Influence of Particle Size and Volume Fraction on Damage and Fracture in Al-Al3Ti Composites and Micromechanical Modelling Using the GTN Model PDF Download
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Author: Rue He
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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Book Description
Author: Rue He
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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Book Description
Author:
Publisher:
ISBN:
Category : Metallurgy
Languages : en
Pages : 972
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Author: Shihua Nie
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 744
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Book Description
"The main aim of this dissertation was to characterize the damage mechanism and fatigue behavior of the acrylic particulate composite. This dissertation also investigated how the failure mechanism is influenced by changes in certain parameters including the volume fraction of particle, the interfacial bonding strength, the stiffness and thickness of the interphase, and the CTE mismatch between the particle and the matrix. Monotonic uniaxial tensile and compressive testing under various temperatures and strain rates, isothermal low-cycle mechanical testing and thermal cycling of a plate with a cutout were performed. The influence of the interfacial bonding strength between the particle and the matrix on the failure mechanism of the ATH filled PMMA was investigated using in situ observations under uniaxial loading conditions. For composites with weak interfacial bonding, the debonding is the major damage mode. For composites with strong interfacial bonding, the breakage of the agglomerate of particles is the major damage mode. Experimental studies also demonstrated the significant influence of interfacial bonding strength on the fatigue life of the ATH filled PMMA. The damage was characterized in terms of the elastic modulus degradation, the load-drop parameter, the plastic strain range and the hysteresis dissipation. Identifying the internal state variables that quantify material degradation under thermomechanical loading is an active research field. In this dissertation, the entropy production, which is a measure of the irreversibility of the thermodynamic system, is used as the metric for damage. The close correlation between the damage measured in terms of elastic modulus degradation and that obtained from the finite element simulation results validates the entropy based damage evolution function. A micromechanical model for acrylic particulate composites with imperfect interfacial bonds was proposed. Acrylic particulate composites are treated as three-phase composites consisting of agglomerated particles, bulk matrix and an interfacial transition zone around the agglomerate. The influence of the interfacial bonding and the CTE mismatch between the matrix and the filler on the overall thermomechanical behavior of composites is studied analytically and experimentally. The comparison of analytical simulation with experimental data demonstrated the validity of the proposed micromechanical model for acrylic particulate composites with an imperfect interface. A damage-coupled viscoplastic constitutive model was also developed to predict the thermomechanical behavior and fatigue life of the acrylic particulate composites. The damage coupled constitutive model simulates the interaction between damage and response of the composite material under thermomechanical loading. The material parameters involved in the constitutive model have been experimentally determined and been implemented into the commercial general-purpose finite element package ABAQUS through user-defined subroutines. The finite element simulation results agree well with the test data from monotonic uniaxial tensile tests and fatique tests at various temperatures. It is shown that the proposed damage coupled viscoplastic constitutive model can be used to predict the fatique life of an acrylic particulate composite under thermomechanical fatigue loading"--Leaves xxvii-xxviii.
