Nano science breakthrough set to improve composites

Japanese material scientists have developed multi walled carbon nanotubes (MWCNT) that can be embedded into composite materials.

Strengthening of MWCNT in a solid material environment will permit materials engineers to develop new classes of reinforced advanced composites that have much better mechanical properties.

Mehdi Estili, a Fellow of the Japan Society for the Promotion of Science in the Department of Materials Processing at Tohoku University, claims the development will yield nano composite structures that are stronger, stiffer, lighter and with more desirable electrical conductivity.

Creating MWCNTs has been difficult due to the extremely small dimensions of individual nano tubes. Additionally, the strength can neither be exploited nor measured due to inter facile sliding between multiple tubes when under load.

Estili explains the problem to nanotechnology website Nanowerk, he said: "If several SWCNTs are nested concentrically in a confined space, the sliding issue can be resolved and the SWCNTs may share the applied tensile load to realise nanometre scale materials [that are] remarkably stronger than the individual SWCNTs. However, MWCNTs suffer from extremely weak interwall shear resistance (ISR), allowing only the defective outermost wall carry load."

To resolve this drawback, strong ISR must be created throughout the MWCNT structure. Estili, together with other material experts, have now engineered strong ISR in the entire MWCNT structure by embedding MWCNTs into a compressive stressing ceramic environment.

The strategy is to apply uniform radial compressive stress on the MWCNT to exploit inwall irregularities. This creates strong inter wall mechanical interlocking (strong ISR) under axial tensile loading, increasing the strength of MWCNT by distributing the load among the inner walls.

Graham Pitcher

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