Cantilever Bending Length and Flexural Rigidity

Cantilever bending length test (ISO 4674-2 Part 1 for coated fabrics; BS 3356 for apparel fabrics; ASTM D1388 Option A and B) measures the bending length C (cm) of fabric strips that overhang a horizontal platform under gravity until the free end deflects to 41.5° below horizontal — the angle at which the restoring bending moment equals the gravitational bending moment for a cantilever of length C. Procedure: fabric strip 25 mm wide × 200 mm long slid at 2 mm/s over platform edge until free end touches inclined (41.5°) reference plane — overhang length measured to ±1 mm. Four specimens per direction (warp and weft, both faces), average reported. Bending length C values: georgette chiffon 1.0–1.5 cm; cotton shirting 2.5–3.5 cm; denim 5–8 cm; canvas 8–15 cm; glass fibre woven 3–8 cm (surprisingly low due to high weight). Flexural rigidity calculation: G (µN·m) = W × C³ × 9.8 × 10⁻⁶ where W = fabric areal mass (g/m²), C = bending length (cm) — example: cotton shirting W = 120 g/m², C = 3.0 cm → G = 120 × 27 × 9.8 × 10⁻⁶ = 0.032 µN·m. Finishing effects on bending length: mercerisation −10 to −15% (softens); starch finishing +40–80% (stiffens, temporary); resin easy-care treatment +20–40% (permanent stiffening from polymer cross-linking); calendering +15–30% (fibre compaction increases modulus); enzyme treatment −5–15% (cellulase degradation of surface reduces inter-yarn friction). Bending length specification by application: shirt collar interlining C ≥ 6 cm (firm support); dress lining C ≤ 2.5 cm (fluid, no structure); uniform jacket C 4–6 cm (moderate body).