Astm C 297

 

Designation: C 297/C 297M – 04

Standard Test Method for

Flatwise Tensile Strength of Sandwich Constructions 1 This standard is issued under the fixed designation C 297/C 297M; the number immediately following the designation indicates the year of 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 superscript epsilon (e) indicates an editorial change since the last revision or reapproval.

D 5229 5229/D /D 522 5229M 9M Test Met Method hod for Moi Moistu sture re Abs Absorp orpti tion on Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials E 4 Practices for Force Verification Verification of Testing Machines E 6 Ter Terminology minology Relating to Methods of Mechanical TestTesting E 122 Pra Practi ctice ce for Choice Choice of Sam Sample ple Size to Est Estima imate te a Measure of Quality for a Lot or Process E 177 Prac Practice tice for Use of the Terms Terms Precision Precision and Bias in ASTM Test Methods E 456 Terminology Relating to Quality and Statistics E 130 1309 9 Gui Guide de for Ide Identi ntifica ficatio tion n of Fib Fiber er-Re -Reinf inforc orced ed Polymer-Matrix Composite Materials in Databases

1. Sco Scope pe 1.1 This test method determines determines the flatwise tensile tensile strength of th thee co core re,, th thee co core re-t -too-fa faci cing ng bo bond nd,, or th thee fa faci cing ng of an assembled assem bled sand sandwich wich panel panel.. Perm Permissi issible ble core mate material rial form formss include those with continuous bonding surfaces (such as balsa wood and foams) as well as those with discontinuous bonding surfaces (such as honeycomb). 1.2 The values stated stated in either SI units or inch-pound inch-pound units are to be regarded separately as standard. Within the text the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.3   This sta standa ndard rd does not purport purport to add addre ress ss all of the safe sa fety ty co conc ncer erns ns,, if an anyy, as asso soci ciat ated ed wi with th it itss us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.

E 1434 Guide for Recording Mechanical Tes Testt Data of FiberReinforced Composite Materials in Databases E 1471 Guide for Identificati Identification on of Fiber Fibers, s, Fillers, Fillers, and Core Materials in Computerized Material Property Databases 3. Terminology 3.1   Definitions—Terminology D 3878 defines terms relating to high high-modu -modulus lus fibers and thei theirr compo composite sites. s. Termi erminolo nology gy C 274 defines terms relating to structural sandwich constructions. tion s. Termi erminolo nology gy D 883 883 define definess term termss relat relating ing to plas plastics tics.. Terminology E 6 defines terms relating to mechanical testing. Terminology E 456 and Practice E 177 define terms relating to statistics. In the event of a conflict between terms, Terminology D 3878 shall have precedence over the other terminologies. 3.2   Symbols:

2. Referenced Documents 2.1   ASTM Standards:   2 C 274 Ter Terminology minology of Structural Sandwich Constructions D 792 Tes Testt Methods for Density and Specific Specific Gravity (Relative Density) of Plastics by Displacement D 883 Termi erminolog nology y Relat Relating ing to Plast Plastics ics D 2584 Test Method for Ignition Ignition Loss of Cured Reinforced Reinforced Resins D 2734 Test Method for Void Content of Reinf Reinforce orced d Plas Plas-tics D 303 3039/D 9/D 303 3039M 9M Test Met Method hod for Tens ensile ile Pro Proper pertie tiess of  Polymer Matrix Composite Materials D 3171 Test Method for Const Constitue ituent nt Content of Compo Composite site Materials D 3878 Ter Terminology minology for Composite Materials

 A  = = area of a statistic test specimen CV    =cross-sectional coefficient of variation of a sample population for a given property (in percent) F  z ftu = ultimate flatwise tensile strength Pmax   = ma maxim ximum um for force ce car carrie ried d by tes testt spe specim cimen en bef before ore failure S n-1 = standard deviation statistic of a sample population for a given property  x1 = test result for an individual specimen from the sample population for a given property  x¯  ¯  = = mean or average (estimate of mean) of a sample population for a given property

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Thiss test method Thi method is und under er the jurisdicti jurisdiction on of ASTM Committee Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.09 on Sandwich Construction. Curren Cur rentt edit edition ion app approv roved ed May 1, 200 2004. 4. Pub Publish lished ed May 200 2004. 4. Orig Origina inally lly approved in 1952. Last previous edition approved in 1999 as C 297 – 94 (1999). 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@ [email protected] astm.org. g. For For   Annual Book of ASTM  Standards volume Standards  volume information, refer to the standard’s Document Summary page on the ASTM website website..

