nogreater rate than 500 V rms/s.7.3.5 Electrically Conductive Coating TestTest each TypeA specimen for electrically conductive coating uniformity byenergizing with the same level of controlled power as proposedin the design while viewing between polarized p
28、lates. Identifyall detectable coating hot spots during this heat-up cycle. Thesethermally induced stress concentrations are generally charac-terized by a “butterfly” shape and are to be noted for laterspecimen evaluation.7.3.6 Overvoltage TestSubject each of the electrical heat-ing circuits of Type
29、A specimens to the application of anovervoltage 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 bei
30、ng on the bus bars for signs ofarcing.7.3.7 Bond Integrity TestTest individual Type B speci-mens in accordance with Test Methods F 521.7.4 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 Weath
31、eringExpose test specimens to arti-ficial weathering in accordance with one of the two standardslisted below.7.5.1.1 Practice G 53 for Operating Light- and Water-Exposure Apparatus (Fluorescent UV-Condensation Type) forExposure of Nonmetallic MaterialsUse UVB-313 bulbs anda cycle of7hUVfollowed by 5
32、 h condensation, all at aconstant temperature of 120F. Apply the cycle continuouslyfor 168 h (1 week) to simulate 1 year of equivalent naturalexposure.7.5.1.2 Practice G 26 for Operating Light-Exposure Appa-ratus (Xenon-Arc Type) With and Without Water for Exposureof Nonmetallic MaterialsUse a cycle
33、 of 102 min of lightfollowed by 18 min of spray in accordance with Test MethodA of Practice G 26.NOTE 2Practice G 53 and Practice G 26 have both been shown toproduce acceptable accelerated weathering results. Practice G 53 is usedmost extensively in the Transparency Community due to its simplicity,e
34、ase of use and low operational costs. Practice G 26 is preferred by someorganizations for its flexibility in tuning the wavelength of the light sourceand its ability to provide more energy throughout the UV spectrum. Bothpractices have been included to enhance the applicability of the testmethod.NOT
35、E 3Accelerated weathering results may 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 the te
36、st specimens to 10 cycles ofcondensing humidity in a chamber with a controlled tempera-ture of 49 6 3C (120 6 5F) and relative humidity of 95 toF 520 97 (2004)2100 %. Water used to maintain the humidity shall not containmore than 200 ppm total solids. Each cycle shall be a 24-hexposure in the conden
37、sing humidity chamber and an 8-hexposure to ambient temperature and humidity.7.5.3 Thermal ShockPlace the test specimen in an oven ata temperature of 71C (160F) and leave until stabilized at71C (160F) as determined by a thermocouple attached to thespecimen face. After the temperature has stabilized,
38、 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). After each 54C (65F) cold soak,and while the specimen is stabilized at 54C (65F), ener-gize the condu
39、ctive 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 wi
40、th either 7.5.1, 7.5.2, 7.5.3, or any combinationthereof, allow all specimens to return to ambient conditionsand examine them for signs of delamination, cracking, spal-ling, or other deterioration.7.7 Repeat tests 7.1-7.4.8. Report8.1 The test report shall include the following:8.1.1 A complete and
41、detailed identification of the materialsand configurations tested, including type, source, manufactur-ers code or serial number, face ply materials, interlayerdescription, coatings, principal dimensions of all panels tested,and previous history,8.1.2 Results of all visual examinations including (if
42、ob-tained) photographs and photomicrographs,8.1.3 Luminous transmittance, haze measurements, and lo-cation diagram (if necessary) to describe results,8.1.4 Test results in accordance with Test Method F 521,8.1.5 Bus bar-to-bus bar resistance of Type A specimenbefore and after environmental exposure,
43、8.1.6 Results of applied standard, controlled energizingcurrent, and overpower voltage tests, and8.1.7 The practice used for artificial weathering and appro-priate details required by the report section of the practice.8.1.8 All other results required by the individual test proce-dures, referenced h
44、erein, where these are applicable.9. Precision and Bias9.1 Precision and BiasVisual Examination:9.1.1 No statement is made concerning either precision orbias for this portion of the test method since the result merelystates whether there is conformance to the criteria for successspecified in the pro
45、cedure.9.2 Precision and BiasOptical Tests:9.2.1 The precision and bias of the portion of the testmethod measuring haze and luminous transmittance are asspecified in Test Method D 1003.9.3 Precision and BiasElectrical Tests:9.3.1 No statement is made concerning either precision orbias for the follow
46、ing portions of the test method since theresult merely states whether there is conformance to the criteriafor success specified in the procedure: Bus Bar-to-Bus BarResistance, Sensing Element, Electrical Insulation, ElectricallyConductive Coating Test, Overvoltage Test.9.4 Precision and BiasBond Int
47、egrity Test:9.4.1 The precision and bias of the portion of the testmethod measuring bond integrity are as specified in TestMethod F 521.9.5 Precision and BiasEnvironmental Exposure:9.5.1 No statement is made concerning either precision orbias for this portion of the test method since the result mere
48、lystates whether there is conformance to the criteria for successspecified in the procedure.10. Keywords10.1 environmental resistance; humidity; thermal shock;transparency; transparency coating; weatheringASTM International takes no position respecting the validity of any patent rights asserted in c
49、onnection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to
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