Experimental and numerical investigation of the transverse impact damage and deformation of 3-D circular braided composite tubes from meso-structure approach

Abstract

The transverse impact deformation and damage of 3-D circular braided composite tubes were studied both in experimental and numerical approaches. A meso-structure geometrical model based on the braided architecture was established to analyze the impact damage and morphology. The transverse impact tests were conducted on a modified split Hopkinson pressure bar (SHPB) apparatus driven with high pressure Nitrogen gas under different pressures. The load-time histories and deformations of the 3-D circular braided composite tubes under transverse impact were obtained from experimental and compared with those in finite element analysis (FEA). The FEA results show satisfactory agreements with experimental data and demonstrate the validity of the model. Based on the finite element results, the deformation process and stress propagation were obtained to analyze the failure mechanism. The stress distribution on the composite tubes showed that the 3-D circular braided reinforcement was the main load-carrying component and absorbed most of the impact energy. The impact region was dented along the impact direction and a clear shear band was found around the impacted region.

Introduction

The high strength-to-weight and stiffness-to-weight ratios of 3-D braided composites offer definite advantages as compared to traditional materials and have been widely applied in structural engineering. Compared with laminated composites, 3-D braided composites are superior in impact damage tolerance and performance along the thickness direction [1]. These excellent features make the 3-D braiding composites to have tremendous potential applications in aviations, high-speed vehicles and engineering structures.

A number of investigations have focused on the dynamic behaviors of the braided composites. Gu et al. [2], [3]explored the ballistic impact damage of 3-D braided composites. O.Dorival et al. [4] studied the impact energy absorption behavior of reinforcement braided composite structures. Pei et al. [5] explored the effect of microstructure on the dynamic parameters of 3D and four directional braided composite. Li et al. [6], [7] and Sun et al. [8], [9] focused on the high strain rate behaviors of 3-D braided composites under tension and compression. A lot of researchers have established finite element models of braided composites [2], [10], [11], [12], [13]. Compared with the macroscopic approach which can predict the global response, a meso-structure model composed of various isotropic or anisotropic materials is easy to represent stress distribution and damage in each component.

However, in the case of impact properties of braided composites, most studies have focused on plates and few researches investigated 3-D circular braided tubes. Chiu et al. [14] investigated the effects of braiding angle and axial yarn content on the axial compression damage and crash energy absorption of 2-D triaxially braided composite tubes. Karbhari et al. [15] discussed the effects of fibers, axial yarns and crushing rate on the axial crushing of composite tubes. Karbhari et al. [16] also studied the influences of lateral impact simulating prior damage, on the progressive crush characteristics of 2-D braided composite tubes with different number of layers. Zeng et al. [17] developed an FE model with LS-DYNA to simulate the effects of geometrical and braiding parameters on the crash behaviors of 3-D braided composite tubes with axial impact loading.

The aim of the current work is to investigate the transverse impact properties of 3-D circular braided composite tubes from meso-structure approach. Three impact gas pressures were chosen to study the transverse impact responses of 3-D circular braided composite tubes under different impact velocities. A meso-structure numerical model for 3-D circular braided composite was proposed on the basis of the spatial geometrical characteristic of the yarns. The ductile damage criterion and shear damage criterion were applied to model the damage initiation. In order to validate the model, comparison was done between experimental and Finite Element Method (FEM) results including the time histories of load and displacement, energy absorption and the damage morphology. Furthermore, the failure process and stress distribution were obtained from FEM results.