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

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C 297/C 297M – 04 4. Summa Summary ry of Test Method

thickness, specimen shape (square or circular), adhesive thickness, facing thickness, and facing per-ply thickness. 6.4   Environment —Results —Results are affected by the environmental conditions under which the tests are conducted. Specimens tested in various environments can exhibit significant differences enc es in bot both h str streng ength th beh behavi avior or and fai failur luree mod mode. e. Cri Critic tical al environments must be assessed independently for each facing, adhesive and core material tested. 6.5   Conditioning—A —Ass it is in inap appr prop opri riat atee to bo bond nd a

4.1 This tes testt met method hod con consis sists ts of sub subjec jectin ting g a san sandwi dwich ch construction to a uniaxial tensile force normal to the plane of  the sandwich. The force is transmitted to the sandwich through thick loading blocks, which are bonded to the sandwich facings or directly to the core. 4.2 The only acce acceptabl ptablee fail failure ure modes for flatwi flatwise se tensile strength are those which are internal to the sandwich construction. Failure of the loading block-to-sandwich bond is not an acceptable failure mode.

moisture-cond moisture -conditio itioned ned spec specimen imen to the bondi bonding ng bloc blocks, ks, it is necess nec essary ary to per perfor form m the bon bondin ding g ope operat ration ion pri prior or to suc such h conditioning. The presence of the bonding blocks will affect the degree of moisture intake into the specimen, in comparison to a non-bonded sample.

5. Signi Significanc ficancee and Use 5.1 In a san sandwi dwich ch pan panel, el, cor core-t e-to-f o-faci acing ng bon bond d int integr egrity ity is necessary to maintain facing stability and permit load transfer between the facings and core. This test method can be used to provide provi de info informat rmation ion on the strength and quali quality ty of core core-to-tofacing bonds. It can also be used to produce flatwise tensile strength data for the core material. While it is primarily used as a quality control test for bonded sandwich panels, it can also be used to prod produce uce flatwise tensile strength strength data for stru structur ctural al design desig n prope propertie rties, s, mate material rial spec specificat ifications ions,, and rese research arch and development applications. 5.2 Facto Factors rs that influe influence nce the flatwi flatwise se tensile strength strength and shall sha ll the theref refore ore be rep report orted ed inc includ ludee the fol follow lowing ing:: fac facing ing material, core material, adhesive material, methods of material fabricati fabri cation, on, faci facing ng stac stacking king seque sequence nce and overa overall ll thick thickness, ness, core geom geometry etry (cel (celll size) size),, core densi density ty,, adhes adhesive ive thick thickness, ness, specimen speci men geom geometry etry,, speci specimen men prep preparati aration, on, speci specimen men condi condi-tioning, environment of testing, specimen alignment, loading procedure, speed of testing, facing void content, adhesive void content, and facing volume percent reinforcement. Properties thatt may be der tha derive ived d fro from m thi thiss tes testt met method hod inc includ ludee flat flatwis wisee tensile strength.

