Three dimensional modelling of closed-cell aluminium foams with predictive macroscopic behaviour. (September 2019)

• Record Type: Journal Article
• Authors: Vengatachalam, B.; Poh, L.H.; Liu, Z.S.; Qin, Q.H.; Swaddiwudhipong, S.
• Is Part Of: Mechanics of materials. Volume 136(2019)
• Publication Date: 2019-09
• Subjects: Closed-cell foams -- 3D Voronoi -- Aluminum -- Irregular geometry -- Deformation mechanism; Strength of materials -- Periodicals; Mechanics, Applied -- Periodicals; Résistance des matériaux -- Périodiques; Mécanique appliquée -- Périodiques; Mechanics, Applied; Strength of materials; Periodicals; Electronic journals; 620.11
• DOI: 10.1016/j.mechmat.2019.103067
• Languages: English
• ISSNs: 0167-6636

Abstract

Highlights: A direct 3D Voronoi modeling approach for closed-cell aluminium foam is presented, with a single calibrated parameter characterizing the underlying irregular geometry. The numerical results for uniaxial compression, uniaxial tension and triaxial compression match well against experimental data, over range of commercially available relative densities. The underlying 3D relief mechanism, as well as a dominant cell wall bending mode during hydrostatic compression, are elaborated and illustrated. An asymmetric yield surface in the effective stress space is obtained for closed-cell aluminum foams. Abstract: This study presents an efficient approach to generate a realistic micromechanical model for closed-cell foams using irregular Voronoi models. Starting with a reference microstructure consisting of regular Kelvin cells, the nucleating points underlying each reference unit cell is subjected to a random displacement, the magnitude of which depends on the pore size and a misalignment parameter. For convenience, the misalignment parameter is calibrated from available statistical data on unit cell geometries for the commercially available closed-cell aluminium foam, and a common value is utilised for all cases considered. Numerical analyses with the irregular 3D micromechanical models are done using ABAQUS/Explicit. Considering both uniaxial and hydrostatic compressive loading cases, the numerical responses compare well with the experimental data in literature, over a wide range of relative densities. The deformation mechanism is next elaborated. In uniaxial compression, the deformation initiates at the weaker regions induced by the geometrical irregularities, before evolving into a localized deformation band through the coalescence between neighbouring regions of local weakness. This localized deformation band forms an irregular 3D relief in space, a phenomenon which cannot be captured by regular periodic microstructures. In hydrostatic compression, the irregular geometry also induces deformation through cell wall bending. In tension, a stretching mode induces a shift in the yield surface towards the positive mean stress quadrant, which is consistent with experimental observations. The proposed approach thus generates the irregular 3D microstructures efficiently through a single calibrated misalignment parameter, leading to realistic deformation mechanisms, with good predictions on the macroscopic behaviour, over a wide range of relative densities and different loading conditions.