Information on the most widely used ASTM standards within the materials testing industry
ASTM D4533 Trapezoid Tearing Strength Test of Geotextiles
ASTM D4533 test used to measure the force required to continue or propagate tearing in woven or non-woven geotextiles, using the trapezoidal method for testing. The trapezoidal tearing method is a test that generates tension along a reasonably defined path, allowing the tear to propagate across the width of the specimen. The trapezoidal tear strength of woven fabrics is mainly determined by the characteristics of the yarns clamped in the fixture.
Test principle
Draw an isosceles trapezoid contour on a rectangular specimen, make a cut along the centerline of the trapezoid's short side, and clamp both ends of the specimen in the fixture of the strength testing machine. Apply longitudinal tensile force at a constant rate of 50mm/min until the specimen is completely torn, and record the maximum force value during the test as the tear strength result.
Sample specifications:
Original dimensions: 200mm (vertical) x 75mm (horizontal);
Trapezoidal parameters: bottom 100mm, height 60mm, top 25mm;
Cut requirement: Make a 15mm long longitudinal cut at the centerline of the trapezoidal top and bottom;

In this test, a trapezoidal outline is marked centrally on a rectangular test specimen Fig. Note that an initial 15-mm cut is made to start the tearing process.
The specimen is gripped along the two non-parallel sides of the trapezoid in the jaws of a tensile testing machine. A continuously increasing force is applied in such a way that the tear propagates across the width of the specimen.
The load actually stresses the individual fibres gripped in the clamps rather than stressing the geosynthetic structure.
The value of tearing strength of the specimen is obtained from the force–extension curve and is taken as the maximum force thus recorded.
Instrument requirements
The test requires the use of testing equipment that meets the following conditions in a standard atmospheric environment (temperature 20 ± 2 ℃, humidity 65 ± 4%):
The precision of the strong testing machine needs to reach ± 1%.
The fixture spacing is fixed at 25mm.
The fixture should have a clamping surface that prevents the specimen from slipping.
Equipped with a device that automatically records the force curve during the tearing process.
Related Standard
ASTM D1004: Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting
ASTM D1004 is a test method that determines the tear strength of flexible plastic film and sheeting at very low rates of loading using a constant-rate-of crosshead-movement type tensile testing machine. Tearing is produced in a small area of stress concentration of the plastic film or sheeting specimen at controlled speeds below the rate encountered in real world applications in order to produce the most reliable data, which can be used to compare and analyze the tear resistance. Actual use of performance in tearing of certain plastics may not necessarily corralate with the data acquired from this test method. The specimen geometry of this test method produces a stress concentration in a small area of the specimen. The maximum stress, usually found near the onset of tearing, is recorded as the tear resistance in newtons (or pounds-force). The method is not applicable for film or sheeting material where brittle failures occur during testing or where maximum extension is greater than 101.6 mm (4 in.).
Trapezoid tear test for Geotextiles, Tearing Strength of Geotextiles
An outline of an isosceles trapezoid is marked on a rectangular specimen and cut. A small tear is introduced on one side of the specimen. The nonparallel sides of the trapezoid marked on the specimen are clamped in parallel jaws of a tensile testing machine. The separation of the jaws is initiated and increased so the tear propagates across the specimen. The force is measured throughout the test.
Trapezoidal method:
Draw two diagonal lines at the ends of the strip to form an isosceles triangle in the middle and then cut at the bottom. Try to clamp and follow the two diagonal lines and add tensile loading. The first yarn that is close to the incision will bear more external force, while the other yarns will endure less force. When the first yarn experience cracks, it will split. Then the line below will become the first yarn. It will endure strong tension until tears apart. At last, the maximum force in the process is the tearing strength of the fabric. It is directly related to the tearing force, and is used to evaluate the tenacity of the fabric. The comparability and stability of the results are good, easy to measure and can be carried out in normal machine with general strength.

Number of Test Specimens: 10 machine direction 10 cross machine direction
Test Specimen Size: 3" x 8"
Keywords: Tearing, trapezoidal tear
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