7. Appa Apparatus ratus 7.1   Micrometers—The micrometer(s) shall use a 4- to 5-mm [0.16- to 0.20-in.] nominal diameter ball-interface on irregular surfaces such as the bag-side of a facing laminate, and a flat anvil anv il int interf erface ace on mac machin hined ed edg edges es or ver very y smo smooth oth-to -toole oled d surfaces. The accuracy of the instrument(s) shall be suitable for read re adin ing g to wi with thin in 1 % of th thee sa samp mple le le leng ngth th,, wi widt dth h an and d thickness. For typical specimen geometries, an instrument with an accuracy of  625 mm [60.001 in.] is desirable for thickness, length and width measurement. 7.2   Loading Fixture Fixturess—The loading fixtures fixtures shal shalll be selfaligning and shall shall not apply eccentric eccentric loads. A satisfactory type of apparatus is shown in Fig. 1. The loading blocks shall be

6. Interferences 6.1   Mate material rial Material rial and Speci Specimen men Pr Prepara eparation tion—Poor mate fabrication fabricati on pract practices ices,, lack of cont control rol of fiber alignment, alignment, and damage induced by improper specimen machining are known causes of high data scatter in composites in general. Specific material factors that affect sandwich composites include variability in core density and degree of cure of resin in both facing matrix material and core bonding adhesive. Important aspects of sandwich panel specimen preparation that contribute to data scatter are incomplete or nonuniform core bonding to facings, misalignm misa lignment ent of core and faci facing ng elem elements ents,, the existence existence of   joints, voids or other core and facing discontinuities discontinuities,, out-ofplane curvature, facing thickness variation, and surface roughness. 6.2   System Alignment —Excessive —Excessive bending will cause premature failure. Every effort should be made to eliminate excess bending from the test system. Bending may occur as a result of  misaligne misa ligned d grips grips,, poor specimen preparation preparation,, or poor alignment of the bonding blocks and loading fixture. If there is any doubt as to the alignment inherent in a given test machine, then the alignment should be checked as discussed in Test Method D 3039/D 3039M. 6.3   Geometry—Specific geometric factors that affect sandwich flatwise tensile strength include core cell geometry, core

FIG. 1 Flatwise Tension Test Setup

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C 297/C 297M – 04 sufficiently stiff to keep the bonded core or facings essentially flat under load. Loading blocks 40 to 50 mm [1.5 to 2.0 in.] thick have been found to perfo perform rm satis satisfact factoril orily y. Perm Permissi issible ble tolerances toler ances for the loading blocks (alo (along ng with alignment alignment requirements) are provided in Fig. 2. 7.3   Testing Machine—T —The he te test stin ing g ma mach chin inee sh shal alll be in accordance with Practices E 4 and shall satisfy the following requirements: 7.3.1  Testing Machine Configuration—The testing machine

to within  6 3 %. Chamber conditions shall be monitored either on an aut autom omate ated d con contin tinuou uouss bas basis is or on a man manual ual basis basis at regular intervals. 7.5   Environmental —An envi environme ronmental ntal test Environmental Test Chamber —An chamber is required for test environments other than ambient testing laboratory conditions. This chamber shall be capable of  mainta mai ntaini ining ng the gage sec sectio tion n of the test spe specim cimen en at the required test environment during the mechanical test.

shall have both an essentially stationary head and a movable head. 7.3.2  Drive Mechanism—The testing machine drive mechanism nis m sha shall ll be cap capabl ablee of im impar partin ting g to the movable movable head a controlled contr olled velocity velocity with respect to the stationary stationary head. The velo ve loci city ty of th thee mo mova vabl blee he head ad sh shal alll be ca capa pabl blee of be bein ing g regulated in accordance with 11.6. 7.3.3   Load Indi Indicator  cator —The test testing ing mach machine ine load load-sens -sensing ing device dev ice sha shall ll be cap capabl ablee of ind indica icatin ting g the tot total al for force ce bei being ng carried by the test specimen. This device shall be essentially free from inertia lag at the specified rate of testing and shall indicate the force with an accuracy over the force range(s) of  interest of within  6 1 % of the indicated value. 7.4   Conditioning Conditioning Chamber —When —When conditioning materials at non-l non-laborat aboratory ory envir environment onments, s, a tempe temperatur rature/vap e/vapor-l or-level evel

