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CAN CGSB 4.2 No. 9.3-M90 (2013): Breaking Strength of Fabrics – Grab Method
A comprehensive guide to the Canadian standard for determining the breaking force of textile fabrics using the grab test procedure
1. Scope and Application
CAN CGSB 4.2 No. 9.3-M90 (2013) is a Canadian national standard developed by the Canadian General Standards Board (CGSB) as part of the CAN/CGSB-4.2 series of textile test methods. This standard specifically addresses the determination of the breaking strength of textile fabrics using the grab method. It provides a uniform procedure for measuring the maximum force required to rupture a fabric specimen when a tensile force is applied under specified conditions.
The grab method is widely employed in the textile industry because it simulates the restraining effect of fabric edges during real-world use. Unlike the strip method (which tests a completely clean-cut or raveled strip), the grab method clamps only a narrow central portion of a wider specimen, leaving the edge yarns intact. This configuration typically yields higher breaking strength values and better represents the in-service performance of woven fabrics.
Applicable fabric types: The standard is primarily intended for woven fabrics, but it can also be applied to other textile structures where a full-width test is not feasible or where edge effects are of interest. It is commonly used for apparel fabrics, industrial textiles, geotextiles, and upholstery materials.
Importance: Breaking strength is a critical quality indicator for textile materials. Compliance with this standard ensures that products meet specification requirements, quality control criteria, and regulatory standards within Canada and internationally.
Tip: For accurate results, verify that the fabric specimen is uniformly tensioned and free from wrinkles before clamping. Use a pre‑tension weight (typically 0.1 N) to remove slack unless otherwise specified in the product standard.
2. Technical Requirements and Procedures
2.1 Principle
A rectangular fabric specimen is clamped centrally between two jaws (each 25 mm wide) and the specimen is extended at a constant rate until rupture. The force at break is recorded in newtons or pounds‑force.
2.2 Specimen Preparation
Specimens shall be cut to dimensions of 100 ± 1 mm in width and 150 ± 5 mm in length. The clamping width is 25 mm; the remaining fabric provides edge support. At least five specimens are tested in each principal direction (warp and weft), or as agreed upon. Specimens should be representative of the full fabric width and free from creases or damage.
2.3 Conditioning
All specimens must be conditioned in the standard atmosphere for textile testing: 21 ± 1 °C and 65 ± 2 % relative humidity. A minimum conditioning period of 24 hours is required, or until equilibrium is reached (usually when successive weighings differ by no more than 0.1 %).
2.4 Apparatus
The tensile testing machine must be of the constant‑rate‑of‑extension (CRE) or constant‑rate‑of‑traverse (CRT) type, with an accuracy of ±1 % of the indicated force. The gauge length is set at 75 ± 1 mm. The rate of extension is 300 ± 10 mm/min. Jaws must be smooth, flat, and parallel, with sufficient clamping pressure to prevent slippage without causing damage or jaw breaks.
2.5 Test Procedure
- Condition specimens as specified.
- Set the gauge length and speed on the testing machine.
- Place the specimen centrally between the jaws, ensuring no tension is applied before starting the test.
- Apply a slight pre‑tension (0.1 N) if required.
- Start the test and record the maximum force at rupture.
- Discard any results that occur within 5 mm of the jaw edge (jaw break).
- Calculate the mean breaking force for each direction, and optionally the standard deviation and coefficient of variation.
| Parameter | Requirement |
|---|---|
| Specimen width (cut) | 100 ± 1 mm |
| Clamped width (jaw) | 25 mm |
| Specimen length | 150 ± 5 mm |
| Gauge length | 75 ± 1 mm |
| Rate of extension | 300 ± 10 mm/min |
| Pre‑tension | 0.1 N (or as specified) |
| Conditioning atmosphere | 21 °C ± 1 °C / 65 % ± 2 % RH |
| Minimum conditioning time | 24 hours |
| Number of specimens per direction | 5 (warp and weft) |
Warning: If the fabric exhibits high elongation or pronounced necking, the grab method may not fully capture the true failure behavior. Consider using a strip method (CAN/CGSB‑4.2 No. 9.2) for inherently stretchable or high‑strain fabrics.
3. Implementation Highlights
3.1 Equipment Selection and Calibration
Laboratories should use a tensile testing machine that complies with the force range and speed requirements. Calibration should be performed regularly according to ISO 7500‑1 or equivalent. Jaw pressure must be checked to prevent sample slippage or jaw breaks.
