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Tensile Testing of Plastics & Composites | Equipment for ASTM D638

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Tensile Testing of Plastics & Composites | Equipment for ASTM D638

Summary: Description of tensile testing plastics and plastic composites, along with machines and equipment that meet the requirements of ASTM D638.

Tensile properties of plastics are important for engineering quality control and design. Results of plastic tensile testing can be influenced by testing speed, environmental conditions, and sample preparation. For these reasons, it is important to control these parameters to obtain testing results that can be used for material compassion purposes, and ultimately design purposes.

There are four major steps to tensile test plastics; specimen preparation, setup, actual tension testing, and calculations/analysis. Specimen preparation for plastic tensile testing involves molding and cutting the plastic specimen into the dogbone coupons. Setup for plastic tensile testing requires proper grips and alignment to ensure accurate repeatable results. Actual tensile testing of plastic is as simple as hitting the start button on one of TestResources plastic tension tester machines. Finally, analysis is the interpretation of the plastic tensile stress-strain data.

Plastics and plastic composites have a number of tensile properties that can be determined through tensile testing:

  • Tensile Strength of Plastic at Yield and Tensile Strength at Break
  • Percent Elongation of plastic
  • Percent Elongation at Yield of Plastic
  • Percent Elongation at Break of Plastic
  • Nominal Strain of Plastic
  • Nominal Strain at Break of Plastic
  • Modulus of Elasticity of Plastic
  • Secant Modulus of Plastic Poisson

Standard Test Method for Tension Testing Plastics and Composites

ASTM D638 is the standard test method for tension testing plastics and composites. ASTM D638 covers tensile testing of plastics in a dogbone shaped (dumbbell shapped) form. Plastics with a thickness between 1.0 mm and 14 mm can be used with the testing practices of ASTM D638. Specimen preparation, setup, testing, calculations/analysis, and machine requirements for tensile testing plastics is covered extensively in ASTM D638. Follow the link to learn more.

Recommended Plastic Tensile Testing Equipment

Plastic tensile testing, specifically following the practices of ASTM D638, requires the use of a CRE (constant rate of extension) test machine, with a fixed grip and movable grip attached to the CRE loading unit. Plastic tensile tester machines need to be equipped with an extensometer to measure the strain of the plastic with in tension.