Standard Test Method for Stiffness of Fabric by the Circular Bend Procedure - PDF

ASTM D4032 Puncture Fixture – Universal Grip Data Sheet (PDF)

 

ASTM D4032 Circular Bend Stiffness Test

ASTM D4032 measures the stiffness of fabrics by the circular bend procedure. A folded fabric specimen is laid over a round hole in a platform and a round plunger pushes it down through the hole. Because the fabric is bent in every direction at once, the peak force is an average of its stiffness in all directions. It is used for woven, knit and nonwoven fabrics, and for coated fabrics, where a single number for "how stiff it feels" is needed.

Fixture Geometry

• Orifice: 38.1 mm (1.5 in) diameter hole in a smooth, flat platform

• Plunger: 25.4 mm (1 in) diameter, centered over the orifice

• Specimen: cut 102 × 204 mm (4 × 8 in) and folded in half to a two-ply 102 × 102 mm (4 × 4 in) square, or as the material specification states

• Cut specimens in both length and width directions and handle them as little as possible

• Condition in the standard textile atmosphere of 21 ± 2 °C and 65 ± 5% RH (ASTM D1776)

Confirm specimen size, number of specimens and plunger speed against your copy of D4032.

Test Procedure

• Center the folded specimen over the orifice, fold line placed as the standard directs

• Drive the plunger down through the orifice at the speed set in the standard

• Record the peak force as the fabric is forced through the hole

• Turn or replace specimens and repeat; average the results

Result

Circular bend stiffness = peak force in N (or gf, lbf)

Example: five specimens of a nonwoven read 2.6, 2.9, 2.7, 2.8 and 2.5 N. The circular bend stiffness is the average, 2.7 N. A higher force means a stiffer, less drapeable fabric.

Equipment

• Universal testing machine with a low-capacity load cell (10–50 N) and compression mode

• D4032 circular bend fixture: 38.1 mm orifice platform and 25.4 mm plunger that mount on the machine

• Specimen cutting template

Related Standards

• ASTM D1388 – fabric stiffness by cantilever bending

• ASTM D1776 – textile conditioning

• ISO 9073-7 – bending length of nonwovens

• ASTM D747 – stiffness of plastics by cantilever beam

ASTM D4032 FAQ

What does ASTM D4032 measure?

The force needed to push a folded fabric specimen through a 38.1 mm hole with a 25.4 mm plunger. The peak force is reported as the circular bend stiffness.

What are the D4032 plunger and orifice sizes?

A 25.4 mm (1 in) diameter plunger and a 38.1 mm (1.5 in) diameter orifice.

How is D4032 different from D1388?

D1388 bends a strip under its own weight in one direction and gives bending length. D4032 bends the fabric in all directions at once with a plunger and gives a force.

What load cell do I need?

Most fabrics read a few newtons or less, so a 10 N to 50 N load cell keeps the readings in the accurate part of its range.