Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its mi...Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its microscopic computational model was established. The interface mechanical response was modeled by the bilinear cohesive zone model. The effects of interface properties and particle sizes on the macroscopic mechanical behavior were investigated. Numerical simulation of debonding damage evolution of composite propellant under finite deformation was carried out. The debonding damage nucleation, propagation mechanism and non-uniform distribution of microscopic stress-strain fields were discussed. The results show that the finite element simulation method based on microstructure model can effectively predict the trend of macroscopic mechanical behavior and particle/matrix debonding evolution process. It can be used for damage simulation and failure assessment of composite propellants.展开更多
This paper investigates the dynamic behavior of a buried rigid elliptic cylinder partially debonded from surrounding matrix under the action of anti-plane shear waves (SH waves). The debonding region is modeled as an ...This paper investigates the dynamic behavior of a buried rigid elliptic cylinder partially debonded from surrounding matrix under the action of anti-plane shear waves (SH waves). The debonding region is modeled as an elliptic arc-shaped interface crack with non-contacting faces. By using the wave function (Mathieu function) expansion method and introducing the dislocation density function as an unknown variable, the problem is reduced to a singular integral equation which is solved numerically to calculate the near and far fields of the problem. The resonance of the structure and the effects of various parameters on the resonance are discussed.展开更多
A multiscale method for simulating the dynamic response of ceramic matrix composite （CMC） with matrix cracks is developed. At the global level, the finite element method is employed to simulate the dynamic response ...A multiscale method for simulating the dynamic response of ceramic matrix composite （CMC） with matrix cracks is developed. At the global level, the finite element method is employed to simulate the dynamic response of a CMC beam. While at the local level, the multiscale mechanical method is used to estimate the stress/strain response of the material. A distributed computing system is developed to speed up the simulation. The simulation of dynamic response of a Nicalon/CAS-II beam being subjected to harmonic loading is performed as a numerical example. The results show that both the stress/strain responses under tension and compressive loading are nonlinear. These conditions result in a different response compared with that of elastic beam, such as： 1） the displacement response is not symmetric about the axis of time; 2） in the condition of small external load, the response at first order natural frequency is limited within a finite range; 3） decreasing the matrix crack space will increase the displace- ment response of the beam.展开更多
The problem of elastic wave scattering from a partially debonded elastic cylindrical inclusion is investigated by using the wave function expansion method and singular integral equation technique. The debonding region...The problem of elastic wave scattering from a partially debonded elastic cylindrical inclusion is investigated by using the wave function expansion method and singular integral equation technique. The debonding regions are modeled as interface cracks with non-contacting faces. The mixed boundary conditions of the problem lead to a set of simultanious dual series equations which, by introducing the dislocation density functions as unknowns, can be further converted to a set of singular integral equations of the second type. Solving these equations numerically, we obtain the dynamic stress intensity factor(DSIF), the scattered far-field pattern and the scattering cross section(SCS). The numerical results for an inclusion with one debond are presented to show the distinguishing feature of the problem-the low frequency resonances in both DSIF and SCS. Finally, as a special example, we discuss the scattering of elastic waves by a circular arc-shaped crack in a homogeneous medium. The presented method is valid when stresses have oscillatory behavior.展开更多
A plane-strain unit-cell finite element model was proposed to study the effects of resin/sand interface adhesive and resin cohesive strength on the overall tensile strength of resin sand,as well as the fracture modes....A plane-strain unit-cell finite element model was proposed to study the effects of resin/sand interface adhesive and resin cohesive strength on the overall tensile strength of resin sand,as well as the fracture modes.The main micro-scale characteristics of the numerical model were extracted from the micrograph of resin sand specimens by three-dimensional X-ray microscopy(3 D-XRM).The extended finite element method(XFEM)and cohesive behavior method were employed to explicitly describe the resin fracture and sand/resin interface debonding,separately.The corresponding experimental observation of micro-scale failure behavior based on the scanning electron microscopy(SEM)was presented for a comparison.The numerical results show that the initial failure of the model occurs at the sand/resin interface,followed by consequent resin failure.Dependent on the resin cohesive strength,the location of resin failure varies from the