Materials / Compare
Plastic PEEK vs. Steel AISI 1018
Compare Plastic PEEK vs. Steel AISI 1018 strength, stiffness, weight and thermal properties.
| Try it on a partA bracket to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | 98MPasourcetypical, tensile yield | 372MPasourceproducer-stated, cold drawn |
| Ultimate tensile strength | not sourced | 441MPasourceproducer-stated, cold drawn |
| Compressive strength | 125MPasourcetypical, 23 C | not sourced |
| Flexural strength | 165MPasourcetypical, flexural stress at yield, 23 C | not sourced |
| Elongation at break | 25%sourcetypical, at break | 15%sourcein 2 in (50.8 mm) |
| Young's modulus (stiffness) | 4GPasourcetypical (nominal) | 200GPasourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Density | 1,300kg/m³sourcetypical (crystalline) | 7,861kg/m³sourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Strength to weight | 75.4kN·m/kg1.59x higher | 47.3kN·m/kg |
| Stiffness to weight | 3.08MN·m/kg | 25.4MN·m/kg8.26x higher |
| Poisson's ratio | 0.38sourcetypical | 0.32sourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Shear modulus | 1.45GPa | 75.7GPa52.2x stiffer in shear |
| Bulk modulus | 5.56GPa | 185GPa |
| Speed of sound | 1,754m/s | 5,043m/s |
| Thermal | ||
| Thermal conductivity | 0.29W/m·Ksourcetypical, average, 23 C | 51.9W/m·Ksourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Thermal expansion | 55µm/m·Ksourceaverage of flow/cross-flow, below Tg (<143 C) | 12µm/m·Ksourcebase material: unalloyed carbon steel, Ovako family table (S275JR, 'none alloyed structural steels', C <= 0.21%); mean 20-300 °C |
| 100 mm part over a 50 °C swing | 275µm growth | 60µm growth4.58x less |
| Specific heat | 2,200J/kg·Ksourcetypical, 23 °C, DSC (Victrex PEEK 450G TDS, revision Jul 2012) | 486J/kg·Ksourcebase material: AISI 1025 plain carbon steel (MIL-HDBK-5J design value; ASTM A108 bar is the cold-finished carbon-steel bar spec that also covers 1018) |
| Heats up and cools (diffusivity) | 0.101mm²/s | 13.6mm²/s134x faster |
| Thermal shock resistance | 80.1W/m | 5,473W/m68.3x more resistant |
| Melting point | 343°Csourcetypical, DSC | not sourced |
| Glass transition | 143°Csourceonset (midpoint 150 C) | not sourced |
| Max service temperature | 240°CsourceUL 746B RTI, mechanical strength (continuous use index) | not sourced |
| Values for | Victrex PEEK 450G (unreinforced, injection moulded), Victrex TDS rev. March 2026; Poisson from Victrex fluid-management flyer (2020-07) | AISI 1018 cold drawn bar (Niagara LaSalle, cold-finished bar producer) |
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Is Plastic PEEK stronger than Steel AISI 1018?
Steel AISI 1018 is stronger: its yield strength is 372 MPa against 98 MPa for Plastic PEEK (3.8x).
Which is lighter, Plastic PEEK or Steel AISI 1018?
Plastic PEEK is lighter: 1,300 kg/m³ against 7,861 kg/m³ for Steel AISI 1018.
Which is stiffer, Plastic PEEK or Steel AISI 1018?
Steel AISI 1018 is stiffer: Young's modulus 200 GPa against 4 GPa for Plastic PEEK, so the same part in Steel AISI 1018 deflects less under the same load.
Which is lighter for the same job, Plastic PEEK or Steel AISI 1018?
For the same stiffness or strength: Plastic PEEK is lighter for a stiff panel or plate, strong rod or tie, strong beam, strong panel or plate; Steel AISI 1018 is lighter for a stiff rod or tie (tension), stiff beam (bending).
| Part that must be | Plastic PEEK | Steel AISI 1018 |
|---|---|---|
| Stiff rod or tie (tension) | 8.26x heavier | lighter |
| Stiff beam (bending) | 17% heavier | lighter |
| Stiff panel or plate | lighter | 1.64x heavier |
| Strong rod or tie | lighter | 1.59x heavier |
| Strong beam | lighter | 2.48x heavier |
| Strong panel or plate | lighter | 3.1x heavier |
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Which conducts heat better, Plastic PEEK or Steel AISI 1018?
Steel AISI 1018 conducts heat better: 51.9 W/m·K against 0.29 W/m·K for Plastic PEEK.
Which expands less with temperature?
Steel AISI 1018 expands less: 12 µm/m·K against 55 µm/m·K for Plastic PEEK.