ISO 7854 Rubber or Plastic Coated Fabrics - Determination of Resistance to Tear by Stretching

The standard “ISO 7854 Rubber or plastic coated fabrics - Determination of resistance to tearing by flexing” developed by the International Organization for Standardization (ISO) describes three test methods for assessing the resistance of coated fabrics to damage by repeated flexing:

• Method A De Mattia method: In this method, a rectangular strip of coated fabric is folded twice with the long edges meeting to form a strip measuring 125 mm x 12,5 mm. This folded strip is mounted between a pair of flat grippers, one moving back and forth, causing the folded test piece to bend outward five times per second. This high-speed folding of the test piece is continued for a predetermined number of cycles or until damage to the test piece is evident.

This test method uses a flexibility testing machine with flat grip pairs, as specified in ISO standard 132. One of the grips in each pair is capable of reciprocating in a vertical plane with a stroke length of 57 plus 0,5 mm and a frequency of 5,0 Hz plus/minus 0,2 Hz.

When preparing the test pieces, six test pieces, each 2286 mm plus/minus 37,5 mm wide x 1 mm long, are selected from the usable width of the roll defined in ISO 125. Three test pieces are selected with the longer dimension in the longitudinal direction of the coated fabric roll and three test pieces with the longer dimension in the transverse direction of the coated fabric roll. The test pieces are selected from equally spaced positions along the entire width and length of the sample.

The test pieces are conditioned in atmosphere A, B or C of the ISO 2231 standard and the test is performed in this atmosphere.

• Method B Schildknecht method: In this method, a rectangular strip of coated fabric is placed around two opposing cylinders so that the test piece assumes a cylindrical form. One cylinder moves back and forth along its axis, causing the coated fabric cylinder to be alternately compressed and relaxed, thus producing folds in the test piece. This folding of the coated fabric cylinder is continued for a predetermined number of cycles or until the test piece is damaged.

This test method uses a testing machine consisting of one or more metal cylinders suitably mounted so that the axes of each pair extend along an arc of at least 450 mm radius. The cylinders have an outer diameter of 25,4 mm plus/minus 0,1 mm, and one cylinder of each pair reciprocates along its axis at a frequency of 8,3 Hz plus/minus 0,4 Hz. The stroke length of the reciprocating cylinder is 11,7 mm plus/minus 0,35 mm. The tests also use hose clips or tool clips, 10 mm plus/minus 1 mm wide, to hold the test pieces to the cylinders.

When preparing the test pieces, six test pieces, each 2286 mm long x 105 mm wide, are selected from the usable width of the roll as defined in ISO 50. Three test pieces are selected with the longer dimension in the longitudinal direction of the coated fabric roll and three test pieces are selected with the longer dimension in the transverse direction of the coated fabric roll. The test pieces are selected from positions equally spaced along the entire width and length of the sample.

• Method C Crumplelflex method: In this method, a rectangular test piece of coated fabric is sewn into a cylindrical shape. The cylinder of coated fabric is placed between two discs and fixed in place. One of the discs oscillates on its axis for approximately 229 cm. This causes bending of the cylinder of coated fabric test piece. At the same time, the other disc moves back and forth along its axis, thus causing compression of the cylindrical test piece along its length. This bending and simultaneous compression of the cylindrical test piece is continued for a preset number of cycles or until damage to the test piece is apparent.

The apparatus used in this test method consists essentially of two opposing flanged or shouldered disks having a maximum disk separation of 180 plus 3 mm between the inside surfaces of the flanges. The flangeless portion of each disk is 63,5 mm in diameter x 15,0 mm in face width. The disks are mounted along the same axis with their edges 152,4 mm apart at their maximum separation. One disk shall be capable of moving toward the other along their common axis a distance of 70,0 mm and thus be capable of applying compression to the cylindrical test piece at a rate of 2,53 Hz plus/minus 0,07 Hz, or 152 plus/minus 4 compression strokes per minute. The second disk shall be capable of rotating through an angle of 90 degrees plus/minus 2 degrees and thus be capable of applying compression to the cylindrical test piece at a frequency of 3,33 Hz plus/minus 0,17 Hz, or 200 plus/minus 10 bends per minute. The counters record the total number of compression strokes added during a test and the frequency at which the machine is operating.

Among the numerous tests, measurements, analyses and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the standard “ISO 7854 Rubber or plastic coated fabrics - Determination of resistance to tearing by stretching” with its trained and expert staff and advanced technological equipment.