central zones to resin neck arc zones.A typical mixed mode fracture is observed,which is consistent with the corresponding micro-scale experimental observation.When the resin cohesive strength ranges between 8 and 12 MPa,the resin cracks occur at the central zone of resin bridges and propagate perpendicularly to the tensile direction until through cracks happen.At a higher range(between 12 and 16 MPa),interface cracks cross with resin cracks,bonding bridges of resin sand are broken.The interface adhesive strength has a more significant effect on the overall tensile strength of resin sand than the resin cohesive strength.The overall tensile strength of resin sand increases first then keeps stable with the increase of the resin cohesive strength.This work attempts to establish a numerical model which accurately describes the complicated mixed mode fracture of resin sand,which is beneficial to understand deeply the fracture mechanism of resin sand.展开更多
An analytical methodology was developed to investigate the effect of fiber/matrix interface debonding on matrix multicracking evolution of fiber-reinforced CMCs(ceramic-matrix composites).The Budiansky-Hutchinson-Evan...An analytical methodology was developed to investigate the effect of fiber/matrix interface debonding on matrix multicracking evolution of fiber-reinforced CMCs(ceramic-matrix composites).The Budiansky-Hutchinson-Evans shear-lag model was adopted to analyse the micro-stress field of the damaged composites.The critical matrix strain energy criterion,which presupposes the existence of an ultimate or critical matrix strain energy with matrix,was obtained to simulate the matrix multicracking evolution of CMCs.With the increase of the applied stress,the matrix multicracking and fiber/matrix interface debonding occurred to dissipate the additional energy entered into the composites.The fiber/matrix interface debonded length under matrix multicracking evolution was obtained by treating the interface debonding as a particular crack propagation problem.The conditions for no-debonding and debonding during the evolution of matrix multicracking were discussed in terms of two interfacial properties,i.e.,the interface shear stress and interface debonded toughness.When the fiber/matrix interface was bonded,the matrix multicracking evolution was much more intense compared with the interface debonding;when the fiber/matrix interface was debonded,the matrix crack density increased with the increasing of interface shear stress and interface debonded energy.The theoretical results were compared with experimental data of unidirectional SiC/CAS(calcium alumina silicate),SiC/CAS-Ⅱand SiC/borosilicate composites.展开更多
基金Sponsored by the General Armament Department Advanced Research Project (20101019)
文摘Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its microscopic computational model was established. The interface mechanical response was modeled by the bilinear cohesive zone model. The effects of interface properties and particle sizes on the macroscopic mechanical behavior were investigated. Numerical simulation of debonding damage evolution of composite propellant under finite deformation was carried out. The debonding damage nucleation, propagation mechanism and non-uniform distribution of microscopic stress-strain fields were discussed. The results show that the finite element simulation method based on microstructure model can effectively predict the trend of macroscopic mechanical behavior and particle/matrix debonding evolution process. It can be used for damage simulation and failure assessment of composite propellants.
文摘This paper investigates the dynamic behavior of a buried rigid elliptic cylinder partially debonded from surrounding matrix under the action of anti-plane shear waves (SH waves). The debonding region is modeled as an elliptic arc-shaped interface crack with non-contacting faces. By using the wave function (Mathieu function) expansion method and introducing the dislocation density function as an unknown variable, the problem is reduced to a singular integral equation which is solved numerically to calculate the near and far fields of the problem. The resonance of the structure and the effects of various parameters on the resonance are discussed.
基金Jiangsu Postdoctoral Science Foundation (0902013C)Innovation Foundation for Young Teachers in University of Aeronautics and Astronautics (Y1024-054)
文摘A multiscale method for simulating the dynamic response of ceramic matrix composite （CMC） with matrix cracks is developed. At the global level, the finite element method is employed to simulate the dynamic response of a CMC beam. While at the local level, the multiscale mechanical method is used to estimate the stress/strain response of the material. A distributed computing system is developed to speed up the simulation. The simulation of dynamic response of a Nicalon/CAS-II beam being subjected to harmonic loading is performed as a numerical example. The results show that both the stress/strain responses under tension and compressive loading are nonlinear. These conditions result in a different response compared with that of elastic beam, such as： 1） the displacement response is not symmetric about the axis of time; 2） in the condition of small external load, the response at first order natural frequency is limited within a finite range; 3） decreasing the matrix crack space will increase the displace- ment response of the beam.
