ASTM D3786-13

Designation: D3786/D3786M − 13 Standard Test Method for Bursting Strength of Textile Fabrics—Diaphragm Bursting Strength Tester Method1 This standard is issued under the fixed designation D3786/D3786M; 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 epsilon (´) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. 1. Scope 1.1 This test method describes the measurement of the resistance of textile fabrics to bursting using a hydraulic or pneumatic diaphragm bursting tester. This test method is generally applicable to a wide variety of textile products. 1.2 This test method may also be applicable for stretch woven and woven industrial fabrics such as inflatable re- straints. 1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. NOTE 1—For the measurement of the bursting strength by means of a ball burst mechanism, refer to Test Method D3787. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility 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 2.1 ASTM Standards:2 D123 Terminology Relating to Textiles D1776 Practice for Conditioning and Testing Textiles D3787 Test Method for Bursting Strength of Textiles— Constant-Rate-of-Traverse (CRT) Ball Burst Test D4850 Terminology Relating to Fabrics and Fabric Test Methods 2.2 Other Standard: TAPPI Method T 403 , Bursting Strength of Paper3 3. Terminology 3.1 For all terminology related to D13.59, Fabric Test Methods, see Terminology D4850. 3.1.1 The following terms are relevant to this standard: bursting strength, knitted fabric, nonwoven fabric, stretch woven fabric, woven fabric. 3.2 For all other terminology related to textiles, see Termi- nology D123. 4. Summary of Test Method 4.1 A specimen is clamped over an expandable diaphragm. The diaphragm is expanded by fluid pressure to the point of specimen rupture. The difference between the total pressure required to rupture the specimen and the pressure required to inflate the diaphragm is reported as the bursting strength. 5. Significance and Use 5.1 This method for the determination of diaphragm burst- ing strength of knitted, nonwoven and woven fabrics is being used by the textile industry for the evaluation of a wide variety of end uses. 5.2 In cases where test results obtained using the procedures in Test Method D3786 have not been correlated with actual performance, Test Method D3786 is considered satisfactory for acceptance testing of commercial shipments of textile fabrics for bursting strength since the method has been used exten- sively in the trade for acceptance testing. In cases where disagreement arising from differences in values reported by the purchaser and the supplier when using Test Method D3786 for acceptance testing, the statistical bias, if any, between the laboratory of the purchaser and the laboratory of the supplier should be determined with comparison based on testing speci- mens randomly drawn from one sample of material of the type being evaluated. 1 This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.59 on Fabric Test Methods, General. Current edition approved Jan. 1, 2013. Published January 2013. Originally approved in 1979. Last previous edition approved in 2012 as D3786–12. DOI: 10.1520/D3786_D3786M-13. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 3 Available from Technical Association of the Pulp and Paper Industry (TAPPI), 15 Technology Parkway South, Norcross, GA 30092, http://www.tappi.org. Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States 1 NOTE 2—The kind of load transfer and stretch that occur when knitted goods and nonwoven fabrics are worn are prevented by clamping them as described in this method. 6. Apparatus and Materials 6.1 Inflated Diaphragm Bursting Tester 4— A testing ma- chine that meets the requirements of 6.1.1-6.1.4. Mounted so as to be free of externally induced vibrations. 6.1.1 Clamps, for firmly and uniformly securing the test specimen between two annular, parallel, and durable surfaces, without slippage during the test. Use sufficient pressure to effect the practicable minimization of slippage. The upper and lower clamping surfaces shall have a circular coaxial aperture of 31 6 0.75 mm (1.22 6 0.03 in.) in diameter: The surfaces of the clamps shall be durable and any edge which might cause a cutting action shall be rounded to a radius of not more than 0.4 mm. The lower clamp shall be integral with the chamber in which a pressure medium inflates the rubber diaphragm. NOTE 3—Since the clamping mechanism and clamping surfaces are subject to considerable wear and distortion, they should be examined periodically and repaired or replaced when necessary. The effectiveness of grooving the clamping surfaces in the manner specified has not been determined. 6.1.2 Diaphragm—A diaphragm of molded synthetic or natural rubber, clamped between the lower clamping plate and the rest of the apparatus so that before the diaphragm is stretched by pressure underneath it the center of its upper surface is nominally level with the plane of the clamping surface. The diaphragm should be inspected frequently for permanent distortion and renewed as necessary. 6.1.3 Pressure Gage—The instrument must be fitted with a pressure measuring system, accurate throughout the entire range of its scale to within a value of 1 % of its maximum capacity. For those instruments with a Bourdon type gage the capacity of the gage shall be such that the individual readings will be not less than 25 % nor more than 75 % of the total capacity of the gage. 6.1.4 Pressure System—A means of applying controlled increasing pressure to the underside of the diaphragm until the specimen bursts. This can be achieved by two methods; hydraulic or pneumatic. 