Author: Yi Wu
Publisher:
ISBN:
Category :
Languages : en
Pages : 183
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Book Description
The primary objective of this research work is to investigate the effective mechanical responses of continuous fiber reinforced composites by modifying and extending the available micromechanical framework. A major part of the work conducted involves the investigation of the effective damage responses due to damage evolutions of matrix microcracks and fiber breakages. Chapter 3 presents the effective elastic damage behavior of continuous fiber reinforced composites with evolutionary matrix microcracks. A cohesive penny-shape microcrack model is proposed within a two-step homogenization framework to achieve the effective elastic damage behavior of continuous fiber reinforced composites. In the proposed model, the size and the number density of microcracks are defined as two damage parameters to control the matrix microcrack evolution. In addition, the thermal effect is taken into account by taking advantage of the thermal eigenstrain and the Eshelby's equivalent inclusion principle. The overall coefficient of thermal expansion (CTE) of the composite is systematically derived under the framework of micromechanics to describe the overall damage behavior of composites due to matrix microcrack evolution under temperature changes. Chapter 4 proposes a micromechanical evolutionary damage framework capable of predicting the overall mechanical behavior of and damage evolution in continuous fiber reinforced composites. In the framework, the effective stress fields in a single fiber due to an embedded penny-shaped fiber breakage are systematically derived by applying the double-inclusion theory. The notion of effective length denoting the distance between two adjacent breakages is introduced as a damage parameter while determining the damage evolution within a single fiber. This enables the modeling of the effective damage behavior of a single-fiber reinforced composite. As an application of the proposed framework, a micromechanical damage model is further proposed to simulate the fiber-dominated failure mechanism within a multi-fiber composite. A Weibull probability function is adopted to estimate the varying volume fractions of damaged fibers and intact fibers. Numerical simulations are presented to demonstrate the effectiveness of the proposed methodology. In Chapter 5, based on the linear elastic fracture mechanics (LEFM) and ensemble-volume averaging technique, an effective eigenstrain is newly proposed to quantify the homogenized stress fields in a single fiber due to multiple fiber breakages. In the proposed model, the number density evolution of fiber breakages is characterized by a two-parameter Weibull statistic with the temperature effect implicitly enclosed by properly adjusting the Weibull parameters. The damage criterion in the evolutionary damage model is theoretically derived. Utilization of the proposed damage framework, a homogeneous damage evolution model capable of simulating the material behavior of multi-fiber reinforced composite materials is developed. Chapter 6 presents two stochastic risk-competing models to simulate the fiber breakage evolution in a multi-fiber composite with an inhomogeneous fashion by considering different load sharing mechanisms. A unit cell model is adopted with each cell being assigned an initial weakness based on a normal distribution. Damage evolution inside each cell structure follows the micromechanical model presented in Chapter 5. Two risk-competing models are introduced subsequently to determine the damage sequence within the multi-fiber composite by computing the fracture probability based on the weakness of cells at each time step. It is observed that one risk-competing model tends to generate a concentrated damage pattern with broken fibers clustering in a T-shape or a cross-shape, while the other model yields a more diffused damage pattern. Finally, the overall stress-strain responses and the fiber breakage evolution are predicted and verified against experimental data. Chapter 7 examines the effective elastoplastic behavior of metal matrix composites (MMCs) containing unidirectionally aligned continuous fibers. A homogenization procedure is utilized to derive the overall yield function for the composite based on the probabilistic spatial distribution of aligned inclusions. Based on continuum plasticity, a plastic flow rule and a hardening law are postulated. These laws together with the proposed overall yield function then characterized the macroscopic elastoplastic behavior of the composite under three-dimensional arbitrary loading/unloading histories. The overall uniaxial elastoplastic stress-strain behavior of MMCs with aligned continuous fibers is investigated. Comparisons between theoretical predictions and experimental data for the composite are performed to illustrate the capability of the proposed method. Chapter 8 concludes the present research on micromechanics and effective elastic and elastoplastic behavior of continuous fiber reinforced MMCs. Finally, related future research topics are discussed briefly.
Author: Ram B. Bhagat
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 272
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Book Description
Contains 26 papers presented at the International Conference on [title], held to address the latest ideas concerning the mechanisms and mechanics of composite fractures. The main focus was on the "driving forces" behind the various damage events in the inorganic composites at both micro and macro levels. The papers are grouped in five sections: deformation and damage in particulate composites; crack initiation and propagation; micromechanical modeling; fracture and fatigue; and microstructural tailoring, impact, and creep. No index. Annotation copyright by Book News, Inc., Portland, OR
Author: George Voyiadjis
Publisher: Elsevier
ISBN: 0080463673
Category : Technology & Engineering
Languages : en
Pages : 741
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Book Description
The book presents the principles of Damage Mechanics along with the latest research findings. Both isotropic and anisotropic damage mechanisms are presented. Various damage models are presented coupled with elastic and elasto-plastic behavior. The book includes two chapters that are solely dedicated to experimental investigations conducted by the authors. In its last chapter, the book presents experimental data for damage in composite materials that appear in the literature for the first time.· Systematic treatment of damage mechanics in composite materials· Includes special and advanced topics· Includes basic principles of damage mechanics· Includes new experimental data that appears in print for the first time· Covers both metals and metal matrix composite materials· Includes new chapters on fabric tensors· Second edition includes four new chapters
Author: Thomas H. Courtney
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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Book Description
Tensile testing of high volume fraction tungsten-aluminum and molybdenum-aluminum composites has been carried out at temperatures ranging from 25 to -196 C and elongation rates of 0.002 and 0.1 in./min respectively. The effect of constant strain rate tensile tests on observed fracture modes was investigated theoretically. Stress-strain behavior was analyzed by fiber size, inter-fiber spacing, character of flows, temperature, strain-rate and condition of material. (P.S.-PL).
