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CAN CGSB 4.2 No. 9.4-M91 (2013): Standard Test Method for Breaking Strength of Textile Fabrics – Grab Method
Understanding the Canadian Standard for Grab Tensile Testing of Woven and Nonwoven Textiles
Scope and Application
CAN CGSB 4.2 No. 9.4-M91 (2013) defines the grab test method for measuring the breaking strength of textile fabrics, including most woven and nonwoven materials. The method is designed to simulate the stresses encountered by a fabric in a seam application, where a narrow width of fabric is subjected to tensile force. It is applicable to fabrics that do not experience excessive elongation or jaw slippage. The standard is technically equivalent to ASTM D5034 and is widely used in Canadian textile quality assurance, product certification, and research laboratories.
Technical Requirements and Apparatus
Tensile Testing Machine
The machine shall be of the constant-rate-of-extension (CRE) type, with a force measurement accuracy of ±1% of the indicated load. Alternative machines (e.g., constant-rate-of-traverse) are permitted if they meet the specified calibration requirements. The moving jaw speed must be maintained at 300 ± 10 mm/min.
Dimensions and Grips
Each jaw shall have a smooth, flat gripping surface 25 mm wide and at least 50 mm long. The faces must be parallel and capable of clamping the specimen without slippage. The gauge length (distance between jaws at the start) is set at 75 ± 1 mm. The jaws are aligned so that the line of pull is centered on the specimen.
| Parameter | Requirement |
|---|---|
| Specimen width | 100 ± 1 mm |
| Jaw face width | 25 ± 1 mm |
| Gauge length | 75 ± 1 mm |
| Testing speed | 300 ± 10 mm/min |
| Conditioning atmosphere | 20 ± 2 °C, 65 ± 4 % RH |
| Minimum number of specimens | 5 warp and 5 weft (or as agreed) |
Test Procedure and Calculations
Conditioning
Specimens shall be conditioned in a standard atmosphere (20 ± 2 °C, 65 ± 4 % RH) for at least 24 hours. If wet testing is specified, the standard outlines separate soaking procedures.
Specimen Preparation
Cut each specimen 100 mm wide and at least 150 mm long. For woven fabrics, prepare separate sets in the warp (machine) and weft (cross) directions. For nonwovens, prepare in the machine and cross directions as applicable. Avoid areas containing creases or visible defects.
Mounting and Testing
Clamp the specimen centrally in the jaws, aligning one edge of the jaw width with the fabric edge to ensure a 25 mm grip. Ensure the fabric is free from tension before applying preload (typically 2–5 N). Activate the machine and record the force at break. If a specimen breaks at the jaw edge or slips, discard and retest.
Calculations
For each direction, calculate the mean breaking force (N), standard deviation, and coefficient of variation. Report results to three significant figures. If the coefficient of variation exceeds 10%, test additional specimens until the variability stabilizes.
Tip: Always condition specimens for a minimum of 24 hours under standard atmospheric conditions. Even brief exposure to ambient humidity can shift breaking force values by several percent.
Important: The grab method is not suitable for highly stretchable fabrics, narrow fabrics (<100 mm wide), or materials that elongate more than 50% at break. In such cases, consider the strip test (CGSB 4.2 No. 9.2) or an elongation-adjusted method.
Compliance and Quality Assurance
Laboratories seeking accreditation to ISO/IEC 17025 often include CAN CGSB 4.2 No. 9.4-M91 among their test methods. To maintain compliance, the following must be observed:
- Calibration of the tensile tester at least once per year using certified weights.
- Verification of jaw alignment and grip pressure before each test series.
- Use of reference fabrics (e.g., NIST standard reference materials) for ongoing precision monitoring.
- Adherence to the rounding rules and reporting requirements outlined in the standard.
Compliant Approach: Consistent use of this method enables reliable comparison of breaking strength data between fabrics, runs, and laboratories. It supports quality control, product development, and regulatory compliance across the textile sector.
Caution: Failing to calibrate the machine or using worn jaw faces can produce erroneously low breaking force values. Always inspect jaw surfaces for wear and ensure the machine is leveled before operation.
Frequently Asked Questions
Q: How does the grab method differ from the strip method?
A: The grab method uses a wide specimen (100 mm) but grips only the central 25 mm width, leaving the edges free. This simulates seam loading and reduces edge-effects. The strip method uses full-width jaws (e.g., 50 mm), testing the entire fabric width. Results from the two methods are not directly comparable.
A: The grab method uses a wide specimen (100 mm) but grips only the central 25 mm width, leaving the edges free. This simulates seam loading and reduces edge-effects. The strip method uses full-width jaws (e.g., 50 mm), testing the entire fabric width. Results from the two methods are not directly comparable.
Q: Is CAN CGSB 4.2 No. 9.4-M91 (2013) equivalent to ASTM D5034?
A: Yes, the two standards are technically harmonized. Differences are minor and relate to referencing other CGSB standards for conditioning and sampling. Most laboratories treat them as interchangeable for woven and nonwoven fabrics.
A: Yes, the two standards are technically harmonized. Differences are minor and relate to referencing other CGSB standards for conditioning and sampling. Most laboratories treat them as interchangeable for woven and nonwoven fabrics.
Q: Can this standard be used for wet testing?
A: Yes. The standard includes an optional procedure for testing specimens after soaking in distilled or deionized water containing a wetting agent. The soaking time and drying procedure are specified, but dry testing remains the default unless otherwise agreed.
A: Yes. The standard includes an optional procedure for testing specimens after soaking in distilled or deionized water containing a wetting agent. The soaking time and drying procedure are specified, but dry testing remains the default unless otherwise agreed.
© 2026 – Technical Overview of CAN CGSB 4.2 No. 9.4-M91 (2013)