Information on the most widely used ASTM standards within the materials testing industry
ASTM D2256 Standard Test Method for Tensile Properties of Yarns by the Single-Strand Method
ASTM D2256 is the standard test method for tensile properties of yarns by the single-strand method. It is the predominant standard used in North America and is technically very similar to ISO 2062. It quantifies breaking force, elongation at break, and derived properties (tenacity, modulus, toughness) under diverse conditions, serving as a benchmark for quality control, product development, and material specification.
Test methods:
ASTM D2256 defines three specimen configurations and six environmental test conditions, offering high flexibility for different yarn types and use cases.
| Method A (Straight) | Standard direct tensile test on straight yarn; used for general strength and elongation measurement; |
| Method B (Knotted) | Tests yarn with a standard knot to simulate stress concentrations (e.g., sewing, knotting); critical for assessing knot strength; |
| Method C (Looped) | Tests yarn in a looped configuration to evaluate loop strength (relevant for knitting, netting, and thread applications). |
ASTM D2256 Test principle:
A single yarn specimen (straight, knotted, or looped) is mounted between two grips at a fixed gauge length.
The machine applies a controlled, constant rate of extension to achieve a 20‑second nominal time‑to‑break.
Force and elongation are continuously recorded until the yarn fractures.
Key parameters are captured:
Breaking force: Maximum force at failure.
Elongation at break: Stretch percentage at break.
Derived values: Breaking tenacity (force/linear density), initial modulus, chord modulus, and breaking toughness.
Test equipment required for ASTM D2256 textile yarns:
| Universal Testing Machine | Recommend UnitedTest tensile testing machine. Constant Rate of Extension (CRE) is preferred; Constant Rate of Loading (CRL) and Constant Rate of Travel (CRT) are also permitted. It must measure force and elongation accurately and record the force-elongation curve until specimen failure. Maintains a 20‑second nominal time‑to‑break (adjustable speed to achieve this target). |
| Tensile Test Grips | Pneumatic or mechanical yarn grips (flat or V‑jaws) to prevent slippage and jaw breaks; compatible with straight, knotted, and looped specimens.
|
| Long travel extensometer | To measure elongation (as a percentage of the initial gauge length). |
Test Specimen Information:
Form: Single‑strand yarn (monofilament, multifilament, spun, plied, or cabled) from packages or extracted from fabrics (by agreement).
Gauge Length: Standard lengths: 250 mm (10 in) or 500 mm (20 in); specified based on yarn type and test purpose.
Conditioning: Equilibrate in standard atmosphere (21 ± 1 °C / 70 ± 2 °F, 65 ± 2% RH) for a minimum period before testing (for Condition 1).
Sample Size: Minimum 50 specimens per test (100 preferred) to ensure statistical validity; discard jaw breaks and slippage failure
ASTM D2256 Tensile Test Procedure:
1, Conditioning: Equilibrate specimens in the required environment (standard or specified thermal/moisture condition).
2, Sample Preparation:
Straight: Cut to gauge length, no pre‑tension.
Knotted: Tie a standard knot (per method) in the specimen center.
Looped: Form a loop and mount in grips.
3, Machine Setup:
Set the gauge length (e.g., 250 mm or 500 mm).
Select test configuration (A/B/C) and environmental condition.
Adjust speed to target 20‑second time‑to‑break.
Zero load and elongation reading.
4, Testing:
Mount a single yarn specimen in the grips, ensuring no slack or pre‑tension.
Start the machine. The yarn will stretch and eventually break.
Record the breaking force and elongation. Discard breaks that occur within 1/4 inch (6 mm) of the jaw.
Repeat the test for the required number of specimens.
5, Calculation & Reporting:
Compute mean, standard deviation, and coefficient of variation (CV%) for breaking force and elongation.
the average breaking strength, elongation, and their coefficients of variation.
