ASTM D2256 - Standard Test Method for Tensile Properties of Yarns by the Single-Strand Method

Due to its high data capture rate, we recommend our high tier 6800 Series test frame as the optimal solution for ASTM D2256 testing, although our more affordable 3400 Series is also appropriate. A single column frame is adequate for most single-strand yarn specimens as the loads rarely exceed 5 kN. In cases where yarn specimens require greater force, a dual column system may be needed.

The most common gripping solution for ASTM D2256 are pneumatic cord and yarn grips with smooth clamping blocks, which are well suited for testing nearly all types of yarn specimens while maintaining high throughput. A specially designed horn with a smooth finish and a contoured surface with a graduated cam allows for easy loading and a stress reduced clamping area on the specimen. By incorporating a design that evenly distributes gripping force over the surface of a curved half capstan, the chances of specimen failures are reduced. 

Instron’s 2 kN capacity cord and yarn grips can also be paired with jaw faces with several other finishes to provide adequate clamping and avoid damage to the specimens during testing. The pneumatic grips allow users to fine-tune the gripping pressure in order to avoid jaw breaks or slippage. In some cases with strong or slippery yarn specimens, use of extra padding material within the clamping blocks, such as paper or emery cloth, can also be helpful.

• ASTM D2256 is available as a pre-built test method within Bluehill Universal software. This method includes pre-configured calculations to help expedite test setup and simplify the testing process.
  
  
• This standard recommends a Constant Rate of Extension (CRE) test frame for operating at a 20 second time-to-break, paired with grips that provide adequate clamping throughout testing. If the frame cannot provide a 20 second time-to-break or the grips allow for slippage while testing, the standard allows for alternative testing methods. These alternatives will likely be dependent on each yarn’s material properties.