Micromechanics Modeling And Numerical Simulation Of Asphalt Concrete

Asphalt concrete (AC) is a typical complex multi-phase material. When loading rate is very high and the temperature is low, it can be approximated as an equivalent elastic body in engineering application, while at high temperature and high pressure, it shows apparent viscoelasticity characteristics. To date, the prediction and determination of the bulk behavior of AC is largely based on experiments as well as experience, and it is often time-consuming and can not reflect the influence of the microstructure of AC. To this end, a systematical study will be conducted in this dissertation, to investigate the elastic and viscoelastic properties of the composite and the mechanical behavior of AC.First of all, the basic concept of the fast multipole boundary element method (FMBEM) will be introduced, and the corresponding algorithm for 2D multi-inclusion elastic problems will be reviewed. The influence of the interfacial zone on the overall mechanical properties of the composites is investigated, where two different models, the spring layer model and the interphase model, are used to simulate the imperfect interface. Based on these models, the corresponding FMBEM formulations have been developed. A two-layer built-in micromechanical model and a stepping scheme are proposed to predict the effective properties of the multi-inclusion composite with interface imperfection.Secondly, a new FMBEM algorithm for 2D viscoelastic problems is formulated by virtue of the elastic-viscoelastic correspondence principle and is solved by the time stepping scheme. The FMBEM formulations are derived by assuming a Kelvin type viscoelastic model, which is adopted to simulate the interface bonding imperfection. Besides, a micromechanical approach is also obtained by introducing the idea of effective properties of inclusions to estimate the creep behavior of the viscoelastic solids, which contain elastic particles but with in-between viscoelastic interfaces.Thirdly, the obtained numerical and analytical methods are applied to investigating the mechanical behavior of AC. By means of digital image processing, the cross-sectional digital images of asphalt concrete samples are created for numerical modeling. Then the elastic modulus and creep compliance of AC are predicted by the developed FMBEM arithmetic and micromechanical models. The influence of some factors on the behaviour of AC is investigated, including the asphalt matrix, coarse aggregate, air void, aggregate gradations, the largest aggregate and interface between asphalt matrix and coarse aggregates. It has shown that all of these factors may have significant effects on the mechanical properties of AC.Finally, a 2D FMBEM analysis of magneto-electro-elastic media has been developed. Fourier transformation is employed to derive the fundamental solution for the generalized plane-strain magneto-electro-elasticity. The numerical examples of multi-inclusion magneto-electro-elastic composites illustrate the validity and advantages of the proposed approach in the smart structure applications.The present study indicates that the developed FMBEM is not only easy in the meshing of complicated geometries, accurate for solving singular fields, but also practical and often superior in solving large class problems, such as AC. It is also shown that the developed micromechanical method is very comprehensive and efficient for fast prediction of effective properties of composites, which makes it possible to be applied in the engineering practice.