Modelling of behaviour of carbon nanotube-reinforced composites

F. OTERO; S. OLLER; X. MARTINEZ; O. SALOMON

Congreso; MATCOMP?11. IX Congreso Nacional de Materiales Compuestos; 2011

Carbon nanotubes (CNTs) have been regarded as ideal reinforcements of highperformancecomposites. A key factor for the reinforcement efficiency is the interfacebonding between the CNTs and the matrix. The present work presents a newconstitutive model to predict the performance of composites made of CNTs that takesinto account explicitly the mechanical performance of the interface between the matrixand the CNTs. The constitutive model is based in the mixing theory, which allowsrepresenting each composite component with its own constitutive law.The new formulation divides the composite in matrix and a new element result of thecoupling of CNTs with the interface material. The matrix and the CNTs-interface arerelated with the parallel mixing theory; this is, they are assumed to have an isostrainbehaviour. On the other hand, CNTs and interface material are bonded together with acombination of parallel and serial mixing theories.The relation defined between interface and CNTs components considers that there aretwo regions situated at both ends of the nanotube, where the stress of the interface andthe CNTs are coincident. In these regions the load is transferred from the interface tothe nanotube and has a serial performance. On the other hand, the central section of theCNTs has a parallel performance; in it CNTs are capable to develop their full strength.When de stress in the region of ends of the nanotube reaches to the limit tension of theinterface starts nonlinear behaviour. The properties of the interface zone are degradedand the region of ends of the nanotube starts to grow, in other words, is like if thenanotube is shortened. Finally, for high nonlinear behaviour the interface and CNTs arebonded together with a full serial theory, but at this point of the interface properties arehighly degraded. Then, the final properties of the composite are similar to the propertiesof the matrix component.The numerical results of the model presented have been compared with experimentaldata showing good agreement.