ASTM_D_2734_-_16.pdf

Designation:D273416Standard Test Methods forVoid Content of Reinforced Plastics1This standard is issued under the fixed designation D2734;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()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.Scope*1.1 These test methods cover the void content of reinforcedplastics or“composites.”The test methods are applicable tocomposites for which the effects of ignition on the materials areknown.Most plastics,glass,and reinforcements fall into thisclass.These test methods are not applicable to composites forwhich the effects of ignition on the plastics,the reinforcement,and any fillers are unknown.This class may include siliconeresins,which do not burn off completely,reinforcementsconsisting of metals,organic materials,or inorganic materialswhich may gain or lose weight,and fillers consisting of oxides,carbonates,etc.,which may gain or lose weight.Note thatseparate weight loss tests of individual materials will usually,but not necessarily,give the same result as when all thematerials are combined.NOTE1There is no known ISO equivalent to these test methods.1.2 The values stated in SI units are to be regarded asstandard.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:2D618 Practice for Conditioning Plastics for TestingD792 Test Methods for Density and Specific Gravity(Rela-tive Density)of Plastics by DisplacementD1505 Test Method for Density of Plastics by the Density-Gradient TechniqueD2584 Test Method for Ignition Loss of Cured ReinforcedResins3.Summary of Test Methods3.1 The densities of the resin,the reinforcement,and thecomposites are measured separately.Then the resin content ismeasured and a theoretical composite density calculated.Thisis compared to the measured composite density.The differencein densities indicates the void content.A good composite mayhave 1%voids or less,while a poorly made composite canhave a much higher void content.Finite values under 1%should be recognized as representing a laminate densityquality,but true void content level must be established bycomplementary tests or background experience,or both.4.Significance and Use4.1 The void content of a composite may significantly affectsome of its mechanical properties.Higher void contentsusually mean lower fatigue resistance,greater susceptibility towater penetration and weathering,and increased variation orscatter in strength properties.The knowledge of void content isdesirable for estimation of quality of composites.5.Interferences5.1 The density of the resin,in these test methods,isassumed to be the same in the composite as it is in a large castmass.Although there is no realistic way to avoid thisassumption,it is nevertheless not strictly correct.Differences incuring,heat and pressure,and molecular forces from thereinforcement surface all change the composite resin densityfrom the bulk resin density.The usual change is that bulkdensity is lower,making void content seem lower than it reallyis.5.2 For composites with high void contents,this error willlower the true value an insignificant amount,from a true 7%down to a calculated 6.7%,for example.For composites withlow and void contents,the value may be lowered from a true0.2%to a calculated 0.1%.This would indicate an obviouserror,and illustrates that as the void content gets lower theconstant error in resin density gets progressively more impor-tant.Note that these values are for example only,that differentresin systems can give different errors,and that it is left to the1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.18 on ReinforcedThermosetting Plastics.Current edition approved Sept.1,2016.Published September 2016.Originallyapproved in 1968.Last previous edition approved in 2009 as D2734 09.DOI:10.1520/D2734-16.2For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 individual tester to determine the accuracy of the calculatedresult in his particular measurement.5.3 For the special case of semi-crystalline plastics,such aspolyphenylene sulfide(PPS)and polyetheretherketone(