Cyclic deformation behavior and fatigue life modeling of CNT-reinforced heterogeneous aluminum-based nanocomposite

Abstract

Heterogeneous materials are regarded as an emerging class of structural materials with superior balanced performance relative to the conventional unimodal counterparts. In the present study, the cyclic deformation behavior of carbon nanotube (CNT)-reinforced 2009Al nanocomposite with a bimodal-grain structure was studied via strain-controlled fatigue tests. Both bimodal-grained base alloy and nanocomposite exhibited basically cyclic stabilization during cyclic deformation. A higher cyclic stress level was observed to sustain by the nanocomposite at all strain amplitudes applied, along with a superior fatigue life at lower strain amplitudes due to its higher monotonic strength. However, at higher strain amplitudes, the base alloy exhibited better fatigue properties because of its higher ductility. A strain-energy density based approach integrated with accumulative damage process was used to predict fatigue life via a modified method for the evaluation of intrinsic fatigue toughness, which is defined as the sum of all hysteresis loop areas from the first cycle to the number of cycles to failure. The application of the proposed method for the intrinsic fatigue toughness was observed to give a better fatigue life prediction.