MESO SCALE MODELING AND PREDICTING THE MECHANICAL PROPERTIES OF CLOSED-CELL ALUMINUM FOAMS UNDER COMPRESSION LOADING

• Main Author: Aji Warsiyanto, Budi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67556
• Institution: Institut Teknologi Bandung

Closed-cell foam is a class of cellular material with excellent physical and mechanical properties, such as low weight, low heat conductivity, high energy absorbing capacity, and high strength-weight ratio. As a consequence, in recent years, closed-cell foam has been used in the aerospace, construction, and transportation industries. The biggest challenge in predicting the mechanical properties of closed-cell aluminum foams is to accurately and efficiently capture the actual geometric and topological characteristics so that the model can be used to predict their mechanical properties accurately. The mechanical properties of the foam are influenced by design parameters, such as base material, cell shape and topology, and relative density. This study aims to validate the foam model resulting from numerical simulations with experimental data. In addition, the deformation mechanism and the effect of design parameters on the macro response and mechanical properties of the foam model were also analyzed. The geometry of closed-cell foam specimens was modeled based on the Laguerre-Voronoi tessellation (LVT) algorithm and the Kelvin structure using NEPER. The LVT model consists of a set of cells which are irregular polyhedrons with a certain distribution, average size, and standard deviation. The foam model was meshed using a triangular shell element (S3R) using NEPER and simulations of uniaxial quasi-static compression loading were performed using the ABAQUS/Explicit finite element method software. Numerical simulation of uniaxial compression loading was carried out using two parallel rigid plates located on the top and bottom surfaces of the LVT model. In uniaxial compression, numerical simulations show qualitative resemblance for macro response to the experimental data, even though there is a delay in densification. The deformation initiates at the weaker regions induced by the geometrical irregularities, before evolving and merging with other weak regions. The cell wall deformation of the LVT model is dominated by bending, a phenomenon which cannot be captured by Kelvin cell structure. The yield stress of the base material, cell aspect ratio, and relative density are parameters that significantly affect the macro response and mechanical properties, especially the relative Young's modulus and plateau stress of the foam model. Strain densification iv is only sensitive to the yield stress of the base material and cell shape. The LVT model has a relative Young's modulus 2.2 times higher than the experimental data. Densification strain values for the difference in relative density cannot follow the trend of experimental data. This discrepancy can be attributed to differences in the detailed microstructure characteristics between the LVT model and the foam specimen. However, the plateau stress value resulting from the numerical simulation is reasonably good in predicting the experimental data. This indicates that the cell wall collapse process of the LVT model is similar to the foam specimen.