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

 

ASTM D4032 – Circular Bend Stiffness Test for Fabrics

ASTM D4032 is a standardized test method used to evaluate the stiffness or drape resistance of fabrics and textiles using a circular bend test. Unlike linear bending tests, ASTM D4032 provides a multidirectional measure of stiffness that better reflects how a fabric will behave in real-world applications such as apparel, upholstery, and industrial textiles.

What Does ASTM D4032 Measure?

This test method measures the resistance of fabric to deformation when pushed through a circular orifice. It is especially useful for:

• Measuring hand feel and drape behavior

• Comparing stiffness across fabric types

• Quality control during textile manufacturing

It provides a single numeric result called the bending stiffness, expressed in Newtons (N) or grams-force (gf).

Test Specimen

Specimen Dimensions

• Size: Square fabric samples measuring 102 mm x 102 mm (4 in x 4 in)

• Cut Direction: Can be tested in warp, weft, or bias direction, or unspecified if the material is nonwoven

At least 10 specimens are recommended for statistical reliability.

Test Equipment and Fixture

Universal Testing Machine (UTM)

The test can be performed using a UTM with compression control or with a dedicated circular bend tester. The equipment must include a force gauge capable of measuring low-force values (typically up to 10 N).

ASTM D4032 Circular Bend Fixture

The test fixture includes:

• A circular orifice (diameter: 38 mm ± 0.13 mm)

• A plunger (diameter: 25.4 mm ± 0.13 mm), with a hemispherical end

• A clamping ring to secure the fabric during testing

The plunger is driven downward through the center of the fabric, forcing it to deform into the circular opening.

Test Procedure

1. Specimen Mounting: Center the fabric specimen over the circular orifice and secure with the clamping ring.

2. Load Application: Lower the hemispherical plunger at a uniform speed (typically 300 mm/min) until it passes through the orifice.

3. Data Capture: Record the peak force required for the plunger to deform the fabric and push it through the opening.

The result is the force at maximum resistance to bending, reported in Newtons or grams-force.

What the Results Mean

• Higher force values = Stiffer fabric (less drape)

• Lower force values = More flexible fabric (better drape or flow)

Because this test simulates multi-directional bending, it offers a better indicator of how a material will feel in use—particularly for garments, medical fabrics, and technical textiles.

Typical Applications

ASTM D4032 is widely used in:

• Apparel and performance wear testing

• Medical textiles (e.g., surgical drapes, gowns)

• Automotive and upholstery fabrics

• Outdoor and industrial textile evaluation

It’s especially helpful for nonwoven, woven, and knitted fabrics, and is often used when subjective feel (or “hand”) must be quantified for consumer or engineering use.

Tips for Accurate Testing

• Use flat, wrinkle-free specimens

• Ensure plunger is centered and moves smoothly

• Calibrate the force gauge for accurate low-force measurements

• Average multiple specimens to reduce data variability

Related Standards

• ASTM D1388 – Fabric stiffness using cantilever and heart loop methods

• ASTM D747 – Stiffness of plastics (more rigid materials)

• ISO 9073-7 – Bending length and stiffness of nonwoven fabrics

Conclusion

ASTM D4032 provides a quick and reliable measure of fabric stiffness using a circular deformation method that mimics real-world drape behavior. Its straightforward setup and reproducible results make it an essential tool for textile developers, manufacturers, and quality control labs.

If you’re looking to perform ASTM D4032 testing, we provide compatible fixtures, universal testing machines, and complete turnkey systems tailored to textile applications.