Standard Test Method for Tearing Strength of Nonwoven Fabrics by the Trapezoid Procedure
APP-D5733Ensure the 15mm starter slit is cut perfectly perpendicular to the specimen edge using a razor blade; any slant will cause the tear path to drift into the jaws.
Challenge & Testing Gap
Localized fiber bundling and jaw-edge slippage mask the true individual filament rupture resistance, smoothing out critical tear profiles.
The Solution
Deploy wide pneumatic side-action clamps with matching serrated and rubber hybrid jaw faces to prevent material neck-down.
Mechanics & Specimen Behavior
Primary Mechanics
Continuous linear extension driving a tear across a pre-slit nonwoven specimen secured along non-parallel template lines.
Specimen Details
Rectangular nonwoven fabric block cut to 76mm x 201mm, marked with an isosceles trapezoid blueprint and an initial 15mm edge cut.
Mechanical Ratios & Properties
Clamping plates align along the 102mm and 25mm offset trapezoidal paths, focusing stress directly onto the 15mm starter notch.
Expert Engineering Commentary
Core Problem Identification
Specimen slipping out of the jaw faces during the tear propagation or tearing directly along the clamp edge matrix line instead of across the center body.
Root Cause Analysis
Inadequate clamping pressure from manual fixtures or sharp, over-aggressive jaw serrations that slice the external nonwoven fibers.
Hardware Specific Solutions
Pneumatic parallel grips featuring extra-wide 50mm x 100mm faces lined with smooth, high-friction neoprene inserts.
Analysis & Calculation Standards
Event & Failure Detection
Continuous multi-peak cluster recording across a defined travel plateau, discarding the initial material expansion envelope.
Required Calculations
Trapezoid Tearing Strength (defined as the average of the five highest peak forces or the absolute max peak force), and total energy.
Statistical Outputs
Mean tearing values, standard deviation of peak heights, and cross-directional variance analysis across 5 machine and 5 cross-direction lots.
Real-time 1000Hz multi-peak tracking algorithm captures thousands of discrete yarn failures natively, preventing data-averaging smoothing.
Additional Commentary
Although this standard was officially withdrawn by ASTM without a direct replacement, it remains widely referenced in quality control pipelines for structural nonwovens.
Use pneumatic actuation exclusively to maintain constant clamping pressure on the fabric tabs, compensating for material thinning as fibers unravel.
Common Pitfalls
Utilizing jaw inserts narrower than the fabric specimen width, which allows the outer margins to bunch up and distort the tearing vectors.