Standard Test Method for Breaking Strength and Elongation of Textile Fabrics (Grab Test)
APP-D5034Draw a straight reference line parallel to the front edge of the specimen to verify perfectly perpendicular alignment inside the jaws.
Challenge & Testing Gap
Fabric jaw-clipping and side-bunching at the grip boundaries introduce complex shear stresses that cause premature thread breakage.
The Solution
Incorporate parallel pneumatic grips featuring a specialized offset jaw layout where the front face is smaller than the back face.
Mechanics & Specimen Behavior
Primary Mechanics
Axial tensile force applied to the central section of a wide fabric panel, pulling until structural macro-rupture occurs.
Specimen Details
Rectangular fabric coupon measuring 100mm wide by 150mm long, gripped exclusively along its central vertical axis line.
Mechanical Ratios & Properties
The front jaw face measures exactly 25.4mm x 25.4mm while the rear jaw face is wider (at least 25.4mm x 50.8mm) to eliminate edge slicing.
Expert Engineering Commentary
Core Problem Identification
Jaw breaks or specimen slippage where threads pull out of the clamp zone rather than fracturing within the unsupported middle matrix.
Root Cause Analysis
Uneven manual clamping pressure allowing the outer un-gripped fabric wings to twist and distort the central vertical pull path.
Hardware Specific Solutions
Pneumatic side-action grips fitted with 25.4mm x 25.4mm front inserts and 50mm x 75mm rubber or wave-profile rear faces.
Analysis & Calculation Standards
Event & Failure Detection
Automated first-derivative sharp force drop detection marking the ultimate bulk breaking threshold of the fabric structure.
Required Calculations
Breaking Force (expressed in Newtons or pounds-force), Elongation at Break, Apparent Tensile Strength, and Effective Gauge Strain.
Statistical Outputs
Lot averages, standard deviation of breaking forces, coefficient of variation (CV%), and range metrics across 5 warp and 5 filling panels.
High-frequency 1000Hz sampling layer captures the rapid cascade breakdown of individual structural yarns without data clipping.
Additional Commentary
Modified front-vs-back jaw sizing prevents sharp perimeter shearing by easing the stress transition zone into the free fabric body.
If a specimen breaks directly at the jaw face edge and the result is below 80% of the batch average, discard it immediately.
Common Pitfalls
Using identical wide jaw faces for both front and back inserts, which turns the procedure into an invalid strip test.