Three-Point Bending Flexural Test of Plastics (ISO 178, JIS K 7171)

Previous testing standards described a three-point bending flexural test for plastics did not require the deflection-measuring system. As a result, tests detected specimen, instrument deflection and indenter depression together as a total, which is a method not suited to accurate measurements of flexural modulus of elasticity. New standards (ISO178:2010, Amd.1:2013 and JIS K 7171:2016) have been revised and include either use of a deflection-measuring system with "JIS B 7741 Class 1" absolute accuracy of within 1 %, or use of compliance correction to remove testing machine deflection. A three-point bending flexural test was performed on PC, PVC, and GFRP specimens in compliance with the new standards, where the flexural modulus of elasticity of each plastic was calculated using compliance correction and the deflection-measuring instrument.