The ability of a material to undergo significant plastic deformation before fracture, quantified by elongation at break or area reduction.
Ductility is quantified as %EL = (L_f − L₀)/L₀ × 100 or %RA = (A₀ − A_f)/A₀ × 100. %EL > 5% is ductile; < 2-3% is brittle. Ductility depends on crystal structure, temperature, strain rate, and microstructure. Polymer ductility depends on chain mobility, molecular weight, and crystallinity.
Ductile filaments (PETG, ABS, nylon) suit parts needing impact resistance and the ability to deform before catastrophic failure. PLA is relatively brittle (%EL ~3-6%); TPU and nylon are far more ductile. For safety-critical parts, ductile failure (visible deformation warning) is preferred over brittle (sudden fracture).
FDM layer adhesion makes parts effectively brittle in Z even if bulk filament is ductile. Ductility is strongly temperature-dependent: PLA embrittles below 0°C. Notches and stress concentrations locally convert ductile to brittle failure modes.
Related terms: Elongation at Break, Brittleness, Toughness, Yield Strength, Necking
| Field | mechanics, engineering |
|---|---|
| Also called | Plastic Deformability |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert