Tension & Elongation of Elastic Fabric by ASTM D4964

What Is ASTM D4964?

ASTM D4964 is the Standard Test Method for Tension and Elongation of Elastic Fabrics, published by ASTM International. The standard provides a procedure for measuring the elongation, tensile strength, and elastic recovery of elastic fabrics — woven, knitted, or braided textile structures that contain rubber, spandex (Lycra), elastane, or other elastic yarns that impart stretch and recovery characteristics.

Elastic fabrics are used extensively in apparel, medical compression garments, sportswear, lingerie, industrial webbing, and protective equipment. Accurate tensile and elongation testing is essential for product performance validation, quality control, and regulatory compliance.

Scope of ASTM D4964

ASTM D4964 applies to elastic fabrics in the following product categories:

• Narrow elastic fabrics (waistbands, straps, trims)
• Broad elastic fabrics (swimwear, sportswear, medical compression bandages)
• Woven, knitted, and braided elastic constructions
• Elastic webbing for industrial and military applications

The standard addresses both the stretch direction (warp or filling/wale or course, depending on construction) and the recovery behaviour — critical for assessing long-term performance of elastic garment components.

Key Parameters Measured

Elongation at Break

The elongation at break is the percentage increase in specimen length from the original unstrained length to the point of fabric rupture. It indicates the maximum stretch capacity of the elastic fabric.

Elongation at Specified Load

Many elastic fabric specifications require elongation measurement at defined load levels rather than at break, reflecting the functional stretch range of the product. For example, a waistband specification may require 40% elongation at 5 N/cm width.

Tensile Strength

Tensile strength of the elastic fabric at break provides a measure of structural integrity — relevant for industrial, military, and safety applications where the elastic must not fail under maximum loading conditions.

Elastic Recovery (Permanent Set)

After stretching to a defined elongation and releasing, the specimen is measured after a defined recovery period to calculate the permanent set — the percentage of the original stretch that is retained as permanent deformation. Low permanent set is essential for garments and medical compression devices that must maintain consistent compression forces after repeated use cycles.

Test Procedure Overview

Specimens are cut to defined dimensions in the stretch direction, conditioned at standard atmospheric conditions (23°C, 65% RH per ASTM D1776), and mounted in a constant-rate-of-extension (CRE) tensile testing machine. Load and elongation are recorded as the specimen is extended at a defined rate until fracture. For elastic recovery, the specimen is extended to a specified elongation, held, and then released, and the residual permanent set is measured after a defined recovery interval.

Industrial Importance of ASTM D4964 Testing

Apparel and Activewear

Waistband elastic, bra straps, swimwear, and performance sportswear rely on precisely characterised elongation and recovery properties to deliver comfort, fit, and dimensional stability after repeated laundering and use.

Medical Compression Products

Compression bandages, support hosiery, and orthopaedic braces must maintain defined compression forces throughout wear. ASTM D4964 data informs compression class assignment and product durability validation for regulatory submissions.

Industrial and Protective Equipment

Elastic components in personal protective equipment (PPE), safety harnesses, and industrial webbing require validated tensile strength and elongation to meet safety standards.

Conclusion

ASTM D4964 provides a standardised and reliable method for evaluating the tensile behaviour and elastic recovery of elastic fabrics. By measuring elongation, tensile strength, and permanent set, the test ensures that elastic materials perform consistently under real-world stretching conditions. This is critical for applications where fit, durability, and long-term elasticity are essential, such as apparel, medical textiles, and industrial webbing.

Why Choose Infinita Lab for ASTM D4964 Elastic Fabric Testing?

Infinita Lab provides ASTM D4964 elastic fabric tensile and elongation testing through our nationwide accredited textile testing laboratory network. Our textile testing specialists ensure correct specimen preparation, conditioning, and testing per all standard requirements.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.

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