文摘The problem of elastic wave scattering from a partially debonded elastic cylindrical inclusion is investigated by using the wave function expansion method and singular integral equation technique. The debonding regions are modeled as interface cracks with non-contacting faces. The mixed boundary conditions of the problem lead to a set of simultanious dual series equations which, by introducing the dislocation density functions as unknowns, can be further converted to a set of singular integral equations of the second type. Solving these equations numerically, we obtain the dynamic stress intensity factor(DSIF), the scattered far-field pattern and the scattering cross section(SCS). The numerical results for an inclusion with one debond are presented to show the distinguishing feature of the problem-the low frequency resonances in both DSIF and SCS. Finally, as a special example, we discuss the scattering of elastic waves by a circular arc-shaped crack in a homogeneous medium. The presented method is valid when stresses have oscillatory behavior.
基金Fundamental Research Funds for the Central Universities(WUT:2018III066GX)Nature Science Foundation of Hubei Province(2017CFC809)+1 种基金China Postdoctoral Science Foundation(No.2018M632933)the Foreign Science and Technology Cooperation Project of Hubei Provenience(Grant No.2013BHE008).
文摘A plane-strain unit-cell finite element model was proposed to study the effects of resin/sand interface adhesive and resin cohesive strength on the overall tensile strength of resin sand,as well as the fracture modes.The main micro-scale characteristics of the numerical model were extracted from the micrograph of resin sand specimens by three-dimensional X-ray microscopy(3 D-XRM).The extended finite element method(XFEM)and cohesive behavior method were employed to explicitly describe the resin fracture and sand/resin interface debonding,separately.The corresponding experimental observation of micro-scale failure behavior based on the scanning electron microscopy(SEM)was presented for a comparison.The numerical results show that the initial failure of the model occurs at the sand/resin interface,followed by consequent resin failure.Dependent on the resin cohesive strength,the location of resin failure varies from the central zones to resin neck arc zones.A typical mixed mode fracture is observed,which is consistent with the corresponding micro-scale experimental observation.When the resin cohesive strength ranges between 8 and 12 MPa,the resin cracks occur at the central zone of resin bridges and propagate perpendicularly to the tensile direction until through cracks happen.At a higher range(between 12 and 16 MPa),interface cracks cross with resin cracks,bonding bridges of resin sand are broken.The interface adhesive strength has a more significant effect on the overall tensile strength of resin sand than the resin cohesive strength.The overall tensile strength of resin sand increases first then keeps stable with the increase of the resin cohesive strength.This work attempts to establish a numerical model which accurately describes the complicated mixed mode fracture of resin sand,which is beneficial to understand deeply the fracture mechanism of resin sand.
基金Supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20140813)Postdoctoral Science Foundation of China(Grant No.2012M511274)Introduction of Talents Scientific Research Foundation of Nanjing University of Aeronautics and Astronautics(Grant No.56YAH12034)
文摘An analytical methodology was developed to investigate the effect of fiber/matrix interface debonding on matrix multicracking evolution of fiber-reinforced CMCs(ceramic-matrix composites).The Budiansky-Hutchinson-Evans shear-lag model was adopted to analyse the micro-stress field of the damaged composites.The critical matrix strain energy criterion,which presupposes the existence of an ultimate or critical matrix strain energy with matrix,was obtained to simulate the matrix multicracking evolution of CMCs.With the increase of the applied stress,the matrix multicracking and fiber/matrix interface debonding occurred to dissipate the additional energy entered into the composites.The fiber/matrix interface debonded length under matrix multicracking evolution was obtained by treating the interface debonding as a particular crack propagation problem.The conditions for no-debonding and debonding during the evolution of matrix multicracking were discussed in terms of two interfacial properties,i.e.,the interface shear stress and interface debonded toughness.When the fiber/matrix interface was bonded,the matrix multicracking evolution was much more intense compared with the interface debonding;when the fiber/matrix interface was debonded,the matrix crack density increased with the increasing of interface shear stress and interface debonded energy.The theoretical results were compared with experimental data of unidirectional SiC/CAS(calcium alumina silicate),SiC/CAS-Ⅱand SiC/borosilicate composites.
