1、Designation: E2661/E2661M 10E2661/E2661M 15Standard Practice forAcoustic Emission Examination of Plate-like and Flat PanelComposite Structures Used in Aerospace Applications1This standard is issued under the fixed designation E2661/E2661M; the number immediately following the designation indicates t
2、he yearof original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This practice covers acoustic emission (AE
3、) examination or monitoring of panel and plate-like composite structures madeentirely of fiber/polymer composites.1.2 The AE examination detects emission sources and locates the region(s) within the composite structure where the emissionoriginated. When properly developed AE-based criteria for the c
4、omposite item are in place, the AE data can be used fornondestructive examination (NDE), characterization of proof testing, documentation of quality control or for decisions relative tostructural-test termination prior to completion of a planned test. Other NDE methods may be used to provide additio
5、nal informationabout located damage regions. For additional information see X1.1 in Appendix X1.1.3 This practice can be applied to aerospace composite panels and plate-like elements as a part of incoming inspection, duringmanufacturing, after assembly, continuously (during structural health monitor
6、ing) and at periodic intervals during the life of astructure.1.4 This practice is meant for fiber orientations that include cross-plies, angle-ply laminates or two-dimensional woven fabrics.This practice also applies to 3-D reinforcement (for example, stitched, z-pinned) when the fiber content in th
7、e third direction isless than 5 % (based on the whole composite).1.5 This practice is directed toward composite materials that typically contain continuous high modulus greater than 20 GPa 3Msi fibers.1.6 The values stated in either SI units or inch-pound units are to be regarded separately as stand
8、ard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.7 This standard does not purport to address all of the safety concerns, if any, a
9、ssociated 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 to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructive
10、 TestingE976 Guide for Determining the Reproducibility of Acoustic Emission Sensor ResponseE1067 Practice for Acoustic Emission Examination of Fiberglass Reinforced Plastic Resin (FRP) Tanks/VesselsE1106 Test Method for Primary Calibration of Acoustic Emission SensorsE1316 Terminology for Nondestruc
11、tive ExaminationsE1781 Practice for Secondary Calibration of Acoustic Emission SensorsE2533 Guide for Nondestructive Testing of Polymer Matrix Composites Used in Aerospace Applications1 This practice is under the jurisdiction ofASTM Committee E07 on Nondestructive Testing and is the direct responsib
12、ility of Subcommittee E07.04 on Acoustic EmissionMethod.Current edition approved June 1, 2010June 1, 2015. Published July 2010July 2015. Originally approved in 2010. Last previous edition approved in 2010 asE2661/E2661M-10. DOI:10.1520/E2661_E1661M-15.2 For referencedASTM standards, visit theASTM we
13、bsite, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer 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 indicat
14、ion of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes 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 cons
15、idered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 Other Documents:ANSI/ASNT CP-189 ASNT Standard for Qualification and Certification of No
16、ndestructive Testing Personnel3ISO 9712 Non-destructive TestingQualification and Certification of NDT Personnel4NAS-410 NAS Certification and Qualification of Nondestructive Personnel (Quality Assurance Committee)5SNT-TC-1A Recommended for Personnel Qualification and Certification of Nondestructive
17、Testing Personnel33. Terminology3.1 DefinitionsSee Terminology E1316 for general terminology applicable to this practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 characteristic damage statetransverse matrix cracking during the virgin loading of a composite; often resulting inreaching
18、 a limit of the crack density prior to reaching failure. Results in a reduction of stiffness of the composite. For additionalinformation see X1.2.3.2.2 flat panel compositeany fiber reinforced composite lay-up consisting of laminas (plies) with one or more orientationswith respect to some reference
19、direction that result in a two-dimensionally flat article of finite thickness (typically relatively thin).3.2.3 plate-like compositeany fiber-reinforced composite lay-up consisting of laminas (plies), which is not strictly flat, but forpurposes of the AE examination, can be considered as a two-dimen
