D40 vs D80

D80 is about twice as stiff as D40. It is 1.6 times as dense. Per unit mass D80 is 1.1 times as stiff. Strength: f_m,k = 40 MPa for D40, f_m,k = 80 MPa for D80.

D40 EN 338:2016 D80 EN 338:2016

Side by side

ratio = D80 / D40 · log scale

Property	D40	D80	Unit	Ratio
E₁ Modulus, direction 1	13	24	GPa	1.85×
E₂ Modulus, direction 2	0.87	1.6	GPa	1.84×
E₃ Modulus, direction 3	0.87	1.6	GPa	1.84×
G₁₂ Shear modulus 1-2	0.81	1.5	GPa	1.85×
G₁₃ Shear modulus 1-3	0.81	1.5	GPa	1.85×
E₀,₀₅ Modulus parallel to grain, 5 % fractile	10.9	20.2	GPa	1.85×
ρ Density	660	1080	kg/m³	1.64×
ρ_k Density, characteristic (5 % fractile)	550	900	kg/m³	1.64×
f_m,k Bending strength	40	80	MPa	2×
f_t,0,k Tension parallel to grain	24	48	MPa	2×
f_t,90,k Tension perpendicular to grain	0.6	0.6	MPa	1×
f_c,0,k Compression parallel to grain	27	38	MPa	1.41×
f_c,90,k Compression perpendicular to grain	5.5	13.5	MPa	2.45×
f_v,k Shear strength	4.2	5	MPa	1.19×
E/ρ Specific stiffness E/ρ · derived	19.7	22.22	MJ/kg	1.13×
c₀ Bar wave speed √(E/ρ) · derived	4438	4714	m/s	1.06×
f/ρ Specific strength f/ρ · derived	60.61	74.07	kJ/kg	1.22×

Values at the first thickness band or product form of each material (EN 338:2016; EN 338:2016). A minimum and a characteristic value are not the same kind of number — read the ratio as a guide. Each material's page lists every band and every source.