Physical Testing

Elmendorf Tear Strength & Energy Calculator (ASTM D1424)

Two divisions stand between the dial and the answer: the capacity the pendulum was fitted with, and the number of plies torn together.

Pendulum Instrument
gf
% of capacity
no.
Specimen Fabric
g/m²
mm

Tear Force per Ply

— gf

Capacity-corrected and divided by the plies torn

Force, Index & Energy

Total Tear Force
— gf
Tear Force per Ply
— N
Tear Index
— mN·m²/g
Work Absorbed per Ply
— mJ
Margin Inside Valid Scale Window
— pp

A negative scale margin means the reading fell outside the 20–80% window and the result is not reportable — refit with a pendulum of appropriate capacity and retest. Tear index normalises for fabric weight and is the fair way to compare constructions of different areal weight.

Elmendorf Tear Strength & Energy Calculator (ASTM D1424) — free, with the formula and a worked example, at Textile School.