1、Designation: D 2718 00 (Reapproved 2006)Standard Test Methods forStructural Panels in Planar Shear (Rolling Shear)1This standard is issued under the fixed designation D 2718; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods determine the shear properties ofstructural panels associated with shear distortion of the pla
3、nesparallel to the edge planes of the panels. Both shear strengthand modulus of rigidity may be determined. Primarily, the testsmeasure the planar shear (rolling shear) strength developed inthe plane of the panel.1.2 Structural panels in use include plywood, waferboard,oriented strand board, and com
4、posites of veneer and ofwood-based layers.1.3 Two test methods are included:1.3.1 Test Method APlanar shear loaded by plates.1.3.2 Test Method BPlanar shear induced by five-pointbending.1.3.3 The choice of method will be dictated by the purposeof the test and equipment available.1.3.4 Test Method A,
5、 Planar Shear Loaded by PlatesThistest method uses a rectangular panel section adhered betweensteel plates with protruding knife edges to create load at thepanel faces. This test method has been used to develop shearproperties of plywood and oriented strand board for thepurpose of confirming design
6、values. This test method does notproduce pure shear, but the specimen length is prescribed sothat the secondary stresses have a minimum effect. The methoddetermines shear strength and modulus of rigidity.1.3.5 Test Method B, Planar Shear Induced by Five-PointBendingPlanar shear stress is induced on
7、the panel whileloaded in bending using two continuous spans. This testmethod determines planar shear strength consistent with panelapplications under transverse loading. This test method is ableto determine shear strength at any moisture condition.1.4 This standard does not purport to address all of
8、 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 Standards:2D 2395 Test Methods for
9、Specific Gravity of Wood andWood-Based MaterialsD 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base Materials3. Significance and Use3.1 Planar shear (rolling shear) characteristics of structuralpanels determined by these test methods are essential for therigorous desig
10、n of various glued wood-panel structural com-ponents, such as box beams, folded plate roofs, and stressedskin panels. Planar shear also may govern the design at lowspan-depth ratios encountered in floors subjected to highconcentrated loads, concrete forms at high pouring pressures,and bulk storage s
11、tructures.3.2 The modulus of rigidity determined from Test MethodAis a composite of the entire specimen acting as a unit. Forplywood panels for which the ratio between the shear moduliof the plies with grain oriented parallel and perpendicular to theshear forces is known, the rolling shear modulus o
12、f theperpendicular plies can be calculated.3.3 Veneer produced by slicing or rotary peeling maycontain fine checks or separations parallel to the grain on theknife side of the veneer that are produced as the knife is forcedthrough the wood. These checks are termed “knife checks” todistinguish them f
13、rom occasional checks that may be formedon the opposite side of the veneer by forces at the compressionbar, and from checks caused by drying. Knife checks can havea significant effect on rolling shear properties in plywoodpanels and may be of significance in other veneer containingpanels. Test Metho
14、dArequires (when applicable) the testing of1This test method is under the jurisdiction of ASTM Committee D07 on Woodand is the direct responsibility of Subcommittee D07.03 on Panel Products.Current edition approved Oct. 1, 2006. Published October 2006. Originallyapproved in 1969. Last previous editi
15、on approved in 2000 as D 2718 00e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Internatio
16、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.matching specimens having knife checks oriented both openand closed wherever possible (see Fig. 1).3.4 To control or define other variables influencing rollingshear, these test methods require determination of m
17、oisturecontent, specific gravity, and elapsed time-to-failure. Condi-tioning of test material in controlled atmospheres, determina-tion of depth of knife checks (when applicable), and determi-nation of percent of wood and plywood glueline failure (whenapplicable) are recommended.4. Control of Moistu
18、re Content4.1 The structural panel samples to be tested at specificmoisture contents or equilibrium relative humidities shall beconditioned to approximately constant weight in controlledatmospheric conditions before gluing to plates. For approxi-mating moisture conditions of structural panel used un
