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Title: Meso-damage modelling of polymer based particulate composites using finite element technique
Authors: Tsui, Chi-pong
Degree: Ph.D.
Issue Date: 2003
Abstract: To develop a new paniculate polymer composite (PPC) with desired mechanical properties is usually accomplished by an experimental trial-and-error approach. So far, there is no method by which damage phenomenon of PPC can be satisfactorily predicted. Conventional computation methods that neglect the gradual degradation of material are no longer suitable for designing this category of material. A new technique, which predicts the damage mechanism and its effects on the mechanical properties of PPC. has been proposed. This meso-mechanical modelling technique, which offers a means to bridge the micro-damage mechanism and the macro-structural behaviour, has been implemented in a finite element code. A three-dimensional finite element meso-cell model has been designed and constructed to simulate the damage mechanism of PPC. The meso-cell model consists of a micro-particle, an interface, and a matrix. The initiation of the particle/polymer matrix debonding process has been predicted on the basis of a tensile criterion. Hence, the complete damage mechanism of PPC can be simulated. By considering the meso-cell model as a representative volume element (RVE). the effects of damage on the macro-structural constitutive behaviour of PPC have been determined. An experimental investigation has been made on glass beads (GB) reinforced polyphenylene oxides (PPO) for verification of the meso-cell model and the meso-mechanical finite element technique. In-situ scanning electron microscopy has been adopted to study the particle-matrix debonding process in real time under both shear and tensile deformation. A load-and-unloading test has been used to determine the macro-structural constitutive behaviour of the composites under different degrees of damage. The predicted constitutive relation has been found to be in good agreement with the experimental results. The results of the in-situ microscopic test also verify the correctness of the meso-cell model. The application of the meso-mechanical finite element modelling technique has been extended to a macro-structural analysis to simulate the response an engineering structure made of PPC under a static load. In the simulation, a damage variable has been defined in terms of the computational results of the cell model in meso-scale. Hence, the damage-coupled constitutive relation of the GB/PPO composite could be derived. A user-defined subroutine VUMAT in FORTRAN language describing the damage-coupled constitutive behaviour has then been incorporated into the ABAQUS finite element code. On a macro-scale, the ABAQUS finite element code has been used to simulate the process of deformation and failure of the PPC structure. This project has been conducted, in the first instance, to incorporate the concept of damage mechanics to develop a meso-damage finite element modelling technique that can be applied to simulate the damage process and the constitutive behaviour of PPC. In addition, the technique has been developed to predict the deformation and the failure of PPC structures. In this project, various effects on the accuracy of the simulation results, such as the RVE size effect, have also been studied. The deliverables of the project do not only provide a means for designing PPC, but also lay down a foundation for further research in the multi-scale damage analysis.
Subjects: Hong Kong Polytechnic University -- Dissertations
Polymers -- Mechanical properties
Polymers -- Mathematical models
Finite element method
Pages: xxxi, , 165, 17, [103], 34 leaves : ill. ; 30 cm
Appears in Collections:Thesis

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