Question

In the ravelled strip strength test of measurement of fabric strength, the dimensions of specimen between the jaws are

• A. 22 cm x 6 cm
• B. 18 cm x 4 cm
• C. 20 cm x 5 cm
• D. $25~cm\times7$ cm

Hint:

Remember "5 and 20" for strip tests: 5 cm width and 20 cm gauge length. If the specimen is not ravelled, it's called a "cut strip" test.

Answer 1

The Correct Option is C

Concept: The ravelled strip test is one of the most common methods to determine the breaking strength and elongation of woven fabrics. Unlike the "grab test," the strip test ensures that only the yarns actually held between the jaws are being broken, providing a more accurate measure of the fabric's inherent strength.

Step 1: Specimen Preparation.
In a "ravelled" strip test, the specimen is initially cut wider than the testing width. Yarns are then manually removed (ravelled) from both long edges until the strip reaches the exact required width. This prevents the edges from fraying during the test and ensures that all longitudinal yarns are securely gripped.

Step 2: Standard Dimensions.
According to standard testing procedures (such as ISO or ASTM), the effective width of the strip should be 5 cm (50 mm). The distance between the testing machine's jaws, known as the gauge length, is set to 20 cm (200 mm). Therefore, the dimensions of the specimen actively being tested between the jaws are 20 cm x 5 cm.