4.Summary of Test Method
4.1An outline of an isosceles trapezoid is marked on a rectangular specimen cut for the determinatio
n of tearing strength (e Fig.1).The specimen is slit at the center of the smallest ba of the trapezoid to start the tear.The nonparallel sides of the trapezoid marked on the specimen are clamped in parallel jaws of a tensile testing machine.The paration of the jaws is continuously incread to apply a force to propagate the tear across the specimen.At the same time,the force developed is recorded.The maximum force to continue the tear is calculated from autographic chart recorders,or microprocessor data collection systems.
5.Significance and U
5.1This test method is ud in the trade for acceptance testing of commercial shipments of nonwoven fabrics,how-ever,caution is advid since information about between-laboratory precision is incomplete.Comparative tests as di-rected in 5.1.1may be advisable.
5.1.1In ca of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments,the purchar and the sup-plier should conduct comparative tests to determine if there is a statistical bias between their laboratories.Competent statis-tical assistance is recommended for the investigation of bias.As a minimum,the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot
of material of the type in question.Test specimens should then be randomly assigned in equal numbers to each laboratory for testing.The average results from the two laboratories should be compared using the appropriate Stu-dent’s t -test and an acceptable probability level chon by the two parties before testing is begun.If a bias is found,either its cau must be found and corrected or the purchar and the supplier must agree to interpret future test results in view of the known bias.
5.2The trapezoid tear method is a test that produces tension along a reasonably defined cour such that the tear propagates across the width of the specimen.It is uful for estimating the relative tear resistance of different fabrics or different direc-tions in the same fabric.
5.3For nonwoven fabrics,becau the individual fibers are more or less randomly oriented and capable of some reorien-tation in the direction of the applied force,the maximum trapezoid tearing strength is reached when the resistance to further reorientation is greater than the force required to
rupture one or more fibers or the fiber interlocking,simulta-neously.The tearing strength is determined primarily by the bonding or interlocking of fibers in the structure.
5.4Depending on the nature of the specimen,the data recording devices usually will show the tearing force in the form of single peak.The highest peak appears to reflect the strength combination needed
to stop a tear in a fabric of the same construction.
5.5Most nonwoven fabrics can be tested by this test method.Some modification of clamping techniques may be necessary for a given fabric,depending upon its structure.Special adaptation may be necessary with strong fabrics,or fabrics made from glass fibers,to prevent them from slipping in the clamps or being damaged as a result of being gripped in the clamps.
treasure是什么意思5.6The CRE-type is the preferred tensile testing machine.This test method allows the u of the CRT-type tensile machine when agreed upon between the purchar and the supplier.However,there may be no overall correlation between the results obtained with the CRT machine and the CRE machine.Conquently,the two tensile testers cannot be ud interchangeably unless the degree of quantitative corre-lation has been established between the purchar and the supplier.In any event,the CRE machine shall prevail.六级报名网站
6.Apparatus
6.1Tensile Testing Machine ,of the constant-rate-of-extension (CRE)type conforming to the requirements of Specification D 76with autographic recorder,or automatic microprocessor data gathering systems.
6.2Clamps ,having all gripping surfaces parallel,flat,and capable of preventing slipping of the specimen during a test,and measuring 50by no less than 75mm (2by no less than 3in.),with the longer dimension perpendicular to the direction of application of the force.
6.2.1The u of hydraulic pneumatic clamping systems with a minimum of 50by 75-mm (2by 3-in.)rrated or rubber jaw faces having a clamping force at the grip faces of 13to 14kN (2900to 3111lbf)is recommended.Manual clamping is permitted providing no slippage of the specimen is obrved.6.2.2For some materials,to prevent slippage when using jaw faces other than rrated,such as rubber-faced jaws,they may be covered with a No.80to 120medium-grit emery cloth.Secure the emery cloth to the jaw faces with pressurensitive tape.
6.3Cutting Die or Template ,having esntially the shape and dimensions with tolerances of 60.5%shown in Fig.2(a ).6.4Trapezoidal-Shaped Template ,having dimensions with tolerances of 60.5%as shown in Fig.2(b ).
英语口译7.Sampling and Test Specimens
7.1Lot Sample —As a lot sample for acceptance testing,take at random the number of rolls,or pieces,of nonwoven fabric directed in an applicable material specification or other agreement between the purchar and the supplier.Consider the rolls,or pieces,of nonwoven fabric to be the primary sampling units.In the abnce of such an agreement,take the number of nonwoven fabric rolls specified in Table 1.
N OTE 1—An adequate specification or other agreement betweengo ahead
the
FIG.1Diagram of Marked Trapezoid
Specimen
purchar and the supplier requires taking into account the variability between rolls or pieces of fabric and between specimens from a swatch from a roll or pieces of fabric to provide a sampling plan with a meaningful producer’s risk,consumer’s risk,acceptable quality level,and limiting quality level.
