1、Designation: D 7028 071Standard Test Method forGlass Transition Temperature (DMA Tg) of Polymer MatrixComposites by Dynamic Mechanical Analysis (DMA)1This standard is issued under the fixed designation D 7028; the number immediately following the designation indicates the year oforiginal adoption or
2、, 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.1NOTEReference to a research report was added and figures corrected in August 2008.1. Scope
3、1.1 This test method covers the procedure for the determi-nation of the dry or wet (moisture conditioned) glass transitiontemperature (Tg) of polymer matrix composites containinghigh-modulus, 20 GPa ( 3 3 106psi), fibers using a dynamicmechanical analyzer (DMA) under flexural oscillation mode,which
4、is a specific subset of the Dynamic Mechanical Analysis(DMA) method.1.2 The 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 a
5、s“DMA Tg”) may not be the same as that reported by othermeasurement techniques 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 devia
6、tions from this test method to achievemeaningful results.1.4 The values stated 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 con
7、cerns, 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:2D 3878 Terminology for Composite Mater
8、ialsD 4065 Practice for Plastics: Dynamic Mechanical Proper-ties: Determination and Report of ProceduresD 4092 Terminology for Plastics: Dynamic MechanicalPropertiesD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite MaterialsE 177 P
9、ractice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE 1434 Guide for Recording Mechanical
10、Test Data of Fiber-Reinforced Composite Materials in DatabasesE 1471 Guide for Identification of Fibers, Fillers, and CoreMaterials in Computerized Material Property DatabasesE 1640 Test Method for Assignment of the Glass TransitionTemperature By Dynamic Mechanical AnalysisE 1867 Test Method for Tem
11、perature Calibration of Dy-namic Mechanical Analyzers3. Terminology3.1 DefinitionsTerminology D 3878 defines terms relatingto polymer matrix composites. Terminology D 4092 definesterms relating to dynamic mechanical property measurementson polymeric materials.3.2 Symbols:E = storage modulusE” = loss
12、 modulustan d = E”/E = tangent deltaDMA 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 curve4. Summary of Test Method4.1 Aflat rectangular strip of lami
13、nate 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 same1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.04 onLamina and L
14、aminate Test Methods.Current edition approved Dec. 15, 2007. Published January 2008.2For 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 p
15、age onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.loading frequency and heating rate is used for both dry and wetspecimens (moisture conditioned) to allow for comparison.The temperature at which a significant dro
16、p in storage modulus(E) begins is assigned as the glass transition temperature(DMA Tg). The peak temperature of the tangent delta curve(Tt) is identified along with DMATg for comparison purposes.5. Significance and Use5.1 This test method is designed to determine the glasstransition temperature of c
17、ontinuous fiber reinforced polymercomposites using the DMA method. The DMA Tg value isfrequently used to indicate the upper use temperature ofcomposite materials, as well as for quality control of compositematerials.6. Interferences6.1 The standard testing machine shall be of the DynamicMechanical A
18、nalysis (DMA) type of instrument that operateswith forced oscillation and applies a flexural loading mode(either three-point bend or dual cantilever) to the test specimen.Refer to Practice D 4065 for a summary of various other DMApractices. Other loading modes (such as tensile, torsion orshear) may
19、produce different test results. If another equipmenttype or loading mode is used the non-standard approach shallbe described in the report and the test 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 frequ
20、encyproduces a higher DMA Tg value than this standard, while useof the resonance mode will yield a different DMA Tg that maybe either higher or lower than the standard. If a non-standardfrequency, or the resonance mode, is used, the non-standardapproach shall be described in the report and the test
21、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 glasstransition temperature result; the standard heating rate is thebest available compromise for comparing DMA Tg results ofdry and wet laminates. If a
22、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 rate of 5C/minrepresents a compromise between various issues related to Tg measure-ment precision and bias. It is widely known that heat transfer lim
23、itationsare more pronounced in DMA apparatus compared to other thermalanalysis techniques, such as differential scanning calorimetry (DSC) andthermomechanical analysis (TMA). For greatest precision, it has beenrecommended that heating rates be 2C/min or less. Test Method E 1640specifies a heating ra
24、te of 1C/min. However, in many cases 5C/min isrecommended as a compromise between Tg measurement accuracy andtest method convenience, especially for wet laminate measurements, sincethe slower heating rate will cause specimen drying that will itself bias theresults.6.4 Purge gas type and flow rate an
25、d the position of thethermocouple can affect the DMA Tg test result and shall benoted and reported. The same conditions shall be used for bothcalibration and testing runs. Instrumentation manufacturerrecommendations should be followed.6.5 It is standard in this test method that one of the majorfiber
26、 directions shall be parallel to the length of the specimen.The span-to-depth ratio, ply orientation, and ply stackingsequence of a specimen with respect to the testing fixture havea profound effect on the DMA Tg result. A meaningfulcomparison of data requires that the specimen configuration bethe s
