1、Designation: D7905/D7905M 14Standard Test Method forDetermination of the Mode II Interlaminar FractureToughness of Unidirectional Fiber-Reinforced PolymerMatrix Composites1This standard is issued under the fixed designation D7905/D7905M; the number immediately following the designation indicates the
2、year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the determination of the
3、mode II interlaminar fracture toughness, GIIc, of unidirectionalfiber-reinforced polymer matrix composite laminates undermode II shear loading using the end-notched flexure (ENF) test(Fig. 1).1.2 This method is limited to use with composites consistingof unidirectional carbon-fiber- and glass-fiber-
4、reinforced lami-nates. This limited scope reflects the experience gained inround robin testing. This test method may prove useful forother types and classes of composite materials; however,certain interferences have been noted (see Section 6).1.3 The values stated in either SI units or inch-pound un
5、itsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3.1 Within the text the inch-pound units a
6、re shown inbrackets.1.4 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
7、 use.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD2584 Test Method for Ignition Loss of Cured ReinforcedResinsD2734 Test Methods for Void Content of Reinforced Plasti
8、csD3171 Test Methods for Constituent Content of CompositeMaterialsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for MoistureAbsorption Prop-erties and Equilibrium Conditioning of Polymer MatrixComposite MaterialsD5687/D5687M Guide for Preparation of Flat CompositePanels with Proc
9、essing Guidelines for Specimen Prepara-tionD7264/D7264M Test Method for Flexural Properties ofPolymer Matrix Composite MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE18 Test Methods for Rockwell Hardness of Metallic Ma-terials
10、E122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaborato
11、ry Study toDetermine the Precision of a Test MethodE1309 Guide for Identification of Fiber-ReinforcedPolymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fillers, an
12、d CoreMaterials in Computerized Material Property Databases3. Terminology3.1 Terminology D3878 defines terms relating to high-modulous fibers and their composites. Terminology D883defines terms relating to plastics. Terminology E6 defines termsrelating to mechanical testing. Terminology E456 and Pra
13、cticeE177 define terms relating to statistics. In the event of conflictbetween terms, Terminology D3878 shall have precendenceover the other terminology standards.1This test method is under the jurisdiction of ASTM Committee D30 onComposite Materials and is the direct responsibility of Subcommittee
14、D30.06 onInterlaminar Properties.Current edition approved Oct. 1, 2014. Published November 2014. DOI:10.1520/D7905_D7905M-142For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
15、efer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1NOTE 1If the term represents a physical quantity, its analyticaldimensions are stated immediately following the term (or le
16、tter symbol) infundamental dimension form, using the following ASTM standard sym-bology for fundamental dimensions, shown within square brackets: Mfor mass, L for length, T for time, u for thermodynamic temperature,and nd for non-dimensional quantities. Use of these symbols is restrictedto analytica
17、l dimensions when used with square brackets, as the symbolsmay have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 Compliance Calibration (CC) Methodthe method ofdata reduction where the relationship between specimen com-pliance T2/M and del
18、amination length L is determined priorto testing by measuring specimen compliance T2/M at mul-tiple simulated delamination lengths.3.2.2 Mode II Interlaminar Fracture Toughness, GIIcM/T2the critical value of strain energy release rate, G,M/T2for delamination growth L due to an in-plane shear forceM/
19、T2 or displacement L oriented perpendicular to thedelamination front.3.2.3 Non-precracked (NPC) toughness M/T2an inter-laminar fracture toughness value that is determined from thepreimplanted insert.3.2.4 Precracked (PC) Toughness M/T2an interlaminarfracture toughness value that is determined after
20、the delamina-tion has been advanced from the preimplanted insert.3.2.5 Strain Energy Release Rate, G M/T2the loss ofstrain energy, dU ML2/T2, in the test specimen per unit ofspecimen width L for an infinitesimal increase in delamina-tion length, da L, for a delamination growing self-similarlyunder c
