Materials / Compare
Plastic HDPE vs. Steel AISI 1018
Compare Plastic HDPE 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 | 24MPasourcetypical, tensile stress at yield 23 °C, 50 mm/min ISO 527 | 372MPasourceproducer-stated, cold drawn |
| Ultimate tensile strength | not sourced | 441MPasourceproducer-stated, cold drawn |
| Elongation at break | not sourced | 15%sourcein 2 in (50.8 mm) |
| Young's modulus (stiffness) | 0.9GPasourcetypical, tensile modulus 23 °C ISO 527 | 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 | 950kg/m³sourcetypical, ISO 1183 | 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 | 25.3kN·m/kg | 47.3kN·m/kg1.87x higher |
| Stiffness to weight | 0.947MN·m/kg | 25.4MN·m/kg26.8x higher |
| Poisson's ratio | 0.4–0.45sourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) | 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 | 0.316GPa | 75.7GPa240x stiffer in shear |
| Bulk modulus | 2GPa | 185GPa |
| Speed of sound | 973m/s | 5,043m/s |
| Thermal | ||
| Thermal conductivity | 0.4–0.49W/m·Ksourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) | 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 | 120µm/m·Ksourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) | 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 | 600µm growth | 60µm growth10x less |
| Specific heat | 2,250J/kg·Ksourcebase material: high-density polyethylene family (INEOS Olefins & Polymers USA, Typical Engineering Properties of HDPE) | 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) | 0.208mm²/s | 13.6mm²/s65.3x faster |
| Thermal shock resistance | 56.9W/m | 5,473W/m96.3x more resistant |
| Values for | LyondellBasell Hostalen 23050 B high density polyethylene, typical ISO values | 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 HDPE stronger than Steel AISI 1018?
Steel AISI 1018 is stronger: its yield strength is 372 MPa against 24 MPa for Plastic HDPE (15.5x).
Which is lighter, Plastic HDPE or Steel AISI 1018?
Plastic HDPE is lighter: 950 kg/m³ against 7,861 kg/m³ for Steel AISI 1018.
Which is stiffer, Plastic HDPE or Steel AISI 1018?
Steel AISI 1018 is stiffer: Young's modulus 200 GPa against 0.9 GPa for Plastic HDPE, so the same part in Steel AISI 1018 deflects less under the same load.
Which is lighter for the same job, Plastic HDPE or Steel AISI 1018?
For the same stiffness or strength: Plastic HDPE is lighter for a stiff panel or plate, strong beam, strong panel or plate; Steel AISI 1018 is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie.
| Part that must be | Plastic HDPE | Steel AISI 1018 |
|---|---|---|
| Stiff rod or tie (tension) | 26.8x heavier | lighter |
| Stiff beam (bending) | 1.8x heavier | lighter |
| Stiff panel or plate | lighter | 37% heavier |
| Strong rod or tie | 1.87x heavier | lighter |
| Strong beam | lighter | 33% heavier |
| Strong panel or plate | lighter | 2.1x 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 HDPE or Steel AISI 1018?
Steel AISI 1018 conducts heat better: 51.9 W/m·K against 0.445 W/m·K for Plastic HDPE.
Which expands less with temperature?
Steel AISI 1018 expands less: 12 µm/m·K against 120 µm/m·K for Plastic HDPE.