27、ame. A non-standard specimen configuration shall bedescribed in the report and the result recorded as non-standard.6.6 The standard definition in this test method for DMA Tgis based on intersecting two tangent lines from a semi-logarithmic plot of the storage modulus versus temperature.Other Tgdefin
28、itions typically produce different test results. Forexample, a linear plot scale will result in a lower value of DMATg. A non-standard DMA Tg definition shall be described inthe report and the result recorded as non-standard. For com-parison purposes the peak temperature of the tangent deltacurve (T
29、t) 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 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 D
30、ynamic Mechanical Analyzer (DMA), with oven ca-pable of heating to above the glass transition temperature andof controlling the heating rate to the specified value.8. Sampling and Test Specimens8.1 Two specimens shall be tested for each sample. If thetesting is part of a designed experiment, other s
31、amplingtechniques may be used if described in the test plan.8.2 Consult the instrument manufacturers manual for speci-men size. A span-to-thickness ratio greater than ten is recom-mended. Specimen absolute size is not fixed by this method asvarious dynamic mechanical analyzers require different size
32、s.Depending on the analyzer, typical specimen size can rangefrom 56 6 4 3 12 6 1 3 2.0 6 0.5 mm (2.21 6 0.16 3 0.476 0.04 3 0.08 6 0.02 in.) (L 3 W 3 T) to 22 6 1 3 3 6 13 1.0 6 0.5 mm (0.9 6 0.04 3 0.12 6 0.04 3 0.04 6 0.02in.).8.3 One of the major fiber directions in the specimen shallbe oriented
33、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-axisplies shall not be used. Any deviations from the standardorientation shall be reported and the test results noted asnon-st
34、andard.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 essentially parallel andintersecting surfaces perpendicular. Tolerances in thickness andwidth must be better than 62%.8.5 The se
35、lected sample shall be taken from a representativeportion of the laminate. Laminate edges or other irregularitiescreated in the laminate by mold or bagging techniques shouldbe avoided.9. Calibration9.1 The DMA equipment shall be calibrated in accordancewith Test Method E 1867 for temperature signals
36、 and inD70280712accordance with the equipment manufacturers recommenda-tion for the storage modulus. The equipment must be calibratedin the same loading mode as will be used for testing, either dualcantilever or three-point bending. The temperature calibrationpoints must span the DMA Tg result.10. C
37、onditioning10.1 Moisture has significant effect on DMA Tg. Therefore,it is recommended that the test specimens should be weighedbefore and after DMA Tg testing to quantify the moisturechange in the specimen resulting from the DMA Tg test.10.2 Dry SpecimensTo minimize the presence of moisturein the s
38、pecimens, 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 D 5229/D 5229M, Procedure D, then stored untiltest in a desiccator or sealed MIL-PRF-1313(or equivalent)aluminized bag, or10.2.2 S
39、tore 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 for removal during specimen preparation and testing.The maximum time between cure (lamination) and testing shallbe 30 days, a
40、fter which, prior to testing, specimens shall beoven-dried in accordance with 10.2.1.10.3 Wet SpecimensCondition in accordance with TestMethod D 5229/D 5229M, Procedure B. The conditionedspecimens shall be tested within 30 minutes after removal fromthe conditioning chamber, or stored in sealed MIL-P
41、RF-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 length to 0.025 mm (0.001 in.) and record. Weigh thespecimen to the nearest milligram (0.001 g) and record.11.2 Specimen Inst
42、allationInstall the specimen in theDMA test equipment oven based upon clamping method to beemployed.11.3 Positioning of SpecimenFollow the manufacturersprocedure for positioning the specimen in the clamps. Gener-ally, the specimen should be centered between the clamp facesand be parallel to the base
43、 of the instrument. Mount thespecimen in dual cantilever mode or three-point bending mode.11.4 Heating RateThe standard heating rate is 5 61C/min (9 6 2F/min). The same heating rate shall be usedfor all samples whose results are to be compared. Anydeviations from this heating rate shall be noted in
44、the reportand the result shall be reported as non-standard.11.5 FrequencyThe standard frequency to be used in thisstandard is 1 Hz, and the instrument should be operated inconstant strain mode.11.6 Strain AmplitudeThe maximum strain amplitudeshould be kept within the linear viscoelastic range of the
45、material. 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 and to end at a temperature at least 50C(90F) above DMA Tg, but below decomposition temperature.11.8 Purge Gas Flow RateFo
46、llow 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 mechanical analyzers, a purge gasflow setting is not required.11.9 Thermocouple PositioningFollow the manufactur-ers manual o
47、r recommendations to position the thermocouple.Typically the thermocouple should be as close to the sample aspossible.11.10 TestConduct DMA Tg measurements using theinstrument settings specified and record the load and displace-ment data as a function of temperature. Allow the oven to coolbefore rem
48、oving 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 afterthe test and inspect for any visual anomalies (that is, delami-nation, blisters, cracks, etc.). Record any visual anom
49、aliesobserved.12. Interpretation of Results12.1 Glass Transition Temperature (DMA Tg)Plot thelogarithm of storage modulus (E) and linear tangent delta (tand) 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 first tangent line (Line A, Fig. 1)isselected at a temperature before the transition. This tempera-ture is designated as TA. The second