8. Sampling Sampling and Test Test Speci Specimens mens 8.1   Sampling—Test at least five specimens per test condition unless valid results can be gained through the use of fewer spec sp ecim imen ens, s, as in th thee ca case se of a de desi sign gned ed ex expe peri rime ment nt.. Fo Forr statistically significant data, consult the procedures outlined in Practice E 122. Report the method of sampling. 8.2   Geometry—Test specimens shall have a square or circular cul ar cro crossss-sec sectio tion, n, and sha shall ll be equ equal al in thi thickn ckness ess to the sandwich panel thickness. Minimum specimen facing areas for various types of core materials are as follows: 8.2.1   Contin Continuou uouss Bon Bondin ding g Sur Surfac faces es (fo (forr exa exampl mple, e, bal balsa sa wood, foams foams))—Th —Thee min minimu imum m fac facing ing are areaa of the spe specim cimen en shall be 625 mm2 [1.0 in.2]. 8.2.2   Discon Discontin tinuou uouss Cel Cellul lular ar Bon Bondin ding g Sur Surfac faces es (fo (forr example, honeycomb)—The required facing area of the specimen

controlled environmental conditioning chamber is required shall be capa capable ble of main maintain taining ing the requ required ired temperature tempera turethat to within  6 3°C [65°F] and the required relative humidity level

is upon Minimum the cell size, to ensure a minimum number of dependent cells are tested. facing areas are recommended in Table 1 for the more common cell sizes. These are intended to

FIG. 2 Permissible Bonded Assembly Tolerances

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C 297/C 297M – 04 TABLE TAB LE 1 Recommended Minimum Specimen Facing Area Minimum Cell Size (mm [in.])

Maximum Cell Size (mm [in.])

Minimum Facing Area (mm2 [in.2])

3.0 [0.125] 6.0 [0.250]

3.0 [0.125] 6.0 [0.250] 9.0 [0.375]

625 [1.0] 2500 [4.0] 5625 [9.0]

transduce transd ucerr sel select ection, ion, cal calibr ibratio ation n of equi equipme pment, nt, and dete determi rminati nation on of  equipment settings.

11.1.3 The environmental conditioning conditioning test parameters. 11.1.4 If performed, sampling method, specimen geometry geometry,, and tes testt par parame ameter terss use used d to det determ ermine ine fac facing ing den densit sity y and reinforcement volume. 11.2   General Instructions: 11.2.1 Report any deviations from from this test method, whether whether intentional or inadvertent. 11.2.2 If specific gravity, density, density, facing reinforcement volume, or facing void volume are to be reported, then obtain these the se sam sample pless fro from m the sam samee pan panels els bei being ng tes tested ted.. Spe Specifi cificc gravity and density may be evaluated in accordance with Test Methods D 792. Volume percent of composite facing constituents may be evaluated by one of the matrix digestion proceduress of Test Method D 3171, or, for cert dure certain ain reinf reinforcem orcement ent materials such as glass and ceramics, by the matrix burn-off  technique in accordance with Test Method D 2584. The void content equations of Test Method D 2734 are applicable to both Test Method D 2584 and the matrix digestion procedures. 11.2.3 11 .2.3 Follow Following ing fina finall spe specim cimen en mac machin hining ing,, but bef before ore condition condi tioning ing and test testing, ing, meas measure ure the speci specimen men leng length th and width or diameter. The accuracy of these measurements shall be wit within hin 0.5 % of the dim dimens ension ion.. Mea Measur suree the spe specim cimen en

