Thermo-mechanical behavior analysis of 3D braided composites by multiscale finite element method

Abstract

A new multiscale method was developed for the thermo-mechanical performance analysis of three-dimensional (3D) braided composites. This method is the extended of multiscale asymptotic expansion homogenization (MAEH) method and multiphase finite element (MPFE) approach. The analysis was performed under a representative unit cell (RUC) scale and tow architecture scale. The effective thermo-physical properties of 3D braided composites were predicted. The bending mechanical response under thermal and mechanical loading was determined by the present multiscale finite element method. The effects of braiding angle and temperature difference on the thermo-mechanical behaviors were studied. The three-point bending tests were performed under thermal and mechanical loading and the measured results were compared to the predicted ones to illustrate that the new method is effective and valid for predicting the thermo-mechanical performance of 3D braided composites.

Introduction

3D braided composites gains a wide interest due to its excellent mechanical performance compared to the conventional laminated composites, including better out-of-plane stiffness, strength, high damage tolerance, etc. Because of these benefits of mechanical properties, 3D braided composites have potential applications in aerospace, automobile, etc. In order to take full advantage of the braided composites efficiently, safely and reasonably [1], it has become the main subject of substantial research to study the micro-structures and mechanical behavior of 3D braided composites by many scholars in recent years [2], [3], [4], [5], [6], [7], [8]. The typical micro-structural models for studying the effective elastic properties of 3D braided composites were the fiber interlock model, the fiber inclination model and the fabric geometric model established by Ma et al. [2], Yang et al. [3] and Byun et al. [4]. With the rapid development of engineering technology, the investigations on thermal properties of 3D braided composite have gradually attracted the attentions of many scholars [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21]. Mohajerjasbi [9] predicted the thermal expansion coefficients (CTEs) of 3D braided composites using the finite element method. Liang et al. [10] predicted the CTEs of 3D braided composites with penny-shaped cracks through the Eshelby-Mori-Tanaka theory combined with the modified stiffness averaging method. Zhao et al. [11] and Liao et al. [12] investigated the CTEs of 3D C/C braided composites experimentally. Yao et al. [13] and Wang et al. [14] studied the thermal expanding behavior of 3D resin matrix braided structure experimentally. Cheng et al. [15] investigated the effective thermo-elastic properties of 3D braided composites by means of the experimental method and the theoretical approach. Xia et al. [16] proposed the periodic nonadiabatic temperature boundary conditions, and further investigated the thermo-physical properties of 3D braided composites without considering the yarn/matrix interface. Jiang et al. [17] presented the MPFE method to investigate the thermo-mechanical properties of 3D braided composite. Pan et al. [18] and Li et al. [19] presented an approach to simulate the compressive behavior of 3D braided composite materials under some special temperatures. Li et al. [20] reported the effect of temperature on the bending properties and failure mechanism of a 3D E-glass/epoxy braided composite. Li et al. [21] presented thermal postbuckling analysis for 3D braided composite cylindrical shells subjected to uniform temperature rise. These great achievements are very useful in probing the thermal performance of 3D braided composites.

However, the complicated micro-structure of 3D braided composites makes it very difficult to study the thermo-mechanical properties theoretically and experimentally. Numerical methods are suitable for analysis of 3D braided composites. With the rapid development of computer simulation technology, more attention was paid to establish the solid structure model of 3D braided composites and study the thermo-mechanical properties by using the MAEH methods. MAEH approaches, which is a distinct advantage over other homogenizing techniques, e.g. rule of mixtures, have capability to reduce the degrees of freedom at different scales and find the stress and strain microscopic fields associated with a given macroscopic equilibrium state. Feng et al. [22] and Wang et al. [23] used MAEH methods to predict the effective modulus of 3D braided composites. Visrolia et al. [24] used a MAEH method to determine the local response of 3D weave composite by incorporating a continuum damage model. Yu and Cui [25] studied the stiffness and elasticity strength parameters of 3D braided composites by MAEH method, and the influences of the braiding angle and the fiber volume fraction on the strength of 3D braided composites were discussed. Francfort [26] developed asymptotic expansion technique for the case of linear thermo-elasticity. Liu and Cheng [27] used the MAEH method to investigate the thermal expansion properties of unidirectional fiber reinforced composites. Dasgupta and Agarwa [28] predicted the orthotropic thermal conductivity of plain-weave fiber reinforced composites by the MAEH method. Dasgupta et al. [29] and Nasution et al. [30], [31] calculated the homogenized thermo-mechanical properties of composite materials based on MAEH method. Lu et al. [32] investigated the effect of interfacial properties on the thermo-physical properties of 3D braided composites via multiscale finite element study. Shi et al. [33] presented a procedure for predicting equivalent thermal property parameter through a combined approach of the generalized method of cells and multiscale heat transfer analysis. Dong et al. [34] presented the research on the thermal conductive behaviors of braided composites both at meso-scale and full-scale structure level.

Although the MAEH methods is effective in predicting material properties from different scales, the huge workload of modeling and large meshing cost limit its application in 3D braided composites. In response to this, we presented a modified MAEH method, which can simplify the discretization process of RUCs, to study the mechanical properties of 3D braided composites in our previous work [35]. In this work, we extended this multiscale method to investigate the effective CTEs, the local stress distribution and global strength of 3D braided composite structures under thermal and mechanical loading.