Tuneable piezoresistive characteristics of MWCNT/HDPE auxetic composite structures enabled by additive manufacturing

Abstract

Here we report the mechanical and piezoresistive characteristics of 3D printed high density polyethylene (HDPE) 2D auxetic structures reinforced with multi-walled carbon nanotubes (MWCNTs). Nano-engineered MWCNT/HDPE filament feedstocks were in-house developed by melt-blending extrusion. 2D auxetic MWCNT/HDPE composite structures were additively manufactured via fused deposition modeling (FDM). Mechanical and piezoresistive response of the 3D printed auxetic MWCNT/HDPE composite structures were measured under tensile loading for various weight fractions of MWCNTs and relative densities. Experimental results were corroborated with results predicted by micromechanics based two-parameter model. We further show that by varying MWCNT weight fraction, relative density and auxetic geometry we can achieve tuneable piezoresistive response capable of providing a range of sensitivities. In this study, we utilized the previously developed S-Shape auxetic structure which showed 300% increase in sensitivity when compared to the well-known Re-Entrant and Chiral structures. Moreover, the effects of auxetic degree on the piezoresistive performance of different auxetic structures were explored to optimize their self-sensing capabilities. The findings reported provide a promising approach for the design and additive manufacturing of self-sensing structures with tuneable sensitivity.

Date of Award	Jul 2020
Original language	American English