provide approximately 60 cells minimum in the test specimen. 2

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The largest facing area listed in the table (5625 mm [9.0 in. ]) is a practical maximum for this test method. Cores with cell sizes siz es lar larger ger than 9 mm [0.375 in.] may req requir uiree a sma smalle llerr number of cells to be tested in the specimen. 8.3   Speci Specimen men Pr Prepar eparatio ation n and Mac Machini hining ng—Specimen preparation is extremely important for this test method. Take precautions when cutting specimens from large panels to avoid notches, undercuts, rough or uneven surfaces, or delaminations due to inappropriate machining methods. Obtain final dimensions by water-lubricated precision sawing, milling, or grinding. in g. Th Thee us usee of di diam amon ond d to tool olin ing g ha hass be been en fo foun und d to be extremely effective for many material systems. Edges should be flat and parallel within the specified tolerances. Record and report the specimen cutting preparation method. 8.4   Labeling—Label the test specimens so that they will be dis distin tinct ctand from fro m each h oth other er and traceabl trace e bac back the panel of  origin, willeac neither influence theable test norkbetoaffected by it. 8.5   Loading Fixture Bonding—The loading blocks shall be bonded to the core or facings of the test specimen using a suitable adhesive. To minimize thermal exposure effects upon the existing core-to-facing bonds, it is recommended that the assembly bonding temperature be at room temperature, or at least 28°C [50°F] lower than that at which the sandwich was originally origi nally bonde bonded. d. Simi Similarl larly y, the asse assembly mbly bondi bonding ng pres pressure sure shall not be greater than the original facing-to-core bonding pressu pre ssure. re. Per Permis missib sible le tol tolera erance ncess for the bon bonded ded ass assemb embly ly (along with alignment requirements) are provided in Fig. 2.

thickness; the accuracy of this measurement shall be within 625 mm [60.001 in.]. Record the dimensions to three significant figures in units of millimetres [inches]. 11.3 11 .3 Bon Bond d the specimen specimen to the bonding bonding blo blocks cks,, in acc accor or-dance with the requirements of 8.5. 11.4 Condition the bonded specimens specimens as required. Store the specimens in the conditioned environment until test time, if the test envi environme ronment nt is dif differe ferent nt than the condi conditioni tioning ng envi environronment. 11.5 11 .5 Fol Follow lowing ing fina finall spe specim cimen en con condit dition ioning ing,, but bef before ore testing, re-measure the specimen length and width or diameter as in 11.2.3. 11.6   Speed of Testi esting ng—S —Set et the sp spee eed d of te test stin ing g so as to produce failure within 3 to 6 min. If the ultimate strength of the material cannot be reasonably estimated, initial trials should be

9. Cali Calibrati bration on 9.1 The acc accura uracy cy of all mea measur suring ing equ equipm ipment ent sha shall ll hav havee certified calibrations that are current at the time of use of the equipment.

conducted using standard speeds until the ultimate strength of  the material and the compliance of the system are known, and speed of testing can be adjusted. The suggested standard head displacement rate is 0.50 mm/min [0.020 in./min]. 11.7   Test Environment —If —If possible, test the specimen under the same fluid exposure level used for conditioning. However, cases such as elevated temperature testing of a moist specimen place unrealistic requirements on the capabilities of common testing test ing mach machine ine envi environme ronmental ntal chambers. chambers. In such cases, the mecha me chanic nical al tes testt env enviro ironme nment nt may nee need d to be mod modifie ified, d, for exampl exa mple, e, by tes testin ting g at ele elevat vated ed tem temper peratu ature re wit with h no flui fluid d exposure control, but with a specified limit on time to failure from withdrawal from the conditioning chamber. Record any modifications to the test environment. 11.8   Specimen Installation—Ins —Install tall the spec specimen imen/bond /bonding ing

10. Condi Conditioni tioning ng 10.1   Standard Conditioning Procedure—Unless a different environment is specified as part of the experiment, condition the tes testt spe specim cimens ens in acc accord ordanc ancee wit with h Pro Proced cedure ure C of Test Method Met hod D 522 5229/D 9/D 522 5229M, 9M, and sto store re and tes testt at sta standa ndard rd laboratory atmosphere (23   6  3°C [73   6  5°F] and 50   6   5 % relative humidity). 11. Procedure 11.1   Parameters to Be Specified Before Test : 11.1.1 The specimen sampling method, method, specimen geometry, geometry, and conditioning travelers (if required). 11.1.2 11.1 .2 The properties properties and data repor reporting ting format desired. desired.

block assembly into the test machine test fixture. 11.9   Loading—Apply a tensile force to the specimen at the specified rate while recording data. Load the specimen until rupture.