21、onstant displacement L. In mathematical form,G 521BdUda(1)where:U = total elastic strain energy in the specimen;a = delamination length; andB = specimen width.3.3 Symbols:3.3.1 Aintercept of the linear fit of compliance versuscrack length cubed data3.3.2 adelamination length3.3.3 aiinsert length in
22、the trimmed specimen3.3.4 ajthe jthcrack length used during compliance cali-bration (j = 1,2)3.3.5 aodelamination length used in fracture test3.3.6 acalccrack length calculated from an unloadingcurve after the NPC test3.3.7 aPCactual crack length used during the PC test3.3.8 avisvisually determined
23、crack length after the NPCtest3.3.9 Bspecimen width3.3.10 Cspecimen compliance3.3.11 C0specimen compliance during load-up of thefracture test (See Figure 6 in 13.1)3.3.12 Cuspecimen compliance from unloading after thenon-precracked test3.3.13 displacement of loading roller during testing per-pendicu
24、lar to the plane of the specimen (Fig. 1)3.3.14 E1fflexural modulus of the specimen3.3.15 Gtotal strain energy release rate3.3.16 GIICmode II interlaminar fracture toughness3.3.17 GQcandidate mode II interlaminar fracture tough-ness3.3.18 %GQpeak percentage of GQachieved during com-pliance calibrati
25、on3.3.19 hspecimen half-thickness (Fig. 2)3.3.20 Lspecimen half-span (Fig. 2)3.3.21 Lcdistance from the center of the support roller atthe cracked end of the specimen to the cracked end of thespecimen (Fig. 2)3.3.22 Ludistance from the center of the support roller atthe uncracked end of the specimen
26、 to the uncracked end of thespecimen (Fig. 2)3.3.23 mslope of the linear fit of compliance versus cracklength cubed data3.3.24 Pforce applied to center loading roller and perpen-dicular to the plane of the specimen (Fig. 1)3.3.25 Pccritical force for mode II fracture3.3.26 Pjthe compliance calibrati
27、on force used at cracklength aj3.3.27 PMaxmaximum value of force on the force-displacement curve3.3.28 r1radius of the loading roller (Fig. 2)FIG. 1 ENF Test Fixture and Specimen NomenclatureD7905/D7905M 1423.3.29 r2radius of the support rollers (Fig. 2)3.3.30 r2correlation coefficient of linear fit
28、 of complianceversus crack length cubed3.3.31 sMaximum measured difference in crack lengthalong the delamination front of the precrack3.3.32 Utotal elastic strain energy in the specimen4. Summary of Test Method4.1 The ENF specimen shown in Fig. 1 consists of arectangular, uniform thickness, unidirec
29、tional laminated com-posite specimen containing a non-adhesive insert at the mid-plane that serves as a delamination initiator. Forces are appliedto the specimen through an ENF fixture under displacementcontrolled loading.4.2 Delamination growth is not stable in the ENF test. Amethod is presented so
30、 that the initiation values of the mode IIinterlaminar fracture toughness are obtained from the preim-planted insert as well as from a precrack.4.3 A record of the applied force versus center rollerdisplacement is to be obtained using an x-y recorder orequivalent real-time plotting device, or else i
31、t may be obtainedand stored digitally. The mode II interlaminar fracturetoughness, GIIc, is obtained using the compliance calibration(CC) method. This is the only acceptable method of datareduction for this test (1).34.4 This standard recommends that static mode II precrack-ing is performed and a re
32、commended method is described.Other precracking methods may be used provided that a recordof the shape of the precracked delamination front is obtainedprior to the PC test. Precracking methods that typically leavecrack front markings for post-test evaluation of these valuesinclude mode I and fatigue
33、 mode II.5. Significance and Use5.1 Susceptibility to delamination is one of the major designconcerns for many advanced laminated composite structures.Knowledge of a laminated composite materials resistance tointerlaminar fracture is useful for product development andmaterial selection. Furthermore,
34、 a measurement of the mode IIinterlaminar fracture toughness that is independent of specimengeometry or method of force introduction is useful for estab-lishing design allowables used in damage tolerance analyses ofcomposite structures. Knowledge of both the non-precrackedand precracked toughnesses
35、allows the appropriate value to beused for the application of interest.5.2 This test method can serve the following purposes:5.2.1 To establish quantitatively the effect of fiber surfacetreatment, local variations in fiber volume fraction, and pro-cessing and environmental variables on GIIcof a part
