Research on compression-compression fatigue properties of carbon nanotubes reinforced closed-cell aluminum matrix composite foams by reinforcement content design.

• The carbon nanotubes (CNTs) reinforced closed-cell Al-Si composite foams (C-ASCFs) with CNTs content of 0.50 wt% have fatigue strength of 0.697 σ s (7.40 MPa), showing a superior improvement of the fatigue properties. • The appropriate incorporation of CNTs can change the fatigue failure mode, reduce the crack growth rate, and delay the fracture, hence raising the fatigue life. • The microstructure optimization of C-ASCFs influenced by CNT and its content was deeply investigated to interpret the influences on the fatigue properties of C-ASCFs. • The load transfer effect of CNTs in composite foams was firstly revealed, the contribution of which exhibits the largest of 2.07 MPa in 0.50 wt% C-ASCFs accounting for 22.5 % of its yield strength. As the requirement of compressive fatigue loading on the mechanical properties of aluminium foams increase rapidly, the limited fatigue performance of them significantly restricts their engineering applications. In this study, the compression-compression fatigue properties of carbon nanotubes (CNTs) reinforced closed-cell Al-Si composite foams (C-ASCFs) were investigated. The fatigue strength of C-ASCFs with 0.50 wt% CNTs increased by 54% than that of Al-Si foams, where the CNTs contributed to decrease the crack expansion rate, transfer the fatigue load and hence change the fatigue failure mode, causing a combination of plastic and brittle deformation in them. Meanwhile, the appropriate incorporation of CNTs decreased pore nucleation threshold, optimized the pore morphology, and promoted the formation and refinement of eutectic Si. Such inhibited the probability of fatigue cracks initiation, resulting in the enhancement of fatigue life. This work provides theoretical and practical basis of design strategy of Al-Si composite foams and broadens their application prospect. [ABSTRACT FROM AUTHOR]