Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Röhm PLEXIGLAS GS 0F00 cast acrylic sheet, typical values at 23 °C / 50 % RH (Röhm Technical Information Ref. No. 211-1)
Wood
Northern red oak (Quercus rubra), clear straight-grained specimens at 12% MC, parallel to grain unless stated; USDA FPL Wood Handbook FPL-GTR-282 (2021) Ch. 4 and Ch. 5
1
PLEXIGLAS GS and XT Technical Information (Ref. No. 211-1)Röhmarchived copyPlastic PMMA · Ultimate tensile strength: typical, 23 °CPlastic PMMA · Compressive strength: compressive yield stress, typicalPlastic PMMA · Flexural strength: typicalPlastic PMMA · Elongation at break: typicalPlastic PMMA · Young's modulus (stiffness): typical, short-termPlastic PMMA · Density: typicalPlastic PMMA · Poisson's ratio: typicalPlastic PMMA · Thermal conductivity: typicalPlastic PMMA · Thermal expansion: 0-50 °CPlastic PMMA · Specific heat: typicalPlastic PMMA · Max service temperature: max. permanent service temperature
2
Wood Handbook (FPL-GTR-282), Chapter 5: Mechanical Properties of WoodUSDA Forest Products LaboratoryWood · Ultimate tensile strength: modulus of rupture (no direct tensile value)Wood · Compressive strength: compression parallel to grain (maximum crushing strength), 12% MCWood · Flexural strength: modulus of rupture (static bending), 12% MCWood · Young's modulus (stiffness): bending MOE, parallel to grainWood · Poisson's ratio: mu_LR (red oak group, ~12% MC)
3
Technical Note 218: Weights of Various Woods Grown in the United States (1953)USDA Forest Products LaboratoryWood · Density: average weight of clear wood at 8% and 15% moisture content
4
Wood Handbook (FPL-GTR-282), Chapter 4: Moisture Relations and Physical Properties of WoodUSDA Forest Products LaboratoryWood · Thermal conductivity: across grain, 12% MC (Table 4-7, approximate)Wood · Thermal expansion: parallel to grain, ovendry wood, range across speciesWood · Specific heat: solid wood (all species), 12% MC, 27 C
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Plastic PMMA stronger than Wood?
Wood is stronger: its tensile strength is 99 MPa against 80 MPa for Plastic PMMA (24%).
Which is lighter, Plastic PMMA or Wood?
Wood is lighter: 692 kg/m³ against 1,190 kg/m³ for Plastic PMMA.
Which is stiffer, Plastic PMMA or Wood?
Wood is stiffer: Young's modulus 12.5 GPa against 3.3 GPa for Plastic PMMA, so the same part in Wood deflects less under the same load.
Which is lighter for the same job, Plastic PMMA or Wood?
For the same stiffness or strength: Wood is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Plastic PMMA
Wood
Stiff rod or tie (tension)
6.52x heavier
lighter
Stiff beam (bending)
3.35x heavier
lighter
Stiff panel or plate
2.68x heavier
lighter
Strong rod or tie
2.13x heavier
lighter
Strong beam
1.98x heavier
lighter
Strong panel or plate
1.91x heavier
lighter
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).
Thermal
Which conducts heat better, Plastic PMMA or Wood?
Plastic PMMA conducts heat better: 0.19 W/m·K against 0.18 W/m·K for Wood.
Which expands less with temperature?
Wood expands less: 3.8 µm/m·K against 70 µm/m·K for Plastic PMMA.