ASTM D1833 specifies a simple test to measure the flexural rigidity of a fabric or textile. The flexural rigidity is calculated based on the bend length of the fabric. While these measurements are not as important for garment fabrics, they are vitally important for engineered textiles used in industrial applications.
Flexural rigidity is very important for forming fabrics that are used in the paper manufacturing industry. A thin film of paper pulp is deposited onto a forming fabric and then dried to form a sheet of paper. This forming fabric is like a giant belt which is continuously rolling and making sheet paper.
The fixture is about 1.5 feet wide and 1 ft. tall. The bending ledge has a width of 40mm. The indicating bending ledge is set at a 41.5 degree angle, however this can be changed to 45 degrees if needed.
Universal Grip offers a simple cantilever bend fixture. The sample is pushed out by hand until it fully bends and hits the angled ledge. Upgrades to the simple fixture design can be made, such as controlled hand cranks.
ASTM D1388 is a simple test and does not require a testing machine or any additional fixtures. The sample is extended out from the fulcrum point until it bends under its own weight and touches the angled ledge. At this point the bend length and taken. From this value, the flexural rigidity can be counted by using the formula in the official publication.