Materials / Compare
Plastic PMMA vs. Steel
Compare Plastic PMMA vs. Steel 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 | not given (tensile used) | 385MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey), as reported by AISC |
| Ultimate tensile strength | 80MPasourcetypical, 23 °C | 505MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey) |
| Compressive strength | 110MPasourcecompressive yield stress, typical | not sourced |
| Flexural strength | 115MPasourcetypical | not sourced |
| Elongation at break | 5.5%sourcetypical | not sourced |
| Young's modulus (stiffness) | 3.3GPasourcetypical, short-term | 200GPasourcedesign value (AISC 360-16) |
| Density | 1,190kg/m³sourcetypical | 7,850kg/m³sourcenominal (constructional data) |
| Strength to weight | 67.2kN·m/kg37% higher | 49kN·m/kg |
| Stiffness to weight | 2.77MN·m/kg | 25.5MN·m/kg9.19x higher |
| Poisson's ratio | 0.37sourcetypical | 0.3sourcedesign value (AISC 360-16 Commentary) |
| Shear modulus | 1.2GPa | 76.9GPa63.9x stiffer in shear |
| Bulk modulus | 4.23GPa | 167GPa |
| Speed of sound | 1,665m/s | 5,048m/s |
| Thermal | ||
| Thermal conductivity | 0.19W/m·Ksourcetypical | 48W/m·Ksourcenominal at 20 °C |
| Thermal expansion | 70µm/m·Ksource0-50 °C | 12µm/m·Ksourcenominal (constructional data, no temperature range stated) |
| 100 mm part over a 50 °C swing | 350µm growth | 60µm growth5.83x less |
| Specific heat | 1,470J/kg·Ksourcetypical | 460–480J/kg·Ksourcebase material: EN S275JR unalloyed structural steel (the EN counterpart of A36), typical, 50/100 °C |
| Heats up and cools (diffusivity) | 0.109mm²/s | 13mm²/s120x faster |
| Thermal shock resistance | 41.5W/m | 5,390W/m130x more resistant |
| Max service temperature | 80°Csourcemax. permanent service temperature | not sourced |
| Values for | Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1) | Generic structural steel, cited as ASTM A992 (the current US structural grade): ASTM A992 W-shapes; Fy/Fu specified minimums from AISC publications (AISC 360-16 Commentary; Modern Steel Construction); elastic constants AISC 360; physical constants from the bauforumstahl structural-steel EPD, which names A992 among covered product standards. |
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 PMMA stronger than Steel?
Steel is stronger: its yield strength is 385 MPa against tensile strength 80 MPa for Plastic PMMA (4.81x).
Which is lighter, Plastic PMMA or Steel?
Plastic PMMA is lighter: 1,190 kg/m³ against 7,850 kg/m³ for Steel.
Which is stiffer, Plastic PMMA or Steel?
Steel is stiffer: Young's modulus 200 GPa against 3.3 GPa for Plastic PMMA, so the same part in Steel deflects less under the same load.
Which is lighter for the same job, Plastic PMMA or Steel?
For the same stiffness or strength: Plastic PMMA is lighter for a stiff panel or plate, strong rod or tie, strong beam, strong panel or plate; Steel is lighter for a stiff rod or tie (tension), stiff beam (bending).
| Part that must be | Plastic PMMA | Steel |
|---|---|---|
| Stiff rod or tie (tension) | 9.19x heavier | lighter |
| Stiff beam (bending) | 18% heavier | lighter |
| Stiff panel or plate | lighter | 1.68x heavier |
| Strong rod or tie | lighter | 37% heavier |
| Strong beam | lighter | 2.31x heavier |
| Strong panel or plate | lighter | 3.01x 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 PMMA or Steel?
Steel conducts heat better: 48 W/m·K against 0.19 W/m·K for Plastic PMMA.
Which expands less with temperature?
Steel expands less: 12 µm/m·K against 70 µm/m·K for Plastic PMMA.