Enhanced load transfer by designing mechanical interfacial bonding in carbon nanotube reinforced aluminum composites

Abstract

The interfacial native oxide layer always acts as barriers preventing effective interfacial bonding and load transfer in carbon nanotube reinforced aluminum (CNT/Al) composites. In this work, annealing-controlled reaction between the interfacial native oxide layer and Mg element was attempted to improve interfacial bonding in CNT/AlMg composite, and mechanical interfacial bonding featured with direct CNT-Al contact and well-reserved CNTs was achieved in the 1 h annealed composite. For the 2 h annealed composite, chemical interfacial bonding featured with interfacial aluminum carbide (Al4C3) was established due to progressive interfacial reaction. Further tensile tests and numerical analysis revealed that, owing to barrier-free load path and increased interfacial friction stress, the mechanical interfacial bonding significantly enhanced CNT load transfer effect from 30.9 MPa to 59.4 MPa, which was close to shear-lag model prediction of 59.9 MPa. While, the chemical interfacial bonding led to a combined strengthening effect of 58.8 MPa from CNT-Al4C3 hybrid as a comprised outcome of Al4C3 strengthening and CNT damage. Thus, the design of mechanical interfacial bonding should be a superior strategy for improving interfacial bonding and enhancing mechanical performance in CNT/Al composites, considering its effective protection of CNT structure integrity and suppressed formation of hydrolysable Al4C3 phase.