Computational analysis of fatigue behavior of 3D 4-directional braided composites based on unit cell approach

https://doi.org/10.1016/j.advengsoft.2014.12.007Get rights and content

Highlights

  • The unit cell of 3D 4-directional braided composites were built up using ABAQUS.

  • The fatigue behavior of the 3D 4-directional braided composites was analyzed.

  • Effect of braiding angles and fiber volume fraction of on fatigue behavior was analyzed.

Abstract

The fatigue behavior of 3D 4-directional braided composites was investigated based on the unit cell approach. First, the unit cell models of 3D 4-directional braided composites with different braiding angles and fiber volume fraction were built up using ABAQUS. Then, the fatigue behavior of the 3D 4-directional braided composites was analyzed, and the effect of fatigue loading direction on the fatigue damage evolution and fatigue life was studied. Finally, the effect of braiding angles and fiber volume fraction of the unit cell on the fatigue behavior of 3D 4-directional braided composites was analyzed. These results will play an important role for evaluating the fatigue behavior of 3D 4-directional braided composites in engineering.

Introduction

Three-dimensional (3D) braided composite has been used widely in engineering. The distinct feature of 3D braided composites is that there is not interlaminar crack and delamination compared with that of laminated composites. However, only when mechanical properties of 3D braided composites are correctly characterized could the composite structures applied in engineering be optimized.

The mechanical properties and strength characterizations of the 3D braided composite using the representative unit cell were reported in many references. Yu et al. [1] predicted the mechanics parameters of 4-step three dimensional braided composites, including stiffness parameters and strength parameters using the two-scale method (TSM). Zheng et al. [2] studied the yarn architecture of 3-D braided composites products by the four-step 1 × 1 braiding technique by means of a control volume method in conjunction with experimental investigation and a numerical method, respectively. Sun et al. [3] used digital element approach, which treats textile composite manufacturing process as a nonlinear solid mechanics problem, to investigate the complicated microstructure of 3D braided rectangular preform. Gu et al. [4], [5] studied the influence of the strain rate on the uniaxial tensile behavior of 4-step 3D braided composites, and the ballistic perforation test results of 4-step 3D braided Twaron/epoxy composites, which were subjected to impact by conically cylindrical steel projectile, were presented. Also, the damage evolution of the 3D braided composite is simulated. Fang et al. [6] studied the effect of yarn distortion on the mechanical properties of 3D four-directional braided composites, and analyzed the progressive damage behavior of 3D four-directional braided composites with large braid angle subjected to uniaxial tension [7]. Lu et al. [8] studied the effect of interfacial properties on the uniaxial tensile behavior of three-dimensional braided composites. Drach et al. [9] proposed an efficient procedure to process the textile simulation data and generate realistic finite element meshes of woven composites. Dong et al. [10], [11] studied tensile strength of 3D braided composites in the microscope view, where non-linear progressive damages under tensile loading steps were conducted in their article. However, the experimental studies on the properties and strength characterizations of the 3D braided composite are scarce as yet. Zaman et al. [12] fabricated a high density 3D-four directional carbon/carbon composite by hot isostatic pressure impregnation carbonisation using coal tar pitches. And the thermo-oxidative, thermophysical and ablation properties of the composite were determined. Li et al. [13] preformed compressive experiments on the 3D braided composites with different braiding parameters in three directions (longitudinal, in-plane and transverse) at room and liquid nitrogen temperature (low as −196 °C). Li et al. [14] presented experimental characterization of the effect of cut-edge on the tensile, compressive and flexure properties in the braiding direction of the 3D braided composites.

It is obvious that most of numerical and analytical works devoted to mechanical properties and strength characterizations of the 3D braided composite. However, the fatigue behavior of 3D 4-directional braided composites has not been reported till now. In this paper, the fatigue behavior of 3D 4-directional braided composites was analyzed based on unit cell approach, and the effect of braiding angles and fiber volume fraction of the unit cell on the fatigue behavior was studied.

Section snippets

Microstructure modeling of 3D 4-directional braided composites

The basic Cartesian braiding process involves four distinct Cartesian motions of groups of yarns termed rows and columns. For a given step, alternate rows are shifted a prescribed distance relative to each other. The next step involves the alternate shifting of the columns a prescribed distance. The third and fourth steps are simply the reverse shifting sequence of the first and second steps, respectively. A complete set of 4-directionals is called a machine cycle, which is shown in Fig. 1 [12].

Stiffness degeneration analysis

In this section, the unit cell model with a braided angle of 30°and fiber volume fraction of 40% was used to analysis the effect of loading direction on the fatigue behavior of 3D 4-directional braided composites. Fig. 11 shows the elastic modulus of the unit cell varied with the fatigue cycles in 90% stress ratio under uniaxial and biaxial tensile–tensile fatigue load. The elastic modulus of the unit cell is decreased with the increasing of fatigue cycles. The elastic modulus of the unit cell

Braided angle

Fig. 15 and Table 4 show the S–N curves of unit cell with 40% fiber volume fraction and different braided angles. It can be seen from Fig. 15 that the fatigue life along the braided direction under 90% stress level and 50% stress level is decreased from 9800 cycles to 6300 cycles, from 853,200 cycles to 627,400 cycles, respectively, when the braided angle is varied from 25° to 40°. However, the fatigue life perpendicular to the braided direction under 90% stress level and 50% stress level is

Conclusion

Unit cell models of 3D 4-directional braided composites were build up, and the tensile-tensile fatigue life and fatigue damage evolution was simulated. The effect of loading direction, braided angle and fiber volume fraction on the fatigue behavior was analyzed. Some important conclusions are summarized as follow:

  • (1)

    The unit cell models of 3D 4-directional braided composites, whose braided angles was varied from 20°to 40°and fiber volume fraction was varied from 30% to 50%, were build up using

Acknowledgment

This work is supported by the National Basic Research Program (973) of China under Grant No. 2011CB606105.

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