1、Designation: D7857 16Standard Test Method forEvaluating the Flexural Properties and Internal BondStrength of Fire-Retarded Mat-Formed Wood StructuralComposite Panels Exposed to Elevated Temperatures1This standard is issued under the fixed designation D7857; the number immediately following the desig
2、nation indicates the year oforiginal 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. Scope1.1 This test method is designed as
3、 a laboratory screeningtest. It is intended to establish an understanding of therespective contributions of the many wood material, fire-retardant, resin and processing variables, and their interactions,upon the mechanical properties of fire-retarded mat-formedwood structural composite (FRSC) panels
4、 as they affectflexural and internal bond (IB) performance and as they areoften affected later during exposure to high temperature andhumidity. Once the critical material and processing variableshave been identified through these small-specimen laboratoryscreening tests, additional testing and evalu
5、ation shall berequired to determine the effect of the treatment on the panelstructural properties and the effect of exposure to high tem-perature on the properties of commercially produced FRSCpanels. In this test method, treated structural composite panelsare exposed to a temperature of 77C (170F)
6、and at least 50%relative humidity.1.2 The purpose of the preliminary laboratory-based testmethod is to compare the flexural properties and IB strength ofFRSC panels relative to untreated structural composite panelswith otherwise identical manufacturing parameters. The resultsof tests conducted in ac
7、cordance with this test method providea reference point for estimating strength temperature relation-ships for preliminary purposes. They establish a starting pointfor subsequent full-scale testing of commercially producedFRSC panels.1.3 This test method does not cover testing and evaluationrequirem
8、ents necessary for product certification and qualifica-tion or the establishment of design value adjustment factors forFRSC panels.NOTE 1One potentially confounding limitation of this preliminaryscreening test method is that it may be conducted with laboratory panelsthat may not necessarily represen
9、t commercial quality panels. A finalqualification program should likely be conducted using commercialquality panels and the scope of the review should include evaluation of theeffects of the treatment and elevated temperature exposure on all relevantmechanical properties of the commercially produced
10、 panel.1.4 This test method is not intended for use with structuralplywood.1.5 The values stated in SI units are to be regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.6 This
11、 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 the applica-bility of regulatory limitations prior to use.2. Referenced Documents
12、2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD198 Test Methods of Static Tests of Lumber in StructuralSizesD1037 Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel MaterialsD1165 Nomenclature of Commercial Hardwoods and Soft-woodsD2395 Test Me
13、thods for Density and Specific Gravity (Rela-tive Density) of Wood and Wood-Based MaterialsD2915 Practice for Sampling and Data-Analysis for Struc-tural Wood and Wood-Based ProductsD3043 Test Methods for Structural Panels in FlexureD5516 Test Method for Evaluating the Flexural Properties ofFire-Reta
14、rdant Treated Softwood Plywood Exposed toElevated TemperaturesD6305 Practice for Calculating Bending Strength DesignAdjustment Factors for Fire-Retardant-Treated PlywoodRoof Sheathing1This test method is under the jurisdiction of ASTM Committee D07 on Woodand is the direct responsibility of Subcommi
15、ttee D07.07 on Fire Performance ofWood.Current edition approved March 1, 2016. Published April 2016. DOI: 10.1520/D785716.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
16、er 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 States1E84 Test Method for Surface Burning Characteristics ofBuilding MaterialsE176 Terminology of Fire StandardsE2768 Test Method f
17、or Extended Duration Surface BurningCharacteristics of Building Materials (30 min Tunnel Test)2.2 Other Standards:AWPA U-1 Commodity Specification H: Fire Retardants3NFPA 703 Standard for Fire Retardant Impregnated Woodand Fire Retardant Coatings for Building Materials4PS 2 U.S. Performance Standard
18、 for Structural-Use Panels53. Terminology3.1 DefinitionsDefinitions used in this test method are inaccordance with Terminologies D9 and E176 and Nomencla-ture D1165.3.1.1 Structural Composite Panels: wood composite panelsof various sizes and thicknesses manufactured using flakes,strands, wafers or p