Author: Sun-Myung Kim
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Based on continuum damage mechanics (CDM), an isotropic and anisotropic damage model coupled with a novel plasticity model for plain concrete is proposed in this research. Two different damage evolution laws for both tension and compression are formulated for a more accurate prediction of the plain concrete behavior. In order to derive the constitutive equations, the strain equivalence hypothesis is adopted. The proposed constitutive model has been shown to satisfy the thermodynamics requirements, and detailed numerical algorithms are developed for the Finite Element implementation of the proposed model. Moreover, the numerical algorithm is coded using the user subroutine UMAT and then implemented in the commercial finite element analysis program Abaqus, and the overall performance of the proposed model is verified by comparing the model predictions to various experimental data on macroscopic level. Using the proposed coupled plasticity-damage constitutive model, the effect of the micromechanical properties of concrete, such as aggregate shape, distribution, and volume fraction, the ITZ thickness, and the strength of the ITZ and mortar matrix on the tensile behavior of concrete is investigated on 2-D and 3-D meso-scale. As a result of simulation, the tensile strength and thickness of the ITZ is the most important factor that control the global strength and behavior of concrete, and the aggregate shape and volume fraction has somewhat effect on the tensile behavior of concrete while the effect of the aggregate distribution is negligible. Furthermore, using the proposed constitutive model, the pull-out analysis of the single straight and curved CNT embedded in cement matrix is carried out. In consequence of the analysis, the interfacial fracture energy is the key parameter governing the CNT pull-out strength and ductility at bonding stage, and the Young's modulus of the CNT has also great effect on the pull-out behavior of the straight CNT. In case of the single curved CNT, while the ultimate pull-out force of the curved CNT at sliding stage is governed by the initial sliding force when preexisting normal force is relatively high, the ultimate pull-out force, when the preexisting normal force is not significant, is increased linearly proportional to the curvature and the Young's modulus of the CNT due to the additionally induced normal force by the bending stiffness of the curved CNT.
Author: Khémais Saanouni
Publisher: Elsevier Science & Technology
ISBN:
Category : Computers
Languages : en
Pages : 342
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Book Description
These collected writings gather recent advances in numerical and computational aspects of damage mechanics with the intention of stimulating current research and future challenges in this field.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722356088
Category :
Languages : en
Pages : 58
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Book Description
Three multiaxial isothermal continuum damage mechanics models for creep, fatigue, and creep/fatigue interaction of a unidirectional metal matrix composite volume element are presented, only one of which will be discussed in depth. Each model is phenomenological and stress based, with varying degrees of complexity to accurately predict the initiation and propagation of intergranular and transgranular defects over a wide range of loading conditions. The development of these models is founded on the definition of an initially transversely isotropic fatigue limit surface, static fracture surface, normalized stress amplitude function and isochronous creep damage failure surface, from which both fatigue and creep damage evolutionary laws can be obtained. The anisotropy of each model is defined through physically meaningful invariants reflecting the local stress and material orientation. All three transversely isotropic models have been shown, when taken to their isotropic limit, to directly simplify to previously developed and validated creep and fatigue continuum damage theories. Results of a nondimensional parametric study illustrate (1) the flexibility of the present formulation when attempting to characterize a large class of composite materials, and (2) its ability to predict anticipated qualitative trends in the fatigue behavior of unidirectional metal matrix composites. Additionally, the potential for the inclusion of various micromechanical effects (e.g., fiber/matrix bond strength, fiber volume fraction, etc.), into the phenomenological anisotropic parameters is noted, as well as a detailed discussion regarding the necessary exploratory and characterization experiments needed to utilize the featured damage theories. Arnold, S. M. and Kruch, S. Glenn Research Center...