7.2Laboratory Sample —For the laboratory sample,take a sample extending the width of the fabric and approximately 1m (1yd)along the machine direction from each roll,or piece,in the lot sample.For rolls of fabric,take a sample that will exclude fabric from the outer wrap of the roll or the inner wrap around the core.同意的英文
7.3Test Specimens —From each laboratory sampling unit,take five specimens from the lengthwi direction and five specimens from the widthwi direction,for each test condition described in 8.1-8.3
as,applicable to a material specification or contract order.U the cutting die or template described in 6.3and shown in Fig.2.Mark each specimen with an isosceles trapezoid template (e Figs.1and 2).Make a preliminary cut 15mm (0.625in.)long at the center of the 25-mm (1-in.)edge,as shown in Figs.1and 2.
7.3.1Direction of Test —Consider the short direction as the direction of test.
7.3.2Cutting Test Specimens —Take the specimens for the measurement of the lengthwi direction from different posi-tions across the fabric width.Take the specimens for the measurement of the widthwi direction from different posi-tions along the length of the fabric.Cut the specimens to be ud for the measurement of the lengthwi direction with the shorter dimension parallel to the lengthwi direction.Cut the specimens to be ud for the measurement of the widthwi direction with the shorter dimension parallel to the widthwi direction.When specimens are to be tested wet,take the specimens from areas adjacent to the dry test specimens.Label to maintain specimen identity.
7.3.2.1Cut specimens reprenting a broad distribution across the width of the laboratory sample and no nearer the edge than one tenth its width.Ensure specimens are free of folds,creas,or wrinkles.Avoid getting oil,water,grea,and so forth,on the specimens when handling.
7.3.2.2Refer to Fig.3for illustration of the relationship of specimen orientation with respect to test direction.
8.Preparation of Apparatus
8.1Set the distance between the clamps at the start of the test at 2561mm (160.05in.).Select the full-scale force range of the testing machine such that the maximum force occurs between 15and 85%of full-scale force.cnki在线翻译
8.2Set the testing speed to 300610mm (1260.5in./min).8.3Verify calibration of the tensile testing machine as directed in the manufacturer’s instructions or Specification D 76.
8.4When using microprocessor automatic data gathering systems,t the appropriate parameters as defined in the manufacturer’s instructions.
9.Conditioning
9.1Condition 1,Unspecified Testing Conditioning —No conditioning is required unless otherwi specified in a mate-rial specification or contract order.
9.2Condition 2,Standard Testing Conditioning :
9.2.1When specified,precondition the specimens by bring-ing them to approximate moisture equilibrium in the standard atmosphere for preconditioning textiles as directed in Practice D 1776.
9.2.2After preconditioning,bring the test specimens to moisture equilibrium for testing in the standard atmosphere for testing textiles as directed in Practice D 1776or,if applicable,in the specified atmosphere in which the testing is to be performed.
9.3Condition 3,Wet Specimen Conditioning Testing :
9.3.1Place the specimens in a container and submerge in distilled or deionized water at ambient temperature until thoroughly soaked (e 9.3.1.1).
9.3.1.1The time of immersion must be sufficient to wet out the specimens,as indicated by no significant change in tearing force followed by longer periods of immersion.For most fabrics this time period will be about one hour.For fabrics not readily wet out with water,such as tho treated with water-repellent or water-resistance materials,add a 0.1%solution
of
N OTE 1—All tolerances 60.5%.
FIG.2Templates for Cutting (a)and Marking (b)Trapezoid Test
Specimens TABLE 1Number of Rolls,or Pieces,of Nonwoven Fabric in the
Lot Sample
Number of Rolls,Pieces in Lot,
Inclusive
Number of Rolls or Pieces in Lot,
Sample
1to 3all 4to 24425to 505
非诚勿扰开场音乐
over 50
10%to a maximum of ten rolls or
pieces
a nonionic wetting agent to the water bath.
10.Procedure
10.1Test the specimens in the atmosphere as directed in an applicable material specification or contract order.
10.2Secure the test specimen in the machine,clamping along the nonparallel sides of the trapezoid such that the end edges of the clamps are in line with the 25-mm (1-in.)long side of the trapezoid,an
d the cut is halfway between the clamps.Hold the short edge taut and let the remaining fabric lie in folds.
10.2.1For wet specimens,remove the specimens from the water and immediately mount it on the testing machine in the normal tup.Perform the test within 2min after removal of the specimen from the water.If more than 2min elap between taking the wet specimen from the water bath and starting a tensile testing machine,discard the specimen and take another.
10.2.2Start the machine and record the tearing force on the recording device.The tearing force may increa to a simple maximum value,or may show veral maxima and minima,as shown in Fig.4.
10.2.3After the crosshead has moved to produce approxi-mately 6mm (0.25in.)of fabric tear,record the maximum tearing force (e Fig.4).Stop the crosshead motion after a total clamp paration of approximately 75mm (3in.)or the fabric has torn completely across and return the crosshead to its starting position.
