1、Designation: D7750 12Standard Test Method forCure Behavior of Thermosetting Resins by DynamicMechanical Procedures using an Encapsulated SpecimenRheometer1This standard is issued under the fixed designation D7750; the number immediately following the designation indicates the year oforiginal adoptio
2、n 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 method covers the use of dynamic mechanicalinstrumentation for determi
3、nation and reporting of the thermaladvancement of cure behavior of thermosetting resin on aninert filler or fiber in a laboratory. It may also be used fordetermining the cure properties of filled resins and resinswithout reinforcements. These encapsulated specimens aredeformed in torsional shear usi
4、ng dynamic mechanical meth-ods.1.2 This method is intended to provide means for determin-ing the cure behavior of thermosetting resins on fibers over arange of temperatures from room temperature to 250C byforced-constant amplitude techniques (in accordance withPractice D4065). Plots of complex modul
5、us, complexviscosity, and damping ratio or tan delta as a function of timeor temperature, or both, quantify the thermal advancement orcure characteristics of a resin or a resin on fiber.1.3 Test data obtained by this method is relevant andappropriate for optimizing cure cycles.1.4 The values stated
6、in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4.1 ExceptionThe fahrenheit temperature measurementin 10.1 is provided for information only and is not consideredstandard.1.5 This standard does not purport to address all of thesafety concerns, i
7、f 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:2D3878 Terminology for Composite MaterialsD4000
8、 Classification System for Specifying Plastic Materi-alsD4065 Practice for Plastics: Dynamic Mechanical Proper-ties: Determination and Report of ProceduresD4092 Terminology for Plastics: Dynamic MechanicalPropertiesD4473 Test Method for Plastics: Dynamic Mechanical Prop-erties: Cure BehaviorD6507 Pr
9、actice for Fiber Reinforcement Orientation Codesfor Composite MaterialsD7028 Test Method for Glass Transition Temperature (DMATg) of Polymer Matrix Composites by Dynamic Mechani-cal Analysis (DMA)E380 Practice for Use of the International System of Units(SI) (the Modernized Metric System) (Withdrawn
10、 1997)33. Terminology3.1 Definitions: For most definitions applicable to thismethod refer to Terminology D4092.3.2 Definitions of Terms Specific to This Standard:3.2.1 Encapsulated Sample Parallel Plate RheometerDynamic Mechanical Analyzer apparatus that holds the speci-men under pressure within a c
11、onfined cavity. The apparatus isdesigned to contain the resin within the specimen throughoutthe progress of the cure.4. Summary of Test Method4.1 A small circular specimen is assembled from uncuredthermoset resin materials that correspond to a representation of1This test method is under the jurisdic
12、tion of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.03 onConstituent/Precursor Properties.Current edition approved Nov. 15, 2012. Published January 2013. DOI: 10.1520/D7750-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
13、ntact 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 International, 100 Barr Harbor Drive
14、, PO Box C700, West Conshohocken, PA 19428-2959. United States1a composite part. This specimen is placed in mechanicaloscillation at a fixed frequency at either isothermal conditions,a linear temperature increase or a time-temperature relationsimulating a processing condition. The lower plate oscill
15、atesand transmits torque from the lower plate through the sampleinto the upper plate. The resulting torque measured at the upperplate is converted to shear modulus using equations thatcompensate for the shape and size of the sample. The shearmodulus is separated into a component that is in phase wit
16、h theapplied strain or elastic shear modulus and a component that is90 out of phase with the applied strain or loss shear modulus.The elastic and loss modulus of the specimen are measured asa function of time. During cure, the elastic shear modulus willinitially decrease as the temperature is increa
17、sed due to adecrease in the viscosity of the resin in the sample. When cureoccurs in the sample, the elastic shear modulus increases.5. Significance and Use5.1 This method provides a simple means of characterizingthe cure behavior of a thermosetting resin specimen that is arepresentation of a compos
18、ite part. The diameter of thespecimen is approximately 38 mm and the thickness rangesfrom 2.6 to 3.2 mm. This corresponds to a sample volume ofapproximately 3 to 4 cm3. The data may be used for qualitycontrol, research and development, and verifying the curewithin processing equipment including auto