6.1.4.1 Hydraulic pressure is produced by a fluid displaced at the rate of 95 6 5 mL/min. The fluid is displaced by a piston in the pressure chamber of the apparatus. The recommended chamber fluid is USP chemically pure 96 % glycerin. NOTE 4—Ethylene glycol may be substituted for the glycerine if desired. 6.1.4.2 Pneumatic pressure is produced by controlling the flow of clean dry air through a valve. The valve is configured as per 11.4.1 6.1.5 Aluminum Sheet For Checking Performance of Tester5—Pieces of pretested aluminum sheet having a known bursting strength in the range of 70 to 790 kPa (10 to 115 psi) may be used for checking the overall performance of the tester. NOTE 5—Use of an aluminum sheet from one tester manufacturer may not be suitable for burst testing machines from other tester manufacturers. Manufacturers’ instructions for checking should be followed. 6.1.6 Pressure Recording. 6.1.6.1 Hydraulic Instruments—Means shall be provided at the instant of rupture of the specimen for stopping any further application of the loading pressure and for holding unchanged the contents of the pressure chamber until the total bursting pressure and the pressure required to inflate the diaphragm indicated on the gage have been recorded. 6.1.6.2 Pneumatic Instruments—Means shall be provided for recording the loading pressure at the point of rupture. Diaphragm correction (tare pressure) is achieved by inflating the diaphragm to the same distension recorded at bursting and recording the amount of pressure to achieve this. 7. Sampling 7.1 Lot Sample—As a lot sample for acceptance testing, take at random the number of rolls of fabric directed in an applicable material specification or other agreement between the purchaser and the supplier. Consider rolls of fabric to be the primary sampling units. NOTE 6—An adequate specification or other agreement between the purchaser and the supplier requires taking into account the variability between rolls of fabric and between specimens from a swatch from a roll of fabric to provide a sampling plan with a meaningful producer’s risk, consumer’s risk, acceptable quality level, and limiting quality level. 7.2 Laboratory Sample—As a laboratory sample for accep- tance testing, take a full width swatch 1 m (1 yd) long from the end of each roll of fabric in the lot sample, after first discarding a minimum of 1 m (1 yd) of fabric from the very outside of the roll. From each roll or piece of circular knit fabric selected from the lot sample, cut a band at least 305 mm (1 ft) wide. 7.3 Test Specimens—Cut ten test specimens from each swatch in the laboratory sample with each specimen being 125 mm (5 in.) square. 8. Calibration 8.1 Routine Verification of Testing Machine—The operation of the testing machine may be checked periodically (such as once each month) by bursting five specimens of standard aluminum sheet. The average of the indicated bursting resis- tance for the five specimens of aluminum sheet should be between 65 % of that marked on the package of the pretested aluminum sheet standard. Use of the aluminum sheet may not be suitable for all burst testing machines. See the manufactur- er’s instructions for routine verification procedures applicable to individual testing machines. 8.2 Calibration of Pressure Measuring System—Calibrate the pressure measuring system, while inclined at the same angle at which it is used, by means of a dead-weight tester of the piston type. Alternatively, a traceable electronic pressure gage may be used or other calibration instrumentation recom- mended by the equipment manufacturer. Such calibration is preferably carried out with the gage in its normal position in the tester. 8.3 Where agreement is not attained, check the tester according to the instructions given in TAPPI Method T 403. 4 Hydraulic and pneumatic bursting strength testers and accessories are commercially available. 5 Standardized aluminum sheets are commercially available. D3786/D3786M − 13 2 NOTE 7—Possible causes of low readings are gage error (bias or nonlinearity), gage expansivity too high, excessive gage pointer friction, air in hydraulic system or gage, diaphragm collapsed too far at zero, and low pumping rate (hand-driven tester). Possible causes of high readings are: gage error (bias nonlinearity), loose gage pointer (overshoot), gage pointer bent by stop-pin, insufficient clamping force (slipping), nonuni- form clamping (partial slipping), stiff or inelastic diaphragm, diaphragm above clamping plate at zero, multiple sheet testing, high pumping rate (hand-driven tester), and double bursts. If a gage is accidentally used beyond its capacity, it must be recalibrated before it is used again. 9. Conditioning 9.1 Bring the specimens (or laboratory samples) from the prevailing atmosphere to moisture equilibrium for testing in the standard atmosphere for textile testing as directed in Practice D1776. 10. Selection and Number of Specimens 10.1 Unless otherwise agreed upon, as when specified in an applicable material specification, take ten specimens of the laboratory sample(s) of fabric. Each specimen shall be at least 125 mm (5 in.) square, or a circle 125 mm (5 in.) in diameter. Specimens need not be cut for testing. No two specimens from knitted fabric should contain the same wale or course yarns. Take no specimens nearer the selvage than one tenth the fabric width. This restriction does not apply to tubular knitted fabric. 11. Procedure 11.1 Make all tests on specimens conditioned in the stan- dard atmosphere for testing textiles as directed in 9.1. 11.2 Hand Driven Hydraulic Tester: 11.2.1 Insert the conditioned specimen under the tripod, drawing the specimen taut across the plate, and clamp speci- men in place by bringing the clamping lever as far to the right as possible. NOTE 8—For specimens with considerable stretch, it may be necessary to extend the fabric uniformly over the plate to remove some of the stretch before clamping. 