D18 vs D55

D55 is 1.6 times as stiff as D18. It is 1.4 times as dense. Per unit mass D55 is 1.2 times as stiff. Strength: f_m,k = 18 MPa for D18, f_m,k = 55 MPa for D55.

D18 EN 338:2016 D55 EN 338:2016

Side by side

ratio = D55 / D18 · log scale

Property	D18	D55	Unit	Ratio
E₁ Modulus, direction 1	9.5	15.5	GPa	1.63×
E₂ Modulus, direction 2	0.63	1.03	GPa	1.63×
E₃ Modulus, direction 3	0.63	1.03	GPa	1.63×
G₁₂ Shear modulus 1-2	0.59	0.97	GPa	1.64×
G₁₃ Shear modulus 1-3	0.59	0.97	GPa	1.64×
E₀,₀₅ Modulus parallel to grain, 5 % fractile	8	13	GPa	1.62×
ρ Density	570	790	kg/m³	1.39×
ρ_k Density, characteristic (5 % fractile)	475	660	kg/m³	1.39×
f_m,k Bending strength	18	55	MPa	3.06×
f_t,0,k Tension parallel to grain	11	33	MPa	3×
f_t,90,k Tension perpendicular to grain	0.6	0.6	MPa	1×
f_c,0,k Compression parallel to grain	18	32	MPa	1.78×
f_c,90,k Compression perpendicular to grain	4.8	6.6	MPa	1.38×
f_v,k Shear strength	3.5	4.7	MPa	1.34×
E/ρ Specific stiffness E/ρ · derived	16.67	19.62	MJ/kg	1.18×
c₀ Bar wave speed √(E/ρ) · derived	4082	4429	m/s	1.08×
f/ρ Specific strength f/ρ · derived	31.58	69.62	kJ/kg	2.2×

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.