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In this work the effect of carbon nanotube length on the nanofluidic energy absorption system is investigated by using molecular dynamic simulation. For this purpose, four rigid armchair carbon nanotubes (8,8), (10,10), (12,12) and (14,14), and six lengths (5.0 nm, 6.0 nm, 7.0 nm, 8.0 nm, 9.0 nm and 10.0 nm ) for each one are studied. Results of simulations show that the surface of carbon nanotube is frictionless in all length and diameters, causing water molecules defiltrated from carbon nanotubes after applying the loading-unloading cycle on the system. Contact angle which represents hydrophobic intensity of carbon nanotube is decreased averagely 4 and 2 % by increasing length and diameter of carbon nanotube, respectively; therefore, infiltration pressure of water molecules through carbon nanotube is decreased averagely 30 and 15 %, respectively. Moreover, the mass and size of carbon nanotube increase by increasing length and diameter of carbon nanotube, leading to the reduction of energy absorption density and efficiency. Also, density of water molecules in carbon nanotube unlike the bulk of liquid phase is non uniform, decreases in the first and second shells, and increases along the distance between them by increasing length of carbon nanotube.

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Delamination is one the most important defect that reduces strength of part. Many researchers have been studied delamination in drilling of composite materials and they tried to formulate this phenomenon by developing of analytical, numerical and experimental models. In this models up to now, only effect of modeΙ and modeΙΙΙ of crack propagation is considered and effect of modeΙΙ is neglected. The goal of this research is determination of modeΙΙ effect on propagation of interlaminar cracks during drilling of multilayered composites by means of finite element analysis (FEA).Thus the numerical analysis of delamination of unidirectional Carbon/epoxy composite during drilling is performed by modification of previous numerical models. The numerical method which is used for determination of strain energy release rates in modeΙ and modeΙΙ is Virtual Crack Closure Technique (VCCT). This analysis is performed for crack propagation under chisel edge when the drill have not come out from the workpiece and for crack propagation under cutting edges when the drill have come out from the workpiece. By determination of strain energy release rates in modeΙ and modeΙΙ and comparing with critical values G_Ιc andG_ΙΙc, the critical thrust force that causes to delamination is determined and contribution of each crack propagation mode in delamination is discussed. At the end of this research, it was found that the effect of modeΙ is more than modeΙΙ in all of cases such that more than 95percent of crack propagation parameter in power law criteria is due to strain energy release rates in modeΙ.