ASTM_F_320_-_10.pdf

Designation:F32010Standard Test Method forHail Impact Resistance of Aerospace TransparentEnclosures1This standard is issued under the fixed designation F320;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,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.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 impactresistance of an aerospace transparent enclosure,hereinaftercalled windshield,during hailstorm conditions using simulatedhailstones consisting of ice balls molded under tightly con-trolled conditions.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For specific hazardstatements see Section 7.2.Terminology2.1 Definitions:2.1.1 damageany modification in visual properties orintegrity of a windshield as a result of hail impact includingscratches,crazing,delamination,cracks,or shattering.2.1.2 ice balla frozen mass of water,with filler,thatsimulates a natural hailstone in weight,size,and toughness.2.1.3 impact anglethe angle between the ice ball flightpath and the target normal.2.1.4 sabota plastic device for protecting the ice ballwhile in the launch tube.One type of sabot(see Fig.1)consistsof a split polycarbonate rod containing a central cavity forholding the ice ball.Each sabot half is designed to assureaerodynamic separation from the ice ball after ejection fromthe launch tube.3.Summary of Test Method3.1 The test method involves launching a series of ice ballsof specified sizes at a sample windshield at a designatedvelocity and angle and in a specified pattern.Requirements arespecified for the ice ball,test specimen,procedure,and dataacquisition.The ice ball is photographed in flight to verify itsintegrity.3.2 Requirements are specified for a particular apparatusand test procedure,but options are permitted for certain areas.However,it must be possible to demonstrate that the optionsused result in an ice ball impacting the test panel with the samesize,consistency,and velocity as with the specified apparatusand procedure.Following are areas where options are allowed:3.2.1 Ice Ball Mold Material.3.2.2 LauncherAny type of launcher is allowable as longas the iceball reaches the test specimen intact at the correctspeed.The use of sabots and sabot material and geometry areoptional.3.2.3 Method of Determining Ice Ball Integrity.3.2.4 Ice Ball Speed Measurement,Optional as long asaccuracy standards are met.3.2.5 Test Specimen SizesThose given are minimum.3.2.6 SafetySafety must satisfy the safety standards of thetest facility being used.4.Significance and Use4.1 This test method may be used to determine the hailimpact resistance of windshields for acceptance,design,service,or research purposes.By coupling this method with theinstalled angle and velocity of a specific aerospace vehicle,design allowables,criteria,and tolerances can be establishedfor that vehicles windshield.5.Apparatus5.1 The facilities and equipment required for the perfor-mance of this test procedure include a suitable firing rangeequipped with an ice ball mold,a launcher,blast deflector,sabot trap,velocity measuring system,test specimen holder,and a camera with strobe lights to verify ice ball integrity.Ancillary equipment required for this test include test1This 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 May 1,2010.Published June 2010.Originallyapproved in 1978.Last previous edition approved in 2005 as F320 05.DOI:10.1520/F0320-10.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 specimen,ice balls,sabots,and firing cartridges.An examplefacility is described below.5.2 Firing RangeThe firing range shall be a minimum of9 by 18 ft(3 by 6 m)enclosed to contain flying debris and toexclude unauthorized personnel.5.3 Ice Ball Mold,two aluminum blocks with hemisphericalcavities and vent holes for filling with water and for waterexpansion during freezing.5.4 Launcher,any launcher may be used as noted in 3.2.2.Inaddition to the powder gun described in this test method,laboratories have also successfully utilized compressed gas gunlaunchers.An example of a powder gun launcher is shown inFig.2,consisting of a barrel