Fused Filament Fabrication of Piezoresistive Carbon Nanotubes Nanocomposites for Strain Monitoring

Abstract

Conductive carbon nanotubes (CNT)/acrylonitrile butadiene styrene (ABS) nanocomposites parts were easily and successfully manufactured by fused filament fabrication (FFF) starting from composite filaments properly extruded at a laboratory scale. Specific specimens for strain monitoring application were properly evaluated in both short term and long term mechanical testing. In particular, samples of ABS filled with 6 wt.% of CNT were additively manufactured in two different infill patterns: HC (0 • /0 • ) and H45 (−45 • /+45 • ). The piezoresistivity behavior was investigated under various loading conditions such as ramp tensile tests at different rate and extension, and also creep and cyclic loading at room temperature. Experimental work revealed that the resistance changes in the conductive samples were properly detectable during stress or strain modification, as consequence of damage and/or reassembling of the percolation network. The measurement of the gauge factor in various testing conditions evidenced an initial higher sensitivity of the 3D-built parts within H45 pattern in comparison to the correspondent HC counterparts. The CNT conductive network path in the investigated samples seems to be reformed during creep and cycling experiments, showing a progressive reduction of gauge factor that seems to stabilize at about 2.5 for both HC and H45 samples after long term testing. These findings suggest that conductive CNT/ABS nanocomposites at 6 wt.% of loading can be successfully processed by FFF to produce stable strain sensors in the range −25 • and +60 • C, as confirmed by the constancy of resistivity in these temperatures.

Poly(vinylidene fluoride)/thermoplastic polyurethane flexible and 3D printable conductive composites

“…The addition of carbonaceous nanofillers in materials for additive manufacturing has been recently explored. 11 Various fillers, such as carbon nanotubes (CNT), 5,6,9,[12][13][14] carbon black (CB), 8 graphene (GR) [15][16][17] and others, have been added to polymer matrices to improve the electrical and thermal conductivity, mechanical strength, modulus of elasticity and toughness of components fabricated by FFF. These materials have the potential to be used in several technological applications, including chemical sensors, 6 flexible electronic devices, 1,5,9,15,18 electrical circuit printing, 8,19 electromagnetic interference (EMI) shielding.…”

Review on Conductive Polymer/CNTs Nanocomposites Based Flexible and Stretchable Strain and Pressure Sensors

“…The performance of the filament sensor showed two linear regions (for strain from 0% to 5%, GF = 48 and linearity of 0.99, and for strain from 20% to 100%, GF = 425 linearity of 0.98. Additionally, CNT/acrylonitrile butadiene styrene (ABS) composite (CNT content 6 wt.%) were melt blended at 190 °C to form starting composite materials for filament fabrication which was prepared by laboratory scale extruder at 220 °C [ 68 ]. The CNT conductive network paths in the filament sensors can be reformed during creep and cycling tests along with continuous decrease of gauge factor that eventually stabilizes at about 2.5.…”

An Overview of Additive Manufacturing of Polymers and Associated Composites

“…With the advancements of AM technologies and the availability of a wide variety of printing materials, AM is rapidly seeping into many sectors of engineering. One of the most benefited sectors is the electromechanical systems [ 220 , 221 ] and various other sensor design fields [ 222 , 223 , 224 , 225 , 226 ]. A recent study demonstrated the fabrication of a polypropylene-based thermoplastic composite for 2D and 3D circuits by FDM printing [ 227 ].…”

“…The piezoresistive effect is a change in electrical resistivity with applied strain. FDM printed polymer matrix and CNT nanocomposite can be used to make strain sensors with tunable piezoresistive properties [ 223 , 224 , 225 ]. 3D printing of a multiaxial force sensor can eliminate the sequential steps of individual sensor fabrication followed by assembly steps [ 226 ].…”