1、Designation: C 394 00Standard Test Method forShear Fatigue of Sandwich Core Materials1This standard is issued under the fixed designation C 394; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers determination of the effect ofrepeated shear loads on sandwich core materials.1.2 The values stated in SI units are to
3、be regarded as thestandard. The inch-pound units given may be approximate.1.3 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
4、 the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 273 Test Method for Shear Properties of Sandwich CoreMaterials2E 4 Practices for Force Verification of Testing Machines33. Significance and Use3.1 Usually the most critical stress to which a sandwi
5、chpanel core is subjected is shear. The effect of repeated shearstresses on the core material can be very important.3.2 These test methods provide a standard method ofobtaining the sandwich core shear fatigue properties.4. Apparatus4.1 Fatigue Testing Machine, any standard constant loadfatigue testi
6、ng machine capable of applying a direct stress tothe specimen and equipped with a counter. The load measuringsystem used shall have an accuracy of 61 % of the indicatedvalue. The accuracy of the test machine shall be verified inaccordance with Practices E 4.4.2 Testing Machine, any standard universa
7、l testing machinecapable of operation at a constant rate of motion of thecross-head. The load measuring system used shall have anaccuracy of 61 % of the indicated value. The accuracy of thetest machine shall be verified in accordance with Practices E 4.4.3 Test Fixtures, test fixtures similar to tho
8、se described inTest Method C 273.4.4 Micrometer, Gage, or Caliper, capable of measuringaccurately to 0.025 mm (0.001 in.).5. Test Specimens5.1 The test specimens shall be similar to those described inTest Method C 273, except that the core material shall bebonded directly to the fixture plates. The
9、dimensions of thespecimen shall be such that the line of load action passesthrough the diagonally opposite corners of the core material.5.2 The number of test specimens and the method of theirselection depend on the purpose of the particular test underconsideration. It is recommended that at least f
10、ive specimensare used for static control tests, and three specimens for eachstress level to be tested. For establishment of an S-N curve ofstress versus number of cycles to failure, test at least threestress levels.6. Conditioning6.1 When the physical properties of the component materi-als are affec
11、ted by moisture, bring the test specimens toconstant weight (61 %) before testing, preferably in a condi-tioning room having temperature and humidity control. Con-duct the tests under the same temperature and humidityconditions. A temperature of 23 6 3C (73 6 5F) and arelative humidity of 50 6 5 % a
12、re recommended as standardconditions.7. Procedure7.1 The length and width dimensions of the specimen shallbe measured to the nearest 0.25 mm (0.01 in.) and the thicknessdimension to the nearest 0.025 mm (0.001 in.). Weight thespecimen to the nearest 0.1 g and calculate the specimendensity.7.2 Before
13、 the fatigue tests, test a minimum of five controlspecimens statically in a standard test machine in accordancewith Test Method C 273. Use the average of the five specimensas the 100 % level for the fatigue tests.7.3 The stress levels to be tested shall be agreed upon by thepurchaser and the seller,
14、 or other parties involved. The stresslevel is defined as the maximum repeated stress to which thespecimen is subjected.7.4 For standard tests, use a stress ratio of minimum tomaximum load of 0.10, unless agreed upon previously by theparties involved. Apply the mean load (50 % of differencebetween m
15、aximum and minimum) through the preloading1This specification is under the jurisdiction of ASTM Committee D-30 onComposite Materials and is the direct responsibility of Subcommittee D30.09 onSandwich Construction.Current edition approved Jan. 10, 2000. Published April 2000. Originallypublished as C
16、394 57 T. Last previous edition C 394 94 .2Annual Book of ASTM Standards, Vol 15.03.3Annual Book of ASTM Standards, Vol 03.01.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.mechanism and the dynamic load (the remaining 50 %)through the dynamic loading mechani
17、sm.7.5 After testing has begun, check the loading frequentlyunless the test machine is equipped with automatic loadmaintainers. Also check the specimens temperature to be surethat the loading rate is not heating the specimen more than 3C(5F).7.6 Record the maximum load and number of cycles tofailure
18、.7.7 Specimens that have core-to-plate adhesive adhesionbond failures or adhesive cohesive failures are not valid andshall be retested.8. Calculation8.1 Calculate the core shear stress in accordance with TestMethod C 273.t5PPb(1)where:t5core shear stress, MPa (psi);P 5 load on specimen, N (lb);L 5 l
19、ength of specimen, mm (in.); andb 5 width of specimen, mm (in.).9. Report9.1 The report shall include the following:9.1.1 Description of test specimens; core material, adhesive,9.1.2 Dimensions and densities of the test specimens, coreorientation,9.1.3 Method of bonding specimens to plates; cure cyc
20、leand pressure,9.1.4 Description of test machines, including loading rate onstatic control specimen and testing speed (number of cycles persecond) on fatigue test specimens and mode of testing (tensileor compressive).9.1.5 Testing conditions, including temperature and relativehumidity.9.1.6 Maximum
21、load and maximum stress obtained on staticcontrol test, and a description of the type of failure.9.1.7 Stress levels and stress ratio used in fatigue tests.9.1.8 Number of cycles to failure. If test is stopped at aspecified number of cycles without failure occurring, it shall beso noted.9.1.9 A curv
22、e of maximum stress versus number of cycles tofailure (S-N curve) shall be plotted.10. Precision and Bias10.1 PrecisionThe precision of the procedure in TestMethod C 394 for measuring sandwich core material shearfatigue is not available.10.2 BiasSince there is no accepted reference materialsuitable
23、for determining the bias for the procedure in this testmethod, bias has not been determined.11. Keywords11.1 fatigue; sandwich core; shear strength; shear stressThe American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connectionwith an
24、y item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any suchpatent rights, and the risk of infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technica
25、l committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting o
26、f the responsibletechnical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make yourviews known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website (www.astm.org).C 3942