19、der dryconditions a relative humidity of 65 6 2 % at a temperature of68 6 6F (20 6 3C) is recommended. Specimens shall betested without undue delay after the adhesive is cured. Testingin similarly controlled atmospheres is recommended whereverpossible.Test Method APlanar Shear Loaded by Plates5. Sco
20、pe5.1 The specimen having the form of a rectangular flat plateis bonded between steel plates beveled at opposite ends of thespecimen to provide knife edges for loading the plate at theface bonded to the specimen. The knife edges project beyondthe ends of the specimen. This test method is conducted b
21、yloading the knife edges in compression at a uniform rate whilea suitable gage measures slip between the plates due tospecimen deformation. Shear strength is computed from maxi-mum load, and effective shear modulus for the specimen isdetermined from a plot of load versus slip.6. Test Specimen6.1 Spe
22、cimen thickness shall be that of the material. Speci-mens from material that is expected to vary significantly withinthe specimen due to growth or manufacturing features or fromother causes shall be 6 in. (15 cm) wide by 18 in. (45 cm) longor larger as shown in Fig. 2. This size is recommended forun
23、iform material as well. However, smaller specimens ofuniform material may be used if these are not less than fourtimes the thickness in width nor twelve times the thickness inlength.6.2 From each sample of panels containing veneer, twomatching specimens shall be cut. Knife edges of loading platesfor
24、 one specimen of each matching pair shall be orientedperpendicular to one of the primary panel directions or forplywood to cause opening of knife checks during test as shownin Fig. 1(a). Knife edges of plates loading the other specimenshall be positioned perpendicular to one of the primary paneldire
25、ctions or for plywood to cause knife checks to close duringtest as shown in Fig. 1(b). Proper plywood orientation may bedetermined from check depth specimens described in 16.3.Itmay not be possible to test samples having two or more pliesstressed in rolling shear in both “open” and “closed” orienta-
26、tions if these plies are oriented in opposite directions causinga“ checks open” failure regardless of direction of loading.6.3 Specimen length and width shall be measured to thenearest 0.01 in. (0.25 mm) and thickness to the nearest 0.001in. (0.025 mm). When applicable, the direction of knife checks
27、in plies having grain perpendicular to its length shall bedetermined and the specimens marked for position of knifeedges. At the time specimens are cut matching samples fordetermination of moisture content and specific gravity inaccordance with 16.1 and 16.2 shall be obtained. Whenmeasurement of kni
28、fe checks is included as discussed in 16.3,a sample for this measurement also may be cut at this time.7. Loading7.1 Figs. 1 and 2 illustrate the specimen and suitable loadingplates and blocks for loading the knife edges of the plates. The(a) Knife Checks Open(b) Knife Checks ClosedFIG. 1 Orientation
29、 of Knife Checks in PlywoodNOTEThe “V” block is supported on a seat that provides rotationabout the axis perpendicular to the knife edge only.Metric Equivalentsin. 6 18mm 15 45FIG. 2 Planar (Rolling) Shear Test Using a Dial Gage forMeasuring Plate SlipD 2718 00 (2006)2specimen shall be loaded by ste
30、el plates bonded to both facesof the specimen with an adhesive sufficiently rigid to precludecontribution of adhesive creep to measured deformation. Widthof plates shall be that of the specimen. One end of each plateshall be provided with a knife edge projecting14 in. (6 mm)beyond the end of the spe
31、cimen at one end and flush with thesurface glued to the specimen. The other end of the plate shallbe square and flush with the end of the specimen. Knife edgesof the two plates shall be at opposite ends of the specimen andshall be oriented to load the specimen in the desired directionin relation to
32、the knife checks. Planar shear properties ofstructural panels should be determined in both directions.Plates for specimens 18 in. (45 cm) long shall be 1 in. (2.5 cm)thick. The thickness of plates for shorter specimens may bereduced proportionately. Loading of at least one V-block shallprovide for u
33、niform load distribution along the knife edge byloading through a pivot having its axis perpendicular to theknife edge and centered along it. Pivots permitting rotationabout an axis parallel to the knife edge or spherical seats freeto pivot in this manner shall not be used as they create unstableloa
34、ding which may cause violent ejection of the specimen fromthe machine and hazard to operating personnel. The V-blocksshall be vertically positioned in the machine, one above theother, causing the forces applied to the specimen to act parallelto the axis of the machine. The specimen itself will be sl