19、articles derived from wood or similarbio-based resources assembled together with thermoset resinsand other complementary materials, such as waxes or chemicaladditives in a hot-press intended for load-bearing applicationsas building materials.4. Summary of Test Method4.1 The purpose of this test meth
20、od is to determine the effectof fire-retarded chemical treatment on flexural properties andIB strength of FRSC panels and to evaluate the effect ofexposure to elevated temperatures on these properties.4.2 Specimens of both the FRSC panel and an untreatedpanel manufactured with otherwise identical pa
21、rameters arepreconditioned to constant moisture content under conditionssufficient to produce moisture content of 10 6 2%intheuntreated specimens.4.3 After preconditioning (see section 6.4), 203-mm (8-in)wide specimens of treated and untreated treated structuralcomposite panels are exposed to 77C (1
22、70F) temperature andrelative humidity equal to or greater than 50 % for various timeperiods.4.4 After the elevated-temperature exposure, the specimensare subjected to post-exposure conditioning under the sametemperature and relative humidity used for preconditioning.4.5 After post-exposure condition
23、ing (see section 7.2), flex-ure and internal bond tests are conducted on exposed speci-mens. Flexural properties considered include maximummoment, bending stiffness, and work to maximum load.5. Significance and Use5.1 The properties evaluated by this test method are in-tended to provide comparative
24、information on the effects offire-retardant chemical formulations and environmental condi-tions on the flexural properties and IB strength of FRSC panels.5.2 This practice uses a controlled elevated-temperatureenvironment to produce temperature-induced losses in themechanical properties of FRSC pane
25、ls and untreated panels.5.3 Prediction of performance in natural environments hasnot been directly correlated with the results of this test method.5.4 The reproducibility of results in elevated-temperatureexposure is highly dependent on the type of specimens testedand the evaluation criteria selecte
26、d, as well as the control of theoperating variables. In any testing program, sufficient repli-cates shall be included to establish the variability of the results.Variability is often observed when similar specimens are testedin different chambers even though the testing conditions arenominally simil
27、ar and within the ranges specified in this testmethod.6. Test Specimens6.1 Material Selection:6.1.1 Source panels for this test shall be selected fromlaboratory panels manufactured on a hot press large enough toprovide flexural specimens having a span-to-depth ratio notless than 48:1 after allowance
28、s for both sufficient edge trim-ming to remove panel edges and ensuring the D3043 requiredoverhang beyond the flexural test supports. The nominal panelthickness shall be between 9 mm (1132 in.) and 19 mm (34 in.).NOTE 2The initial experiments that provide the scientific basis for thismethod used spe
29、cimens cut from larger mat-formed structural compositesand evaluated at approximately a 70:1 span-to-depth ratio. (1, 2, 3).6NOTE 3If larger panels and hot presses are used, more test specimenscan be expected. If smaller panels and presses are used fewer specimenscan be obtained. In all cases experi
30、ence suggests that at least 25-mmshould be trimmed from all four panel edges prior to cutting any testspecimens.6.1.2 Both treated and matched untreated panels shall bemanufactured from a single batch of matched wood materials.Other than the fire-retardant treatment, both sets of panels shallbe manu
31、factured using the same manufacturing parametersincluding, but not limited to, thickness, density, resin content,wax content, and press schedule.NOTE 4For the resulting data to have maximum utility, it is recom-mended that both materials and process conditions be selected to closelyparallel those us
32、ed in manufacturing commercial panels.6.1.3 Each panel shall be free of manufacturing defects,such as abnormally large surface voids, internal blows, orvisible damage. Orientation, size, and shape, of surface flakes,strands or fibers shall be uniform and representative of normalcommercial production
33、. Ensure that enough materials areproduced or obtained because it is required that all materials inthis study be obtained from a single batch of structuralcomposite panels.NOTE 5Depending on the initial size of panels used, users shouldensure that a number of additional untreated and FRSC source pan
34、els areavailable because potential culling of small 200-mm (8-in) wide speci-mens may require additional FRSC panels.6.2 Treatment:3Available from American Wood Protection Association (AWPA), P.O. Box361784, Birmingham, AL 35236-1784, http:/.4Available from National Fire Protection Association (NFPA
