1、Designation: D7028 07 (Reapproved 2015)Standard Test Method forGlass Transition Temperature (DMA Tg) of Polymer MatrixComposites by Dynamic Mechanical Analysis (DMA)1This standard is issued under the fixed designation D7028; the number immediately following the designation indicates the year oforigi
2、nal 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.1. Scope1.1 This test method covers the procedure for the determi-nation of
3、the dry or wet (moisture conditioned) glass transitiontemperature (Tg) of polymer matrix composites containinghigh-modulus, 20 GPa (3106psi), fibers using a dynamicmechanical analyzer (DMA) under flexural oscillation mode,which is a specific subset of the Dynamic MechanicalAnalysis(DMA) method.1.2 T
4、he glass transition temperature is dependent upon thephysical property measured, the type of measuring apparatusand the experimental parameters used. The glass transitiontemperature determined by this test method (referred to as“DMA Tg”) may not be the same as that reported by othermeasurement techn
5、iques on the same test specimen.1.3 This test method is primarily intended for polymermatrix composites reinforced by continuous, oriented, high-modulus fibers. Other materials, such as neat resin, may requirenon-standard deviations from this test method to achievemeaningful results.1.4 The values s
6、tated in SI units are standard. The valuesgiven in parentheses are non-standard mathematical conver-sions to common units that are provided for information only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us
7、er 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:2D3878 Terminology for Composite MaterialsD4065 Practice for Plastics: Dynamic Mechanical Proper-ties: Determina
8、tion and Report of ProceduresD4092 Terminology for Plastics: Dynamic MechanicalPropertiesD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice
9、 for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in Databases (With-drawn 2015)3E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases (
10、Withdrawn2015)3E1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property Databases(Withdrawn 2015)3E1640 Test Method for Assignment of the Glass TransitionTemperature By Dynamic Mechanical AnalysisE1867 Test Method for Temperature Calibration of DynamicMe
11、chanical Analyzers3. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto polymer matrix composites. Terminology D4092 definesterms relating to dynamic mechanical property measurementson polymeric materials.3.2 Symbols: E = storage modulusE” = loss modulustan = E”/E = tangent deltaDM
12、A Tg = glass transition temperature defined from dy-namic mechanical analysis measurementL = length of specimenW = width of specimenT = thickness of specimenTt= peak temperature from tangent delta curve1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the
13、 direct responsibility of Subcommittee D30.04 onLamina and Laminate Test Methods.Current edition approved Aug. 1, 2015. Originally approved in 2007. Lastprevious edition approved in 2007 as D7028-071. Published August 2015. DOI:10.1520/D7028-07E01R15.2For referenced ASTM standards, visit the ASTM we
14、bsite, 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM Internation
15、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 Aflat rectangular strip of laminate is placed in the DMAequipment and oscillated at a nominal frequency of 1 Hz. Thespecimen is heated at a rate of 5C/min (9F/min). The sameloading fr
16、equency and heating rate is used for both dry and wetspecimens (moisture conditioned) to allow for comparison.The temperature at which a significant drop in storage modulus(E) begins is assigned as the glass transition temperature(DMA Tg). The peak temperature of the tangent delta curve(Tt) is ident
17、ified along with DMATg for comparison purposes.5. Significance and Use5.1 This test method is designed to determine the glasstransition temperature of continuous fiber reinforced polymercomposites using the DMA method. The DMA Tg value isfrequently used to indicate the upper use temperature ofcompos
18、ite materials, as well as for quality control of compositematerials.6. Interferences6.1 The standard testing machine shall be of the DynamicMechanical Analysis (DMA) type of instrument that operateswith forced oscillation and applies a flexural loading mode(either three-point bend or dual cantilever
19、) to the test specimen.Refer to Practice D4065 for a summary of various other DMApractices. Other loading modes (such as tensile, torsion orshear) may produce different test results. If another equipmenttype or loading mode is used the non-standard approach shallbe described in the report and the te