10.2.4If a fabric slips in the jaws or if 25%or more of the specimens break at a point within 5mm (0.25in.)of the
edge
FIG.3Illustration of Test Direction and Orientation of Specimens Within Laboratory
Sample
FIG.4Typical Trapezoid Tearing Force-Extension Curves for Individual Test
Specimens
of the jaw,then the jaws may be padded;the fabric may be coated under the jaw face area;or the jaw face may be modified.If any of the modifications are ud,state the method of modification in the report.
10.2.5If25%or more of the specimens break at a point within5mm(0.25in.)of the edge of the jaw after making the modifications described in10.2.4consider the fabric untearable by this test method.
10.2.6Report if the tear occurs crosswi to the direction of applied force.
10.2.7Remove the tested specimen and continue as directed in10.2-10.2.6untilfive specimens have been tested for each principal direction from each laboratory sampling unit.
11.Calculation
11.1Tearing Force,Individual Specimens—Calculate the trapezoid tearing force for individual specimens using readings directly from the data collection system.Record the maximum tearing forc有关春节的资料
e to the nearest0.5N(0.1lbf),unless otherwi agreed upon between the purchar and the supplier.
11.2Tearing Strength—Calculate the average trapezoid tearing for each principal direction of each laboratory sample and the lot.
11.3Standard Deviation,Coeffıcient of Variation—Calculate when requested.
11.4Computer-Procesd Data—When data is automati-cally computer procesd,calculations are generally contained in the associated software.Record values as read from the direct reading scale to the nearest0.5N(0.1lbf).In any event, it is recommended that computer-procesd data be verified against known property values and its software described in the report.
12.Report
12.1Report that the trapezoid tearing strength was deter-mined as directed in this test method.Describe the material or product sampled and the method of sampling ud.
12.2Report the following information for both the labora-tory sampling unit and the lot as applicable to a material specification or contract order:
12.2.1Trapezoid tearing strength for each principal direc-tion,as requested,
12.2.2Number of specimens tested for each direction, 12.2.3Condition of the specimens(dry or wet),
12.2.4When calculated,the standard deviation or the coef-ficient of variation,
12.2.5For computer procesd data,identify the program (software)ud,
12.2.6Make,model,and capacity of testing machine, 12.2.7Type of clamps ud,
12.2.8Test room conditioning,and
12.2.9Any modification of the test method.
13.Precision and Bias
13.1Summary—Preliminary interlaboratory test data have shown that the variance in testing tearing strength of nonwoven fabrics by this test method is dependent upon the nominal tearing strength and to some extent the manufacturing method of the material under evaluation;therefore,no general state-ment can be made concerning least critical differences.The following data were generated during the interlaboratory test and are prented for reference.In comparing two averages of five obrvations,the difference between averages should not exceed the following values in95out of100
cas when all the obrvations are taken by the same well-trained operator using the same piece of equipment and specimens are randomly drawn from the same sample having a nominal tearing strength indicated:
Nominal Tearing Strength(lbf)
(Critical Differences)
Tearing Strength(lbf)
(Critical Differences) Machine Direction
0.500.09
2.300.42
股本溢价
3.150.82
18.60 3.52
Transver Direction
0.45(Meltblown)0.11
0.50(Wet Laid)0.06
0.55(Dry Laid)0.12
0.70(Resin Bonded)0.16
0.84(Thermal)0.29
7.75(Hydroentangled)0.83
Larger differences are likely to occur under all other circum-stances.This procedure for determining thickness has no other known bias and is considered a referee method.
13.2Interlaboratory Test Data—A preliminary interlabora-tory test was run in1992in which randomly drawn samples of six materials were tested in each of six laboratories utilizing the “dry”conditions.Data from two laboratories was deleted as obvious outliers when procedural errors were found to be prent.Two operators in each laboratory testedfive specimens of each material.The six materials ud in this evaluation were all manufactured by different process.Analy
sis of the data using the adjunct to Practice D2904suggested reporting the components of variance and least critical differences bad upon nominal tearing strength,with some interaction bad on the manufacturing method.The components of variance,ex-presd as standard deviations,for each nominal tearing strength,and where appropriate the method of manufacturing are listed in Table2(e Note2).Further testing is in progress to elucidate the ruggedness of this test method and possible revision.
13.3Precision—For the components of variance listed in Table2,the averages of two obrved values should be
TABLE2Components of Variance as Standard Deviations A
N OTE1—Tearing strength expresd in pounds-force.
Nominal Tearing Strength
Single-
Operator
Component
Within-
Laboratory
Componentyes or no 2
Between-
Laboratory
Component Machine Direction
0.500.070.060.06
2.300.330.440.57
3.150.660.460.76
18.60 2.84 1.89 2.00 Transver Direction
0.45(Meltblown)0.090.080.06
0.50(Wet laid)0.050.100.03
0.55(Dry laid)0.100.100.06
0.70(Resin bonded)0.130.160.12
0.84(Thermal)0.230.130.08
7.75(Hydroentangled)0.67 1.250.00
A Ibf34.455
newtons
