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Hassaan A. Butt, Stepan V. Lomov, Iskander S. Akhatov, Sergey G. Abaimov

Centre for Design, Manufacturing and Materials

Skolkovo Institute of Science and Technology, Moscow, Russia

hassaan.butt@skoltech.ru

Functional nanocomposites are allowing fundamental changes to the way system and material monitoring and testing takes place, both during manufacturing as well as during composite usage lifecycle [1, 2]. One such application of these materials is the replacing of traditional sensors for deformation sensing, allowing the reduction in cost and weight of systems and potential usage has already been highlighted in fields such as the automotive, aerospace, renewable energy and sensor manufacturing sectors [3, 4].

In recent years, nano-carbon particles, in particular, carbon nanotubes and graphene/derivatives, have been under intense scientific scrutiny as additives for composite manufacturing, not only increasing the mechanical properties of composites but allowing the final composites to be electrically conductive and piezoresistive in nature [5, 6].

In this work, industrial masterbatches have been used to manufacture functional nanocomposites and evaluate their feasibility for large scale production of strain sensing thermoplastic nanocomposites. Masterbatches are high weight/volume fraction compounds premixed with nanoadditives in a selected matrix and provide a safe medium for implementing nanomaterials on an industrial scale. From a safety, production line modification and financial standpoint, masterbatches are the most feasible implementation medium for large scale production. However, very few publications deal masterbatch-based nanocomposites and of those available, even fewer deal with piezoresistivity or self-diagnostics.

Six types of carbon nanoparticle masterbatches were employed during this study, each type containing either single-wall carbon nanotubes (SWCNT), multi-wall carbon nanotubes (02 types, MWCNT), graphene (G), reduced graphene oxide (RGO) or nitrogen doped graphene (NDG). These particles were added to an epoxy matrix at three weight percentages of interest, 0.5 %, 1.0 % and 2 %. The electrical and piezoresistive properties of the formulated nanocomposites were studied, with higher weight fractions yielding higher electrical conductivities whereas the same yielded lower piezoresistive response. Carbon nanotube (CNT) based nanocomposites outperformed graphene/derivative nanocomposites in terms of electrical conductance, showing resistivities between 2 – 10⁶ Ohm∙cm as compared to G/RGO/NDG samples, with values between 10¹¹-10¹² Ohm∙cm. CNT based nanocomposites showed strain based gauge factors between ~2–7, while graphene/derivative nanocomposites showed extremely high resistivities infeasible for piezoresistive monitoring at the studied weight percentages. A clear relationship between the attained electrical conductance of CNT nanocomposites and their strain sensing ability (gauge factor) has also been established, with the dependency following a semi-logarithmic system; GF=A*log(R0)+B.

References

1. Lee, J. and B.L. Wardle. Nanoengineered In Situ Cure Status Monitoring Technique Based on Carbon Nanotube Network. in AIAA Scitech 2019 Forum. 2019. San Diego, California.

2. Cao X., et al., Strain sensing behaviors of epoxy nanocomposites with carbon nanotubes under cyclic deformation. Polymer, 2017. 112: p. 1–9.

3. Kumar A., K. Sharma, and A.R. Dixit, Carbon nanotube- and graphene-reinforced multiphase polymeric composites: review on their properties and applications. Journal of Materials Science, 2019. 55(7): p. 2682–2724.

4. Camilli L. and Passacantando M., Advances on sensors based on carbon nanotubes. Chemosensors, 2018. 6(4): p. 62–80.

5. Atif R., I. Shyha, and F. Inam, Mechanical, thermal, and electrical properties of graphene-epoxy nanocomposites-A Review. Polymers, 2016. 8(8): p. 281–317.

6. Caradonna A., et al., Electrical and thermal conductivity of epoxy-carbon filler composites processed by calendaring. Materials (Basel), 2019. 12(9): p. 1–17.