Abstract
CNTs reinforced metal composites has great potential due to their superior properties, such as light weight, high strength, low thermal expansion and high thermal conductivity. The current strengthening mechanisms of CNT/metal composite mainly rely on CNTs’ interaction with dislocations and CNT’s intrinsic high strength. Here we demonstrated that laser shock loading the CNT/metal composite results in high density nanotwins, stacking fault, dislocation around the CNT/metal interface. The composites exhibit enhanced strength with excellent stability. The results are interpreted by both molecular dynamics simulation and experiments. It is found the shock wave interaction with CNTs induces a stress field, much higher than the applied shock pressure, surrounding the CNT/metal interface. As a result, nanotwins were nucleated under a shock pressure much lower than the critical values to generate twins in metals. This hybrid unique nanostructure not only enhances the strength, but also stabilize the strength, as the nanotwin boundaries around the CNTs help pin the dislocation movement.
Highlights
CNTs reinforced metal composites has great potential due to their superior properties, such as light weight, high strength, low thermal expansion and high thermal conductivity
Carbon nanotubes exhibit super-high strength, stiffness, electrical and thermal properties due to their unique structures[1,2]. These superior properties make CNT as ideal reinforcement for metal matrix nanocomposites composites to be used in aerospace and automotive industries[1,3]. This strong mechanical properties is due to the exceptional properties of the CNTs, the small mean free path between neighboring CNTs and the great constraint provided by the high surface area of CNTs
We present atomistic simulations of shocked CNT/metal composites, in which the extremely short compression time scales are associated with shock loading, and compare the microstructures with those after experimental laser shock loading of CNT/metal composites
Summary
Micro-sized iron (1.96 g) powder and MWNTs (0.04) were mixed in 46 g DI water. The suspension was coated on the substrate surface, which had been mechanically polished, and dried in lab circumstance[29]. A Nd:YAG laser system (wavelength 1064 nm and pulse length 5 ns) was used for LSP. LSP was performed on the nanocomposites with laser intensity of 4 GW/cm[2] and the calculated peak pressure is 8.662 ± 1.614 GPa19. In this work LAMMPS package[30] was used for MD simulation of shock propagation through iron MWNT composite. The micro-hardness of initial AISI 4140, sample with LS and sample with LS plus LSP was measured by Leco M-400-H micro-hardness instrument with 300 g load and 10 s holding time. The load—partial unload method developed by Field and Swain[31] was utilized to make 10 unique indentations in each material
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