Elmendorf Pendulum Tear Test

Elmendorf pendulum tear testing (ISO 13937-1, ASTM D1424) measures the energy required to propagate a tear through 43 mm of woven fabric by swinging a weighted pendulum (capacity 200 mN, 800 mN, 3,200 mN, or 12,800 mN — selected so result falls in 20–80% of scale capacity per ISO 13937-1 clause) from horizontal position through 60° arc, with pre-slit specimen clamped between fixed and moving jaw. Energy dissipated = pendulum capacity × (1 − cosα) where α = angle of pendulum swing with specimen versus without — result in mN (milli-Newtons, not milliNewtons of force — historically reported as grams-force, conversion: 1 gf = 9.81 mN). Test limitations: Elmendorf valid only for woven fabrics where yarn pull-out mechanism operates — results unreliable for knitted (too extensible, pendulum bottoms out), nonwoven (tears without defined crack front), coated (coating bridging changes mechanism), or very light (<50 g/m²) fabrics. For these fabrics trouser tear (ISO 13937-2) is preferred. Specimen preparation: 75 mm × 100 mm specimens, slit 20 mm from long edge parallel to direction being tested (warp tear: slit parallel to warp, tear propagates perpendicular to warp yarns through weft system — tests weft yarn pull-out resistance; weft tear: converse). Result range examples: lightweight PET taffeta (60 g/m²): warp 400–600 mN, weft 350–500 mN; medium cotton twill (200 g/m²): warp 1,500–2,500 mN, weft 1,200–2,000 mN; para-aramid Kevlar woven (200 g/m²): warp 8,000–15,000 mN, weft 6,000–12,000 mN. Yarn crimp exchange effect: in balanced plain weave, warp tear (propagating through weft) easier than twill because plain weave restricts warp mobility — twill weave has 20–40% higher tear than equivalent weight plain weave due to greater yarn mobility in less restrained weave geometry.