ASTM_D_7249_-_D_7249M_-_12e1.pdf

Designation:D7249/D7249M121Standard Test Method forFacing Properties of Sandwich Constructions by LongBeam Flexure1This standard is issued under the fixed designation D7249/D7249M;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.1NOTEFigure 6 was corrected editorially in March 2014.1.Scope1.1 This test method covers determination of facing prop-erties of flat sandwich constructions subjected to flexure insuch a manner that the applied moments produce curvature ofthe sandwich facing planes and result in compressive andtensile forces in the facings.Permissible core material formsinclude those with continuous bonding surfaces(such as balsawood and foams)as well as those with discontinuous bondingsurfaces(such as honeycomb).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.NOTE1Alternate procedures for determining the compressivestrength of unidirectional polymer matrix composites materials in asandwich beam configuration may be found in Test Method D5467/D5467M.2.Referenced Documents2.1 ASTM Standards:2C274 Terminology of Structural Sandwich ConstructionsC393 Test Method for Flexural Properties of SandwichConstructionsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD5467/D5467M Test Method for Compressive Properties ofUnidirectional Polymer Matrix Composite Materials Us-ing a Sandwich BeamD7250/D7250M Practice for Determining Sandwich BeamFlexural and Shear StiffnessE6 Terminology Relating to Methods of Mechanical TestingE122 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 MethodsE251 Test Methods for Performance Characteristics of Me-tallic Bonded Resistance Strain GagesE456 Terminology Relating to Quality and StatisticsE1309 GuideforIdentificationofFiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases3.Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites.TerminologyC274 defines terms relating to structural sandwich construc-tions.Terminology C393 defines terms relating to plastics.Terminology E6 defines terms relating to mechanical testing.Terminology E456 and Practice E177 define terms relating tostatistics.In the event of a conflict between terms,TerminologyD3878 shall have precedence over the other terminologies.3.2 Symbols:b=specimen widthc=core thicknessCV=coefficient of variation statistic of a sample popu-lation for a given property(in percent)d=sandwich total thickness1This 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 Aug.1,2012.Published December 2012.Originallyapproved in 2006.Last previous edition approved in 2006 as D7249/D7249M 06.DOI:10.1520/D7249_D7249M-12.2For 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 DF,nom=effective sandwich flexural stiffnessEf=effective facing chord modulus=measuring strain in facingFu=facing ultimate strength(tensile or compressive)Fs=core shear allowable strengthFc=core compression allowable strengthk=core shear strength factor to ensure facing failurel=length of loading spanL=length of support spanlpad=length of loading padn=number of specimensP=applied forcePmax=maximum force carried by test specimen beforefailureSn1=standard deviation statistic of a sample populationfor a given property=facing stresst=facing thicknessx1=test result for an individual specimen from thesample population for a given propertyx=mean or average(estimate of mean)of a samplepopulation for a given property4.Summa