Papers by Keyword: Periodic Boundary Condition

Abstract: This paper uses a sequential micromechanical method to characterize the thermomechanical properties of a hybrid nanocomposite. It does this by using analytical models (such as the modified rule of mixtures, Tsai-Pagano model, and Schapery model) and numerical models (such as the Finite element model), which are modeled using the commercial software ABAQUS. Investigations are made to determine how the aspect ratio, waviness, and volume fractions of the reinforcement affect the thermo-mechanical performance of the hybrid nanocomposite. It has been shown that adding CNT ESFs to conventional SiC-reinforced titanium alloy composites (TMCs) improves the resulting HTMNC thermo-mechanical properties. It is found that the addition of CNT ESFs to TMCs improves the thermo-mechanical characteristics of the resulting hybrid nanocomposite (i.e., HTMNCs) more in the transverse direction than in the axial direction for all volume fractions of SiC fiber. For instance, it is observed that adding a 2.69% volume fraction of CNT ESFs to the TMCs with a 30% volume fraction of SiC fiber enhances the axial elastic modulus by 2.6% and 2.4% while increasing the transverse elastic modulus by 4.2% and 3.5%, based on the CNT ESFs are straight and wavy. On the other hand, for the same volume fraction of SiC fiber and the addition of 2.69% volume fraction of Straight CNT ESFs, the transverse and axial CTE of the HTMNCs are reduced by 5.33% and 2.53%, respectively. Moreover, when the SiC fiber aspect ratio increases, the axial elastic modulus increases while the transverse elastic modulus exhibits no change. In contrast to the elastic modulus, the CTE increases in the transverse direction while decreasing in the axial direction.

Abstract: Transverse compaction and in-plane shear deformartion are the dominative deformation mode for woven preform during forming process. A full finite element model of the 2.5D woven composites has been established by the computed tomography (CT) in this paper. Based on the energy method, the effective orthotropic/anisotropic stiffness coefficients C_ij are calculated by performing a finite element analysis (FEA) of this full cell model. Using this model, the effects of the compaction and shear deformation of the 2.5D woven preform on the composites stiffness are investigated in detail. Compared the results of the static tensile tests, the rationality of the model and the method is verified.

Abstract: Both micro- and meso-scale structures are involved in the analyses of many composite materials such as filament-wound tubes. In this paper, a unified approach for applying periodic boundary conditions to micro/meso-scale repeated unit cell models in the finite element analysis is presented. As an application example, a two-scale analysis of a ±θ helical filament-wound tube is provided.

Abstract: In the analysis of materials containing regularly placed in-homogeneities, the evaluation of homogenized properties is an important issue. Common procedure for the homogenization is to define a unit cell, load it somehow, and investigate its structural response. A periodic variation of strain appears when the periodically heterogeneous material is under uniform macro-stress, and therefore, the implementation of this characteristic behavior would be essential to the material characterization based on a unit cell analysis. With the method proposed here, conventional finite element analysis tools can be used with no modification, and it is applicable to the skew-arrayed in-homogeneity problems. The orthotropic elastic and creep properties of materials with voids are examined, and the accuracy and effectiveness are demonstrated.