Related standard:
| ISO 3341 | Textile glass - Yarns - Determination of breaking force and breaking elongation; |
| ASTM D7269 | Standard Test Methods for Tensile Testing of Aramid Yarns |
| AS 2001.2.7 | METHODS OF TEST FOR TEXTILES - PHYSICAL TESTS - DETERMINATION OF BREAKING FORCE AND EXTENSION OF YARNS |
| ISO 3342 | Textile glass - Mats - Determination of tensile breaking force |
Comparison Table: ASTM D2256 vs ISO 2062 - Key Differences
| Item | ASTM D2256 | ISO 2062 |
|---|---|---|
| Standard Title | Tensile Properties of Yarns by the Single‑Strand Method | Yarns from packages — Determination of single‑end breaking force and elongation at break (CRE) |
| Region | North America / Global | Global / Europe |
| Permitted Tester Types | CRE (preferred), CRT, CRL | Only CRE (Constant Rate of Extension) |
| Speed Control | Speed adjusted for nominal 20‑s time‑to‑break | Fixed rate: 100% extension per minute of gauge length |
| Test Configurations | 3 methods:• Method A: Straight• Method B: Knotted• Method C: Looped | Straight single‑end only (no knot/loop) |
| Environmental Modes | 6 conditions: standard, wet (immersed/not), oven‑dry, high/low temp | Dry (A/B/C) + wet (Method D only) |
| Standard Gauge Lengths | 250 mm (10 in), 500 mm (20 in) | 250 mm, 500 mm |
| Dispute Method | Agreed procedure | Method C (relaxed skein) for elongation disputes |
| Main Outputs | Breaking force, elongation, tenacity, modulus, toughness, CV% | Breaking force, elongation at break, CV% |
| Yarn Exclusions | Glass, flax, hemp, ramie, paper yarn, highly elastic yarn | Glass, carbon, aramid, elastomeric, ceramic, polyolefin tape yarn |
| Conditioning | ASTM D1776 (21 °C, 65% RH) | Standard textile atmosphere (20 °C, 65% RH) |
| Minimum Specimens | Min 50; 100 preferred | Typically 50–100 (statistically valid number) |
| Related Equivalent | — | EN ISO 2062 (European version) |
Related products and device
Related Standard
ISO 3341:2000 Textile glass — Yarns — Determination of breaking force and breaking elongation
ISO 3341 specifies a method for the determination of the tensile breaking force and elongation at break of glass yarns taken from packages.
The method is applicable to various types of glass yarn (single, folded, cabled, strands, structures without twist, rovings, etc.). It is basically intended for single, folded and cabled glass yarns having a diameter of less than 2 mm, or a linear density lower than 2000 tex, taken from packages. This test is applicable to various types of glass yarn (single, folded, cabled, strands, structures without twist, rovings, etc.). It is basically intended for single, folded and cabled glass yarns having a diameter of less than 2 mm, or a linear density lower than 2000 tex, taken from packages.
ISO 2062 specifies the method for determining the breaking force and elongation at break of textile yarns (single, piled, or cabled) under a constant rate of extension (CRE). It is a fundamental tensile test for yarn quality control.
The test operates on the principle of applying a constant rate of elongation to a single yarn specimen until it breaks:
A single yarn is securely clamped between two grips at a fixed gauge length.
The lower grip moves downward at a constant speed, stretching the yarn at a rate of 100% per minute of the gauge length.
The machine continuously records the force (load) applied and the corresponding elongation.
The test ends when the yarn breaks. The maximum force recorded is the breaking force, and the stretch at that point is the elongation at break (expressed as a percentage).
FAQs on ASTM D2256: Yarn Tensile Testing
Q1: What is the key purpose of the ASTM D2256 test?
A: Its primary purpose is to determine the single-strand breaking strength and elongation of yarn. This data is the foundational metric for specifying yarn quality, ensuring it meets purchase requirements, and predicting its performance in manufacturing and end-use.
Q2: Why is a minimum of 50 breaks recommended? Isn't that excessive?
A: No, it's statistically necessary. Yarn strength has inherent variability. Testing 50 specimens allows for a reliable calculation of both the average breaking force and the coefficient of variation (CV%). The CV% is crucial as it measures consistency; a high CV% indicates uneven yarn quality, which can cause problems even if the average strength is acceptable.
Q3: How do I choose between a 10-inch and a 25-inch gauge length?
A: The choice is often based on material specification or industry practice. The 25-inch (500 mm) length is more common for general testing. A shorter gauge length (e.g., 10-inch) may be used for very high-elongation yarns (like elastane) or when specified. The key is that the chosen length must be documented, as it affects the elongation result.
Q4: What is the correct extension rate, and why does it matter?
A: The rate is typically set as a percentage of the gauge length per minute (e.g., 100% or 60%). A consistent, standardized rate is critical because the speed of extension can affect the results—faster rates can yield slightly higher breaking force readings. The rate must be agreed upon and reported for tests to be comparable.
Q5: Why must breaks near the clamp jaws be discarded?
A: Breaks within 1/4 inch (6 mm) of the jaws are considered invalid because the break may be initiated by stress concentration or damage from the clamp grip, not by the uniform tensile failure of the yarn specimen. Including these would give a non-representative and lower strength value.
Q6: How is ASTM D2256 related to ISO 2062? Can I use the data interchangeably?
A: The two standards are technically very similar in principle and methodology (both are CRE-based). For many practical purposes, data from one can be referenced against the other, especially if test parameters (gauge length, rate) are aligned. However, for formal certification or contractual acceptance testing, the specified standard (ASTM or ISO) must be followed precisely, as there are subtle differences in conditioning atmospheres and procedural details.
Q7: What properties does ASTM D2256 measure?
A: It measures:
Breaking force
Elongation at break
Tenacity (breaking force per linear density)
Modulus (stiffness)
Breaking toughness
CV% (uniformity)
Q8: What are the three test methods in ASTM D2256?
A:Method A: Straight yarn (general tensile test)
Method B: Knotted yarn (knot strength)
Method C: Looped yarn (loop strength)
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