| As a light, high strength and modulus one-dimension-material, carbon nanotubes（CNTs） have been widely used in composite materials&structures for their excellent mechanical properties. Research shows that load-transfer plays a key role for the reinforcement of CNTs. As the composite reinforcement, CNTs reinforced polymer composite could achieve the load transfer from polymer to CNTs, to improve the composite mechanical properties. However, due to inert surface structure of carboatomic ring, the interface between the CNTs and polymer is too weak to perform the load transfer completely in the composite. Limited to the weak interfacial interaction, it is diffic ult to achieve the high mechanical performance in accordance with theoretical predictions and high mechanical properties of CNTs. In order to strengthen the interfacial interactions between the reinforcement and matrix of composite materials, researchers handle the CNTs-reinforcement with surface modifiication methods, such as functionalized CNTs and covalent bonds. But the reinforcement effects of these methods are limited, because the the most important factors to the composite interface reinforment are the structures of reinforcement and matrix. The surface modification method is just the minor change of the CNTs, not involved in the inherent change of the CNTs-reinforcement. Based on CNTs-reinforcement structure, the thesis proposed the carbon nanotube/g raphene hybrid structure（CGHS）.The interfacial reinforcement effects of CGHS reinforced polyethylene composite have been studied by molecular dynamic simulations. CGHS may open a new gate for the research of CNTs reinforcement composite.The most common two failure modes of CNTs/polymer matrix composite are CNTs fracture and the pull-out of CNTs-reinforment from the matrix. Hence, the thesis studied the structure characters and strength of CGHS. The mechanical response and mechanism of CGHS during the unia xial tensile loading were investigated as well as the tensile loading of SWCNT. Furthermore, the structure effects on the strength of CGHS were studied, such as different cutting length, cutting number, and chirality effects. The strength of hybrid structure is just 40 MPa, only half of the CNTs’. The junctional zone will be more likely to be in failure. The strength will be 30 MPa with the cutting number increasing.The strength descends with cutting length and chirality increasing.Moreover, the interfacial reinforcement interaction of CGHS reinforced polyethylene composite was investigated by the pull-out simualtions via molecular simulation methods. The simulations were done by the pull-out of CGHS-reinforcement from the polyethylene matrix. The maximum pull-out force and pull-out-energy during the process were used to evaluate the reinforcement effects. The interfacial reinforcement effects and mechanisms were analysed by energy distribution and the structure deformation, especially the mechanical energy between the reinforcement and matrix. Besides, the effects of pull-out directions, CGHS-reinforcement parameters and polyethylene desity were studied. The relationship between the reinforcement effects and CGHS paramenter has been discovered and the conclusion shows that the CGHS reinforced polymer composite has a great interfacial-reinforcement-interaction improvement compared to CNTs reinforced composite. The reinforcement is mainly due to deformation of hybrid structure and mechan ical energy. For chirality（10,1）, cutting length in 0.8, cutting nummber equal to 4, the pull-out energy and force will be 190×10-19 J and 3.38 n N, 3 and 4 times more than carbon nanotubes reinforcement. For chirality（m,n）, bigger m, cutting length in optinuum, lower cutting number, bigger matrix density, the pullout force and energy will be excellent as well as composite mechanical properties. |
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