20、st result recorded asnon-standard.6.2 Afixed frequency of 1 Hz is standard in this test method.In general, for a given material, a higher testing frequencyproduces a higher DMATg value than this standard, while useof the resonance mode will yield a different DMATg that maybe either higher or lower t
21、han the standard. If a non-standardfrequency, or the resonance mode, is used, the non-standardapproach shall be described in the report and the test resultrecorded as non-standard.6.3 Aheating rate of 5 6 1C/min (9 6 2F/min) is standardin this test method.Achange in heating rate will affect the glas
22、stransition temperature result; the standard heating rate is thebest available compromise for comparing DMA Tg results ofdry and wet laminates. If a different heating rate is used it shallbe described in the report and the result recorded as non-standard.NOTE 1Users should be advised that a heating
23、rate of 5C/minrepresents a compromise between various issues related to Tg measure-ment precision and bias. It is widely known that heat transfer limitationsare more pronounced in DMA apparatus compared to other thermalanalysis techniques, such as differential scanning calorimetry (DSC) andthermomec
24、hanical analysis (TMA). For greatest precision, it has beenrecommended that heating rates be 2C/min or less. Test Method E1640specifies a heating rate of 1C/min. However, in many cases 5C/min isrecommended as a compromise between Tg measurement accuracy andtest method convenience, especially for wet
25、 laminate measurements, sincethe slower heating rate will cause specimen drying that will itself bias theresults.6.4 Purge gas type and flow rate and the position of thethermocouple can affect the DMA Tg test result and shall benoted and reported. The same conditions shall be used for bothcalibratio
26、n and testing runs. Instrumentation manufacturerrecommendations should be followed.6.5 It is standard in this test method that one of the majorfiber directions shall be parallel to the length of the specimen.The span-to-depth ratio, ply orientation, and ply stackingsequence of a specimen with respec
27、t to the testing fixture havea profound effect on the DMA Tg result. A meaningfulcomparison of data requires that the specimen configuration bethe same. A non-standard specimen configuration shall bedescribed in the report and the result recorded as non-standard.6.6 The standard definition in this t
28、est method for DMA Tgis based on intersecting two tangent lines from a semi-logarithmic plot of the storage modulus versus temperature.Other Tgdefinitions typically produce different test results. Forexample, a linear plot scale will result in a lower value of DMATg. A non-standard DMA Tg definition
29、 shall be described inthe report and the result recorded as non-standard. For com-parison purposes the peak temperature of the tangent deltacurve (Tt) is identified along with DMA Tg.7. Apparatus7.1 Micrometer, suitable for reading to 0.025 mm (0.001 in.)accuracy for measuring the specimen thickness
30、 and width.7.2 Caliper, suitable for reading to 0.025 mm (0.001 in.)accuracy for measuring the specimen length and instrumentclamping distance.7.3 Dynamic Mechanical Analyzer (DMA), with oven ca-pable of heating to above the glass transition temperature andof controlling the heating rate to the spec
31、ified value.8. Sampling and Test Specimens8.1 Two specimens shall be tested for each sample. If thetesting is part of a designed experiment, other samplingtechniques may be used if described in the test plan.8.2 Consult the instrument manufacturers manual for speci-men size. A span-to-thickness rati
32、o greater than ten is recom-mended. Specimen absolute size is not fixed by this method asvarious dynamic mechanical analyzers require different sizes.Depending on the analyzer, typical specimen size can rangefrom 56 6 4126 1 2.0 6 0.5 mm (2.21 6 0.16 0.476 0.04 0.08 6 0.02 in.) (L WT)to226 136 11.0
33、6 0.5 mm (0.9 6 0.04 0.12 6 0.04 0.04 6 0.02 in.).8.3 One of the major fiber directions in the specimen shallbe oriented along the length axis of the specimen. It is standardthat one of the major fiber directions shall be parallel to thelength of the specimen, and specimens containing only off-axisp
34、lies shall not be used. Any deviations from the standardorientation shall be reported and the test results noted asnon-standard.8.4 The specimen surfaces shall be flat, clean, straight, anddry to prevent slippage in the grips and mitigate any effects dueto moisture. Opposite surfaces must be essenti
