1、Designation: D7750 12 (Reapproved 2017)Standard 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
2、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.1. Scope1.1 This method covers the use of dynamic mechanicalinstrumen
3、tation for determination 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 t
4、orsional shear using 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). Plot
5、s of complex modulus, 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
6、The values stated 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 the
7、safety 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.1.6 This international standard was developed in accor-dance with inter
8、nationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3878
9、 Terminology for Composite MaterialsD4000 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 Mech
10、anical Prop-erties: Cure BehaviorD6507 Practice 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)
11、(the Modernized Metric System) (Withdrawn 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 hold
12、s the speci-men under pressure within a confined cavity. The apparatus isdesigned to contain the resin within the specimen throughoutthe progress of the cure.1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee D30.0
13、3 onConstituent/Precursor Properties.Current edition approved Aug. 1, 2017. Published September 2017. Originallyapproved in 2012. Last previous edition approved as D775012. DOI: 10.1520/D7750-12R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
14、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, PO Box C700, West Conshoho
15、cken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organi
16、zation Technical Barriers to Trade (TBT) Committee.14. Summary of Test Method4.1 A small circular specimen is assembled from uncuredthermoset resin materials that correspond to a representation ofa composite part. This specimen is placed in mechanicaloscillation at a fixed frequency at either isothe
17、rmal conditions,a linear temperature increase or a time-temperature relationsimulating a processing condition. The lower plate oscillatesand transmits torque from the lower plate through the sampleinto the upper plate. The resulting torque measured at the upperplate is converted to shear modulus usi
18、ng equations thatcompensate for the shape and size of the sample. The shearmodulus is separated into a component that is in phase with 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 s
19、pecimen are measured asa function of time. During cure, the elastic shear modulus willinitially decrease as the temperature is increased 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 me
20、thod provides a simple means of characterizingthe cure behavior of a thermosetting resin specimen that is arepresentation of a composite 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
21、. The data may be used for qualitycontrol, research and development, and verifying the curewithin processing equipment including autoclaves.5.2 Dynamic mechanical testing provides a sensitivemethod for determining cure characteristics by measuring theelastic and loss moduli as a function of temperat
22、ure or time, orboth. Plots of cure behavior and tan delta of a material providegraphical representation indicative of cure behavior under aspecified time-temperature profile. The presence of fiberswithin the resin may change the dynamic properties measuredwithin a material. However, it is still poss
23、ible to comparedifferent resins with the same fiber structure and obtain therelative difference due to the resin cure properties.5.3 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
24、 as changes as a functionof temperature or time, or both,5.3.3 The effects of processing treatments,5.3.4 Relative resin behavioral properties, 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 andre
25、inforcement,5.3.7 The effect of formulation additives that might affectprocessability or performance.5.4 This provides a method to assess 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 oscillationfrequen
26、cies 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 generate more definitive cure-behaviorinformation. Slower frequencies will miss important cure properties.Faster frequencies will reduce sensitivity to cure.6. Interference
27、s6.1 Apparent discrepancies in results may arise when usingdifferent experimental conditions. These apparent differencesfrom results 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 t
28、hedata were obtained. One essential condition within this methodthat must be noted is the presence of pressure within thespecimen chamber 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
29、 specimens be made from representative samplesof uncured material used to make parts. This will ensure thatthe data is representative 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 ma
30、terials used to enhance the bondbetween the resin and reinforcement. The reinforcement can bea fiber or a filler.6.4 The data will represent the cure of the system at themeasured temperature. Parts are often significantly thicker thanthe specimen. There may be a significant difference betweenthe tem
31、perature versus time profile on the inside and theoutside of those composite parts. Thermocouples can be usedto measure both temperatures during a cure process of a thickpart. The measured temperature versus time data can be used todefine temperature versus time profiles for dynamic curespecimens us
32、ing the procedures of this standard. The resultscan be used to compare the cure response for the inside and theoutside of the composite 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
33、resin. Thereby, the fiber to resin ratio willremain constant throughout the test. The material acts as theelastic and dissipative element in a mechanically drivenoscillatory shear system. This dynamic mechanical instrumentoperates in torsional shear using one of the following modesfor measuring cure
34、 behavior:7.1.1 Forced, constant amplitude, fixed frequency,7.1.2 Forced, variable amplitude, fixed frequency.7.2 The apparatus shall 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 b
35、e limited to 1.0 mm or less to keep aconstant fiber to resin ratio.7.2.2 Encapsulated Specimen CavityThe specimen shallbe encapsulated 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.Thes
36、e components shall include an O-ring inserted at the outerD7750 12 (2017)2diameter of the specimen (Fig. 1). The O-ring meets ASTMInternational size No. 2-127.7.2.3 Plate GapThe thickness of the sample shall rangefrom 2.6 to 3.2 mm. The calculation of the sample moduluswill include corrections to th
37、e actual sample thickness.7.2.4 Plate Closing MechanismThe system shall apply apressure of at least 4200 kPa to the sample to prevent slippage.7.2.5 Plate Oscillating System (Strain Device)The plateoscillating system shall consist of a direct drive motor thatimparts a torsional oscillating movement
38、to the lower plate inthe cavity plane. The movement shall produce a continuousoscillatory deformation (strain) on the specimen. The deforma-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 cont
39、inuous measurement ofmaterial state. The preferred amplitude ranges shall be from 60.005 to 6 0.060. The resulting strain at the nominalspecimen 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 dev
40、ice or devices for determining de-pendent and independent experimental parameters, such astorque, frequency, strain amplitude and temperature. 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
41、ControllerAdevice for directly heatingand cooling the plates with the ability to control the tempera-ture of the plates. The temperature can 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 tem
42、perature control system shall be sufficiently stable topermit measurement of plate temperature to within 6 0.3Cduring heating and 6 1C during cooling. Fig. 2 also showsthat the temperature in the part often deviates from therecommended temperature profile. The apparatus shall processa specimen using
43、 either the recommended temperature profileor the actual temperature profile in the part depending on 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
44、a good measure for the final modulus valuesduring cure.8. Sampling and Test Specimens8.1 The neat resin 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 recomme
45、nded by theapparatus manufacturer. Several 38-mm disks of uncuredmaterial shall be laid up to produce 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 v
46、ary withthe type of fiber and fiber architecture. A good initial value forthe thickness before compressing 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
47、 range of a testedspecimen. The number of disks may vary with the resin andfiber present in a specimen. 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
48、determined for eachresin/fiber combination. In all cases, equal weight or thicknessshould be used when 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 twoshee
49、ts of release film to eliminate or reduce clean up after atest. The film prevents the contamination of 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 reinforcement.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 ra
