Before revision: All other factor being equal, a cluster of tubes with a diameter H and a wall thickness e, compared to a solid bar of equal volume in a material caracterised by ρ , σ , E et G , presents an apparent density ρa = 4k(1 − k)ρ with k = e/H, allowable stress σa = 4k(1 − k)σ, The Young's modulus is and the shear modulus is .
After revision: All other factor being equal, a cluster of tubes with a diameter H and a wall thickness e, compared to a solid bar of equal volume in a material characterised by ρ , σ , E et G , presents an apparent density ρa = 4k(1 − k)ρ with k = e/H, allowable stress σa = 4k(1 − k)σ, The Young's modulus is and the shear modulus is .