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W. Zhou et al.
18.1 Introduction
Three-dimensional (3D) textile structural composites reinforced with fibers, yarns
and fabrics have enormous development potentials in the field of aerospace, military
and marine industries owing to their little specific gravity, high specific strength,
large specific modulus, fatigue resistance and strong designability [1–3]. In the longterm applications of the composite materials, the stiffness degrades with the external
loading, and then results in the damage accumulation and destruction eventually [4].
Most researchers focus on the analysis of damage results for composite materials
[5–7]. However, the research on 3D braided composites, especially the analysis of the
effect of the binder yarns to prevent the delamination during the flexural progressive
loading process, is relatively insufficient.
As one of the classic types of three-dimensional textile structural composites,
the 3D five-directional braided composites have attracted a lot of attention due to
their excellent mechanical properties. Liu et al. [8] investigated the high temperature compressive properties and failure mechanism of 3D five-directional braided
composites. The results showed that the compressive modulus and strength decreased
as temperature increased. Hu et al. [9] analyzed the strength characteristics of 3D
braided composite specimens with different braiding angles in a three-point bending
test based on the repeat unit cell model. It was found that the load-deflection curve
and the progressive damage morphology are consistent with the numerical prediction
results. Ouyang et al. [10] studied the bending fatigue behavior of 3D five-directional
braided T-shaped composite from finite element analyses and experimental characterizations. In addition, Zhang et al. [11] and Wang et al. [12] analyzed the progressive
damage behavior and the failure of 3D braided composites subjected to tension.
In order to more accurately grasp the damage evolution process and mechanical
properties of the composites, some effective detection methods are necessary to be
taken.
Recently, a combination experimental mechanics and nondestructive evaluation
(NDE) approach assisted has been widely applied to investigate aspects of the
mechanical behavior and damage process of 3D braided composites, involving
acoustic emission (AE) techniques [13–17], optical methods such as digital image
correlation (DIC) [18], as well as others such as X-ray based micro-computed tomography (micro-CT). Zhou et al. [19] used a method combining AE with DIC to monitor
the compressive buckling behavior of multi-delaminated composites. The analysis
of the AE signal was based on a k-means algorithm and principal component analysis (PCA). The results showed that the AE signal of the compression process can
be divided into three clusters. In addition, it has been found that the size and location of the delaminated defects results in a decrease in the mechanical properties
of the composite. Castaneda et al. [20] used AE, DIC and micro-CT to investigate the role of z-binder for enhanced damage tolerance of 3D woven composites.
The combined evaluation of globally calculated with locally resolved strain patterns
which track the 3D damage evolution was realized and strain localizations related to
damage were cross validated by the AE data and micro-CT analysis. Further, Zhang
W. Zhou et al.
18.1 Introduction
Three-dimensional (3D) textile structural composites reinforced with fibers, yarns
and fabrics have enormous development potentials in the field of aerospace, military
and marine industries owing to their little specific gravity, high specific strength,
large specific modulus, fatigue resistance and strong designability [1–3]. In the longterm applications of the composite materials, the stiffness degrades with the external
loading, and then results in the damage accumulation and destruction eventually [4].
Most researchers focus on the analysis of damage results for composite materials
[5–7]. However, the research on 3D braided composites, especially the analysis of the
effect of the binder yarns to prevent the delamination during the flexural progressive
loading process, is relatively insufficient.
As one of the classic types of three-dimensional textile structural composites,
the 3D five-directional braided composites have attracted a lot of attention due to
their excellent mechanical properties. Liu et al. [8] investigated the high temperature compressive properties and failure mechanism of 3D five-directional braided
composites. The results showed that the compressive modulus and strength decreased
as temperature increased. Hu et al. [9] analyzed the strength characteristics of 3D
braided composite specimens with different braiding angles in a three-point bending
test based on the repeat unit cell model. It was found that the load-deflection curve
and the progressive damage morphology are consistent with the numerical prediction
results. Ouyang et al. [10] studied the bending fatigue behavior of 3D five-directional
braided T-shaped composite from finite element analyses and experimental characterizations. In addition, Zhang et al. [11] and Wang et al. [12] analyzed the progressive
damage behavior and the failure of 3D braided composites subjected to tension.
In order to more accurately grasp the damage evolution process and mechanical
properties of the composites, some effective detection methods are necessary to be
taken.
Recently, a combination experimental mechanics and nondestructive evaluation
(NDE) approach assisted has been widely applied to investigate aspects of the
mechanical behavior and damage process of 3D braided composites, involving
acoustic emission (AE) techniques [13–17], optical methods such as digital image
correlation (DIC) [18], as well as others such as X-ray based micro-computed tomography (micro-CT). Zhou et al. [19] used a method combining AE with DIC to monitor
the compressive buckling behavior of multi-delaminated composites. The analysis
of the AE signal was based on a k-means algorithm and principal component analysis (PCA). The results showed that the AE signal of the compression process can
be divided into three clusters. In addition, it has been found that the size and location of the delaminated defects results in a decrease in the mechanical properties
of the composite. Castaneda et al. [20] used AE, DIC and micro-CT to investigate the role of z-binder for enhanced damage tolerance of 3D woven composites.
The combined evaluation of globally calculated with locally resolved strain patterns
which track the 3D damage evolution was realized and strain localizations related to
damage were cross validated by the AE data and micro-CT analysis. Further, Zhang