FE Modeling of NiTi Elastomeric Composites for Use As Biomaterials

Over the past few years, textiles made from thin NiTi wires have received increasing attention as they are already used as stents in medical field and further applications are being envisaged. To prevent some apparent drawbacks of NiTi textiles such as friction between NiTi wires and low tensile/shear stiffness, NiTi elastomeric composites are being considered as novel functional structures. Moreover, one might tailor the constitutive behavior of those composites through selection of design parameters such as internal textile morphology, macroscopic shape of the reinforcing NiTi textile, shape setting conditions, volume fraction of the matrix etc. However, the high number of design parameter makes it difficult to design a NiTi elastomeric composite for a given application without any numerical modeling tool. Therefore, in this talk, we will focus on some aspects of finite element modeling of superelastic NiTi elastomeric with recoverable strains up to 40% to be used as biomaterials. Modeling of two types of those composites using Abaqus and Auricchio’s SMA model will be considered – i) composites with woven reinforcing NiTi textile shape set into snake-like form; ii) composites integrating flat weft knitted NiTi textile. Moreover, the efficiency and accuracy of two different FE strategies will be discussed. First, a low computation time strategy using beam FE model will be explained and, second, 3D solid model using solid elements will be described. To assess the efficiency and accuracy of the two approaches, results of FE simulations will be compared with each other and, in addition, with outputs of related experiments. In particular, the issues related to geometry modeling, contact boundary conditions as well as interactions between matrix and NiTi wires will be discussed. Finally, relation between local transformation processes and macroscopic constitutive behavior will be rationalized using results of FE simulations.