ASTM D6395 Flatwise Flexural Impact Resistance 

Scope

The resistance of plastics to breakage by flexural shock can be determined by such as ASTM D256. ASTM D6395 covers the scope to measure the relative impact resistance of samples having approximately the same thickness. This method is useful for a series of samples, changes relative to control due to some treatment such as weathering or exposure to environments. Particularly advantageous for a more sensitive indicator of the development of surface cracks or brittle surface. This test method is generally applicable to materials such as non-elastomers, rigid plastics in which there is fracture, permanent deformation, or changes due to yielding in flexure.  

Test procedure

In ASTM D6395 covers the determination of the resistance of plastics to standardised pendulum type hammers mounted in standardized machines, in breaking standard specimens with one pendulum swing. The required standard specimens are made with a milled notch. The stress concentration that is produced by the notch increases the probability of a brittle, rather than a ductile, fracture.

Video 01: Testing to ASTM D256 with Impact Pendulum

Specimen detail:

The test specimens should be 1.6 mm in thickness. If thickness is other than 1.6 m, the ratio of the distance between the top of the clamp and the centreline of the rounded striking edge to the specimen thickness must be 2.5 ± 0.1.

Result:

The results of this test method are reported in terms of energy absorbed per unit of specimen width or per unit cross sectional area with respect to the notch that gives the amount of deformation and brittleness. The existence or formation of cracks in an inherently brittle surface produces marked lowering of impact strength when the surface is subjected to tension in the test.

Conclusion:

ASTM D6395 is used to determine the resistance of rigid plastic specimens to breakage or permanent deformation by flexural shock.