1、Designation: D5528 01 (Reapproved 2007)3D5528 13Standard Test Method forMode I Interlaminar Fracture Toughness of UnidirectionalFiber-Reinforced Polymer Matrix Composites1This standard is issued under the fixed designation D5528; the number immediately following the designation indicates the year of
2、original 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 NOTEAdded research report reference to Section 14 editorially in Marc
3、h 2008.2 NOTECorrected Eq. 3 in July 2008.3 NOTEEq. 3 was rewritten for clarification in August 2009.1. Scope1.1 This test method describes the determination of the opening Mode I interlaminar fracture toughness, GIc, of continuousfiber-reinforced composite materials using the double cantilever beam
4、 (DCB) specimen (Fig. 1).1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber and glass fiber tape laminateswith brittle and tough single-phase polymer matrices. This limited scope reflects the experience gained in round-robin testing. Thistest method may
5、prove useful for other types and classes of composite materials; however, certain interferences have been noted(see 6.5).1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.4 This standard may involve hazardous materials, o
6、perations, and equipment.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior
7、 to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD2651 Guide for Preparation of Metal Surfaces for Adhesive BondingD2734 Test Methods for Void Content of Reinforced PlasticsD3171 Test Methods for Constituent Content of Composite MaterialsD3878 Terminology for C
8、omposite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix CompositeMaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to E
9、stimate, With Specified Precision, the Average for a Characteristic of a Lot orProcessE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Tes
10、t MethodE1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in DatabasesE1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in DatabasesE1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material
11、Property Databases1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.06 on InterlaminarProperties.Current edition approved May 1, 2007Oct. 1, 2013. Published June 2007 November 2013. Originally approved in 19
12、94. Last previous edition approved in 20012009 asD5528 01.D5528 01(2007)3. DOI: 10.1520/D5528-01R07E03.10.1520/D5528-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer
13、to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all chang
14、es accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Uni
15、ted States13. Terminology3.1 Terminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883 defines termsrelating to plastics.Terminology E6 defines terms relating to mechanical testing.Terminology E456 and Practice E177 define termsrelating to statistics. In
16、the event of conflict between terms, Terminology D3878 shall have precedence over the other terminologystandards.NOTE 1If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbol) infundamental dimension form, using the following
17、ASTM standard symbology for fundamental dimensions, shown within square brackets: M for mass,L for length, T for time, u for thermodynamic temperature, and nd for non-dimensional quantities. Use of these symbols is restricted to analyticaldimensions when used with square brackets, as the symbols may
18、 have other definitions when used without the brackets.3.2 Definitions of Terms Specific to This Standard:3.2.1 crack opening mode (Mode I)fracture mode in which the delamination faces open away from each other.3.2.2 Mode I interlaminar fracture toughness, GIc M/T2the critical value of G for delamin
19、ation growth as a result of anopening load or displacement.3.2.3 strain energy release rate, GG M/T2the loss of energy, dU, in the test specimen per unit of specimen width for aninfinitesimal increase in delamination length, da, for a delamination growing self-similarly under a constant displacement
20、. Inmathematical form,G 521b dUda (1)where:U = total elastic energy in the test specimen,b = specimen width, anda = delamination length.3.3 Symbols:3.3.1 A1slope of plot of a/b versus C1/3.3.3.2 adelamination length.3.3.3 a0initial delamination length.3.3.4 bwidth of DCB specimen.3.3.5 Ccompliance,
21、/ P, of DCB specimen.3.3.6 CVcoefficient of variation, %.3.3.7 dadifferential increase in delamination length.3.3.8 dUdifferential increase in strain energy.3.3.9 E11modulus of elasticity in the fiber direction.3.3.10 E1fmodulus of elasticity in the fiber direction measured in flexure.3.3.11 Flarge
22、displacement correction factor.3.3.12 Gstrain energy release rate.3.3.13 GIcopening Mode I interlaminar fracture toughness.3.3.14 hthickness of DCB specimen.3.3.15 Llength of DCB specimen.3.3.16 Lhalf width of loading block.3.3.17 mnumber of plies in DCB specimen.3.3.18 Nloading block correction fac
23、tor.(a) with piano hinges (b) with loading blocksFIG. 1 Double Cantilever Beam SpecimenD5528 1323.3.19 NLpoint at which the load versus opening displacement curve becomes nonlinear.3.3.20 nslope of plot of Log C versus Log a.3.3.21 Papplied load.3.3.22 Pmaxmaximum applied load during DCB test.3.3.23
24、 SDstandard deviation.3.3.24 tdistance from loading block pin to center line of top specimen arm.3.3.25 Ustrain energy.3.3.26 VISpoint at which delamination is observed visually on specimen edge.3.3.27 Vffiber volume fraction, %.3.3.28 load point deflection.3.3.29 effective delamination extension to
25、 correct for rotation of DCB arms at delamination front.3.3.30 xincremental change in Log a.3.3.31 yincremental change in Log C.3.3 Symbols:A1 = slope of plot of a/b versus C1/3.a = delamination length.a0 = initial delamination length.b = width of DCB specimen.C = compliance, / P, of DCB specimen.CV
26、 = coefficient of variation, %.da = differential increase in delamination length.dU = differential increase in strain energy.E11 = modulus of elasticity in the fiber direction.E1f = modulus of elasticity in the fiber direction measured in flexure.F = large displacement correction factor.G = strain e
27、nergy release rate.GIc = opening Mode I interlaminar fracture toughness.h = thickness of DCB specimen.L = length of DCB specimen.L = half width of loading block.m = number of plies in DCB specimen.N =loading block correction factor.NL = point at which the load versus opening displacement curve becom
28、es nonlinear.n = slope of plot of Log C versus Log a.P = applied load.Pmax = maximum applied load during DCB test.SD = standard deviation.t = distance from loading block pin to center line of top specimen arm.U = strain energy.VIS = point at which delamination is observed visually on specimen edge.V