3.2 Operator Training
Consistent results depend on careful specimen preparation and correct placement. Operators must be trained to align the specimen centrally and avoid introducing slack or excessive pre‑tension.
3.3 Data Interpretation
Grab method results are generally higher than strip method results for the same fabric because of the edge yarns’ load‑sharing contribution. This difference must be considered when comparing with specification limits or historical data. The standard provides guidance on reporting mean values, but the end‑user may also require confidence intervals or individual break values.
3.4 Quality Control and Interlaboratory Testing
For routine QC, periodic proficiency testing and control charts are recommended to monitor laboratory performance. Reference fabrics with known breaking strength can be used as internal checks.
Compliance note: When CAN CGSB 4.2 No. 9.3‑M90 (2013) is invoked in a contract or specification, rigorous adherence to its procedures ensures that textile products meet Canadian market requirements and facilitates acceptance in international trade, as the method aligns closely with ASTM D5034 and ISO 13934‑2.
4. Compliance Notes
- Standard Reference: Any test report must clearly cite the full designation “CAN CGSB 4.2 No. 9.3‑M90 (2013)” and indicate any deviations from the standard.
- Conditioning: Failure to condition specimens properly is the most common cause of non‑reproducible results. Temperature and humidity monitoring records should be maintained.
- Calibration: Load cells and extension measuring devices must be calibrated at intervals not exceeding 12 months, with records kept for audit.
- Reaffirmed Standard: The (2013) designation indicates that the standard was reaffirmed in 2013 after a review. It remains current and is widely referenced in Canadian textile specifications as of 2026.
- Adaptation for Non‑Standard Materials: For fabrics that do not fall within the standard’s intended scope (e.g., highly elastic, technical textiles), the user should document the basis of any modifications and consider that results may not be directly comparable.
Common mistake: Using incorrect jaw pressure is a frequent error. Too little pressure allows specimen slippage, producing erroneously low break values; too much pressure can cause “jaw breaks” at the edge of the clamp, invalidating the test. Always set jaw pressure in accordance with the manufacturer’s recommendation and confirm with a slippage check before starting a test series.
FAQs
Q: What is the difference between the grab method and the strip method for fabric tensile testing?
A: The grab method clamps only a 25 mm wide central portion of a 100 mm wide specimen, leaving the outer yarns intact. This simulates edge restraint and generally gives higher breaking strength values. The strip method tests a full-width raveled or cut strip (all yarns are clamped). The grab method is often preferred for woven fabrics where edge effects are important.
A: The grab method clamps only a 25 mm wide central portion of a 100 mm wide specimen, leaving the outer yarns intact. This simulates edge restraint and generally gives higher breaking strength values. The strip method tests a full-width raveled or cut strip (all yarns are clamped). The grab method is often preferred for woven fabrics where edge effects are important.
Q: What conditioning is required for this test?
A: Specimens must be conditioned at 21 ± 1 °C and 65 ± 2 % relative humidity for at least 24 hours before testing. This standard atmosphere is common for all CAN/CGSB‑4.2 textile test methods.
A: Specimens must be conditioned at 21 ± 1 °C and 65 ± 2 % relative humidity for at least 24 hours before testing. This standard atmosphere is common for all CAN/CGSB‑4.2 textile test methods.
Q: Can this standard be used for nonwoven or knitted fabrics?
A: The standard is primarily intended for woven fabrics. For nonwovens, other methods such as the grab test described in ASTM D5035 or CGSB‑4.2 No. 9.4 may be more appropriate. Users should verify the scope of the standard and consult the relevant product specification before application.
A: The standard is primarily intended for woven fabrics. For nonwovens, other methods such as the grab test described in ASTM D5035 or CGSB‑4.2 No. 9.4 may be more appropriate. Users should verify the scope of the standard and consult the relevant product specification before application.
Q: What type of tensile testing machine is required?
A: A constant‑rate‑of‑extension (CRE) machine is recommended, though constant‑rate‑of‑traverse (CRT) machines are acceptable if they meet the required speed and force accuracy. The specified extension rate is 300 mm/min. The machine must be capable of reporting the peak force with an accuracy of ±1 % of the reading.
A: A constant‑rate‑of‑extension (CRE) machine is recommended, though constant‑rate‑of‑traverse (CRT) machines are acceptable if they meet the required speed and force accuracy. The specified extension rate is 300 mm/min. The machine must be capable of reporting the peak force with an accuracy of ±1 % of the reading.
Compliance adherence and technical review reference: 2026