36、icularcomposite material;5.2.2 To compare quantitatively the relative values of GIIcfor composite materials with different constituents;5.2.3 To compare quantitatively the values of GIIcobtainedfrom different batches of a specific composite material, forexample, to use as a material screening criter
37、ion or to developa design allowable; and5.2.4 To develop delamination failure criteria for compositedamage tolerance and durability analyses.6. Interferences6.1 Linear elastic behavior is assumed in the calculation ofG used in this method. This assumption is valid when the zoneof damage or nonlinear
38、 deformation at the delamination front,or both, is small relative to the smallest specimen dimension,which is typically the specimens thickness for the ENF test.6.2 GIIcis obtained for both non-precracked and precrackedspecimens based on the maximum load point. GIIcbased on thenonlinear load point o
39、r other measures, such as a complianceoffset, may also be obtained if desired. However, definitions ofthis type have not been related to any specific physicaloccurrences in the ENF test.6.3 The three loading noses in the ENF test fixture may befixed, rotatable, or rolling. Fixed loading noses or pin
40、s sup-ported in a v-groove are recommended, and loading noses ofthis type were used in the interlaboratory test program that wasconducted in support of this standard. The type of supports thatare used is to be reported as described in Section 14. Theloading noses should uniformly contact the specime
41、n across itswidth. Lack of uniform contact can affect results, most com-monly due to non-uniform loading across the width of the3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.FIG. 2 ENF Specimen, Fixture, and DimensionsD7905/D7905M 143specimen. Formulas
42、 used in this standard assume a uniformline loading across the entire specimen width at the loadingnose and at the specimen supports; deviations from this type ofloading are beyond the scope of this standard.6.4 There is an inherent error associated with the use of Eq7 to obtain the calculated crack
43、 length, and it is not expectedthat the calculated crack length will exactly correspond to thetrue length of the precrack. However, since toughness iscomputed by CC, it has been shown (2) that this error in cracklength will not affect the accuracy of the computed toughnessprovided that the recommend
44、ed approach is followed.6.5 For very tough composites, large deformations at theonset of delamination growth could affect the accuracy of theENF test. For typical unidirectional glass and carbon rein-forced unidirectional composites, it has been shown (1) that thecombined effects of friction and geo
45、metric nonlinearities willaffect the accuracy of the recommended approach by approxi-mately 2.5% or less for glass-reinforced polymer matrixcomposites with toughnesses up to 1.45 kJ/m28.28 in.-lbf/in.2 and by 3% or less for polymer matrix composites withcarbon reinforcement with toughnesses up to 2.
46、10 kJ/m212.0 in.-lbf in.2. Testing of composites that exhibit greatertoughness may produce somewhat larger errors. One means ofchecking for nonlinearities is to examine the difference be-tween the nonlinear point and the maximum load point. If thisis found to be greater than approximately 5% of PMax
47、, furtherinvestigations may be in order to determine the reason for thediscrepancy, for example, material nonlinearity, geometricnonlinearity, or subcritical crack advance. The results of thisinvestigation may be used to choose a new test geometry, forexample to eliminate geometric nonlinearities, o
48、r to choose adefinition of critical load that is different from PMax, forexample in the case of subcritical crack advance.6.6 A precracking method that only produces a short crack“jump,” e.g., by positioning a specimen with a crack tip closeto the center loading roller, may produce precracked toughn
49、essvalues that are significantly higher than those that will beproduced for a long crack jump following the recommendedprocedure (2,3).6.7 The toughness measured using this method is sensitiveto reinforcement volume and void content. Consequently, thetest results may reflect manufacturing quality as much asmaterial properties.6.8 Number of Points for CCThe use of a three-point CCwas studied extensively in References (2,4) and resulted in therecommended approach (subsection 11.9). However, equiva