29、f = fiber volume fraction, %. = load point deflection. = effective delamination extension to correct for rotation of DCB arms at delamination front.x = incremental change in Log a.y = incremental change in Log C.4. Summary of Test Method4.1 The DCB shown in Fig. 1 consists of a rectangular, uniform
30、thickness, unidirectional laminated composite specimencontaining a nonadhesive insert on the midplane that serves as a delamination initiator. Opening forces are applied to the DCBspecimen by means of hinges (Fig. 1a) or loading blocks (Fig. 1b) bonded to one end of the specimen. The ends of the DCB
31、 areopened by controlling either the opening displacement or the crosshead movement, while the load and delamination length arerecorded.4.2 A record of the applied load versus opening displacement is recorded on an X-Y recorder, or equivalent real-time plottingdevice or stored digitally and postproc
32、essed. Instantaneous delamination front locations are marked on the chart at intervals ofdelamination growth. The Mode I interlaminar fracture toughness is calculated using a modified beam theory or compliancecalibration method.D5528 1335. Significance and Use5.1 Susceptibility to delamination is on
33、e of the major weaknesses of many advanced laminated composite structures.Knowledge of a laminated composite materials resistance to interlaminar fracture is useful for product development and materialselection. Furthermore, a measurement of the Mode I interlaminar fracture toughness, independent of
34、 specimen geometry ormethod of load introduction, is useful for establishing design allowables used in damage tolerance analyses of composite structuresmade from these materials.5.2 This test method can serve the following purposes:5.2.1 To establish quantitatively the effect of fiber surface treatm
35、ent, local variations in fiber volume fraction, and processingand environmental variables on GIc of a particular composite material.5.2.2 To compare quantitatively the relative values of GIc for composite materials with different constituents.5.2.3 To compare quantitatively the values of GIc obtaine
36、d from different batches of a specific composite material, for example,to use as a material screening criterion or to develop a design allowable.5.2.4 To develop delamination failure criteria for composite damage tolerance and durability analyses.6. Interferences6.1 Linear elastic behavior is assume
37、d in the calculation of G used in this test method. This assumption is valid when the zoneof damage or nonlinear deformation at the delamination front, or both, is small relative to the smallest specimen dimension, whichis typically the specimen thickness for the DCB test.6.2 In the DCB test, as the
38、 delamination grows from the insert, a resistance-type fracture behavior typically develops where thecalculated GIc first increases monotonically, and then stabilizes with further delamination growth. In this test method, a resistancecurve (R curve) depicting GIc as a function of delamination length
39、 will be generated to characterize the initiation and propagationof a delamination in a unidirectional specimen (Fig. 2). The principal reason for the observed resistance to delamination is thedevelopment of fiber bridging (1-3).3 This fiber bridging mechanism results from growing the delamination b
40、etween two 0unidirectional plies. Because most delaminations that form in multiply laminated composite structures occur between plies ofdissimilar orientation, fiber bridging does not occur. Hence, fiber bridging is considered to be an artifact of the DCB test onunidirectional materials. Therefore,
41、the generic significance of GIc propagation values calculated beyond the end of the implantedinsert is questionable, and an initiation value of GIc measured from the implanted insert is preferred. Because of the significanceof the initiation point, the insert must be properly implanted and inspected
42、 (8.28.3).6.3 Three definitions for an initiation value of GIc have been evaluated during round-robin testing (4). These include GIc valuesdetermined using the load and deflection measured (1) at the point of deviation from linearity in the load-displacement curve (NL),(2) at the point at which dela
43、mination is visually observed on the edge (VIS) measured with a microscope as specified in 7.5, and(3) at the point at which the compliance has increased by 5 % or the load has reached a maximum value (5 %/max) (see Section11). The NL GIc value, which is typically the lowest of the three GIc initiat
44、ion values, is recommended for generating delaminationfailure criteria in durability and damage tolerance analyses of laminated composite structures (5.2.35.2.4). Recommendations forobtaining the NLpoint are given in AnnexA2.All three initiation values can be used for the other purposes cited in the
45、 scope (5.2.1and 5.2.2). However, physical evidence indicates that the initiation value corresponding to the onset of nonlinearity (NL) in the3 The boldface numbers in parentheses refer to the list of references at the end of this test method.FIG. 2 Delamination Resistance Curve (RCurve) from DCB Te
46、stD5528 134load versus opening displacement plot corresponds to the physical onset of delamination from the insert in the interior of thespecimen width (5). In round-robin testing of AS4/PEEK thermoplastic matrix composites, NL GIc values were 20 % lower thanVIS and 5 %/max values (4).6.4 Delaminati
47、on growth may proceed in one of two ways: (1) by a slow stable extension or (2) a run-arrest extension in whichthe delamination front jumps ahead abruptly. Only the first type of growth is of interest in this test method.An unstable jump fromthe insert may be an indication of a problem with the inse
48、rt. For example, the insert may not be completely disbonded from thelaminate, or may be too thick, resulting in a large neat resin pocket, or may contain a tear or fold. Furthermore, rapid delaminationgrowth may introduce dynamic effects in both the test specimen and in the fracture morphology. Trea
49、tment and interpretation ofthese effects is beyond the scope of this test method. However, because crack jumping has been observed in at least one materialin which the guidelines for inserts (see 8.28.3) were not violated, the specimens are unloaded after the first increment ofdelamination growth and reloaded to continue the test. This procedure induces a natural Mode I precrack in the DCB specimen.The first propagation GIc value is referred to as the Mode I precrack GIc.6.5 Application to Other Materia
