Interface analysis and design in carbon nanotube array composite based on cohesive finite element approach

Mechanical properties of composites can be significantly improved by using well-aligned carbon nanotube array (CNTA) as reinforcements. However, damage and cracks at the interface between carbon nanotubes (CNTs) and matrix are still major factors hampering the desired reinforcement effect of the CNTA. In this paper, a micromechanics-based bilinear cohesive law was applied in cohesive finite element model to characterize CNT/matrix interface. The interfacial properties were described by varying the values of cohesive strength and fracture energy of the interface. Then numerical simulation for the interfacial fracture and macroscopic properties of the CNTA composites under transverse loadings was conducted based on the present cohesive finite element method. Remarkable influences of interfacial properties on the overall properties of the CNTA composites were verified. The brittle failure mode of the CNTA composites was found to be shifted to the ductile mode as the interface became more expandable. Moreover, it is proved that the CNTA composites have a potential improvement with increased CNTA volume fraction and optimized interfacial cohesive parameters.