11.2.2 Rotate the hand wheel, clockwise at a uniform speed of 120 rpm until the specimen bursts. 11.2.3 Stop turning the hand wheel at the instant of rupture of the specimen (see Note 9). 11.2.4 Immediately after rupture and in rapid succession, release the clamping lever over the specimen. Immediately release the strain on the diaphragm by turning the wheel counterclockwise to its starting position and record the pres- sure required to inflate the diaphragm (tare pressure). Record the total pressure required to rupture the specimen. NOTE 9—If the pressure stops increasing, as indicated by the dial, and the specimen has not broken, push the operating lever to remove the pressure. Record that the stretch of the fabric exceeds the dimensional limitations of the tester. If slippage of the specimen is noted, discard the result and use a new specimen. 11.3 Motor-Driven Hydraulic Tester: 11.3.1 Insert the specimen between the top and bottom clamp ensuring that the specimen is free from creases and folds. Securely clamp the specimen in place by following the manufacturers instructions appropriate to the machine. Apply pressure to the specimen until it bursts. 11.3.2 Diaphragm Correction (Tare Pressure)—Using the same settings as employed to burst the specimen, record the pressure required to distend only the diaphragm to the same height as used to burst the specimen. 11.4 Pneumatic Tester: 11.4.1 Adjust the control valve of the bursting tester so that the mean time to distend a specimen to burst falls within (20+/-5) s. Preliminary trials may be needed to fix the correct setting of the control valve. Time to burst is to be recorded between the beginning of vaulting and the bursting of the test specimen. 11.4.2 Clamp the specimen securely. Ensuring that the specimen does not slip. Place the distension recording device into the measuring position and adjust it to the zero position. Fasten the safety cover in position according to machine requirements. Apply pressure to the test specimen until the fabric bursts. 11.4.3 Diaphragm correction. With the same setting of the control valve as that employed in the above tests, distend the diaphragm without the presence of a test specimen by an amount equal to the mean height at burst of the test specimen. Note the pressure at this distension of the diaphragm as the “diaphragm pressure”. 12. Calculation 12.1 Calculate the bursting pressure of each specimen by subtracting the tare pressure required to inflate the diaphragm from the total pressure required to rupture the specimen. 12.2 Report the pressure reading of each individual speci- men and the average for each laboratory sampling unit and the lot. 12.3 Report the type of bursting tester used. 13. Report 13.1 State that the specimens were tested as directed in Test Method D3786 using the Inflated Diaphragm Bursting Tester. Describe the material or product sampled and the method of sampling used. 13.2 Report the bursting strength of each individual speci- men and their average in kPa (psi). 13.3 Report the type of bursting tester used. 14. Precision and Bias 14.1 Summary—In comparing two averages of ten observa- tions each, the difference should not exceed the following critical differences in 95 out of 100 cases when both sets of observations are taken by the same well-trained operator using the same piece of test equipment and specimens randomly drawn from the same sample of material. Spun yarn in circular knit 41 kPa (6.0 psi) Filament yarn in tricot knit 14 kPa (2.0 psi) Larger differences are likely to occur under all other circum- stances. The value of the bursting strength of knitted goods can only be defined in terms of a specific test method. Within this limitation, the procedure for bursting strength in Test Method D3786 has no known bias. Sections 14.2-14.4 D3786/D3786M − 13 3 explain the basis for this summary and for evaluations made under other conditions. 14.2 Interlaboratory Test Data6—An interlaboratory test was run in 1977 in which randomly drawn specimens of six fabrics were tested in each of four to five laboratories. Three fabrics were circular knit fabrics containing spun yarns and three of the fabrics were tricot knit fabrics containing filament yarns. The components of variance for bursting strength results expressed as standard deviations were calculated to be the values reported in Table 1. NOTE 10—The difference in variability between the two groups of fabrics is thought to be the result of the differences between the source yarns rather than the type of equipment on which the fabrics were knit. There is no objective evidence to substantiate this belief. NOTE 11—The interlaboratory test data were obtained with motor- driven hydraulic testers. The precision of the method using a hand- operated tester has not been determined. 14.3 Critical Differences—For the components of variance reported in 14.2, two averages of observed values should be considered significantly different at the 95 % probability level if the difference equals or exceeds the critical differences listed in Table 2 (Note 10). NOTE 12—The tabulated values of the critical differences should be considered to be a general statement particularly with respect to between- laboratory precision. Before a statement can be made about two specific laboratories, the amount of statistical bias, if any, between them must be established, with each comparison being based on recent data obtained on specimens randomly drawn from a sample taken at random from a lot of the material to be evaluated. 14.4 Bias—The procedure in Test Method D3786 has no known bias because the value of bursting is defined in terms of this test method. 15. Keywords 15.1 diaphragm bursting pressure; knitted fabric; non wo- ven fabric ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. 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