ASTM D638 is a method of evaluating the tensile properties of rigid plastic materials.

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Purpose: Measure the strength of a rigid plastic material in tension.

Sample: Seven (7) tensile bars, ASTM D 638 Type I
One (1) square foot of sheet, 0.125 to 0.500 inches thick

Price & Delivery: Contact us for a quote.

Basic Description: The sample is molded or machined into a dog bone shaped tensile bar which is gripped on both ends using a tensile tester. The tensile tester pulls on the bar at a constant speed until it breaks into two pieces. The force on the bar and how much the bar stretches is continuously measured during the test. Tensile strength (stress) is calculated by dividing the maximum load by the original cross sectional area of the test bar. Tensile elongation (strain) is calculated by dividing how much the bar stretched by the original length of the bar. Tensile modulus is a measure of how stiff or rigid a plastic is and is calculated by dividing the change in stress by the change in strain at an early stage of the test. The test method requires testing five bars (5 replicates) and averaging the results but a few extra bars are required to determine the proper test conditions. Data is calculated from the test curves and reported in the form of a results table.

Limitations: The sample must be a rigid plastic in order to test. Other test methods are normally used to test thin films, rubbers, or metals. Our current equipment can break test samples with up to 10,000 pounds of force.


  • MTS Systems, QTest 50LP, Tensile Tester (10,000 lbf, 1000 lbf, 100 lbf, and 10 lbf load cells)
  • MTS Extensometers & Load Cells

Method Publisher:


  • Tensile Strength
  • Tensile Elongation
  • Tensile Modulus
  • Young's Modulus

Related Techniques: