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Dive into the research topics where Li Longbiao is active.

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Featured researches published by Li Longbiao.


Applied Composite Materials | 2013

Estimate Interface Shear Stress of Unidirectional C/SiC Ceramic Matrix Composites from Hysteresis Loops

Li Longbiao; Song Yingdong

The tensile-tensile fatigue behavior of unidirectional C/SiC ceramic matrix composites at room and elevated temperature has been investigated. An approach to estimate the interface shear stress of ceramic matrix composites under fatigue loading has been developed. Based on the damage mechanisms of fiber sliding relative to matrix in the interface debonded region upon unloading and subsequent reloading, the unloading interface reverse slip length and reloading interface new slip length are determined by the fracture mechanics approach. The hysteresis loss energy for the strain energy lost per volume during corresponding cycle is formulatd in terms of interface shear stress. By comparing the experimental hysteresis loss energy with the computational values, the interface shear stress of unidirectional C/SiC ceramic composites corresponding to different cycles at room and elevated temperatures has been predicted.


Applied Composite Materials | 2013

Modeling Loading/Unloading Hysteresis Behavior of Unidirectional C/SiC Ceramic Matrix Composites

Li Longbiao; Song Yingdong

The loading/unloading tensile behavior of unidirectional C/SiC ceramic matrix composites at room temperature has been investigated. The loading/unloading stress–strain curve exhibits obvious hysteresis behavior. An approach to model the hysteresis loops of ceramic matrix composites including the effect of fiber failure during tensile loading has been developed. By adopting a shear-lag model which includes the matrix shear deformation in the bonded region and friction in the debonded region, the matrix cracking space and interface debonded length are obtained by matrix statistical cracking model and fracture mechanics interface debonded criterion. The two-parameter Weibull model is used to describe the fiber strength distribution. The stress carried by the intact and fracture fibers on the matrix crack plane during unloading and subsequent reloading is determined by the Global Load Sharing criterion. Based on the damage mechanisms of fiber sliding relative to matrix during unloading and subsequent reloading, the unloading interface reverse slip length and reloading interface new slip length are obtained by the fracture mechanics approach. The hysteresis loops of unidirectional C/SiC ceramic matrix composites corresponding to different stress have been predicted.


Applied Composite Materials | 2015

Modeling the Effect of Interface Wear on Fatigue Hysteresis Behavior of Carbon Fiber-Reinforced Ceramic-Matrix Composites

Li Longbiao

An analytical method has been developed to investigate the effect of interface wear on fatigue hysteresis behavior in carbon fiber-reinforced ceramic-matrix composites (CMCs). The damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding and interface wear, fibers fracture, slip and pull-out, have been considered. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Upon first loading to fatigue peak stress and subsequent cyclic loading, the fibers failure probabilities and fracture locations were determined by combining the interface wear model and fiber statistical failure model based on the assumption that the loads carried by broken and intact fibers satisfy the global load sharing criterion. The effects of matrix properties, i.e., matrix cracking characteristic strength and matrix Weibull modulus, interface properties, i.e., interface shear stress and interface debonded energy, fiber properties, i.e., fiber Weibull modulus and fiber characteristic strength, and cycle number on fibers failure, hysteresis loops and interface slip, have been investigated. The hysteresis loops under fatigue loading from the present analytical method were in good agreement with experimental data.


Applied Composite Materials | 2015

Fatigue Life Prediction of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures. Part I: Experimental Analysis

Li Longbiao

This paper presents an experimental analysis on the fatigue behavior in C/SiC ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply and 2.5D woven, at room and elevated temperatures in air atmosphere. The experimental fatigue life S − N curves of C/SiC composites corresponding to different stress levels and test conditions have been obtained. The damage evolution processes under fatigue loading have been analyzed using fatigue hysteresis modulus and fatigue hysteresis loss energy. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different peak stress, fiber preforms and test conditions have been estimated. It was found that the degradation of interface shear stress and fibres strength caused by oxidation markedly decreases the fatigue life of C/SiC composites at elevated temperature.


International Journal of Fracture | 2016

Damage development in fiber-reinforced ceramic-matrix composites under cyclic fatigue loading using hysteresis loops at room and elevated temperatures

Li Longbiao

In this paper, the damage development behavior in fiber-reinforced ceramic-matrix composites (CMCs) with different fiber architectures, i.e., unidirectional, cross-ply and 2D woven, under cyclic fatigue loading at room and elevated temperatures has been investigated using fatigue hysteresis loops, i.e., fatigue hysteresis modulus, fatigue hysteresis dissipated energy, and fatigue hysteresis dissipated energy-based damage parameter. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus, fatigue hysteresis dissipated energy and fatigue hysteresis dissipated energy-based damage parameter have been established. The effects of fiber volume content, fatigue peak stress, fatigue stress ratio, matrix crack spacing, multiple matrix cracking modes, and woven structures on the damage evolution in fiber-reinforced CMCs have been investigated. The experimental fatigue hysteresis modulus, fatigue hysteresis dissipated energy and fatigue hysteresis dissipated energy-based damage parameter versus cycle number have been predicted for unidirectional, cross-ply and 2D woven CMCs at room and elevated temperatures. It was found that the damage parameters derived from the fatigue hysteresis loops can effectively monitor the damage development and predict the fatigue life of fiber-reinforced CMCs.


Applied Composite Materials | 2015

Effect of Fiber Poisson Contraction on Matrix Multicracking Evolution of Fiber-Reinforced Ceramic-Matrix Composites

Li Longbiao

An analytical methodology has been developed to investigate the effect of fiber Poisson contraction on matrix multicracking evolution of fiber-reinforced ceramic-matrix composites (CMCs). The modified shear-lag model incorporated with the Coulomb friction law is adopted to solve the stress distribution in the interface slip region and intact region of the damaged composite. The critical matrix strain energy criterion which presupposes the existence of an ultimate or critical strain energy limit beyond which the matrix fails has been adopted to describe matrix multicracking of CMCs. As more energy is placed into the composite, matrix fractures and the interface debonding occurs to dissipate the extra energy. The interface debonded length under the process of matrix multicracking is obtained by treating the interface debonding as a particular crack propagation problem along the fiber/matrix interface. The effects of the interfacial frictional coefficient, fiber Poisson ratio, fiber volume fraction, interface debonded energy and cycle number on the interface debonding and matrix multicracking evolution have been analyzed. The theoretical results are compared with experimental data of unidirectional SiC/CAS, SiC/CAS-II and SiC/Borosilicate composites.


Journal of Composite Materials | 2015

Micromechanics modeling of fatigue hysteresis loops in carbon fiber-reinforced ceramic-matrix composites

Li Longbiao

When fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress–strain hysteresis loops appear as the frictional slip occurred between the fiber and the matrix in the interface debonded region. The micromechanics fatigue hysteresis loops models of fiber-reinforced CMCs have been developed for different fiber preforms, i.e., unidirectional, cross-ply, and woven CMCs. The interface slip lengths, i.e., the interface debonded length upon first loading, unloading interface counter slip length, and reloading interface new slip length, were determined by fracture mechanics approach. The fatigue hysteresis loops of different interface debonding and slipping cases have been analyzed. The fatigue hysteresis loss energy is formulated in terms of fiber/matrix interface shear stress in the interface debonded region. When the interface shear stress decreases, the fatigue hysteresis loss energy first increases to the maximum value and then decreases to zero. By assuming the mechanical hysteresis behavior of cross-ply and woven CMCs was mainly controlled by interface frictional slip in the 0° plies or longitudinal yarns, considering the effect of matrix multicracking modes in cross-ply or woven CMCs, the fatigue hysteresis loops of fiber-reinforced CMCs with different fiber preforms under different peak stresses corresponding to different number of applied cycles have been predicted.


Applied Composite Materials | 2015

Micromechanical Modeling for Tensile Behaviour of Carbon Fiber − Reinforced Ceramic − Matrix Composites

Li Longbiao

The stress–strain curves of fiber − reinforced ceramic − matrix composites (CMCs) exhibit obvious non-linear behaviour under tensile loading. The occurrence of multiple damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding and fibers fracture, is the mainly reason for the non-linear characteristic. The micromechanics approach has been developed to predict the tensile stress–strain curves of unidirectional, cross-ply and woven CMCs. The shear-lag model was used to describe the micro stress field of the damaged composite. The damage models were used to determine the evolution of micro damage parameters, i.e., matrix crack spacing, interface debonded length and broken fibers fraction. By combining the shear-lag model with damage models and considering the effect of transverse multicracking in the 90° plies or transverse yarns in cross-ply or woven CMCs, the tensile stress–strain curves of unidirectional, cross-ply, 2D and 2.5D woven CMCs have been predicted. The results agreed with experimental data.


Applied Composite Materials | 2015

Modeling for Fatigue Hysteresis Loops of Carbon Fiber-Reinforced Ceramic-Matrix Composites under Multiple Loading Stress Levels

Li Longbiao

In this paper, the fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) under multiple loading stress levels considering interface wear has been investigated using micromechanical approach. Under fatigue loading, the fiber/matrix interface shear stress decreases with the increase of cycle number due to interface wear. Upon increasing of fatigue peak stress, the interface debonded length would propagate along the fiber/matrix interface. The difference of interface shear stress existed in the new and original debonded region would affect the interface debonding and interface frictional slipping between the fiber and the matrix. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading, the interface slip lengths, i.e., the interface debonded length, interface counter-slip length and interface new-slip length, are determined by fracture mechanics approach. The fatigue hysteresis loops models under multiple loading stress levels have been developed. The effects of single/multiple loading stress levels and different loading sequences on fatigue hysteresis loops have been investigated. The fatigue hysteresis loops of unidirectional C/SiC composite under multiple loading stress levels have been predicted.


Journal of Composite Materials | 2017

Modeling of fatigue hysteresis behavior in carbon fiber-reinforced ceramic–matrix composites under multiple loading stress levels

Li Longbiao

The fatigue hysteresis behavior in fiber-reinforced ceramic–matrix composites under multiple loading stress levels has been investigated. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading/reloading, the fatigue hysteresis loops models corresponding to different interface slip cases under multiple loading stress levels have been derived. The fatigue hysteresis loss energy and interface slip corresponding to single/multiple loading stress levels and different loading sequences have been investigated. The fatigue hysteresis loops of unidirectional SiC/CAS−II composite under multiple loading stress levels have been predicted.In this paper, the fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) under multiple loading stress levels considering interface wear has been investigated using micromechanical approach. Under fatigue loading, the fiber/matrix interface shear stress decreases with the increase of cycle number due to interface wear. Upon increasing of fatigue peak stress, the interface debonded length would propagate along the fiber/matrix interface. The difference of interface shear stress existed in the new and original debonded region would affect the interface debonding and interface frictional slipping between the fiber and the matrix. Based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading, the interface slip lengths, i.e., the interface debonded length, interface counter-slip length and interface new-slip length, are determined by fracture mechanics approach. The fatigue hysteresis loops models under multiple loading stress levels have been developed. The effects of single/multiple loading stress levels and different loading sequences on fatigue hysteresis loops have been investigated. The fatigue hysteresis loops of unidirectional C/SiC composite under multiple loading stress levels have been predicted.

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Xu Qinghong

Nanjing University of Aeronautics and Astronautics

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Song Yingdong

Nanjing University of Aeronautics and Astronautics

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Zeng Haijun

Nanjing University of Aeronautics and Astronautics

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Zhang Yongjin

Nanjing University of Aeronautics and Astronautics

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