Session: 12-20-01: Composite Materials and Mechanics

Paper Number: 145232

145232 - Structure-Property Relations of Foam-Filled Lattice Composites: A Computational Study 

Additively manufactured lattice structures provide high specific stiffness and strength but cannot sustain large compression due to the buckling instability of struts. In contrast, cellular foams are relatively soft but can withstand large compression with bending deformation. For light-weighting and energy absorption applications, combining the mechanical properties of lattice structures and foams is desirable. This work focuses on the mechanics of an inter-penetrating composite that combines these two material systems. Specifically, the composite material has a stiff lattice structure, and its pore space is filled with a relatively soft foam matrix. We developed a representative volume element-based 3D finite element model to study the emergent mechanics of such a two-phase composite under quasi-static compression. The 3D solid model of a lattice structure with three-unit cells in each direction was generated first in CAD software, and then the solid model of the foam matrix was generated by the boolean operation of a cube and the lattice geometry. The two solids were meshed with linear tetrahedral elements, and the interface between the phases was assumed to be perfectly bonded. The matrix (foam) phase was modeled as a crushable foam material with a hyperelastic material model to mimic the compression behavior of flexible polymer foams. The reinforcement (lattice) phase was modeled as an elastic-plastic material to represent the resin material commonly used in Stereolithography (SLA) 3D printing of polymeric lattice structures. The material model parameters of both phases were calibrated from experimental measurements. We simulated the FE model under a displacement boundary condition of up to 20% compression strain. We investigated the structure-property relations of the composite as a function of relative density and lattice topology. Our results show that the foam matrix dramatically reduces the strut buckling even at the low-density regime of the matrix, and the effect becomes more pronounced with an increase in the relative density of the foam matrix. The addition of a foam matrix also leads to a reduction in localized strain in the struts and nodal junctions, which indicates improved stability of lattice struts under compression in the presence of the foam matrix. The compressive elastic modulus and yield strength can also be enhanced by the addition of a foam matrix. The composite mechanics also depends on the lattice topology. A stretching-dominated lattice topology (octet-truss lattice) shows a more pronounced enhancement in mechanical properties than a bending-dominated lattice topology (body-centered cubic lattice). Overall, the results indicate that the composite design approach of filling the pore space of a lattice structure with a flexible foam matrix provides a rational strategy to achieve a tunable combination of mechanical properties.       

Presenting Author: Mohammad Refatul Islam University of Texas Rio Grande Valley

Presenting Author Biography: Ehsanul Azim is a graduate student in the Department of Mechanical Engineering at the University of Texas Rio Grande Valley

Authors:

Ehsanul Azim University of Texas Rio Grande Valley
Mohammad Refatul Islam University of Texas Rio Grande Valley