20、sional (2-D) structural plate for wave propagation and forlocation of the region ofAE source origin.Applies for a minimum radius of curvature of greater than about 2 m (6 ft), so curvaturedoes not change group velocities.3.2.4 quasi-isotropic lay-upa plate where the group velocities of both the fund
21、amental modes have been shown to beindependent of propagation direction. For example: +45/-45/0/90s6.3.2.5 wideband AE sensorswideband (broadband) AE sensors, when calibrated according to E1106 or E1781, exhibitdisplacement or velocity response over several hundred kHz with a coefficient of variatio
22、n of the response in dBs that does notexceed 10 %.3.2.6 wideband-based (modal) AE techniquesAE techniques with widebandAE sensors that subject waveforms of the signalsto combined time and frequency analysis to obtain mode-based arrival times (for source location calculations) and modalamplitudes for
23、 potential source identification. Note that mode-based arrival times can also be obtained with resonant sensors, butonly at certain experimentally determined frequencies.4. Summary of Practice4.1 This practice consists of subjecting flat composite panels or plate-like composite structures to loading
24、 or stressing whilemonitoring with sensors that are sensitive to AE (transient displacement waves) caused by the creation of micro-damage, growingflaws and friction-based sources. For additional information see X1.3.4.2 This practice provides an approach to determine the local regions of origin of t
25、heAE sources and any potential local regionsof large accumulation(s) of AE sources.4.3 This practice can provide an approach to use AE-based criteria to determine the significance of flaws.5. Significance and Use5.1 This AE examination is useful to detect micro-damage generation, accumulation and gr
26、owth of new or existing flaws. Theexamination is also used to detect significant existing damage from friction-based AE generated during loading or unloading ofthese regions. The damage mechanisms that can be detected include matrix cracking, fiber splitting, fiber breakage, fiber pull-out,debonding
27、 and delamination. During loading, unloading and load holding, damage that does not emit AE energy will not bedetected.5.2 When the detected signals from AE sources are sufficiently spaced in time so as not to be classified as continuous AE, thispractice is useful to locate the region(s) of the 2-D
28、test sample where these sources originated and the accumulation of thesesources with changing load and/or time.5.3 The probability of detection of the potential AE sources depends on the nature of the damage mechanisms, flawcharacteristics and other aspects. For additional information see X1.4.5.4 C
29、oncentrated damage in fiber/polymer composites can lead to premature failure of the composite item. Hence, the use ofAE to detect and locate such damage is particularly important.3 Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 432
30、28-0518, http:/www.asnt.org.4 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.5 Available from Aerospace Industries Association of America, Inc., 1250 Eye St., NW, Washington, DC 20005.6 Lei Wang,
31、 F.G. Yuan, “Group velocity and characteristic wave curves of Lamb waves in composites: Modeling and experiments,” Composites Science and Technology67 (2007) 13701384.E2661/E2661M 1525.5 AE-detected flaws or damage concentrated in a certain region may be further characterized by other NDE techniques
32、 (forexample, visual, ultrasonic, etc.) and may be repaired as appropriate. Repair procedure recommendations and the subsequentexamination of the repair are outside the scope of this practice. For additional information see X1.5.5.6 This practice does not address sandwich core, foam core or honeycom
33、b core plate-like composites due to the fact thatcurrently there is little in the way of published work on the subject resulting in a lack of a sufficient knowledge base.5.7 Refer to Guide E2533 for additional information about types of defects detected by AE, general overview of AE as appliedto pol
34、ymer matrix composites, discussion of the Felicity ratio (FR) and Kaiser effect, advantages and limitations,AE of compositeparts other than flat panels, and safety hazards.6. Basis of ApplicationPersonnel QualificationContractual Agreement6.1 The following items are subject to contractual agreement
35、between the parties using or referencing this practice.6.2 Personnel QualificationUnless contractually agreed otherwise, personnel performing examinations to this practice shallbe qualified in accordance with a nationally or internationally recognized NDT personnel qualification practice or standard
