ASTM D7250 D7250M-2016 5373 Standard Practice for Determining Sandwich Beam Flexural and Shear Stiffness《测定夹层梁的弯曲和抗剪刚度的标准实施规程》.pdf
《ASTM D7250 D7250M-2016 5373 Standard Practice for Determining Sandwich Beam Flexural and Shear Stiffness《测定夹层梁的弯曲和抗剪刚度的标准实施规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM D7250 D7250M-2016 5373 Standard Practice for Determining Sandwich Beam Flexural and Shear Stiffness《测定夹层梁的弯曲和抗剪刚度的标准实施规程》.pdf(7页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: D7250/D7250M 16Standard Practice forDetermining Sandwich Beam Flexural and Shear Stiffness1This standard is issued under the fixed designation D7250/D7250M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of l
2、ast 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 practice covers determination of the flexural andtransverse shear stiffness properties of flat sandwich construc-t
3、ions subjected to flexure in such a manner that the appliedmoments produce curvature of the sandwich facing planes.Permissible core material forms include those with continuousbonding surfaces (such as balsa wood and foams) as well asthose with discontinuous bonding surfaces (such as honey-comb). Th
4、e calculation methods in this practice are limited tosandwich beams exhibiting linear force-deflection response.This practice uses test results obtained from Test MethodsC393/C393M and/or D7249/D7249M.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standa
5、rd. 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.1.2.1 Within the text the inch-pound units are shown inbrackets.1.3 This standard does
6、 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 use.2. Referenced Documents2.1 ASTM Stand
7、ards:2C273 Test Method for Shear Properties of Sandwich CoreMaterialsC393/C393M Test Method for Core Shear Properties ofSandwich Constructions by Beam FlexureD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD7249/D7249M Test Method for Facing Properties of Sand-wich Cons
8、tructions by Long Beam FlexureE6 Terminology Relating to Methods of Mechanical TestingE122 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 Termi
9、nology Relating to Quality and Statistics3. Terminology3.1 DefinitionsTerminology D3878 defines terms relatingto high-modulus fibers and their composites, as well as termsrelating to sandwich constructions. Terminology D883 definesterms relating to plastics. Terminology E6 defines termsrelating to m
10、echanical testing. Terminology E456 and PracticeE177 define terms relating to statistics. In the event of aconflict between terms, Terminology D3878 shall have prece-dence over the other terminologies.3.2 Symbols: b = sandwich width, mm in.c = core thickness, mm in.d = sandwich thickness, mm in.D =
11、flexural stiffness, N-mm2lb-in.2 = beam mid-span deflection, mm in.G = core shear modulus, MPa psiS = support span length, mm in.L = load span length, mm in. (L = 0.0 for 3-point mid-spanloading configuration)n = number of specimensP = total applied force, N lbt = facing thickness, mm in.U = transve
12、rse shear rigidity, N lb4. Summary of Practice4.1 This practice consists of calculating the flexuralstiffness, transverse (through-thickness) shear rigidity and coreshear modulus of a sandwich beam using deflection and/orstrain data from two or more flexure tests of different loadingconfigurations c
13、onducted under Test Methods C393/C393Mand/or D7249/D7249M. This practice also includes equationsfor calculating the shear rigidity and core shear modulus of a1This practice is under the jurisdiction of ASTM Committee D30 on CompositeMaterials and is the direct responsibility of Subcommittee D30.09 o
14、n SandwichConstruction.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 2006. Last previous edition approved in 2012 as D7250/D7250M 06(2012). DOI: 10.1520/D7250_D7250M-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
15、 Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer 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 States1sandwich beam using deflection data from
16、 a single flexure testconducted under Test Method C393/C393M when the facingmodulus is known.5. Significance and Use5.1 Flexure tests on flat sandwich constructions may beconducted to determine the sandwich flexural stiffness, the coreshear strength and shear modulus, or the facings compressiveand t
17、ensile strengths. Tests to evaluate core shear strength mayalso be used to evaluate core-to-facing bonds.5.2 This practice provides a standard method of determiningsandwich flexural and shear stiffness and core shear modulususing calculations involving measured deflections of sandwichflexure specime
18、ns. Tests can be conducted on short specimensand on long specimens (or on one specimen loaded in twoways), and the flexural stiffness, shear rigidity and core shearmodulus can be determined by simultaneous solution of thecomplete deflection equations for each span or each loading. Ifthe facing modul
19、us values are known, a short span beam can betested and the calculated bending deflection subtracted fromthe beams total deflection. This gives the shear deflection fromwhich the transverse shear modulus can be determined.NOTE 1Core shear strength and shear modulus are best determined inaccordance w
20、ith Test Method C273 provided bare core material isavailable.NOTE 2For cores with high shear modulus, the shear deflection willbe quite small and ordinary errors in deflection measurements will causeconsiderable variations in the calculated shear modulus.NOTE 3To insure that simple sandwich beam the
21、ory is valid, a goodrule of thumb for a four-point bending test is the span length divided bythe sandwich thickness should be greater than 20 (L1/d 20) with the ratioof facing thickness to core thickness less than 0.1 (t/c 0.1).6. Interferences6.1 Material and Specimen PreparationImportant aspectsof
22、 sandwich core specimen preparation that contribute to datascatter include the existence of joints, voids or other corediscontinuities, out-of-plane curvature, and surface roughness.6.2 GeometrySpecific geometric factors that affect sand-wich facing stiffness and thereby the sandwich flexural stiff-
23、ness include facing thickness, core cell geometry, and facingsurface flatness (toolside or bagside surface in compression).6.3 EnvironmentResults are affected by the environmentalconditions under which specimens are conditioned, as well asthe conditions under which the tests are conducted. Specimens
24、tested in various environments can exhibit significant differ-ences in stiffness. Critical environments must be assessedindependently for each specific combination of core material,facing material, and core-to-facing interfacial adhesive (ifused) that is tested.6.4 Core MaterialFor some core materia
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