PSI - Issue 25

Aleksandr Shalimov et al. / Procedia Structural Integrity 25 (2020) 386–393 Author name / Structural Integrity Procedia 00 (2019) 000–000

387

2

materials with potential to fulfill various specific task, such as energy and sound absorption, filtration, weight reduction and others. The inherent complexity of microstructural morphology of such materials demands developing hierarchical approaches to solution of mechanical problems connecting with prediction of their deformation and fracture processes. The effective response for that type of heterogenous structure is strongly influenced by morphological aspects (Jung and Diebels, 2017). The global properties of the foam-type material depend on pore size, geometry and distribution as well as on the local micromechanical properties (Grenestedt and Bassinet, 2000; Jung et al., 2016; Li et al., 2006).

Nomenclature RVE

Representative volume element

FE

Finite elements Molecular dynamics Elastic modulus Poisson’s ratio Volume fraction Edge size of RVE Damage variable Stiffness tensor

MD

E



p

a

D C

The developed approaches for studying of cellular materials are usually connected with mathematical modelling that extensively relies on experimental data about the microstructural geometry as well as on data regarding behavior of individual structural elements. While effective mechanical properties can be obtained with traditional experimental methods (Shunmugasamy and Mansoor, 2018; Siegkas et al., 2016), the randomness of the microstructure makes it difficult to produce variations of samples with controllable micro-scale parameters in order to study the bridging between changes of internal state of material and its effective response. Thus, the solution was found in creating realistic representation of the microstructural morphology in RVE models that are underpinned by results of a range of experimental techniques (such as X-ray computed microtomography, scanning electron microscope and others). The sets of in-situ tensile tests can be also conducted to obtain mechanical properties of individual structural components, such as struts and ligaments (Jung and Diebels, 2017; Matheson et al., 2017; Petit et al., 2017; Zhou et al., 2005). The tomography results are employed to create RVE geometry that can be analyzed using FE or MD models using in-situ tensile tests results to define elastic constants, yield surface and strength parameters (Petit et al., 2017). Despite enhanced capabilities of the modern experimental characterization methods, some loading modes of the heterogeneous materials and their fracture behavior can only be studied using modelling. Thus, it is important to create micro-scale fracture models that would sufficiently enough reflect the real internal structure of samples. The aim of this paper is to develop progressive failure models of the bicontinuous RVEs with aluminum properties basing on FE analysis taking into account microstructural morphological and mechanical features of the materials as well as to study the influence of the geometrical parameters on the processes of damage accumulation, stress redistribution and failure. The RVE geometry was modeled using the level-set method based on random Gaussian functions. Consequently, the meshed geometry was analyzed in ABAQUS with FE method. The UMAT subroutine was specified to control element properties degradation. The results of modelling of bicontinuous RVEs of different volume fraction and size with properties corresponding to aluminum foams were numerically investigated and compared. 2. Creation of geometry models The RVEs of open-cell porous heterogeneous structures based on interpenetrating phases were created. Generally, this type of structures can be defined as a statistical mixture and is formed by complex interpenetrating components, each of which has its own individual load bearing capacity. In the case of porous materials, one phase was assumed to be a matrix, while the other phase represented pores.