Plastic PMMA vs. Steel A992

Compare Plastic PMMA vs. Steel A992 strength, stiffness, weight and thermal properties.

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Plastic PMMABulk polymer (molded or machined)

Mechanical
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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)	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 A992?

Steel A992 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 A992?

Plastic PMMA is lighter: 1,190 kg/m³ against 7,850 kg/m³ for Steel A992.

Which is stiffer, Plastic PMMA or Steel A992?

Steel A992 is stiffer: Young's modulus 200 GPa against 3.3 GPa for Plastic PMMA, so the same part in Steel A992 deflects less under the same load.

Which is lighter for the same job, Plastic PMMA or Steel A992?

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 A992 is lighter for a stiff rod or tie (tension), stiff beam (bending).

Part that must be	Plastic PMMA	Steel A992
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 A992?

Steel A992 conducts heat better: 48 W/m·K against 0.19 W/m·K for Plastic PMMA.

Which expands less with temperature?

Steel A992 expands less: 12 µm/m·K against 70 µm/m·K for Plastic PMMA.

Among 72 materials

Stiffness against density

Strength against density