In this thesis, the mechanical properties of buckypaper composites are evaluated by the molecular dynamics method. In order to obtain precise behavior of the material under different mechanical and thermal loadings, a large number of atoms should be used in the simulation as well as enough time for the system to equilibrate. The fact that the simulations will take a long time (about 100 days with 50000 atoms on a CPU core) makes it impossible to use today’s commercial molecular dynamic programs which are executed on the central processing units . For acquiring the results in a logical period and with a large number of atoms, a molecular dynamic package Buckypaper is made of carbon nanotube sheets. By adding the resin and the hardner to the buckypaper and then curing it in a specific temperature and pressure, the buckypaper composite will be produced. For simulating the detailed behavior of the system and to be sure of the computational accuracy of the package, several benchmarks are considered from the literautre. In the first and second benchmark, one nanotube reaction and a resin molecule and a nanotube reaction and a hardner molecule is considered. The total energy change of the system is monitored and compared with those reported in the references qualitatively. The third model consists of the hardner and the resin molecules. In this benchmark the temperature of the system is decreased under constant atmospheric pressure and the density and the volume of the system is monitored. From this simulation the Young’s modulus, phase transition temperature and longitude expansion coefficient in both phases are acquired. The benchmark results are compared to the available data reported in the literature. After regulating the solution parameters, the last model which was the buckypaper composite is modeled. The results have shown good agreement with the existing experimental tests as well as the available data. The results of the simulation of the short fiber buckypaper composite showed that this material has a Young’s modulus about 35 GPa in the fiber direction, however with the infinite fiber buckypaper composite models the Young’s modulus reached up to 180 GPa in the fiber direction. Nevertheless this material is week in the normal direction of the nanotube sheets and has a Young’ modulus about 10 GPa which is near to the matrix modulus.It is noticableresulting elastic modulus of the composite is bigger than the both resin matrix and also the buckypaper, which is due to a better force transfer between the nanotubes and the resin. Also this material showed auxetic behavior in some directions (e.g. Poisson's ratio from -0.02 to 0.2) which is a good verification for the use of this material in artificial muscles. Key words: Buckypaper, Molecular Dynamics, Composite,GPU computing,Elastic Modulus