36、 suchas ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, ISO 9712, or a similar document. They shall be certified by the employer orcertifying agency, as applicable. The practice or standard used and its applicable revision shall be identified in the contractualagreement between the using parties.6.3 Qualifica
37、tion of Nondestructive AgenciesUnless contractually agreed otherwise, NDT agencies shall be qualified andevaluated as described in E543. The applicable edition of E543 shall be specified in the contractual agreement.6.4 Procedure and TechniquesThe procedures and techniques to be utilized shall be as
38、 specified in the contractual agreement.In particular, the contractual agreement should state whether full monitoring of the test sample is required or if only partialmonitoring of certain expected critical areas is required.6.5 Timing of ExaminationThe timing of examination shall be in accordance w
39、ith 1.3, unless otherwise specified.6.6 Reporting CriteriaReporting criteria for the examination results shall be in accordance with Section 12, unless otherwisespecified.7. Apparatus7.1 Refer to Fig. 1 for a typical AE system block diagram showing key components.7.2 AE Sensors:FIG. 1 AE System Bloc
40、k DiagramE2661/E2661M 1537.2.1 The selection of a wideband or resonant sensor is described here. For information on the frequency content of AE wavessee X1.6. For a scientific method to select sensors whose best frequency response corresponds to the frequency range of the highestamplitudes of the AE
41、 waves see X1.7.7.2.1.1 Wideband sensors can be used along with waveform recording to enhance AE data analysis by the application ofwideband-based AE techniques. A wideband sensor should be chosen with relatively flat response (E1106 or E1781) from about50 kHz to 400 kHz. For additional information
42、see X1.7 for plates less than 2-mm thick and X1.8.7.2.1.2 If resonant sensors are used, the best choice is a sensor with its primary resonance in the lower portion of a 50 kHz to400 kHz frequency band. Sensors with a lower frequency resonance of about 25 kHz to 50 kHz can be used to increase sensors
43、pacing (for example when a limited number of AE channels are available see E1067) in AE testing of composites, but suchsensors increase the likelihood that unwanted extraneous noise will be recorded.To minimize the effects of airborne noise the lowerresonant-frequency sensors can be wrapped with sou
44、nd absorbing material.7.2.2 Sensors should be shielded against electromagnetic interference (EMI) through proper design practice or differential(anti-coincidence) element design, or both.7.2.3 Sensors should have omni-directional response, with directional variations not exceeding 4 dB from the aver
45、age peakresponse of the set of sensors.7.3 Sensor Couplant:7.3.1 The sensors must be acoustically coupled (to remove air from between the sensor face and the composite surface) directlyto the test sample. Commercially available couplants for ultrasonic flaw detection may be used. Silicone-based high
46、-vacuum greasehas been found to be particularly suitable, but it may not be desirable for all test locations and all test samples. Adhesives mayalso be used. Note: the sensor attachment procedure as well as the couplant or adhesive may require approval prior to sensorinstallation due to special requ
47、irements for materials placed in contact with composite structures (compatibility and/orcontamination control).7.3.2 Couplant selection should be made to minimize changes (for example, drying out of the couplant or movement of thecouplant due to gravity over the range of test temperatures and test t
48、ime duration) in coupling sensitivity during a completeexamination.7.4 Sensor Attachment Apparatus:7.4.1 AdhesivesVarious adhesives can be used to attach sensors and provide acoustic coupling. The bond line created by theadhesive must be much thinner than the shortest wavelengths of interest. Adhesi
49、ves such as two-part epoxies, silicone adhesives,and cyanoacrylates have been successfully used for attaching sensors. Sensors attached with some adhesives can be difficult toremove without damaging the sensor or the examination sample.Also, due to the larger design deformations of composite materials(relative to metals designed to operate in their elastic range), adhesively bonded sensors may debond during test sample stressingor during thermal cycling of the test sample.7.4.2 TapeElastic adhesive tapes have been successfully used for mounting transducer
