D40 vs D55

D55 is 1.2 times as stiff as D40. It is 1.2 times as dense. Per unit mass they are about equally stiff (19.7 and 19.62 MJ/kg). Strength: f_m,k = 40 MPa for D40, f_m,k = 55 MPa for D55.

D40 EN 338:2016 D55 EN 338:2016

Side by side

ratio = D55 / D40 · log scale

Property	D40	D55	Unit	Ratio
E₁ Modulus, direction 1	13	15.5	GPa	1.19×
E₂ Modulus, direction 2	0.87	1.03	GPa	1.18×
E₃ Modulus, direction 3	0.87	1.03	GPa	1.18×
G₁₂ Shear modulus 1-2	0.81	0.97	GPa	1.2×
G₁₃ Shear modulus 1-3	0.81	0.97	GPa	1.2×
E₀,₀₅ Modulus parallel to grain, 5 % fractile	10.9	13	GPa	1.19×
ρ Density	660	790	kg/m³	1.2×
ρ_k Density, characteristic (5 % fractile)	550	660	kg/m³	1.2×
f_m,k Bending strength	40	55	MPa	1.38×
f_t,0,k Tension parallel to grain	24	33	MPa	1.38×
f_t,90,k Tension perpendicular to grain	0.6	0.6	MPa	1×
f_c,0,k Compression parallel to grain	27	32	MPa	1.19×
f_c,90,k Compression perpendicular to grain	5.5	6.6	MPa	1.2×
f_v,k Shear strength	4.2	4.7	MPa	1.12×
E/ρ Specific stiffness E/ρ · derived	19.7	19.62	MJ/kg	0.996×
c₀ Bar wave speed √(E/ρ) · derived	4438	4429	m/s	0.998×
f/ρ Specific strength f/ρ · derived	60.61	69.62	kJ/kg	1.15×

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.