19、claves.5.2 Dynamic mechanical testing provides a sensitivemethod for determining cure characteristics by measuring theelastic and loss moduli as a function of temperature or time, orboth. Plots of cure behavior and tan delta of a material providegraphical representation indicative of cure behavior u
20、nder aspecified time-temperature profile. The presence of fiberswithin the resin may change the dynamic properties measuredwithin a material. However, it is still possible to comparedifferent resins with the same fiber structure and obtain therelative difference due to the resin cure properties.5.3
21、This method can be used to assess the following:5.3.1 Cure behavior, as well as changes as a function oftemperature or time, or both,5.3.2 Processing behavior, as well as changes as a functionof temperature or time, or both,5.3.3 The effects of processing treatments,5.3.4 Relative resin behavioral p
22、roperties, including curebehavior, damping and impact resistance,5.3.5 The effects of reinforcement on cure.5.3.6 The effects of materials used to bond the resin andreinforcement,5.3.7 The effect of formulation additives that might affectprocessability or performance.5.4 This provides a method to as
23、sess the cure properties ofa thermosetting resin containing woven fiber or other reinforc-ing materials.5.5 This method is valid for a wide range of oscillationfrequencies typically from 0.002 to 50 Hz.NOTE 1It is recommended that low-frequency test conditions, gener-ally 1 to 2 Hz, be used to gener
24、ate more definitive cure-behaviorinformation. Slower frequencies will miss important cure properties.Faster frequencies will reduce sensitivity to cure.6. Interferences6.1 Apparent discrepancies in results may arise when usingdifferent experimental conditions. These apparent differencesfrom results
25、observed in another study can usually be recon-ciled without changing the observed data, by reporting in full(as described in this method) the conditions under which thedata were obtained. One essential condition within this methodthat must be noted is the presence of pressure within thespecimen cha
26、mber which ensures good precision.6.2 In many cases, the specimens made with this methodwill be significantly smaller than the parts in production. It isessential that specimens be made from representative samplesof uncured material used to make parts. This will ensure thatthe data is representative
27、 of the part cure.6.3 The result is a response to the thermal advancement orcure behavior of the resin. The cure behavior is also influencedby the reinforcement and materials used to enhance the bondbetween the resin and reinforcement. The reinforcement can bea fiber or a filler.6.4 The data will re
28、present the cure of the system at themeasured temperature. Parts are often significantly thicker thanthe specimen. There may be a significant difference betweenthe temperature versus time profile on the inside and theoutside of those composite parts. Thermocouples can be usedto measure both temperat
29、ures during a cure process of a thickpart. The measured temperature versus time data can be used todefine temperature versus time profiles for dynamic curespecimens using the procedures of this standard. The resultscan be used to compare the cure response for the inside and theoutside of the composi
30、te part.7. Apparatus7.1 The function of the apparatus is to hold a resin specimenwith inert reinforcement, such as fibers, under pressure and yetprevent the escape of resin. Thereby, the fiber to resin ratio willremain constant throughout the test. The material acts as theelastic and dissipative ele
31、ment in a mechanically drivenoscillatory shear system. This dynamic mechanical instrumentoperates in torsional shear using one of the following modesfor measuring cure behavior:7.1.1 Forced, constant amplitude, fixed frequency,7.1.2 Forced, variable amplitude, fixed frequency.7.2 The apparatus shall
32、 consist of the following:7.2.1 Parallel plates with serrated or radial grooved sur-faces. The diameter of the dies shall be 40 6 2 mm. The depthof the grooves shall be limited to 1.0 mm or less to keep aconstant fiber to resin ratio.7.2.2 Encapsulated Specimen CavityThe specimen shallbe encapsulate
33、d by the two parallel plates and a series ofmechanical components at the outer plate diameter designed tocontain the specimen under pressure without loss of resin.These components shall include an O-ring inserted at the outerdiameter of the specimen (Fig. 1). The O-ring meets ASTMInternational size
34、No. 2-127.D7750 1227.2.3 Plate GapThe thickness of the sample shall rangefrom 2.6 to 3.2 mm. The calculation of the sample moduluswill include corrections to the actual sample thickness.7.2.4 Plate Closing MechanismThe system shall apply apressure of at least 4200 kPa to the sample to prevent slippa