35、), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.5Available for National Institute for Standards and Technology (NIST), 100Bureau Drive, Stop 1070, Gaithersburg, MD 20899 http:/www.nist.gov.6The boldface numbers in parentheses refer to the list of references at the end ofthis standar
36、d.D7857 1626.2.1 The fire-retardant treatment shall be impregnated intothe panel and shall provide a flame-spread index of 25 or lesswhen tested in accordance with Test Method E2768 or whentested in accordance withASTM E84 for an extended period of30 min, and also show no evidence of significant pro
37、gressionof combustion. Additionally the flame front shall not progressmore than 3.2 m (10.5 ft) beyond the centerline of the burnersat any time during the test.6.2.1.1 Materials listed as fire-retardant-treated wood aredeemed to comply with the provisions of 6.2.1. When alterna-tive performance crit
38、eria for the treatment are being evaluated,the test report on specimens of that treatment shall state clearlythe alternative criteria and that the fire-retardant treatmentretention was limited to that required for those alternativecriteria.6.2.2 Treatment of FRSC panels is done during panelmanufactu
39、re. The fire-retardant retention level of every treatedpanel and each specimen cut from those panels shall not be lessthan the value midway between the median of the retentionrange and the maximum retention desired for the treatedstructural composite panels.6.2.3 Weigh all materials used to produce
40、the structuralcomposite panels before pressing and weigh the manufacturedpanels immediately after pressing. Complete a treating reportfor each batch of panels to document the materials used, presscycle, times, pressures, and fire-retardant retentions.6.3 Specimen Preparation:6.3.1 Source panels and
41、all experimental test specimensshall be inspected and the culling of specimens done asnecessary in accordance with the criteria in 6.1.3.6.3.2 A minimum of 100 untreated and 100 FRSC testspecimens shall be prepared.6.3.3 Each test specimen shall be at least 200-mm (8-in)wide and long enough to meet
42、the span-to-depth requirements(6.1.1). Each test specimen shall be labeled to identify theoriginal panel and location of the specimen within that panel.Care should be taken to avoid assigning more than onespecimen from each panel to any experimental group. Careshall also be taken to ensure assignmen
43、t of equal numbers ofspecimens cut from center and cut from nearer an original edgefor each group of 20 experimental specimens.NOTE 6The initial experiments that provide the scientific basis for thismethod used specimens cut from larger FRSC panels and evaluatedspecimens from 102-mm (4-in) to 305-mm
44、 (12-in) wide and found thatspecimens of at least 200-mm (8-in) wide provide stable coefficient ofvariation for both flexural stiffness and strength (Fig. 1). The above widthlimitation of 200-mm (8-in) specimen width reflects those findings (2, 3,4).6.3.4 Randomly select 20 of the 100 untreated and
45、treatedspecimens to serve as the sets of unexposed controls. Theremaining 80 treated and 80 untreated specimens shall berandomly assigned to 4 sets of 20 specimens for both thetreated and untreated material. Three of these four sets are thensubjected to elevated temperature exposure followed bystren
46、gth testing. This leaves 1 treated and 1 untreated set ofspecimens not assigned to any set for testing (see Note 7).NOTE 7The resulting extra set of 20 treated and 20 untreatedspecimens can be saved as replacement sets if the number of specimens ina set drops below the minimum of 18 (7.3.5). Alterna
47、tively, the extra 20treated and untreated specimens can be used to increase the number ofspecimens in each set.6.4 PreconditioningCondition all sets of treated and un-treated specimens at an ambient temperature and relativehumidity to achieve an equilibrium moisture content in theFIG. 1 An Example o
48、f Relationship Between Strandboard Specimen Width and the Corresponding Mean Test Values and Coefficient ofVariations for Both Flexural Stiffness and Strength for FRSC Over Time of Exposure at 77C (170F) (from 2, 3)D7857 163untreated specimens of 10 6 2 %. Specimens are considered tobe at equilibriu
49、m moisture content when a constant weight hasbeen achieved. A constant weight is assumed when twoconsecutive weighings at a 24-h interval differ by no more than60.2 %.6.5 MeasurementsMeasure the length, width, thicknessand mass of each specimen after pre-conditioning.7. Procedure7.1 Specimen Exposure:7.1.1 After preconditioning, test the unexposed controls (see6.4) as described in 7.3 for initial, unexposed bending strengthand IB properties.7.1.2 Expose three sets of treated and untreated specimensets in a chamber controlled to 77 6 1C (170 6 2F)
