Seam Strength Testing
ASTM D1683 covers a test for measuring the seam strength of a woven fabric. Seams are used to stitch two different pieces of fabric together. Most seams are made with a sewing machine, after the fabric has been woven and then cut.
Seam strength is a comparison test between an unseamed test piece of fabric and the seamed fabric specimen. The specimen is pulled in tension, similar to a grab test, until it breaks. If the unseamed portion fails before the seam fails, the woven textile is said to have 100% seam efficiency. If the seam fails at say, half the breaking strength of the regular test piece, the seam efficiency is said to be 50%.
This ASTM test requires Vise Grips to be used, however in some rare cases, wrap grips can also be used however this should be noted on the test.
This test requires specialized grip jaws inserts. The front of the grip jaw is to be 1x1" or 25.4x25.4mm (Height x Width). The back jaw must be at least 1x2".
Universal Grip offers several different types of vise grips depending on the total load required for the test. Pneumatic Vise Grips are also available along with all of the accompanying hoses and switches. Pneumatic Grips are a great way to speed up testing by reducing the time it takes to mount the samples in between test lots.
The analysis for seam strength or seam efficiency is calculated by dividing the seam strength by the ultimate tensile strength of the base material without a seam. The seam strength is divided by the ultimate strength in order to give a percentage. In cases where the base material fails before the seam does, the seam efficiency is said to be 100%.
ASTM D434 - Resistance to Slippage of Yarn in a Fabric Seam