D18 vs D40

D40 is 1.4 times as stiff as D18. It is 1.2 times as dense. Per unit mass D40 is 1.2 times as stiff. Strength: f_m,k = 18 MPa for D18, f_m,k = 40 MPa for D40.

D18 EN 338:2016 D40 EN 338:2016

Side by side

ratio = D40 / D18 · log scale

Property	D18	D40	Unit	Ratio
E₁ Modulus, direction 1	9.5	13	GPa	1.37×
E₂ Modulus, direction 2	0.63	0.87	GPa	1.38×
E₃ Modulus, direction 3	0.63	0.87	GPa	1.38×
G₁₂ Shear modulus 1-2	0.59	0.81	GPa	1.37×
G₁₃ Shear modulus 1-3	0.59	0.81	GPa	1.37×
E₀,₀₅ Modulus parallel to grain, 5 % fractile	8	10.9	GPa	1.36×
ρ Density	570	660	kg/m³	1.16×
ρ_k Density, characteristic (5 % fractile)	475	550	kg/m³	1.16×
f_m,k Bending strength	18	40	MPa	2.22×
f_t,0,k Tension parallel to grain	11	24	MPa	2.18×
f_t,90,k Tension perpendicular to grain	0.6	0.6	MPa	1×
f_c,0,k Compression parallel to grain	18	27	MPa	1.5×
f_c,90,k Compression perpendicular to grain	4.8	5.5	MPa	1.15×
f_v,k Shear strength	3.5	4.2	MPa	1.2×
E/ρ Specific stiffness E/ρ · derived	16.67	19.7	MJ/kg	1.18×
c₀ Bar wave speed √(E/ρ) · derived	4082	4438	m/s	1.09×
f/ρ Specific strength f/ρ · derived	31.58	60.61	kJ/kg	1.92×

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.