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Flexural Properties - ISO 178

A test specimen is held as a simply supported beam and is subjected to three-point bending. Maximum stress and strain occurs at the underside of the test specimen. The preferred test specimen is 80 mm long, 10 mm wide, and 4 mm thick. Other specimens may be used if the length to thickness ratio is equal to 20.

Flexural Test Configuration

Location of Maximum Fiber Stress/Strain

Term Definition
Flexural Modulus The ratio of outer fiber stress to outer fiber strain.
Flexural Strength The maximum outer fiber stress sustained by a specimen during testing.


Method Description
A A strain rate of 1%/min is used throughout the test.
B A strain rate of 1%/min is used to determine the flexural modulus and a strain rate of 5%/min or 50%/min (depending on the ductility of the material) is used for the remainder of the flexural stress-strain curve

Similar Test Standards

  • ASTM D790