Young’s modulus (stiffness)

What it means in practice

Young’s modulus, also called tensile modulus or elastic modulus, describes stiffness. It tells you how much a material stretches or bends under a load that is well below its breaking point. High modulus means small deflection.

Stiffness often matters more than strength. Most parts fail in service not because they break, but because they bend too much. It is the deciding number for:

• Jigs, fixtures and gauges that must hold a position.
• Long, thin arms and brackets that should not sag.
• Enclosure walls that should not flex when pressed.
• Drone frames and mounts where vibration must stay low.

How it’s measured

It comes from the same pull test as tensile strength. At the very start of the test, stress rises in a straight line with strain. The slope of that line is the modulus.

• Standards: ISO 527 (slope taken between 0.05% and 0.25% strain) and ASTM D638.
• Units: MPa or GPa. 1 GPa = 1,000 MPa. Unit mix-ups between the two are a common source of odd-looking numbers on datasheets.
• Accuracy: modulus needs precise strain measurement, usually with an extensometer. Values taken from crosshead movement tend to read low.

How to read and compare it

• Orientation. Fibre-filled filaments are much stiffer along the print path than across it, and Z is lowest. See print orientation: XY vs Z.
• Temperature. Plastics lose stiffness as they warm, sharply so near the glass transition. A room-temperature value says little about a part in a hot car.
• Time. Under constant load, plastics slowly keep deforming (creep). The modulus describes the first moments, not months of loading.
• Tensile vs flexural. Some sheets only give flexural modulus. The two are often similar but not interchangeable.
• Typical values. Treat them as averages. See typical vs minimum values.

Range in our catalog

• Standard materials: 486.2–3,530 MPa (median 2,246 MPa, 91 materials)
• Resins: 2.4–10,600 MPa (median 1,978 MPa, 148 materials)
• PLA filaments: 1,689–8,500 MPa (median 2,870 MPa, 33 materials)
• Carbon-fibre filled: 2,200–69,000 MPa (median 6,200 MPa, 53 materials)
• Glass-fibre filled: 2,100–21,000 MPa (median 4,236 MPa, 36 materials)

1. PLA 301,689–8,500
2. PETG 171,400–9,000
3. ABS 181,121–5,210
4. PC 122,000–6,980
5. PA6 131,980–15,000
6. PA12 101,400–9,460
7. PEI 162,050–8,790
8. PEEK 132,600–10,100

Bar = lowest to highest, dot = median. 129 materials, live from our database.

Highest and lowest in our catalog

Stiffest overall

Metals and continuous-fibre composites sit at the top, well above any unfilled plastic.

Least stiff flexible materials

Related properties

• Flexural modulus — stiffness measured in bending.
• Tensile strength — the load at failure.
• Elongation at break — stiff materials often stretch less.
• Heat deflection temperature — where stiffness gives way to heat.

See materials with a modulus of 4,000 MPa or more 89 materials