1、Designation:F79196(Reapproved 2013)Standard Test Method forStress Crazing of Transparent Plastics1This standard is issued under the fixed designation F791;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anum
2、ber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers the determination of the criticalc
3、razing stress for a transparent plastic material when exposedto a specific solvent,chemical,or compound at a specifictemperature.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish ap
4、pro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method
5、2.2 Other Method:ARTC(Aircraft Research and Testing Committee of theAircraft Industries Association of America,Inc.)Condi-tioning Method33.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 crazinga group of surface fissures that appear to besmall cracks in the material,although the
6、y are not.3.1.1.1 DiscussionCrazing is a form of yielding in poly-mers characterized by a spongy void filled fibrillar structure.The density in the craze changes resulting in a change in theindex of refraction,which causes light to be reflected off of thecrazes.This light reflection causes the craze
7、s to sparkle whenviewed from certain angles.The crazes are sometimes randomand scattered with varied lengths and depths but usually areoriented perpendicular to a tensile stress.Crazing may bedifficult to detect.It becomes more pronounced when viewedwith a light source that is at an oblique angle.4.
8、Significance and Use4.1 This test method provides a guide for evaluating aspecific solvent,chemical,or compound that may be detrimen-tal to a transparent plastic as a result of a manufacturingprocess,a fabrication operation,or the operational environ-ment.All transparent plastics are susceptible to
9、crazing,thoughin widely varying degree and from a variety of causes.This testmethod is intended to allow establishment of the crazing stresswhen the simultaneous action of both load and a material thatwould cause crazing is applied producing non-reversible dam-age that might limit the usage of that
10、transparent plastic in aspecific application.5.Apparatus5.1 Test Fixture,with fluorescent light source illustrated andconstructed as shown in Figs.1 and 2.5.2 Drill Fixture constructed as shown in Fig.3.5.3 Marking Fixture,constructed as shown in Fig.3.5.4 Portable Specimen Rack,constructed in the m
11、anner asshown in Fig.4 for handling and conditioning test specimens.5.5 WeightsA container and shot for the application ofweight on the rack as shown in Fig.1.5.6 Filter Paper,quantity of 0.50 by 1.0-in.(12.7 by25.4-mm)pieces of filter,medium-retention filter paper.6.Test Specimens6.1 The test speci
12、men shall be machined from the transpar-ent plastic material to be evaluated.A minimum of sixspecimens for each solvent,chemical,or compound is re-quired.It is preferred that the transparent plastic sheet materialthickness be 6.35 6 0.64 mm(0.250 6 0.025 in.),but anythickness material may be used.Or
13、ientation of each testspecimen within the test sheet or part should be recorded.6.2 The test specimens shall be 25.4 6 0.8 mm(1.00 6 0.03in.)wide by 177.8 6 1.27 mm(7.00 6 0.05 in.)long bythickness.1This test method is under the jurisdiction of ASTM Committee F07 onAerospace and Aircraft and is the
14、direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved Dec.1,2013.Published December 2013.Originallyapproved in 1982.Last previous edition approved in 2008 as F791 96(2008).DOI:10.1520/F0791-96R13.2For referenced ASTM standards,visit the ASTM web
15、site,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.3Available from Aircraft Industries Association,1725 DeSales St.NW,Washington,DC 20034.Copyright ASTM International
16、,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.3 The edges shall be smooth machined surfaces withoutcracks,and the test specimen surface shall be free of defects orirregularities.If the test specimen has been machined tothickness,the nonmachined surface shall be the test surface.7.Preparation of Apparatus7.1 Once the load for a particular stress is calculated,thatload will be the sum of the individual weights of the weightrack,rod,lead weights,container,shot,