35、ightlyinclined when placed in the machine. A means of holding theplates in an upright position after the specimen has shearedapart is desirable as a complete separation of the specimenpermits the plates to be thrown out of the machine withattendant hazard to the operator.7.2 Load shall be applied co
36、ntinuously throughout the test atconstant rate of cross-head motion to normally produce failurein the range of 3 to 12 min elapsed time from beginning ofloading. For plywood, the approximate speed may be deter-mined as follows:N 5 0.0075 (T|1 R(T! (1)where:N = crosshead speed, in./min (cm/min),(T|=
37、total thickness of plies having grain parallel todirection of shear force, in. (cm),R = 8 (assumed ratio of shear modulus of parallel pliesto shear modulus of perpendicular plies), and(T= total thickness of plies having grain perpendicularto the direction of shear force, in. (cm).7.2.1 Elapsed time
38、from beginning of load application tofailure of each specimen shall be measured and recorded to thenearest half minute. Machine speeds calculated by the aboveformula will normally produce failure in the range of 3 to 12min elapsed time from the beginning of loading. Shouldelapsed time to failure fal
39、l greatly outside this range, machinespeed should be modified to obtain times within this range.7.3 Both epoxy and polyvinyl adhesives have been foundsatisfactory for bonding steel plates to specimens. Minimumrequired surface preparation of steel plates consists of removalof residual adhesive. This
40、can be accomplished most easily bymild heating of the plate and any portion of the specimenremaining from the previous test in an oven which weakens thebond to the steel sufficiently to permit peeling the remainingwood and adhesive from the plate. The residual adhesive maybe scraped off with a sharp
41、-edged tool. Further degreasing andcleaning has frequently been found necessary in addition to theabove to ensure adequate bond strength. Curing the adhesive ata slightly elevated temperature has also been helpful.8. Measurement of Deformation8.1 Slip between the steel plates during load application
42、shall be measured to at least the nearest 0.0001 in. (0.002 mm)at no less than twelve and preferably more equally spacedincrements of load to proportional limit from which a load-deformation curve shall be plotted. Slip can be measured witha dial gage as illustrated in Figs. 2 and 3 or with appropri
43、ateautomatic measuring and recording equipment. Gage geometryand position on the specimen shall be such as to minimize anyeffects of unsymmetrical loading or deformation.9. Calculation9.1 Shear stress shall be calculated as follows:fv5 P/LW! (2)where:fv= shear stress, psi (N/mm),P = maximum or propo
44、rtional limit load (force), lbf (N),W = specimen width, in. (mm), andL = specimen length, in. (mm).Maximum shear stress obtained from specimens having finalfailure of the bond between the plate and the specimen shall beregarded as defective and shall be clearly indicated in thereport of results.9.2
45、Effective modulus of rigidity for the specimen acting asa unit shall be calculated as follows:G 5 P/D!t/LW!# (3)where:G = apparent modulus of rigidity for the entire speci-men, psi (N/mm),t = specimen thickness, in. (mm),P/D = slope of the force-deformation curve below propor-tional limit load, lbf/
46、in. (N/mm), and other notationis as indicated in 9.1.For plywood, modulus of rigidity of the cross plies may becalculated from that given above if the ratio of moduli ofrigidity and thickness of the parallel and perpendicular plies isknown.D 2718 00 (2006)3Test Method BPlanar Shear Induced by Five-P
47、ointBending10. Scope10.1 Specimens are tested in a two-span continuous beamsupport configuration with line loads applied at midspan ofeach span as shown in Fig. 4. Induced shear stresses areconsistent with those developed in conventional panel appli-cations under transverse loading. Specimens may be
48、 tested inany moisture condition.NOTE 1Research that led to the development of the test method isavailable.3,4Research on the test methods usefulness for determiningelastic constants is also available.511. Test Specimen11.1 The test specimen shall be rectangular in cross-section.The depth of the spe
49、cimen shall be the thickness of thematerial, and the width shall be at least 4.5 in. (115 mm) andno greater than 10 in. (255 mm) (see Note 2).NOTE 2Specimen width may be modified for practical purposes.Since shear strength may vary slightly with specimen width, specimenwidth shall be reported with shear strength results.11.2 MeasurementsSpecimen thickness and width shallbe measured to the nearest 0.001 in. (0.02 mm) at midlength(over center support) and at midspan (under line loads).Thickness measurements shall be determined at these locationson each side of
