ASTM_D_6772_-_D_6772M_-_16.pdf

Designation:D6772/D6772M16Standard Test Method forDimensional Stability of Sandwich Core Materials1This standard is issued under the fixed designation D6772/D6772M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the sand-wich core dimensional stability in the two plan dimensions.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.2.1 Within the text,the inch-pound units are shown inbrackets.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.2.Referenced Documents2.1 ASTM Standards:2C271/C271M Test Method for Density of Sandwich CoreMaterialsD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsE122 Practice for Calculating Sample Size to Estimate,WithSpecified Precision,the Average for a Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and Statistics3.Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites,as well as termsrelating to sandwich constructions.Terminology D883 definesterms relating to plastics.Terminology E456 and Practice E177define terms relating to statistics.In the event of a conflictbetween terms,Terminology D3878 shall have precedenceover the other terminologies.3.2 Symbols:3.2.1 CVcoefficient of variation statistic of a samplepopulation for a given property(in percent)3.2.2 Li initial(pre-test)measured dimension3.2.3 Lfpost-heating measured dimension3.2.4 Sn-1standard deviation statistic of a sample popula-tion for a given property3.2.5 xItest result for an individual specimen from thesample population for a given property3.2.6 x mean or average(estimate of mean)of a samplepopulation for a given property4.Summary of Test Method4.1 This test method consists of placing a small piece ofsandwich core material in an elevated temperature environmentfor a specified period of time.After cooling,the dimensionalchanges in the planar dimensions are measured and comparedto the initial measurements taken prior to thermal exposure,both immediately after heating and after re-conditioning.Atypical honeycomb core specimen is shown in Fig.1.5.Significance and Use5.1 Sandwich panel cores may change planar dimensionswhen heated.This phenomenon can be associated with theeffects of heating upon the core material itself,as well aschanges in core moisture content resulting from the heatingcycle.It is prudent to know if this may be problematic withregard to the intended final part dimensions.5.2 This test method provides a standard method of charac-terizing the dimensional stability of sandwich core materialsfor design properties,material specifications,research anddevelopment applications,and quality assurance.1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved April 1,2016.Published April 2016.Originallyapproved in 2002.Last previous edition approved in 2015 as D6772 15.DOI:10.1520/D6772_D6772M-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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3 Factors that influence dimensional stability of sandwichcore materials and shall therefore be reported include thefollowing:core material,methods of material fabrication,coregeometry,core thickness,core thickness uniformity,cell wallthickness,specimen geometry,specimen preparation,heatingand cooling environments(including temperatures and humid-ity levels),and specimen conditioning(both prior to and afterheating).6.Interferences6.1 Material and Specimen PreparationPoor material fab-rication practices and damage induced by improper specimenmachining are known causes of high data scatter for sandwichcores.Important aspects of sandwich core specimen prepara-tion that contri