ASTM_D_7250_-_D_7250M_-_06_2012.pdf

Designation:D7250/D7250M06(Reapproved 2012)Standard Practice forDetermining Sandwich Beam Flexural and Shear Stiffness1This standard is issued under the fixed designation D7250/D7250M;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 practice covers determination of the flexural andtransverse shear stiffness properties of flat sandwich construc-tions subjected to flexure in such a manner that the appliedmoments produce curvature of the sandwich facing planes.Permissible core material forms include those with continuousbonding surfaces(such as balsa wood and foams)as well asthose with discontinuous bonding surfaces(such as honey-comb).The calculation methods in this practice are limited tosandwich beams exhibiting linear force-deflection response.This practice uses test results obtained from Test MethodsC393/C393M and/or D7249/D7249M.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:2C273 Test Method for Shear Properties of Sandwich CoreMaterialsC274 Terminology of Structural Sandwich ConstructionsC393/C393M Test Method for Core Shear Properties ofSandwich Constructions by Beam FlexureD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD7249/D7249M Test Method for Facing Properties of Sand-wich Constructions by Long Beam FlexureE6 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 MethodsE456 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 D883 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=sandwich width,mm in.c=core thickness,mm in.d=sandwich thickness,mm in.D=flexural stiffness,N-mm2lb-in.2=beam mid-span deflection,mm in.G=core shear modulus,MPa psiS=support span length,mm in.L=load span length,mm in.(L=0.0 for 3-point mid-spanloading configuration)n=number of specimensP=total applied force,N lbt=facing thickness,mm in.U=transverse shear rigidity,N lb4.Summary of Practice4.1 This practice consists of calculating the flexuralstiffness,transverse(through-thickness)shear rigidity and coreshear modulus of a sandwich beam using deflection and/orstrain data from two or more flexure tests of different loadingconfigurations conducted under Test Methods C393/C393M1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is the direct responsibility of Subcommittee D30.09 on SandwichConstruction.Current edition approved Feb.1,2012.Published March 2012.DOI:10.1520/D7250_D7250M-06R12.2For 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 and/or D7249/D7249M.This practice also includes equationsfor calculating the shear rigidity and core shear modulus of asandwich beam using deflection data from a single flexure testconducted under Test Method C393/C393M when the facingmodulus is known.5.Significance and Use5.1 Flexure tests on flat sandwich constructions may beconducted to determine the sandwich flexural stiffness,the coreshear strength and shear modulus,or the facings compressiveand tensile strengths.Tests to evaluate core shear strength mayalso be used to evaluate core-to-fac