Mechanical Simulation Of Carbon Nanotube Reinforced Cement Composites

Carbon nanotube (referred to as CNT) as a reinforced phase has excellent mechanical properties and broad application prospects. In this paper, finite element model of carbon nanotube was constructed based on molecular structural mechanics, and on the basis of this, carbon nanotube was equivalent to continuum model and elastic constants of the continuum model were calculated. Contacting with the equivalent model, finite element model of the carbon nanotube reinforced cement-based materials was established, and tensile stress-strain relationship of the carbon nanotube reinforced cement-based materials was obtained eventually. The main conclusions were in the following:(1) Based on ANSYS 10.0 and molecular structure mechanics method, finite element models of the armchair and sawtooth single-walled carbon nanotube were established, the elastic modulus of the two models were calculated, and effects of diameter and length on modulus were obtained. The conclusions that 1)Young's modulus of carbon nanotubes increases with the increase of diameter; 2) because defects increases with the increase of length, Young's modulus decrease with the increase of length, but converge finally; 3)when the length reach to a certain value, the modulus of carbon nanotubes of different diameters change little, are the foundation of the later chapters.(2) On the basis of molecular structure and Hashin theory, continuum model was established. Making continuum model and molecular structure mechanical model of carbon nanotubes had the same boundary conditions, and then making the strain energy of the two models equal,5 elastic constants of continuum model equivalented to carbon nanotubes were calculated. The conclusion that the constants increases with the increase of diameter of carbon nanotubes and converge finally was obtained. After this, compared with the proposed model of Odegard, the accuracy of the model was verified, and as a foundation for the analysis of carbon nanotubes reinforced cement based composite materials.(3) Based on models in the first two chapters, tensile strength of the carbon nanotubes reinforced cement composites was calculated, and the separation relationship between carbon nanotubes and cement-based interface was simulated by using the coupling of ANSYS and considering the effects of radial stress and shear stress on the failure of interfaces. The failure of carbon nanotubes was considered randomly, so it can be simulated by Monte Carlo on the basis of the Weibull distribution. The separation between interfaces and random breakage of carbon nanotubes were simulated by acting load, then the tensile stress-strain relationship of carbon nanotube reinforced cement based composite materials was obtained.