35、ge.7.2.5 Plate Oscillating System (Strain Device)The plateoscillating system shall consist of a direct drive motor thatimparts a torsional oscillating movement to the lower plate inthe cavity plane. The movement shall produce a continuousoscillatory deformation (strain) on the specimen. The deforma-
36、tion (strain) shall be sinusoidal and shall be applied andreleased continuously as in a forced-vibration device (see Table1 of Practice D4065) to provide a continuous measurement ofmaterial state. The preferred amplitude ranges shall be from 60.005 to 6 0.060. The resulting strain at the nominalspec
37、imen thickness will range from 6 0.07 to 6 0.8 %.NOTE 2The preferred strain for measuring the cure properties ofthermoset resins is 6 0.7 %.7.2.6 DetectorsA device or devices for determining de-pendent and independent experimental parameters, such astorque, frequency, strain amplitude and temperatur
38、e. Tempera-ture shall be measurable with a precision of 6 0.3C at theouter diameter of the plate, frequency to 60.1 % and torque to6 0.001 Nm.7.2.7 Temperature ControllerAdevice for directly heatingand cooling the plates with the ability to control the tempera-ture of the plates. The temperature can
39、 increase in steps or alinear ramp or cool in steps or a linear ramp. Fig. 2 illustratesa typical time-temperature profile for measuring cure proper-ties. A temperature control system shall be sufficiently stable topermit measurement of plate temperature to within 6 0.3Cduring heating and 6 1C durin
40、g cooling. Fig. 2 also showsFIG. 1 Encapsulated specimen parallel plate rheometer plate sys-tem designed to keep a constant fiber to resin ratio during a test.NOTE 1There is often a discrepancy between the typical temperatureprogram and the actual temperature.FIG. 2 Typical temperature program to cu
41、re components and theactual temperature at the component.D7750 123that the temperature in the part often deviates from therecommended temperature profile. The apparatus shall processa specimen using either the recommended temperature profileor the actual temperature profile in the part depending on
42、thespecification of the test requestor. The report shall contain acomment indicating which type of temperature profile wasused.7.3 The system must have instrument compliance compen-sation to ensure a good measure for the final modulus valuesduring cure.8. Sampling and Test Specimens8.1 The neat resi
43、n or the resin with reinforcement should berepresentative of the polymeric material being tested.8.2 The recommended specimen diameter for this apparatusis 38 6 0.5 mm (Fig. 3) or a diameter recommended by theapparatus manufacturer. Several 38-mm disks of uncuredmaterial shall be laid up to produce
44、a specimen for testing. Thereinforcement type and lay-up shall be recorded in accordancewith the laminate orientation code of Practice D6507. Thenumber of disks required to produce a specimen will vary withthe type of fiber and fiber architecture. A good initial value forthe thickness before compres
45、sing the sample is 4 mm. The finalcured specimen should have a thickness of 2.6 to 3.2 mm aftera test is complete. The apparatus will often compress or reducethe initial thickness into the preferred range of a testedspecimen. The number of disks may vary with the resin andfiber present in a specimen
46、. The weight of the specimen can beused in place of the thickness as an alternate method to ensurethat the final specimen has the preferred thickness at the end ofa test. The weight will have to be determined for eachresin/fiber combination. In all cases, equal weight or thicknessshould be used when
47、 comparisons are made.8.3 An elastomeric O-ring shall be placed at the outerdiameter of the specimen to help prevent the loss of resinduring a test. The specimen shall also be placed between twosheets of release film to eliminate or reduce clean up after atest. The film prevents the contamination of
48、 the plate surfacewith resins or other materials that can diffuse out of thespecimen. The film must be capable of the applied temperatureprofile. Different films can be used at different temperatureranges.8.4 Low viscosity neat resins can be measured under pres-sure either with or without reinforcem
49、ent.8.5 A valid result is obtained when the elastomeric O-ringremains intact at the outer diameter of the specimen and thecured sample thickness is within the acceptable range. Also,any shape imparted by the plate surface such as grooves mustmatch the corresponding shape on the cured specimen.9. Calibration and Standardization9.1 Torque calibration shall be performed in accordancewith apparatus manufacturers recommendations.9.1.1 Calibrate the torque measurement system of the appa-ratus whenever the plate seals are changed.9.1.2 Torque Calibration ProcedureA refer