NOTE   1—Deter 1—Determine mine specifi specificc materi material al proper property ty,, accura accuracy cy,, and data reporting requirements prior to test for proper selection of instrumentation and data recording equipment. Estimate the specimen strength to aid in

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C 297/C 297M – 04 11.10  Data Recording—Record force versus head displacement continuously, or at frequent regular intervals. Record the maximum force, the failure force, and the head displacement at, or as near as possible to, the moment of rupture. 11.11   Failure Modes—Adhesive failures that occur at the bond to the loading blocks are not acceptable failure modes and the data shall be noted as invalid. The following failure modes are considered to be acceptable: 11.11.1  Core Failure—Tensile failure of the sandwich core.

samplee coeff coefficie icient nt of variat variation, ion, %, %, CV    = sampl number of speci specimens, mens, and n   = number measured ured or deriv derived ed prope property rty..  x1   = meas 14. Repor Reportt 14.1 Report the following information, information, or references pointpointing to other documentation containing this information, to the maximum maxi mum extent appl applicabl icablee (rep (reporti orting ng of item itemss beyon beyond d the control of a given testing laboratory, such as might occur with material details or panel fabrication parameters, shall be the responsibility of the requestor):

Pieces of the core may remain in the adhesive that bonds the core to the block or facing. 11.11.2   Cohes Cohesive ive Fail Failur uree of Cor Core-Fa e-Facing cing Adhe Adhesiv sivee — Failure in the adhesive layer used to bond the facing to the core, with adhesive generally remaining on both the facing and core surfaces. 11.11.3  Adhesive Failure of Core-Facing Adhesive—Failure in the adhesive layer used to bond the facing to the core, with adhesive generally remaining on either the facing or the core surface, but not both. 11.11.4   Facing Tensile Failure—Tensile failure of the facing, usually by delamination of the composite plies in the case of a fiber-reinforced composite facing.

NOTE  2—Guid  2—Guides es E 1309, 1309, E 1434 1434 and E 1471 1471 con contain tain data rep reporti orting ng recommendations for composite materials and composite materials mechanical testing.

14.1.1 The revision level or date of issue issue of this test method. 14.1.2 The name(s) name(s) of the test operator(s) operator(s).. 14.1.3 Any variations to this this test method, anomalies anomalies noticed during testing, or equipment problems occurring during testing. 14.1.4 Ident Identificat ification ion of all the mate material rialss consi consistuen stuentt to the sandwich panel specimen tested, including for each: material specification, material type, manufacturer’s material designation, manufacturer’s batch or lot number, source (if not from manufacturer), date of certification, expiration of certification, facing filament diameter, tow or yarn filament count and twist, sizing, form or weave, fiber areal weight, matrix type, facing matrix mat rix con conten tentt and vol volati atiles les con conten tent, t, ply ori orient entati ation on and stacking sequence of the facings. 14.1.5 Descr Descripti iption on of the fabrication fabrication steps used to prepa prepare re the sandwich panel including: fabrication start date, fabrication end dat date, e, pro proces cesss spe specifi cificat cation ion,, cur curee cyc cycle, le, con consol solida idatio tion n method, and a description of the equipment used. 14.1.6 Ply orientation orientation and stacking sequence sequence of the facing laminate. 14.1.7 If reque requested, sted, report facing densi density ty,, volum volumee perce percent nt reinforcement, and void content test methods, specimen sampling method and geometries, test parameters and test results. 14.1.8 Resul Results ts of any nondestructi nondestructive ve evalu evaluation ation tests. 14.1.9 Method of prepa preparing ring the test specimen, specimen, incl including uding specimen spec imen label labeling ing schem schemee and meth method, od, speci specimen men geom geometry etry,, sampling method, and specimen cutting method. 14.1.10 Calibration dates dates and methods for all measurements and test equipment. 14.1.11 14.1.1 1 Detai Details ls of loadi loading ng bloc blocks ks and apparatus, apparatus, incl including uding dimensions and material used. 14.1.12 14.1.1 2 Type of test machine, machine, alignment alignment resu results, lts, and data acquisition sampling rate and equipment type. 14.1.13 Measured length and and width (or diameter) diameter) and thicknesss for eac nes each h spe specim cimen en (pr (prior ior to and aft after er con condit dition ioning ing,, if  appropriate). 14.1.14 Weight of specimen. 14.1.15 14.1.1 5 Meth Method od of bonding specimens specimens to block blocks; s; adhesive, cure cycle, and pressure. 14.1.16 Conditioning parameters parameters and results. 14.1.17 14.1.1 7 Relat Relative ive humidity and temp temperat erature ure of the testing

