ASTM_D_7956_-_D_7956M_-_14.pdf

Designation:D7956/D7956M14Standard Practice forCompressive Testing of Thin Damaged Laminates Using aSandwich Long Beam Fixture Specimen1This standard is issued under the fixed designation D7956/D7956M;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 an approach for compressive test-ing thin damaged multidirectional polymer matrix compositelaminates reinforced by high-modulus fibers using a sandwichlong beam flexure specimen.It provides a test configuration inwhich the core does not constrain any protruding back sidedamage.It is limited to testing of monolithic solid laminateswhich are too thin to be tested using typical anti-bucklingfixtures.It does not cover compressive testing of damagedsandwich panel facings.The composite material forms arelimited to continuous-fiber or discontinuous-fiber(tape orfabric,or both)reinforced composites in which the laminate isbalanced and symmetric with respect to the test direction1.2 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:2C274 Terminology of Structural Sandwich ConstructionsD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD3410 Test Method for Compressive Properties of PolymerMatrix Composite Materials with Unsupported Gage Sec-tion by Shear LoadingD6264/D6264M Test Method for Measuring the DamageResistance of a Fiber-Reinforced Polymer-Matrix Com-posite to a Concentrated Quasi-Static Indentation ForceD7136/D7136M Test Method for Measuring the DamageResistance of a Fiber-Reinforced Polymer Matrix Com-posite to a Drop-Weight Impact EventD7137/D7137M Test Method for Compressive ResidualStrength Properties of Damaged Polymer Matrix Compos-ite PlatesD7249/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.4.Summary of Practice4.1 This practice consists of fabricating a compositelaminate,damaging the laminate using either Test MethodD6264/D6264M or Test Method D7136/D7136M,bonding theimpacted or indented side of the laminate onto core and a backside facing to form a sandwich panel,and testing the damagedlaminate in compression using Test Method D7249/D7249M.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 Aug.1,2014.Published September 2014.DOI:10.1520/D7956_D7956M-14.2For 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.Significance and Use5.1 This practice provides a standard method of testingdamaged composite laminates which are too thin to be testedusing typical anti-buckling fixtures,such as those used in TestMethod D7137/D7137M.The laminate is first impacted orindented in order to produce a damage state representative ofactual monolithic solid laminate structure.Impacting or staticindentation is not perfo