35、ally parallel andintersecting surfaces perpendicular.Tolerances in thickness andwidth must be better than 62%.D7028 07 (2015)28.5 The selected sample shall be taken from a representativeportion of the laminate. Laminate edges or other irregularitiescreated in the laminate by mold or bagging techniqu
36、es shouldbe avoided.9. Calibration9.1 The DMA equipment shall be calibrated in accordancewith Test Method E1867 for temperature signals and inaccordance with the equipment manufacturers recommenda-tion for the storage modulus. The equipment must be calibratedin the same loading mode as will be used
37、for testing, either dualcantilever or three-point bending. The temperature calibrationpoints must span the DMA Tg result.10. Conditioning10.1 Moisture has significant effect on DMATg. Therefore,it is recommended that the test specimens should be weighedbefore and after DMA Tg testing to quantify the
38、 moisturechange in the specimen resulting from the DMA Tg test.10.2 Dry SpecimensTo minimize the presence of moisturein the specimens, dry specimens must be conditioned prior totesting by using either of the following techniques:10.2.1 Dry the specimens in an oven in accordance withTest Method D5229
39、/D5229M, Procedure D, then stored untiltest in a desiccator or sealed MIL-PRF-1314(or equivalent)aluminized bag, or10.2.2 Store the material in a desiccator or sealed alumi-nized bag immediately after material curing (lamination),where the material shall remain except for the minimum timerequired fo
40、r removal during specimen preparation and testing.The maximum time between cure (lamination) and testing shallbe 30 days, after which, prior to testing, specimens shall beoven-dried in accordance with 10.2.1.10.3 Wet SpecimensCondition in accordance with TestMethod D5229/D5229M, Procedure B. The con
41、ditioned speci-mens shall be tested within 30 minutes after removal from theconditioning chamber, or stored in sealed MIL-PRF-131 (orequivalent) aluminized bag until test.11. Procedure11.1 Test SpecimenMeasure the specimen thickness andwidth to 0.025 mm (0.001 in.) and record. Measure thespecimen le
42、ngth to 0.025 mm (0.001 in.) and record. Weigh thespecimen to the nearest milligram (0.001 g) and record.11.2 Specimen InstallationInstall the specimen in theDMA test equipment oven based upon clamping method to beemployed.11.3 Positioning of SpecimenFollow the manufacturersprocedure for positioning
43、 the specimen in the clamps.Generally, the specimen should be centered between the clampfaces and be parallel to the base of the instrument. Mount thespecimen in dual cantilever mode or three-point bending mode.11.4 Heating RateThe standard heating rate is 5 6 1C/min (9 6 2F/min). The same heating r
44、ate shall be used for allsamples whose results are to be compared. Any deviationsfrom this heating rate shall be noted in the report and the resultshall be reported as non-standard.11.5 FrequencyThe standard frequency to be used in thisstandard is 1 Hz, and the instrument should be operated inconsta
45、nt strain mode.11.6 Strain AmplitudeThe maximum strain amplitudeshould be kept within the linear viscoelastic range of thematerial. Strains of less than 0.1 % are standard.11.7 Temperature RangeProgram the run to begin at roomtemperature or a temperature at least 50C (90F) below theestimated DMA Tg
46、and to end at a temperature at least 50C(90F) above DMATg, but below decomposition temperature.11.8 Purge Gas Flow RateFollow the manufacturersmanual or recommendations to set the purge gas flow rate. Fivelitres/minute (0.2 CFM) is a typical purge gas flow rate setting.For some types of dynamic mech
47、anical analyzers, a purge gasflow setting is not required.11.9 Thermocouple PositioningFollow the manufacturersmanual or recommendations to position the thermocouple.Typically the thermocouple should be as close to the sample aspossible.11.10 TestConduct DMA Tg measurements using theinstrument setti
48、ngs specified and record the load and displace-ment data as a function of temperature. Allow the oven to coolbefore removing the specimen. Weigh the specimen after thetest to the nearest milligram (0.001 g) after the removal fromthe oven and record.11.11 Specimen ExaminationExamine the specimen afte
49、rthe test and inspect for any visual anomalies (that is,delamination, blisters, cracks, etc.). Record any visual anoma-lies observed.12. Interpretation of Results12.1 Glass Transition Temperature (DMA Tg)Plot thelogarithm of storage modulus (E) and linear tangent delta (tan) versus the linear temperature (Fig. 1). During the glasstransition, the storage modulus of the composite material issignificantly reduced. The DMA Tg is determined to be theintersection of two tangent lines from the storage modulus bythis test method. The
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