ASTM D6272 Flexural Properties of Plastics & Electrical Insulating Materials

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ASTM D6272 Flexural Properties of Plastics & Electrical Insulating Materials

ASTM D6272 is a standard test for determining flexural properties of plastics and electrical insulating materials.

What Is ASTM D6272?

ASTM describes the test equipment, test samples and procedures that are involved in testing flexural properties of unreinforced and reinforced plastics, including high-modulus composites and electrical insulating materials in the form of rectangular bars molded directly or cut from sheets, plates, or molded shapes. ASTM D6272 applies to rigid and semi rigid materials.

What Other Standards Apply to Flexural Testing of Plastic?

Several similar test methods include Three Point Flexure - ASTM D790, ISO 178 and ISO 14125 Method B.

Why Perform Four Point Flexural Tests on Plastics?

Flexural tests are especially useful for quality control and specification purposes, and ASTM D6272 applies specifically to materials that do not meet the strain limit criteria of ASTM D790. The major difference between four point and three point bending modes is the location of the maximum bending moment and maximum axial fiber stress. In four point bending the maximum axial fiber stress is uniformly distributed between the loading noses. In three point bending the maximum axial fiber stress is located immediately under the loading anvil.

Important Considerations When Testing per ASTM D6272

Flexural break strength cannot be determined for those materials that do not break or that do not fail in the outer fibers.

ASTM D6272 Test Method

A rectangular bar rests on two anvils and is loaded by two loading noses, each equally distant from the adjacent support anvil. The load span is either one third or one half of the support span. The support span is 16X the depth (thickness) unless it's suspected that a larger span-to-depth ratio may be required, such as with certain laminated materials. The specimen is tested until rupture occurs in the outer fibers or until the maximum fiber strain of 5% is reached, whichever occurs first.

Procedure A is for materials that break at comparatively small deflections. It is also for measurement of flexural properties, such as flexural modulus.

Procedure B is for materials that undergo large deflections during testing. It can be used to measure flexural strength.

Test Machines for Unreinforced & Reinforced Plastics

Our universal test machines serve multiple plastic testing applications and are capable of performing all quasi static tension/compression tests, such as tensile, peel, adhesion, and flexural testing. The machine force capacity should be chosen by taking into account the highest force needed over the lifetime of the equipment. Machines feature a uniform constant rate of extension (CRE), or constant velocity control mode, with a speed range between 1 and 500 mm per minute (0.04 to 20 in/min). Force measurement complies with ASTM E4 (ISO 7500-1).

The majority of rigid plastics tests can be performed at loads under 25 kN (5500 lbs).

What Bend Fixtures Are Required for ASTM D6272?

Our configurable bend fixtures comply with ASTM D6272 sample dimensions and different anvil loading and support scenarios. Consider our G238, G103 and G22 in four point bend fixture configurations. The standard requires 5 mm radius supports. If the specimen depth (thickness) exceeds 3.2 mm (0.125 in) then the contact cylinder may be 1.6 times the specimen thickness.