12. Validation Value aluess forthat ultimat ultimate e prope propertie rties s shall not beunless calculate calcu lated d for12.1 any specimen breaks at some obvious flaw, such flaw con consti stitut tutes es a var variab iable le bei being ng stu studie died. d. Ret Retest estss sha shall ll be performed for any specimen on which values are not calculated. 12.2 A significant fraction fraction of failures in in a sample sample population occurring at the bond(s) to the loading blocks shall be cause to reexamine the means of force introduction into the material. Factors considered should include the fixture alignment, adhesive mate material rial,, speci specimen men surf surface ace char character acteristi istics, cs, and uneve uneven n machining of specimen ends. 13. Calc Calculati ulation on 13.1  Ultimate Strength—Calculate the ultimate flatwise tensile si le st stre reng ngth th us usin ing g Eq 1 an and d re repo port rt th thee re resu sult ltss to th thre reee significant figures. F  ftu  A  z 5 Pmax  /  A

 

(1)

where: ultimate mate flatwise flatwise tensile strength, strength, MPa [psi], F  z ftu = ulti ultimate mate force force prior prior to failur failure, e, N [lbf], [lbf], and Pmax   = ulti  A   = cross-section cross-sectional al area, mm2 [in.2]. 13.2   Statistics—For each series of tests calculate the average value, standard deviation, and coefficient of variation (in percent) for ultimate flatwise tensile strength: n

 x¯  ¯  5 5 ~ (  x1! i51

Œ (

 

(2)

n

S n21 5

~

i51

 x21 2 n x¯ 2!  /  ~n 2 1!

CV  5 100 3 S n21 /  x  x¯ 

   

(3) (4)

laboratory. 14.1.1 14. 1.18 8 Env Enviro ironme nment nt of the tes testt mac machin hinee env enviro ironme nmenta ntall chamber (if used) and soak time at environment. 14.1.19 14.1.1 9 Numbe Numberr of specimens specimens test tested. ed.

where:  x¯  ¯    = samp sample le mean (ave (average) rage),, sample le standa standard rd devia deviation tion,, S n-1   = samp 5

 

C 297/C 297M – 04 15. Prec Precisio ision n and Bias

14.1.20 Speed of testing. 14.1.20 testing. 14.1.21 14.1.2 1 Indi Individua viduall ulti ultimate mate flatwi flatwise se tens tensile ile stre strengths ngths and average value, standard deviation, and coefficient of variation (in percent) for the population. 14.1.22 14.1.2 2 Forc Forcee vers versus us cros crosshead shead displaceme displacement nt data for each specimen so evaluated. 14.1.2 14. 1.23 3 Fai Failur luree mod mode, e, loc locati ation on of fai failur lure, e, per percen centag tagee of  failure area of core, adhesive (cohesive or adhesive failure), or facing for each specimen.

15.1   Precision—The data required for the development of a precision statement is not available for this method. 15.2   Bias—Bias cannot be determined for this method as no acceptable reference standards exist. 16. Keyw Keywords ords 16.1 16. 1 cor core; e; fac facing ing;; flat flatwis wisee ten tensio sion; n; san sandwi dwich; ch; san sandwi dwich ch construction; tensile strength

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