ASTM D638 - Standard Test Method for Tensile Properties of Plastics

Resin materials (plastics) are found in a wide variety of items used on a daily basis. Recently, plastics have started to be used as structural materials in transportation equipment, such as automobiles and aircraft, due to their strength and light-weight nature. In these applications, it is important to understand the mechanical strength properties of these plastics.

ASTM D638 (Standard Test Method for Tensile Properties of Plastics) specifies methods for testing the tensile strength of plastics and other resin materials and for calculating their mechanical properties, and outlines accuracy requirements for the test frames and accessories used. This test method uses dumbbell-shaped specimens with either a  25 mm or 50 mm gauge length.

For ASTM D638, Shimadzu offers a range of extensometer options including strain gauge extensometers and the TRViewX non-contact digital video extensometer.




ASTM D638 Test force accuracy

Test force accuracy of ±1%

ASTM D638 requires a test force accuracy that meets ASTM E4 Class 1—accuracy within ±1% of the indicated test force. All of Shimadzu’s test frames and load cells meet the test force accuracy requirements for ASTM D638.

Elongation measurements with 10 μm absolute accuracy and ±0.5% relative accuracy

ASTM D638 Elongation Measurements

Specimens for ASTM D638 are dumbbell-shaped with either a 25 mm or 50 mm gauge length; a 50 mm gauge length is recommended. Gauge length changes with ASTM E83 Class B-2 accuracy; an absolute accuracy of 10 μm for a 50 mm gauge length and relative accuracy within ±0.5% are required by ASTM D638 for measuring the tensile modulus of elasticity. Also, for elongation beyond the yield point but less than 20%, Class C accuracy is specified; an absolute accuracy of 50 μm for a 50 mm gauge length and relative accuracy within 1%, and ±10% relative accuracy are required for the rest of the test. For ASTM D638 compliant elongation testing, Shimadzu offers SIE-560SA automatic extensometers, TRViewX non-contact digital video extensometers, and SSG-H one-touch, strain gauge extensometers. In particular, the SIE-560SA automatic extensometer can be programmed to attach and detach automatically from the specimen and can be used for either 25 mm or 50 mm gauge length, improving test efficiency and repeatability.

Recommended Products for ASTM D638

Recommended Literature and Webinars for ASTM D638

Application News - Tensile Properties of Rigid and Semi-rigid Plastics (ASTM D638 and ISO 527)

Application News - Tensile Properties of Rigid and Semi-rigid Plastics (ASTM D638 and ISO 527)

Every manufactured plastic is subjected to mechanical loading conditions throughout its operating lifetime. In order to prevent mechanical failure, it is imperative that the mechanical properties be determined and routinely verified to confirm that the material is suitable for the intended application. Tensile testing is one such method routinely used to determine the mechanical properties of plastics. Manufacturers, consumers, researchers and governing agencies are some examples of groups who perform tensile tests to ensure consistency, verify quality, and develop standards. Tensile tests are most commonly performed using a universal test frame, grips and an extensometer. Shimadzu Scientific Instruments offers a full line of test frames, grips and extensometers that meet or exceed the requirements outlined in testing standards such as ASTM D638 and ISO 527.


Webinar - ASTM D638 and ASTM D790