PSI - Issue 32

Daria Dolgikh et al. / Procedia Structural Integrity 32 (2021) 246–252 D. Dolgikh, M. Tashkinov / Structural Integrity Procedia 00 (2019) 000–000

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material systems have great potential in a broad range of applications ranging from modern aerospace and civil structures to biomedical engineering (Bi et al., 2020). In the process of evolution, nature has brought the morphological structure of materials to perfection, allowing living things to easily adapt to environmental conditions. When creating biomimetic materials, an important issue is the selection of an optimal morphological structure. Cellular structures are a natural solution to the need for efficient, lightweight yet durable materials. Natural cellular materials have an excellent strength-to-weight ratio, which sparkled interest in creating artificial materials that can mimic their behavior, such as foams and honeycombs. Structures affected by predominantly by tensile load – like plant parenchyma, spider webs, fluid-compression elements of squids, to name a few (Wainwright et al., 2020), as well as microstructures characterized by the material randomness of the mutual arrangement of phases (Yang et al., 2018) are the most common in nature. Bioinspired structural optimization often employs a design strategy of redistribution of material in 3D based on natural principles (Alsheghri et al., 2021). The results of such optimization can be implemented in 3D printing. The optimization of internal parameters dealing with connectivity of lattice structures falls into the category of topological optimization (Chen et al., 2007). Topology optimization involves determining an effective material placement scheme for a particular type of structural anisotropy within a certain region of space, taking into account the boundary conditions. The problem of the optimal material placement in a given area is formulated as minimization of the structure's compliance (maximization of stiffness) under a given system of loads, constraints on displacements and mechanical properties or geometric parameters of the design area. This paper presents the results of topological optimization of the morphology of RVEs of polymeric cellular structures with a random internal composition. The level-set methods based on Gaussian random fields were used to create three-dimensional models of biomimetic random bicontinuous structures (Bargmann et al., 2018; Tashkinov, 2021). Topological optimization has been implemented using the finite element method in the Abaqus and Tosca software packages. 2. Parameters of the models RVEs of biomimetic cellular structures with different ( p = 0.612; p = 0.619; p = 0.702) and relatively similar pores volume fraction ( p = 0.5; p = 0.502; p = 0.504; p = 0.512; p = 0.514) were studied in this work. RVEs of cellular structure had a size of 20x20 mm. A finite-element model of a cellular material with a random structure is shown in Figure 1. The PEEK (polyether ether ketone) was specified as a matrix material. It is a thermoplastic material that is often used in additive manufacturing. It has unique properties such as: high wear resistance and strength. In addition, this material is biocompatible, which allows it to be used to create medical implants. The general elastic properties of the PEEK material were taken: material density 9 1.3 10 ρ − = ⋅ , Young’s module 3800 MPa, E = Poisson Ratio 0.38. ν = Tensile strength of PEEK is 87–95 MPa (Verma et al., 2021).

Fig. 1. Finite-element model of a cellular material with a random structure